/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.text.Normalizer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.Set;
import java.util.function.Supplier;
import java.util.regex.Pattern;

Operations on String that are null safe.

 
IsEmpty/IsBlank
     - checks if a String contains text
 
Trim/Strip
     - removes leading and trailing whitespace
 
Equals/Compare
     - compares two strings in a null-safe manner
 
startsWith
     - check if a String starts with a prefix in a null-safe manner
 
endsWith
     - check if a String ends with a suffix in a null-safe manner
 
IndexOf/LastIndexOf/Contains
     - null-safe index-of checks
 
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut
     - index-of any of a set of Strings
 
ContainsOnly/ContainsNone/ContainsAny
     - checks if String contains only/none/any of these characters
 
Substring/Left/Right/Mid
     - null-safe substring extractions
 
SubstringBefore/SubstringAfter/SubstringBetween
     - substring extraction relative to other strings
 
Split/Join
     - splits a String into an array of substrings and vice versa
 
Remove/Delete
     - removes part of a String
 
Replace/Overlay
     - Searches a String and replaces one String with another
 
Chomp/Chop
     - removes the last part of a String
 
AppendIfMissing
     - appends a suffix to the end of the String if not present
 
PrependIfMissing
     - prepends a prefix to the start of the String if not present
 
LeftPad/RightPad/Center/Repeat
     - pads a String
 
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize
     - changes the case of a String
 
CountMatches
     - counts the number of occurrences of one String in another
 
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable
     - checks the characters in a String
 
DefaultString
     - protects against a null input String
 
Rotate
     - rotate (circular shift) a String
 
Reverse/ReverseDelimited
     - reverses a String
 
Abbreviate
     - abbreviates a string using ellipses or another given String
 
Difference
     - compares Strings and reports on their differences
 
LevenshteinDistance
     - the number of changes needed to change one String into another

The StringUtils class defines certain words related to String handling.

 
null - null
 
empty - a zero-length string ("")
 
space - the space character (' ', char 32)
 
whitespace - the characters defined by Character.isWhitespace(char)
 
trim - the characters <= 32 as in String.trim()

StringUtils handles null input Strings quietly. That is to say that a null input will return null. Where a boolean or int is being returned details vary by method.
A side effect of the null handling is that a NullPointerException should be considered a bug in StringUtils.
Methods in this class include sample code in their Javadoc comments to explain their operation. The symbol * is used to indicate any input including null.
#ThreadSafe#
See Also:
String
Since:
1.0/**
 * <p>Operations on {@link java.lang.String} that are
 * {@code null} safe.</p>
 *
 * <ul>
 *  <li><b>IsEmpty/IsBlank</b>
 *      - checks if a String contains text</li>
 *  <li><b>Trim/Strip</b>
 *      - removes leading and trailing whitespace</li>
 *  <li><b>Equals/Compare</b>
 *      - compares two strings in a null-safe manner</li>
 *  <li><b>startsWith</b>
 *      - check if a String starts with a prefix in a null-safe manner</li>
 *  <li><b>endsWith</b>
 *      - check if a String ends with a suffix in a null-safe manner</li>
 *  <li><b>IndexOf/LastIndexOf/Contains</b>
 *      - null-safe index-of checks
 *  <li><b>IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut</b>
 *      - index-of any of a set of Strings</li>
 *  <li><b>ContainsOnly/ContainsNone/ContainsAny</b>
 *      - checks if String contains only/none/any of these characters</li>
 *  <li><b>Substring/Left/Right/Mid</b>
 *      - null-safe substring extractions</li>
 *  <li><b>SubstringBefore/SubstringAfter/SubstringBetween</b>
 *      - substring extraction relative to other strings</li>
 *  <li><b>Split/Join</b>
 *      - splits a String into an array of substrings and vice versa</li>
 *  <li><b>Remove/Delete</b>
 *      - removes part of a String</li>
 *  <li><b>Replace/Overlay</b>
 *      - Searches a String and replaces one String with another</li>
 *  <li><b>Chomp/Chop</b>
 *      - removes the last part of a String</li>
 *  <li><b>AppendIfMissing</b>
 *      - appends a suffix to the end of the String if not present</li>
 *  <li><b>PrependIfMissing</b>
 *      - prepends a prefix to the start of the String if not present</li>
 *  <li><b>LeftPad/RightPad/Center/Repeat</b>
 *      - pads a String</li>
 *  <li><b>UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize</b>
 *      - changes the case of a String</li>
 *  <li><b>CountMatches</b>
 *      - counts the number of occurrences of one String in another</li>
 *  <li><b>IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable</b>
 *      - checks the characters in a String</li>
 *  <li><b>DefaultString</b>
 *      - protects against a null input String</li>
 *  <li><b>Rotate</b>
 *      - rotate (circular shift) a String</li>
 *  <li><b>Reverse/ReverseDelimited</b>
 *      - reverses a String</li>
 *  <li><b>Abbreviate</b>
 *      - abbreviates a string using ellipses or another given String</li>
 *  <li><b>Difference</b>
 *      - compares Strings and reports on their differences</li>
 *  <li><b>LevenshteinDistance</b>
 *      - the number of changes needed to change one String into another</li>
 * </ul>
 *
 * <p>The {@code StringUtils} class defines certain words related to
 * String handling.</p>
 *
 * <ul>
 *  <li>null - {@code null}</li>
 *  <li>empty - a zero-length string ({@code ""})</li>
 *  <li>space - the space character ({@code ' '}, char 32)</li>
 *  <li>whitespace - the characters defined by {@link Character#isWhitespace(char)}</li>
 *  <li>trim - the characters &lt;= 32 as in {@link String#trim()}</li>
 * </ul>
 *
 * <p>{@code StringUtils} handles {@code null} input Strings quietly.
 * That is to say that a {@code null} input will return {@code null}.
 * Where a {@code boolean} or {@code int} is being returned
 * details vary by method.</p>
 *
 * <p>A side effect of the {@code null} handling is that a
 * {@code NullPointerException} should be considered a bug in
 * {@code StringUtils}.</p>
 *
 * <p>Methods in this class include sample code in their Javadoc comments to explain their operation.
 * The symbol {@code *} is used to indicate any input including {@code null}.</p>
 *
 * <p>#ThreadSafe#</p>
 * @see java.lang.String
 * @since 1.0
 */
//@Immutable
public class StringUtils {

    private static final int STRING_BUILDER_SIZE = 256;

    // Performance testing notes (JDK 1.4, Jul03, scolebourne)
    // Whitespace:
    // Character.isWhitespace() is faster than WHITESPACE.indexOf()
    // where WHITESPACE is a string of all whitespace characters
    //
    // Character access:
    // String.charAt(n) versus toCharArray(), then array[n]
    // String.charAt(n) is about 15% worse for a 10K string
    // They are about equal for a length 50 string
    // String.charAt(n) is about 4 times better for a length 3 string
    // String.charAt(n) is best bet overall
    //
    // Append:
    // String.concat about twice as fast as StringBuffer.append
    // (not sure who tested this)

    
A String for a space character.
Since:
3.2/**
     * A String for a space character.
     *
     * @since 3.2
     */
    public static final String SPACE = " ";

    
The empty String "". 
Since:
2.0/**
     * The empty String {@code ""}.
     * @since 2.0
     */
    public static final String EMPTY = "";

    
A String for linefeed LF ("\n").
See Also:
JLF: Escape Sequences
     *      for Character and String Literals
Since:
3.2/**
     * A String for linefeed LF ("\n").
     *
     * @see <a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html#jls-3.10.6">JLF: Escape Sequences
     *      for Character and String Literals</a>
     * @since 3.2
     */
    public static final String LF = "\n";

    
A String for carriage return CR ("\r").
See Also:
JLF: Escape Sequences
     *      for Character and String Literals
Since:
3.2/**
     * A String for carriage return CR ("\r").
     *
     * @see <a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html#jls-3.10.6">JLF: Escape Sequences
     *      for Character and String Literals</a>
     * @since 3.2
     */
    public static final String CR = "\r";

    
Represents a failed index search.
Since:
2.1/**
     * Represents a failed index search.
     * @since 2.1
     */
    public static final int INDEX_NOT_FOUND = -1;

    
The maximum size to which the padding constant(s) can expand.
/**
     * <p>The maximum size to which the padding constant(s) can expand.</p>
     */
    private static final int PAD_LIMIT = 8192;

    
Pattern used in stripAccents(String). /**
     * Pattern used in {@link #stripAccents(String)}.
     */
    private static final Pattern STRIP_ACCENTS_PATTERN = Pattern.compile("\\p{InCombiningDiacriticalMarks}+"); //$NON-NLS-1$

    // Abbreviating
    //-----------------------------------------------------------------------
    
Abbreviates a String using ellipses. This will turn
"Now is the time for all good men" into "Now is the time for..."
Specifically:

  
If the number of characters in str is less than or equal to maxWidth, return str.
  
Else abbreviate it to (substring(str, 0, max-3) + "...").
  
If maxWidth is less than 4, throw an IllegalArgumentException.
  
In no case will it return a String of length greater than maxWidth.

StringUtils.abbreviate(null, *)      = null
StringUtils.abbreviate("", 4)        = ""
StringUtils.abbreviate("abcdefg", 6) = "abc..."
StringUtils.abbreviate("abcdefg", 7) = "abcdefg"
StringUtils.abbreviate("abcdefg", 8) = "abcdefg"
StringUtils.abbreviate("abcdefg", 4) = "a..."
StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException

Params:
str –  the String to check, may be null
maxWidth –  maximum length of result String, must be at least 4
Throws:
IllegalArgumentException – if the width is too small
Returns:
abbreviated String, null if null String input
Since:
2.0/**
     * <p>Abbreviates a String using ellipses. This will turn
     * "Now is the time for all good men" into "Now is the time for..."</p>
     *
     * <p>Specifically:</p>
     * <ul>
     *   <li>If the number of characters in {@code str} is less than or equal to
     *       {@code maxWidth}, return {@code str}.</li>
     *   <li>Else abbreviate it to {@code (substring(str, 0, max-3) + "...")}.</li>
     *   <li>If {@code maxWidth} is less than {@code 4}, throw an
     *       {@code IllegalArgumentException}.</li>
     *   <li>In no case will it return a String of length greater than
     *       {@code maxWidth}.</li>
     * </ul>
     *
     * <pre>
     * StringUtils.abbreviate(null, *)      = null
     * StringUtils.abbreviate("", 4)        = ""
     * StringUtils.abbreviate("abcdefg", 6) = "abc..."
     * StringUtils.abbreviate("abcdefg", 7) = "abcdefg"
     * StringUtils.abbreviate("abcdefg", 8) = "abcdefg"
     * StringUtils.abbreviate("abcdefg", 4) = "a..."
     * StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param maxWidth  maximum length of result String, must be at least 4
     * @return abbreviated String, {@code null} if null String input
     * @throws IllegalArgumentException if the width is too small
     * @since 2.0
     */
    public static String abbreviate(final String str, final int maxWidth) {
        return abbreviate(str, "...", 0, maxWidth);
    }

    
Abbreviates a String using ellipses. This will turn
"Now is the time for all good men" into "...is the time for..."
Works like abbreviate(String, int), but allows you to specify a "left edge" offset. Note that this left edge is not necessarily going to be the leftmost character in the result, or the first character following the ellipses, but it will appear somewhere in the result. 
In no case will it return a String of length greater than maxWidth.
StringUtils.abbreviate(null, *, *)                = null
StringUtils.abbreviate("", 0, 4)                  = ""
StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 0, 10)  = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 1, 10)  = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 4, 10)  = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 5, 10)  = "...fghi..."
StringUtils.abbreviate("abcdefghijklmno", 6, 10)  = "...ghij..."
StringUtils.abbreviate("abcdefghijklmno", 8, 10)  = "...ijklmno"
StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno"
StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno"
StringUtils.abbreviate("abcdefghij", 0, 3)        = IllegalArgumentException
StringUtils.abbreviate("abcdefghij", 5, 6)        = IllegalArgumentException

Params:
str –  the String to check, may be null
offset –  left edge of source String
maxWidth –  maximum length of result String, must be at least 4
Throws:
IllegalArgumentException – if the width is too small
Returns:
abbreviated String, null if null String input
Since:
2.0/**
     * <p>Abbreviates a String using ellipses. This will turn
     * "Now is the time for all good men" into "...is the time for..."</p>
     *
     * <p>Works like {@code abbreviate(String, int)}, but allows you to specify
     * a "left edge" offset.  Note that this left edge is not necessarily going to
     * be the leftmost character in the result, or the first character following the
     * ellipses, but it will appear somewhere in the result.
     *
     * <p>In no case will it return a String of length greater than
     * {@code maxWidth}.</p>
     *
     * <pre>
     * StringUtils.abbreviate(null, *, *)                = null
     * StringUtils.abbreviate("", 0, 4)                  = ""
     * StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..."
     * StringUtils.abbreviate("abcdefghijklmno", 0, 10)  = "abcdefg..."
     * StringUtils.abbreviate("abcdefghijklmno", 1, 10)  = "abcdefg..."
     * StringUtils.abbreviate("abcdefghijklmno", 4, 10)  = "abcdefg..."
     * StringUtils.abbreviate("abcdefghijklmno", 5, 10)  = "...fghi..."
     * StringUtils.abbreviate("abcdefghijklmno", 6, 10)  = "...ghij..."
     * StringUtils.abbreviate("abcdefghijklmno", 8, 10)  = "...ijklmno"
     * StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno"
     * StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno"
     * StringUtils.abbreviate("abcdefghij", 0, 3)        = IllegalArgumentException
     * StringUtils.abbreviate("abcdefghij", 5, 6)        = IllegalArgumentException
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param offset  left edge of source String
     * @param maxWidth  maximum length of result String, must be at least 4
     * @return abbreviated String, {@code null} if null String input
     * @throws IllegalArgumentException if the width is too small
     * @since 2.0
     */
    public static String abbreviate(final String str, final int offset, final int maxWidth) {
        return abbreviate(str, "...", offset, maxWidth);
    }

    
Abbreviates a String using another given String as replacement marker. This will turn
"Now is the time for all good men" into "Now is the time for..." if "..." was defined
as the replacement marker.
Specifically:

  
If the number of characters in str is less than or equal to maxWidth, return str.
  
Else abbreviate it to (substring(str, 0, max-abbrevMarker.length) + abbrevMarker).
  
If maxWidth is less than abbrevMarker.length + 1, throw an IllegalArgumentException.
  
In no case will it return a String of length greater than maxWidth.

StringUtils.abbreviate(null, "...", *)      = null
StringUtils.abbreviate("abcdefg", null, *)  = "abcdefg"
StringUtils.abbreviate("", "...", 4)        = ""
StringUtils.abbreviate("abcdefg", ".", 5)   = "abcd."
StringUtils.abbreviate("abcdefg", ".", 7)   = "abcdefg"
StringUtils.abbreviate("abcdefg", ".", 8)   = "abcdefg"
StringUtils.abbreviate("abcdefg", "..", 4)  = "ab.."
StringUtils.abbreviate("abcdefg", "..", 3)  = "a.."
StringUtils.abbreviate("abcdefg", "..", 2)  = IllegalArgumentException
StringUtils.abbreviate("abcdefg", "...", 3) = IllegalArgumentException

Params:
str –  the String to check, may be null
abbrevMarker –  the String used as replacement marker
maxWidth –  maximum length of result String, must be at least abbrevMarker.length + 1
Throws:
IllegalArgumentException – if the width is too small
Returns:
abbreviated String, null if null String input
Since:
3.6/**
     * <p>Abbreviates a String using another given String as replacement marker. This will turn
     * "Now is the time for all good men" into "Now is the time for..." if "..." was defined
     * as the replacement marker.</p>
     *
     * <p>Specifically:</p>
     * <ul>
     *   <li>If the number of characters in {@code str} is less than or equal to
     *       {@code maxWidth}, return {@code str}.</li>
     *   <li>Else abbreviate it to {@code (substring(str, 0, max-abbrevMarker.length) + abbrevMarker)}.</li>
     *   <li>If {@code maxWidth} is less than {@code abbrevMarker.length + 1}, throw an
     *       {@code IllegalArgumentException}.</li>
     *   <li>In no case will it return a String of length greater than
     *       {@code maxWidth}.</li>
     * </ul>
     *
     * <pre>
     * StringUtils.abbreviate(null, "...", *)      = null
     * StringUtils.abbreviate("abcdefg", null, *)  = "abcdefg"
     * StringUtils.abbreviate("", "...", 4)        = ""
     * StringUtils.abbreviate("abcdefg", ".", 5)   = "abcd."
     * StringUtils.abbreviate("abcdefg", ".", 7)   = "abcdefg"
     * StringUtils.abbreviate("abcdefg", ".", 8)   = "abcdefg"
     * StringUtils.abbreviate("abcdefg", "..", 4)  = "ab.."
     * StringUtils.abbreviate("abcdefg", "..", 3)  = "a.."
     * StringUtils.abbreviate("abcdefg", "..", 2)  = IllegalArgumentException
     * StringUtils.abbreviate("abcdefg", "...", 3) = IllegalArgumentException
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param abbrevMarker  the String used as replacement marker
     * @param maxWidth  maximum length of result String, must be at least {@code abbrevMarker.length + 1}
     * @return abbreviated String, {@code null} if null String input
     * @throws IllegalArgumentException if the width is too small
     * @since 3.6
     */
    public static String abbreviate(final String str, final String abbrevMarker, final int maxWidth) {
        return abbreviate(str, abbrevMarker, 0, maxWidth);
    }
    
Abbreviates a String using a given replacement marker. This will turn
"Now is the time for all good men" into "...is the time for..." if "..." was defined
as the replacement marker.
Works like abbreviate(String, String, int), but allows you to specify a "left edge" offset. Note that this left edge is not necessarily going to be the leftmost character in the result, or the first character following the replacement marker, but it will appear somewhere in the result. 
In no case will it return a String of length greater than maxWidth.
StringUtils.abbreviate(null, null, *, *)                 = null
StringUtils.abbreviate("abcdefghijklmno", null, *, *)    = "abcdefghijklmno"
StringUtils.abbreviate("", "...", 0, 4)                  = ""
StringUtils.abbreviate("abcdefghijklmno", "---", -1, 10) = "abcdefg---"
StringUtils.abbreviate("abcdefghijklmno", ",", 0, 10)    = "abcdefghi,"
StringUtils.abbreviate("abcdefghijklmno", ",", 1, 10)    = "abcdefghi,"
StringUtils.abbreviate("abcdefghijklmno", ",", 2, 10)    = "abcdefghi,"
StringUtils.abbreviate("abcdefghijklmno", "::", 4, 10)   = "::efghij::"
StringUtils.abbreviate("abcdefghijklmno", "...", 6, 10)  = "...ghij..."
StringUtils.abbreviate("abcdefghijklmno", "*", 9, 10)    = "*ghijklmno"
StringUtils.abbreviate("abcdefghijklmno", "'", 10, 10)   = "'ghijklmno"
StringUtils.abbreviate("abcdefghijklmno", "!", 12, 10)   = "!ghijklmno"
StringUtils.abbreviate("abcdefghij", "abra", 0, 4)       = IllegalArgumentException
StringUtils.abbreviate("abcdefghij", "...", 5, 6)        = IllegalArgumentException

Params:
str –  the String to check, may be null
abbrevMarker –  the String used as replacement marker
offset –  left edge of source String
maxWidth –  maximum length of result String, must be at least 4
Throws:
IllegalArgumentException – if the width is too small
Returns:
abbreviated String, null if null String input
Since:
3.6/**
     * <p>Abbreviates a String using a given replacement marker. This will turn
     * "Now is the time for all good men" into "...is the time for..." if "..." was defined
     * as the replacement marker.</p>
     *
     * <p>Works like {@code abbreviate(String, String, int)}, but allows you to specify
     * a "left edge" offset.  Note that this left edge is not necessarily going to
     * be the leftmost character in the result, or the first character following the
     * replacement marker, but it will appear somewhere in the result.
     *
     * <p>In no case will it return a String of length greater than {@code maxWidth}.</p>
     *
     * <pre>
     * StringUtils.abbreviate(null, null, *, *)                 = null
     * StringUtils.abbreviate("abcdefghijklmno", null, *, *)    = "abcdefghijklmno"
     * StringUtils.abbreviate("", "...", 0, 4)                  = ""
     * StringUtils.abbreviate("abcdefghijklmno", "---", -1, 10) = "abcdefg---"
     * StringUtils.abbreviate("abcdefghijklmno", ",", 0, 10)    = "abcdefghi,"
     * StringUtils.abbreviate("abcdefghijklmno", ",", 1, 10)    = "abcdefghi,"
     * StringUtils.abbreviate("abcdefghijklmno", ",", 2, 10)    = "abcdefghi,"
     * StringUtils.abbreviate("abcdefghijklmno", "::", 4, 10)   = "::efghij::"
     * StringUtils.abbreviate("abcdefghijklmno", "...", 6, 10)  = "...ghij..."
     * StringUtils.abbreviate("abcdefghijklmno", "*", 9, 10)    = "*ghijklmno"
     * StringUtils.abbreviate("abcdefghijklmno", "'", 10, 10)   = "'ghijklmno"
     * StringUtils.abbreviate("abcdefghijklmno", "!", 12, 10)   = "!ghijklmno"
     * StringUtils.abbreviate("abcdefghij", "abra", 0, 4)       = IllegalArgumentException
     * StringUtils.abbreviate("abcdefghij", "...", 5, 6)        = IllegalArgumentException
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param abbrevMarker  the String used as replacement marker
     * @param offset  left edge of source String
     * @param maxWidth  maximum length of result String, must be at least 4
     * @return abbreviated String, {@code null} if null String input
     * @throws IllegalArgumentException if the width is too small
     * @since 3.6
     */
    public static String abbreviate(final String str, final String abbrevMarker, int offset, final int maxWidth) {
        if (isNotEmpty(str) && EMPTY.equals(abbrevMarker) && maxWidth > 0) {
            return substring(str, 0, maxWidth);
        } else if (isAnyEmpty(str, abbrevMarker)) {
            return str;
        }
        final int abbrevMarkerLength = abbrevMarker.length();
        final int minAbbrevWidth = abbrevMarkerLength + 1;
        final int minAbbrevWidthOffset = abbrevMarkerLength + abbrevMarkerLength + 1;

        if (maxWidth < minAbbrevWidth) {
            throw new IllegalArgumentException(String.format("Minimum abbreviation width is %d", minAbbrevWidth));
        }
        if (str.length() <= maxWidth) {
            return str;
        }
        if (offset > str.length()) {
            offset = str.length();
        }
        if (str.length() - offset < maxWidth - abbrevMarkerLength) {
            offset = str.length() - (maxWidth - abbrevMarkerLength);
        }
        if (offset <= abbrevMarkerLength+1) {
            return str.substring(0, maxWidth - abbrevMarkerLength) + abbrevMarker;
        }
        if (maxWidth < minAbbrevWidthOffset) {
            throw new IllegalArgumentException(String.format("Minimum abbreviation width with offset is %d", minAbbrevWidthOffset));
        }
        if (offset + maxWidth - abbrevMarkerLength < str.length()) {
            return abbrevMarker + abbreviate(str.substring(offset), abbrevMarker, maxWidth - abbrevMarkerLength);
        }
        return abbrevMarker + str.substring(str.length() - (maxWidth - abbrevMarkerLength));
    }

    
Abbreviates a String to the length passed, replacing the middle characters with the supplied
replacement String.
This abbreviation only occurs if the following criteria is met:

Neither the String for abbreviation nor the replacement String are null or empty 
The length to truncate to is less than the length of the supplied String
The length to truncate to is greater than 0
The abbreviated String will have enough room for the length supplied replacement String
and the first and last characters of the supplied String for abbreviation

Otherwise, the returned String will be the same as the supplied String for abbreviation.

StringUtils.abbreviateMiddle(null, null, 0)      = null
StringUtils.abbreviateMiddle("abc", null, 0)      = "abc"
StringUtils.abbreviateMiddle("abc", ".", 0)      = "abc"
StringUtils.abbreviateMiddle("abc", ".", 3)      = "abc"
StringUtils.abbreviateMiddle("abcdef", ".", 4)     = "ab.f"

Params:
str –  the String to abbreviate, may be null
middle – the String to replace the middle characters with, may be null
length – the length to abbreviate str to.
Returns:
the abbreviated String if the above criteria is met, or the original String supplied for abbreviation.
Since:
2.5/**
     * <p>Abbreviates a String to the length passed, replacing the middle characters with the supplied
     * replacement String.</p>
     *
     * <p>This abbreviation only occurs if the following criteria is met:</p>
     * <ul>
     * <li>Neither the String for abbreviation nor the replacement String are null or empty </li>
     * <li>The length to truncate to is less than the length of the supplied String</li>
     * <li>The length to truncate to is greater than 0</li>
     * <li>The abbreviated String will have enough room for the length supplied replacement String
     * and the first and last characters of the supplied String for abbreviation</li>
     * </ul>
     * <p>Otherwise, the returned String will be the same as the supplied String for abbreviation.
     * </p>
     *
     * <pre>
     * StringUtils.abbreviateMiddle(null, null, 0)      = null
     * StringUtils.abbreviateMiddle("abc", null, 0)      = "abc"
     * StringUtils.abbreviateMiddle("abc", ".", 0)      = "abc"
     * StringUtils.abbreviateMiddle("abc", ".", 3)      = "abc"
     * StringUtils.abbreviateMiddle("abcdef", ".", 4)     = "ab.f"
     * </pre>
     *
     * @param str  the String to abbreviate, may be null
     * @param middle the String to replace the middle characters with, may be null
     * @param length the length to abbreviate {@code str} to.
     * @return the abbreviated String if the above criteria is met, or the original String supplied for abbreviation.
     * @since 2.5
     */
    public static String abbreviateMiddle(final String str, final String middle, final int length) {
        if (isAnyEmpty(str, middle) || length >= str.length() || length < middle.length()+2) {
            return str;
        }

        final int targetSting = length-middle.length();
        final int startOffset = targetSting/2+targetSting%2;
        final int endOffset = str.length()-targetSting/2;

        return str.substring(0, startOffset) +
            middle +
            str.substring(endOffset);
    }

    
Appends the suffix to the end of the string if the string does not
already end with the suffix.
Params:
str – The string.
suffix – The suffix to append to the end of the string.
ignoreCase – Indicates whether the compare should ignore case.
suffixes – Additional suffixes that are valid terminators (optional).
Returns:
A new String if suffix was appended, the same string otherwise./**
     * Appends the suffix to the end of the string if the string does not
     * already end with the suffix.
     *
     * @param str The string.
     * @param suffix The suffix to append to the end of the string.
     * @param ignoreCase Indicates whether the compare should ignore case.
     * @param suffixes Additional suffixes that are valid terminators (optional).
     *
     * @return A new String if suffix was appended, the same string otherwise.
     */
    private static String appendIfMissing(final String str, final CharSequence suffix, final boolean ignoreCase, final CharSequence... suffixes) {
        if (str == null || isEmpty(suffix) || endsWith(str, suffix, ignoreCase)) {
            return str;
        }
        if (ArrayUtils.isNotEmpty(suffixes)) {
            for (final CharSequence s : suffixes) {
                if (endsWith(str, s, ignoreCase)) {
                    return str;
                }
            }
        }
        return str + suffix.toString();
    }

    
Appends the suffix to the end of the string if the string does not
already end with any of the suffixes.
StringUtils.appendIfMissing(null, null) = null
StringUtils.appendIfMissing("abc", null) = "abc"
StringUtils.appendIfMissing("", "xyz") = "xyz"
StringUtils.appendIfMissing("abc", "xyz") = "abcxyz"
StringUtils.appendIfMissing("abcxyz", "xyz") = "abcxyz"
StringUtils.appendIfMissing("abcXYZ", "xyz") = "abcXYZxyz"

With additional suffixes,
StringUtils.appendIfMissing(null, null, null) = null
StringUtils.appendIfMissing("abc", null, null) = "abc"
StringUtils.appendIfMissing("", "xyz", null) = "xyz"
StringUtils.appendIfMissing("abc", "xyz", new CharSequence[]{null}) = "abcxyz"
StringUtils.appendIfMissing("abc", "xyz", "") = "abc"
StringUtils.appendIfMissing("abc", "xyz", "mno") = "abcxyz"
StringUtils.appendIfMissing("abcxyz", "xyz", "mno") = "abcxyz"
StringUtils.appendIfMissing("abcmno", "xyz", "mno") = "abcmno"
StringUtils.appendIfMissing("abcXYZ", "xyz", "mno") = "abcXYZxyz"
StringUtils.appendIfMissing("abcMNO", "xyz", "mno") = "abcMNOxyz"

Params:
str – The string.
suffix – The suffix to append to the end of the string.
suffixes – Additional suffixes that are valid terminators.
Returns:
A new String if suffix was appended, the same string otherwise.
Since:
3.2/**
     * Appends the suffix to the end of the string if the string does not
     * already end with any of the suffixes.
     *
     * <pre>
     * StringUtils.appendIfMissing(null, null) = null
     * StringUtils.appendIfMissing("abc", null) = "abc"
     * StringUtils.appendIfMissing("", "xyz") = "xyz"
     * StringUtils.appendIfMissing("abc", "xyz") = "abcxyz"
     * StringUtils.appendIfMissing("abcxyz", "xyz") = "abcxyz"
     * StringUtils.appendIfMissing("abcXYZ", "xyz") = "abcXYZxyz"
     * </pre>
     * <p>With additional suffixes,</p>
     * <pre>
     * StringUtils.appendIfMissing(null, null, null) = null
     * StringUtils.appendIfMissing("abc", null, null) = "abc"
     * StringUtils.appendIfMissing("", "xyz", null) = "xyz"
     * StringUtils.appendIfMissing("abc", "xyz", new CharSequence[]{null}) = "abcxyz"
     * StringUtils.appendIfMissing("abc", "xyz", "") = "abc"
     * StringUtils.appendIfMissing("abc", "xyz", "mno") = "abcxyz"
     * StringUtils.appendIfMissing("abcxyz", "xyz", "mno") = "abcxyz"
     * StringUtils.appendIfMissing("abcmno", "xyz", "mno") = "abcmno"
     * StringUtils.appendIfMissing("abcXYZ", "xyz", "mno") = "abcXYZxyz"
     * StringUtils.appendIfMissing("abcMNO", "xyz", "mno") = "abcMNOxyz"
     * </pre>
     *
     * @param str The string.
     * @param suffix The suffix to append to the end of the string.
     * @param suffixes Additional suffixes that are valid terminators.
     *
     * @return A new String if suffix was appended, the same string otherwise.
     *
     * @since 3.2
     */
    public static String appendIfMissing(final String str, final CharSequence suffix, final CharSequence... suffixes) {
        return appendIfMissing(str, suffix, false, suffixes);
    }

    
Appends the suffix to the end of the string if the string does not
already end, case insensitive, with any of the suffixes.
StringUtils.appendIfMissingIgnoreCase(null, null) = null
StringUtils.appendIfMissingIgnoreCase("abc", null) = "abc"
StringUtils.appendIfMissingIgnoreCase("", "xyz") = "xyz"
StringUtils.appendIfMissingIgnoreCase("abc", "xyz") = "abcxyz"
StringUtils.appendIfMissingIgnoreCase("abcxyz", "xyz") = "abcxyz"
StringUtils.appendIfMissingIgnoreCase("abcXYZ", "xyz") = "abcXYZ"

With additional suffixes,
StringUtils.appendIfMissingIgnoreCase(null, null, null) = null
StringUtils.appendIfMissingIgnoreCase("abc", null, null) = "abc"
StringUtils.appendIfMissingIgnoreCase("", "xyz", null) = "xyz"
StringUtils.appendIfMissingIgnoreCase("abc", "xyz", new CharSequence[]{null}) = "abcxyz"
StringUtils.appendIfMissingIgnoreCase("abc", "xyz", "") = "abc"
StringUtils.appendIfMissingIgnoreCase("abc", "xyz", "mno") = "abcxyz"
StringUtils.appendIfMissingIgnoreCase("abcxyz", "xyz", "mno") = "abcxyz"
StringUtils.appendIfMissingIgnoreCase("abcmno", "xyz", "mno") = "abcmno"
StringUtils.appendIfMissingIgnoreCase("abcXYZ", "xyz", "mno") = "abcXYZ"
StringUtils.appendIfMissingIgnoreCase("abcMNO", "xyz", "mno") = "abcMNO"

Params:
str – The string.
suffix – The suffix to append to the end of the string.
suffixes – Additional suffixes that are valid terminators.
Returns:
A new String if suffix was appended, the same string otherwise.
Since:
3.2/**
     * Appends the suffix to the end of the string if the string does not
     * already end, case insensitive, with any of the suffixes.
     *
     * <pre>
     * StringUtils.appendIfMissingIgnoreCase(null, null) = null
     * StringUtils.appendIfMissingIgnoreCase("abc", null) = "abc"
     * StringUtils.appendIfMissingIgnoreCase("", "xyz") = "xyz"
     * StringUtils.appendIfMissingIgnoreCase("abc", "xyz") = "abcxyz"
     * StringUtils.appendIfMissingIgnoreCase("abcxyz", "xyz") = "abcxyz"
     * StringUtils.appendIfMissingIgnoreCase("abcXYZ", "xyz") = "abcXYZ"
     * </pre>
     * <p>With additional suffixes,</p>
     * <pre>
     * StringUtils.appendIfMissingIgnoreCase(null, null, null) = null
     * StringUtils.appendIfMissingIgnoreCase("abc", null, null) = "abc"
     * StringUtils.appendIfMissingIgnoreCase("", "xyz", null) = "xyz"
     * StringUtils.appendIfMissingIgnoreCase("abc", "xyz", new CharSequence[]{null}) = "abcxyz"
     * StringUtils.appendIfMissingIgnoreCase("abc", "xyz", "") = "abc"
     * StringUtils.appendIfMissingIgnoreCase("abc", "xyz", "mno") = "abcxyz"
     * StringUtils.appendIfMissingIgnoreCase("abcxyz", "xyz", "mno") = "abcxyz"
     * StringUtils.appendIfMissingIgnoreCase("abcmno", "xyz", "mno") = "abcmno"
     * StringUtils.appendIfMissingIgnoreCase("abcXYZ", "xyz", "mno") = "abcXYZ"
     * StringUtils.appendIfMissingIgnoreCase("abcMNO", "xyz", "mno") = "abcMNO"
     * </pre>
     *
     * @param str The string.
     * @param suffix The suffix to append to the end of the string.
     * @param suffixes Additional suffixes that are valid terminators.
     *
     * @return A new String if suffix was appended, the same string otherwise.
     *
     * @since 3.2
     */
    public static String appendIfMissingIgnoreCase(final String str, final CharSequence suffix, final CharSequence... suffixes) {
        return appendIfMissing(str, suffix, true, suffixes);
    }

    
Capitalizes a String changing the first character to title case as per Character.toTitleCase(int). No other characters are changed.
For a word based algorithm, see WordUtils.capitalize(String). A null input String returns null.
StringUtils.capitalize(null)  = null
StringUtils.capitalize("")    = ""
StringUtils.capitalize("cat") = "Cat"
StringUtils.capitalize("cAt") = "CAt"
StringUtils.capitalize("'cat'") = "'cat'"

Params:
str – the String to capitalize, may be null
See Also:
WordUtils.capitalize(String)
uncapitalize(String)
Returns:
the capitalized String, null if null String input
Since:
2.0/**
     * <p>Capitalizes a String changing the first character to title case as
     * per {@link Character#toTitleCase(int)}. No other characters are changed.</p>
     *
     * <p>For a word based algorithm, see {@link org.apache.commons.lang3.text.WordUtils#capitalize(String)}.
     * A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.capitalize(null)  = null
     * StringUtils.capitalize("")    = ""
     * StringUtils.capitalize("cat") = "Cat"
     * StringUtils.capitalize("cAt") = "CAt"
     * StringUtils.capitalize("'cat'") = "'cat'"
     * </pre>
     *
     * @param str the String to capitalize, may be null
     * @return the capitalized String, {@code null} if null String input
     * @see org.apache.commons.lang3.text.WordUtils#capitalize(String)
     * @see #uncapitalize(String)
     * @since 2.0
     */
    public static String capitalize(final String str) {
        final int strLen = length(str);
        if (strLen == 0) {
            return str;
        }

        final int firstCodepoint = str.codePointAt(0);
        final int newCodePoint = Character.toTitleCase(firstCodepoint);
        if (firstCodepoint == newCodePoint) {
            // already capitalized
            return str;
        }

        final int[] newCodePoints = new int[strLen]; // cannot be longer than the char array
        int outOffset = 0;
        newCodePoints[outOffset++] = newCodePoint; // copy the first codepoint
        for (int inOffset = Character.charCount(firstCodepoint); inOffset < strLen; ) {
            final int codepoint = str.codePointAt(inOffset);
            newCodePoints[outOffset++] = codepoint; // copy the remaining ones
            inOffset += Character.charCount(codepoint);
         }
        return new String(newCodePoints, 0, outOffset);
    }

    // Centering
    //-----------------------------------------------------------------------
    
Centers a String in a larger String of size size using the space character (' ').
If the size is less than the String length, the original String is returned. A null String returns null. A negative size is treated as zero.
Equivalent to center(str, size, " ").
StringUtils.center(null, *)   = null
StringUtils.center("", 4)     = "    "
StringUtils.center("ab", -1)  = "ab"
StringUtils.center("ab", 4)   = " ab "
StringUtils.center("abcd", 2) = "abcd"
StringUtils.center("a", 4)    = " a  "

Params:
str –  the String to center, may be null
size –  the int size of new String, negative treated as zero
Returns:
centered String, null if null String input/**
     * <p>Centers a String in a larger String of size {@code size}
     * using the space character (' ').</p>
     *
     * <p>If the size is less than the String length, the original String is returned.
     * A {@code null} String returns {@code null}.
     * A negative size is treated as zero.</p>
     *
     * <p>Equivalent to {@code center(str, size, " ")}.</p>
     *
     * <pre>
     * StringUtils.center(null, *)   = null
     * StringUtils.center("", 4)     = "    "
     * StringUtils.center("ab", -1)  = "ab"
     * StringUtils.center("ab", 4)   = " ab "
     * StringUtils.center("abcd", 2) = "abcd"
     * StringUtils.center("a", 4)    = " a  "
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @return centered String, {@code null} if null String input
     */
    public static String center(final String str, final int size) {
        return center(str, size, ' ');
    }

    
Centers a String in a larger String of size size. Uses a supplied character as the value to pad the String with.
If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero.
StringUtils.center(null, *, *)     = null
StringUtils.center("", 4, ' ')     = "    "
StringUtils.center("ab", -1, ' ')  = "ab"
StringUtils.center("ab", 4, ' ')   = " ab "
StringUtils.center("abcd", 2, ' ') = "abcd"
StringUtils.center("a", 4, ' ')    = " a  "
StringUtils.center("a", 4, 'y')    = "yayy"

Params:
str –  the String to center, may be null
size –  the int size of new String, negative treated as zero
padChar –  the character to pad the new String with
Returns:
centered String, null if null String input
Since:
2.0/**
     * <p>Centers a String in a larger String of size {@code size}.
     * Uses a supplied character as the value to pad the String with.</p>
     *
     * <p>If the size is less than the String length, the String is returned.
     * A {@code null} String returns {@code null}.
     * A negative size is treated as zero.</p>
     *
     * <pre>
     * StringUtils.center(null, *, *)     = null
     * StringUtils.center("", 4, ' ')     = "    "
     * StringUtils.center("ab", -1, ' ')  = "ab"
     * StringUtils.center("ab", 4, ' ')   = " ab "
     * StringUtils.center("abcd", 2, ' ') = "abcd"
     * StringUtils.center("a", 4, ' ')    = " a  "
     * StringUtils.center("a", 4, 'y')    = "yayy"
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @param padChar  the character to pad the new String with
     * @return centered String, {@code null} if null String input
     * @since 2.0
     */
    public static String center(String str, final int size, final char padChar) {
        if (str == null || size <= 0) {
            return str;
        }
        final int strLen = str.length();
        final int pads = size - strLen;
        if (pads <= 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padChar);
        str = rightPad(str, size, padChar);
        return str;
    }

    
Centers a String in a larger String of size size. Uses a supplied String as the value to pad the String with.
If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero.
StringUtils.center(null, *, *)     = null
StringUtils.center("", 4, " ")     = "    "
StringUtils.center("ab", -1, " ")  = "ab"
StringUtils.center("ab", 4, " ")   = " ab "
StringUtils.center("abcd", 2, " ") = "abcd"
StringUtils.center("a", 4, " ")    = " a  "
StringUtils.center("a", 4, "yz")   = "yayz"
StringUtils.center("abc", 7, null) = "  abc  "
StringUtils.center("abc", 7, "")   = "  abc  "

Params:
str –  the String to center, may be null
size –  the int size of new String, negative treated as zero
padStr –  the String to pad the new String with, must not be null or empty
Throws:
IllegalArgumentException – if padStr is null or empty
Returns:
centered String, null if null String input/**
     * <p>Centers a String in a larger String of size {@code size}.
     * Uses a supplied String as the value to pad the String with.</p>
     *
     * <p>If the size is less than the String length, the String is returned.
     * A {@code null} String returns {@code null}.
     * A negative size is treated as zero.</p>
     *
     * <pre>
     * StringUtils.center(null, *, *)     = null
     * StringUtils.center("", 4, " ")     = "    "
     * StringUtils.center("ab", -1, " ")  = "ab"
     * StringUtils.center("ab", 4, " ")   = " ab "
     * StringUtils.center("abcd", 2, " ") = "abcd"
     * StringUtils.center("a", 4, " ")    = " a  "
     * StringUtils.center("a", 4, "yz")   = "yayz"
     * StringUtils.center("abc", 7, null) = "  abc  "
     * StringUtils.center("abc", 7, "")   = "  abc  "
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @param padStr  the String to pad the new String with, must not be null or empty
     * @return centered String, {@code null} if null String input
     * @throws IllegalArgumentException if padStr is {@code null} or empty
     */
    public static String center(String str, final int size, String padStr) {
        if (str == null || size <= 0) {
            return str;
        }
        if (isEmpty(padStr)) {
            padStr = SPACE;
        }
        final int strLen = str.length();
        final int pads = size - strLen;
        if (pads <= 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padStr);
        str = rightPad(str, size, padStr);
        return str;
    }

    // Chomping
    //-----------------------------------------------------------------------
    
Removes one newline from end of a String if it's there, otherwise leave it alone. A newline is "\n", "\r", or "\r\n".
NOTE: This method changed in 2.0.
It now more closely matches Perl chomp.
StringUtils.chomp(null)          = null
StringUtils.chomp("")            = ""
StringUtils.chomp("abc \r")      = "abc "
StringUtils.chomp("abc\n")       = "abc"
StringUtils.chomp("abc\r\n")     = "abc"
StringUtils.chomp("abc\r\n\r\n") = "abc\r\n"
StringUtils.chomp("abc\n\r")     = "abc\n"
StringUtils.chomp("abc\n\rabc")  = "abc\n\rabc"
StringUtils.chomp("\r")          = ""
StringUtils.chomp("\n")          = ""
StringUtils.chomp("\r\n")        = ""

Params:
str –  the String to chomp a newline from, may be null
Returns:
String without newline, null if null String input/**
     * <p>Removes one newline from end of a String if it's there,
     * otherwise leave it alone.  A newline is &quot;{@code \n}&quot;,
     * &quot;{@code \r}&quot;, or &quot;{@code \r\n}&quot;.</p>
     *
     * <p>NOTE: This method changed in 2.0.
     * It now more closely matches Perl chomp.</p>
     *
     * <pre>
     * StringUtils.chomp(null)          = null
     * StringUtils.chomp("")            = ""
     * StringUtils.chomp("abc \r")      = "abc "
     * StringUtils.chomp("abc\n")       = "abc"
     * StringUtils.chomp("abc\r\n")     = "abc"
     * StringUtils.chomp("abc\r\n\r\n") = "abc\r\n"
     * StringUtils.chomp("abc\n\r")     = "abc\n"
     * StringUtils.chomp("abc\n\rabc")  = "abc\n\rabc"
     * StringUtils.chomp("\r")          = ""
     * StringUtils.chomp("\n")          = ""
     * StringUtils.chomp("\r\n")        = ""
     * </pre>
     *
     * @param str  the String to chomp a newline from, may be null
     * @return String without newline, {@code null} if null String input
     */
    public static String chomp(final String str) {
        if (isEmpty(str)) {
            return str;
        }

        if (str.length() == 1) {
            final char ch = str.charAt(0);
            if (ch == CharUtils.CR || ch == CharUtils.LF) {
                return EMPTY;
            }
            return str;
        }

        int lastIdx = str.length() - 1;
        final char last = str.charAt(lastIdx);

        if (last == CharUtils.LF) {
            if (str.charAt(lastIdx - 1) == CharUtils.CR) {
                lastIdx--;
            }
        } else if (last != CharUtils.CR) {
            lastIdx++;
        }
        return str.substring(0, lastIdx);
    }

    
Removes separator from the end of str if it's there, otherwise leave it alone.
NOTE: This method changed in version 2.0. It now more closely matches Perl chomp. For the previous behavior, use substringBeforeLast(String, String). This method uses String.endsWith(String).
StringUtils.chomp(null, *)         = null
StringUtils.chomp("", *)           = ""
StringUtils.chomp("foobar", "bar") = "foo"
StringUtils.chomp("foobar", "baz") = "foobar"
StringUtils.chomp("foo", "foo")    = ""
StringUtils.chomp("foo ", "foo")   = "foo "
StringUtils.chomp(" foo", "foo")   = " "
StringUtils.chomp("foo", "foooo")  = "foo"
StringUtils.chomp("foo", "")       = "foo"
StringUtils.chomp("foo", null)     = "foo"

Params:
str –  the String to chomp from, may be null
separator –  separator String, may be null
Returns:
String without trailing separator, null if null String input
Deprecated:
This feature will be removed in Lang 4.0, use removeEnd(String, String) instead/**
     * <p>Removes {@code separator} from the end of
     * {@code str} if it's there, otherwise leave it alone.</p>
     *
     * <p>NOTE: This method changed in version 2.0.
     * It now more closely matches Perl chomp.
     * For the previous behavior, use {@link #substringBeforeLast(String, String)}.
     * This method uses {@link String#endsWith(String)}.</p>
     *
     * <pre>
     * StringUtils.chomp(null, *)         = null
     * StringUtils.chomp("", *)           = ""
     * StringUtils.chomp("foobar", "bar") = "foo"
     * StringUtils.chomp("foobar", "baz") = "foobar"
     * StringUtils.chomp("foo", "foo")    = ""
     * StringUtils.chomp("foo ", "foo")   = "foo "
     * StringUtils.chomp(" foo", "foo")   = " "
     * StringUtils.chomp("foo", "foooo")  = "foo"
     * StringUtils.chomp("foo", "")       = "foo"
     * StringUtils.chomp("foo", null)     = "foo"
     * </pre>
     *
     * @param str  the String to chomp from, may be null
     * @param separator  separator String, may be null
     * @return String without trailing separator, {@code null} if null String input
     * @deprecated This feature will be removed in Lang 4.0, use {@link StringUtils#removeEnd(String, String)} instead
     */
    @Deprecated
    public static String chomp(final String str, final String separator) {
        return removeEnd(str, separator);
    }

    // Chopping
    //-----------------------------------------------------------------------
    
Remove the last character from a String.
If the String ends in \r\n, then remove both of them.
StringUtils.chop(null)          = null
StringUtils.chop("")            = ""
StringUtils.chop("abc \r")      = "abc "
StringUtils.chop("abc\n")       = "abc"
StringUtils.chop("abc\r\n")     = "abc"
StringUtils.chop("abc")         = "ab"
StringUtils.chop("abc\nabc")    = "abc\nab"
StringUtils.chop("a")           = ""
StringUtils.chop("\r")          = ""
StringUtils.chop("\n")          = ""
StringUtils.chop("\r\n")        = ""

Params:
str –  the String to chop last character from, may be null
Returns:
String without last character, null if null String input/**
     * <p>Remove the last character from a String.</p>
     *
     * <p>If the String ends in {@code \r\n}, then remove both
     * of them.</p>
     *
     * <pre>
     * StringUtils.chop(null)          = null
     * StringUtils.chop("")            = ""
     * StringUtils.chop("abc \r")      = "abc "
     * StringUtils.chop("abc\n")       = "abc"
     * StringUtils.chop("abc\r\n")     = "abc"
     * StringUtils.chop("abc")         = "ab"
     * StringUtils.chop("abc\nabc")    = "abc\nab"
     * StringUtils.chop("a")           = ""
     * StringUtils.chop("\r")          = ""
     * StringUtils.chop("\n")          = ""
     * StringUtils.chop("\r\n")        = ""
     * </pre>
     *
     * @param str  the String to chop last character from, may be null
     * @return String without last character, {@code null} if null String input
     */
    public static String chop(final String str) {
        if (str == null) {
            return null;
        }
        final int strLen = str.length();
        if (strLen < 2) {
            return EMPTY;
        }
        final int lastIdx = strLen - 1;
        final String ret = str.substring(0, lastIdx);
        final char last = str.charAt(lastIdx);
        if (last == CharUtils.LF && ret.charAt(lastIdx - 1) == CharUtils.CR) {
            return ret.substring(0, lastIdx - 1);
        }
        return ret;
    }

    // Compare
    //-----------------------------------------------------------------------
    
Compare two Strings lexicographically, as per String.compareTo(String), returning :

 
int = 0, if str1 is equal to str2 (or both null)
 
int < 0, if str1 is less than str2
 
int > 0, if str1 is greater than str2

This is a null safe version of :
str1.compareTo(str2)
null value is considered less than non-null value. Two null references are considered equal.
StringUtils.compare(null, null)   = 0
StringUtils.compare(null , "a")   < 0
StringUtils.compare("a", null)    > 0
StringUtils.compare("abc", "abc") = 0
StringUtils.compare("a", "b")     < 0
StringUtils.compare("b", "a")     > 0
StringUtils.compare("a", "B")     > 0
StringUtils.compare("ab", "abc")  < 0

Params:
str1 –  the String to compare from
str2 –  the String to compare to
See Also:
compare(String, String, boolean)
String.compareTo(String)
Returns:
< 0, 0, > 0, if str1 is respectively less, equal or greater than str2
Since:
3.5/**
     * <p>Compare two Strings lexicographically, as per {@link String#compareTo(String)}, returning :</p>
     * <ul>
     *  <li>{@code int = 0}, if {@code str1} is equal to {@code str2} (or both {@code null})</li>
     *  <li>{@code int < 0}, if {@code str1} is less than {@code str2}</li>
     *  <li>{@code int > 0}, if {@code str1} is greater than {@code str2}</li>
     * </ul>
     *
     * <p>This is a {@code null} safe version of :</p>
     * <blockquote><pre>str1.compareTo(str2)</pre></blockquote>
     *
     * <p>{@code null} value is considered less than non-{@code null} value.
     * Two {@code null} references are considered equal.</p>
     *
     * <pre>
     * StringUtils.compare(null, null)   = 0
     * StringUtils.compare(null , "a")   &lt; 0
     * StringUtils.compare("a", null)    &gt; 0
     * StringUtils.compare("abc", "abc") = 0
     * StringUtils.compare("a", "b")     &lt; 0
     * StringUtils.compare("b", "a")     &gt; 0
     * StringUtils.compare("a", "B")     &gt; 0
     * StringUtils.compare("ab", "abc")  &lt; 0
     * </pre>
     *
     * @see #compare(String, String, boolean)
     * @see String#compareTo(String)
     * @param str1  the String to compare from
     * @param str2  the String to compare to
     * @return &lt; 0, 0, &gt; 0, if {@code str1} is respectively less, equal or greater than {@code str2}
     * @since 3.5
     */
    public static int compare(final String str1, final String str2) {
        return compare(str1, str2, true);
    }

    
Compare two Strings lexicographically, as per String.compareTo(String), returning :

 
int = 0, if str1 is equal to str2 (or both null)
 
int < 0, if str1 is less than str2
 
int > 0, if str1 is greater than str2

This is a null safe version of :
str1.compareTo(str2)
null inputs are handled according to the nullIsLess parameter. Two null references are considered equal.
StringUtils.compare(null, null, *)     = 0
StringUtils.compare(null , "a", true)  < 0
StringUtils.compare(null , "a", false) > 0
StringUtils.compare("a", null, true)   > 0
StringUtils.compare("a", null, false)  < 0
StringUtils.compare("abc", "abc", *)   = 0
StringUtils.compare("a", "b", *)       < 0
StringUtils.compare("b", "a", *)       > 0
StringUtils.compare("a", "B", *)       > 0
StringUtils.compare("ab", "abc", *)    < 0

Params:
str1 –  the String to compare from
str2 –  the String to compare to
nullIsLess –  whether consider null value less than non-null value
See Also:
String.compareTo(String)
Returns:
< 0, 0, > 0, if str1 is respectively less, equal ou greater than str2
Since:
3.5/**
     * <p>Compare two Strings lexicographically, as per {@link String#compareTo(String)}, returning :</p>
     * <ul>
     *  <li>{@code int = 0}, if {@code str1} is equal to {@code str2} (or both {@code null})</li>
     *  <li>{@code int < 0}, if {@code str1} is less than {@code str2}</li>
     *  <li>{@code int > 0}, if {@code str1} is greater than {@code str2}</li>
     * </ul>
     *
     * <p>This is a {@code null} safe version of :</p>
     * <blockquote><pre>str1.compareTo(str2)</pre></blockquote>
     *
     * <p>{@code null} inputs are handled according to the {@code nullIsLess} parameter.
     * Two {@code null} references are considered equal.</p>
     *
     * <pre>
     * StringUtils.compare(null, null, *)     = 0
     * StringUtils.compare(null , "a", true)  &lt; 0
     * StringUtils.compare(null , "a", false) &gt; 0
     * StringUtils.compare("a", null, true)   &gt; 0
     * StringUtils.compare("a", null, false)  &lt; 0
     * StringUtils.compare("abc", "abc", *)   = 0
     * StringUtils.compare("a", "b", *)       &lt; 0
     * StringUtils.compare("b", "a", *)       &gt; 0
     * StringUtils.compare("a", "B", *)       &gt; 0
     * StringUtils.compare("ab", "abc", *)    &lt; 0
     * </pre>
     *
     * @see String#compareTo(String)
     * @param str1  the String to compare from
     * @param str2  the String to compare to
     * @param nullIsLess  whether consider {@code null} value less than non-{@code null} value
     * @return &lt; 0, 0, &gt; 0, if {@code str1} is respectively less, equal ou greater than {@code str2}
     * @since 3.5
     */
    public static int compare(final String str1, final String str2, final boolean nullIsLess) {
        if (str1 == str2) {
            return 0;
        }
        if (str1 == null) {
            return nullIsLess ? -1 : 1;
        }
        if (str2 == null) {
            return nullIsLess ? 1 : - 1;
        }
        return str1.compareTo(str2);
    }

    
Compare two Strings lexicographically, ignoring case differences, as per String.compareToIgnoreCase(String), returning :

 
int = 0, if str1 is equal to str2 (or both null)
 
int < 0, if str1 is less than str2
 
int > 0, if str1 is greater than str2

This is a null safe version of :
str1.compareToIgnoreCase(str2)
null value is considered less than non-null value. Two null references are considered equal. Comparison is case insensitive.
StringUtils.compareIgnoreCase(null, null)   = 0
StringUtils.compareIgnoreCase(null , "a")   < 0
StringUtils.compareIgnoreCase("a", null)    > 0
StringUtils.compareIgnoreCase("abc", "abc") = 0
StringUtils.compareIgnoreCase("abc", "ABC") = 0
StringUtils.compareIgnoreCase("a", "b")     < 0
StringUtils.compareIgnoreCase("b", "a")     > 0
StringUtils.compareIgnoreCase("a", "B")     < 0
StringUtils.compareIgnoreCase("A", "b")     < 0
StringUtils.compareIgnoreCase("ab", "ABC")  < 0

Params:
str1 –  the String to compare from
str2 –  the String to compare to
See Also:
compareIgnoreCase(String, String, boolean)
String.compareToIgnoreCase(String)
Returns:
< 0, 0, > 0, if str1 is respectively less, equal ou greater than str2, ignoring case differences.
Since:
3.5/**
     * <p>Compare two Strings lexicographically, ignoring case differences,
     * as per {@link String#compareToIgnoreCase(String)}, returning :</p>
     * <ul>
     *  <li>{@code int = 0}, if {@code str1} is equal to {@code str2} (or both {@code null})</li>
     *  <li>{@code int < 0}, if {@code str1} is less than {@code str2}</li>
     *  <li>{@code int > 0}, if {@code str1} is greater than {@code str2}</li>
     * </ul>
     *
     * <p>This is a {@code null} safe version of :</p>
     * <blockquote><pre>str1.compareToIgnoreCase(str2)</pre></blockquote>
     *
     * <p>{@code null} value is considered less than non-{@code null} value.
     * Two {@code null} references are considered equal.
     * Comparison is case insensitive.</p>
     *
     * <pre>
     * StringUtils.compareIgnoreCase(null, null)   = 0
     * StringUtils.compareIgnoreCase(null , "a")   &lt; 0
     * StringUtils.compareIgnoreCase("a", null)    &gt; 0
     * StringUtils.compareIgnoreCase("abc", "abc") = 0
     * StringUtils.compareIgnoreCase("abc", "ABC") = 0
     * StringUtils.compareIgnoreCase("a", "b")     &lt; 0
     * StringUtils.compareIgnoreCase("b", "a")     &gt; 0
     * StringUtils.compareIgnoreCase("a", "B")     &lt; 0
     * StringUtils.compareIgnoreCase("A", "b")     &lt; 0
     * StringUtils.compareIgnoreCase("ab", "ABC")  &lt; 0
     * </pre>
     *
     * @see #compareIgnoreCase(String, String, boolean)
     * @see String#compareToIgnoreCase(String)
     * @param str1  the String to compare from
     * @param str2  the String to compare to
     * @return &lt; 0, 0, &gt; 0, if {@code str1} is respectively less, equal ou greater than {@code str2},
     *          ignoring case differences.
     * @since 3.5
     */
    public static int compareIgnoreCase(final String str1, final String str2) {
        return compareIgnoreCase(str1, str2, true);
    }

    
Compare two Strings lexicographically, ignoring case differences, as per String.compareToIgnoreCase(String), returning :

 
int = 0, if str1 is equal to str2 (or both null)
 
int < 0, if str1 is less than str2
 
int > 0, if str1 is greater than str2

This is a null safe version of :
str1.compareToIgnoreCase(str2)
null inputs are handled according to the nullIsLess parameter. Two null references are considered equal. Comparison is case insensitive.
StringUtils.compareIgnoreCase(null, null, *)     = 0
StringUtils.compareIgnoreCase(null , "a", true)  < 0
StringUtils.compareIgnoreCase(null , "a", false) > 0
StringUtils.compareIgnoreCase("a", null, true)   > 0
StringUtils.compareIgnoreCase("a", null, false)  < 0
StringUtils.compareIgnoreCase("abc", "abc", *)   = 0
StringUtils.compareIgnoreCase("abc", "ABC", *)   = 0
StringUtils.compareIgnoreCase("a", "b", *)       < 0
StringUtils.compareIgnoreCase("b", "a", *)       > 0
StringUtils.compareIgnoreCase("a", "B", *)       < 0
StringUtils.compareIgnoreCase("A", "b", *)       < 0
StringUtils.compareIgnoreCase("ab", "abc", *)    < 0

Params:
str1 –  the String to compare from
str2 –  the String to compare to
nullIsLess –  whether consider null value less than non-null value
See Also:
String.compareToIgnoreCase(String)
Returns:
< 0, 0, > 0, if str1 is respectively less, equal ou greater than str2, ignoring case differences.
Since:
3.5/**
     * <p>Compare two Strings lexicographically, ignoring case differences,
     * as per {@link String#compareToIgnoreCase(String)}, returning :</p>
     * <ul>
     *  <li>{@code int = 0}, if {@code str1} is equal to {@code str2} (or both {@code null})</li>
     *  <li>{@code int < 0}, if {@code str1} is less than {@code str2}</li>
     *  <li>{@code int > 0}, if {@code str1} is greater than {@code str2}</li>
     * </ul>
     *
     * <p>This is a {@code null} safe version of :</p>
     * <blockquote><pre>str1.compareToIgnoreCase(str2)</pre></blockquote>
     *
     * <p>{@code null} inputs are handled according to the {@code nullIsLess} parameter.
     * Two {@code null} references are considered equal.
     * Comparison is case insensitive.</p>
     *
     * <pre>
     * StringUtils.compareIgnoreCase(null, null, *)     = 0
     * StringUtils.compareIgnoreCase(null , "a", true)  &lt; 0
     * StringUtils.compareIgnoreCase(null , "a", false) &gt; 0
     * StringUtils.compareIgnoreCase("a", null, true)   &gt; 0
     * StringUtils.compareIgnoreCase("a", null, false)  &lt; 0
     * StringUtils.compareIgnoreCase("abc", "abc", *)   = 0
     * StringUtils.compareIgnoreCase("abc", "ABC", *)   = 0
     * StringUtils.compareIgnoreCase("a", "b", *)       &lt; 0
     * StringUtils.compareIgnoreCase("b", "a", *)       &gt; 0
     * StringUtils.compareIgnoreCase("a", "B", *)       &lt; 0
     * StringUtils.compareIgnoreCase("A", "b", *)       &lt; 0
     * StringUtils.compareIgnoreCase("ab", "abc", *)    &lt; 0
     * </pre>
     *
     * @see String#compareToIgnoreCase(String)
     * @param str1  the String to compare from
     * @param str2  the String to compare to
     * @param nullIsLess  whether consider {@code null} value less than non-{@code null} value
     * @return &lt; 0, 0, &gt; 0, if {@code str1} is respectively less, equal ou greater than {@code str2},
     *          ignoring case differences.
     * @since 3.5
     */
    public static int compareIgnoreCase(final String str1, final String str2, final boolean nullIsLess) {
        if (str1 == str2) {
            return 0;
        }
        if (str1 == null) {
            return nullIsLess ? -1 : 1;
        }
        if (str2 == null) {
            return nullIsLess ? 1 : - 1;
        }
        return str1.compareToIgnoreCase(str2);
    }

    
Checks if CharSequence contains a search CharSequence, handling null. This method uses String.indexOf(String) if possible.
A null CharSequence will return false.
StringUtils.contains(null, *)     = false
StringUtils.contains(*, null)     = false
StringUtils.contains("", "")      = true
StringUtils.contains("abc", "")   = true
StringUtils.contains("abc", "a")  = true
StringUtils.contains("abc", "z")  = false

Params:
seq –  the CharSequence to check, may be null
searchSeq –  the CharSequence to find, may be null
Returns:
true if the CharSequence contains the search CharSequence, false if not or null string input
Since:
2.0
Since:
3.0 Changed signature from contains(String, String) to contains(CharSequence, CharSequence)/**
     * <p>Checks if CharSequence contains a search CharSequence, handling {@code null}.
     * This method uses {@link String#indexOf(String)} if possible.</p>
     *
     * <p>A {@code null} CharSequence will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.contains(null, *)     = false
     * StringUtils.contains(*, null)     = false
     * StringUtils.contains("", "")      = true
     * StringUtils.contains("abc", "")   = true
     * StringUtils.contains("abc", "a")  = true
     * StringUtils.contains("abc", "z")  = false
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchSeq  the CharSequence to find, may be null
     * @return true if the CharSequence contains the search CharSequence,
     *  false if not or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from contains(String, String) to contains(CharSequence, CharSequence)
     */
    public static boolean contains(final CharSequence seq, final CharSequence searchSeq) {
        if (seq == null || searchSeq == null) {
            return false;
        }
        return CharSequenceUtils.indexOf(seq, searchSeq, 0) >= 0;
    }

    // Contains
    //-----------------------------------------------------------------------
    
Checks if CharSequence contains a search character, handling null. This method uses String.indexOf(int) if possible.
A null or empty ("") CharSequence will return false.
StringUtils.contains(null, *)    = false
StringUtils.contains("", *)      = false
StringUtils.contains("abc", 'a') = true
StringUtils.contains("abc", 'z') = false

Params:
seq –  the CharSequence to check, may be null
searchChar –  the character to find
Returns:
true if the CharSequence contains the search character, false if not or null string input
Since:
2.0
Since:
3.0 Changed signature from contains(String, int) to contains(CharSequence, int)/**
     * <p>Checks if CharSequence contains a search character, handling {@code null}.
     * This method uses {@link String#indexOf(int)} if possible.</p>
     *
     * <p>A {@code null} or empty ("") CharSequence will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.contains(null, *)    = false
     * StringUtils.contains("", *)      = false
     * StringUtils.contains("abc", 'a') = true
     * StringUtils.contains("abc", 'z') = false
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchChar  the character to find
     * @return true if the CharSequence contains the search character,
     *  false if not or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from contains(String, int) to contains(CharSequence, int)
     */
    public static boolean contains(final CharSequence seq, final int searchChar) {
        if (isEmpty(seq)) {
            return false;
        }
        return CharSequenceUtils.indexOf(seq, searchChar, 0) >= 0;
    }

    // ContainsAny
    //-----------------------------------------------------------------------
    
Checks if the CharSequence contains any character in the given
set of characters.
A null CharSequence will return false. A null or zero length search array will return false.
StringUtils.containsAny(null, *)                  = false
StringUtils.containsAny("", *)                    = false
StringUtils.containsAny(*, null)                  = false
StringUtils.containsAny(*, [])                    = false
StringUtils.containsAny("zzabyycdxx", ['z', 'a']) = true
StringUtils.containsAny("zzabyycdxx", ['b', 'y']) = true
StringUtils.containsAny("zzabyycdxx", ['z', 'y']) = true
StringUtils.containsAny("aba", ['z'])             = false

Params:
cs –  the CharSequence to check, may be null
searchChars –  the chars to search for, may be null
Returns:
the true if any of the chars are found, false if no match or null input
Since:
2.4
Since:
3.0 Changed signature from containsAny(String, char[]) to containsAny(CharSequence, char...)/**
     * <p>Checks if the CharSequence contains any character in the given
     * set of characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code false}.
     * A {@code null} or zero length search array will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.containsAny(null, *)                  = false
     * StringUtils.containsAny("", *)                    = false
     * StringUtils.containsAny(*, null)                  = false
     * StringUtils.containsAny(*, [])                    = false
     * StringUtils.containsAny("zzabyycdxx", ['z', 'a']) = true
     * StringUtils.containsAny("zzabyycdxx", ['b', 'y']) = true
     * StringUtils.containsAny("zzabyycdxx", ['z', 'y']) = true
     * StringUtils.containsAny("aba", ['z'])             = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param searchChars  the chars to search for, may be null
     * @return the {@code true} if any of the chars are found,
     * {@code false} if no match or null input
     * @since 2.4
     * @since 3.0 Changed signature from containsAny(String, char[]) to containsAny(CharSequence, char...)
     */
    public static boolean containsAny(final CharSequence cs, final char... searchChars) {
        if (isEmpty(cs) || ArrayUtils.isEmpty(searchChars)) {
            return false;
        }
        final int csLength = cs.length();
        final int searchLength = searchChars.length;
        final int csLast = csLength - 1;
        final int searchLast = searchLength - 1;
        for (int i = 0; i < csLength; i++) {
            final char ch = cs.charAt(i);
            for (int j = 0; j < searchLength; j++) {
                if (searchChars[j] == ch) {
                    if (Character.isHighSurrogate(ch)) {
                        if (j == searchLast) {
                            // missing low surrogate, fine, like String.indexOf(String)
                            return true;
                        }
                        if (i < csLast && searchChars[j + 1] == cs.charAt(i + 1)) {
                            return true;
                        }
                    } else {
                        // ch is in the Basic Multilingual Plane
                        return true;
                    }
                }
            }
        }
        return false;
    }

    

Checks if the CharSequence contains any character in the given set of characters.

 A null CharSequence will return false. A null search CharSequence will return false. 
StringUtils.containsAny(null, *)               = false
StringUtils.containsAny("", *)                 = false
StringUtils.containsAny(*, null)               = false
StringUtils.containsAny(*, "")                 = false
StringUtils.containsAny("zzabyycdxx", "za")    = true
StringUtils.containsAny("zzabyycdxx", "by")    = true
StringUtils.containsAny("zzabyycdxx", "zy")    = true
StringUtils.containsAny("zzabyycdxx", "\tx")   = true
StringUtils.containsAny("zzabyycdxx", "$.#yF") = true
StringUtils.containsAny("aba", "z")            = false

Params:
cs – 
           the CharSequence to check, may be null
searchChars – 
           the chars to search for, may be null
Returns:
the true if any of the chars are found, false if no match or null input
Since:
2.4
Since:
3.0 Changed signature from containsAny(String, String) to containsAny(CharSequence, CharSequence)/**
     * <p>
     * Checks if the CharSequence contains any character in the given set of characters.
     * </p>
     *
     * <p>
     * A {@code null} CharSequence will return {@code false}. A {@code null} search CharSequence will return
     * {@code false}.
     * </p>
     *
     * <pre>
     * StringUtils.containsAny(null, *)               = false
     * StringUtils.containsAny("", *)                 = false
     * StringUtils.containsAny(*, null)               = false
     * StringUtils.containsAny(*, "")                 = false
     * StringUtils.containsAny("zzabyycdxx", "za")    = true
     * StringUtils.containsAny("zzabyycdxx", "by")    = true
     * StringUtils.containsAny("zzabyycdxx", "zy")    = true
     * StringUtils.containsAny("zzabyycdxx", "\tx")   = true
     * StringUtils.containsAny("zzabyycdxx", "$.#yF") = true
     * StringUtils.containsAny("aba", "z")            = false
     * </pre>
     *
     * @param cs
     *            the CharSequence to check, may be null
     * @param searchChars
     *            the chars to search for, may be null
     * @return the {@code true} if any of the chars are found, {@code false} if no match or null input
     * @since 2.4
     * @since 3.0 Changed signature from containsAny(String, String) to containsAny(CharSequence, CharSequence)
     */
    public static boolean containsAny(final CharSequence cs, final CharSequence searchChars) {
        if (searchChars == null) {
            return false;
        }
        return containsAny(cs, CharSequenceUtils.toCharArray(searchChars));
    }

    
Checks if the CharSequence contains any of the CharSequences in the given array.
 A null cs CharSequence will return false. A null or zero length search array will return false. 
StringUtils.containsAny(null, *)            = false
StringUtils.containsAny("", *)              = false
StringUtils.containsAny(*, null)            = false
StringUtils.containsAny(*, [])              = false
StringUtils.containsAny("abcd", "ab", null) = true
StringUtils.containsAny("abcd", "ab", "cd") = true
StringUtils.containsAny("abc", "d", "abc")  = true

Params:
cs – The CharSequence to check, may be null
searchCharSequences – The array of CharSequences to search for, may be null.
Individual CharSequences may be null as well.
Returns:
true if any of the search CharSequences are found, false otherwise
Since:
3.4/**
     * <p>Checks if the CharSequence contains any of the CharSequences in the given array.</p>
     *
     * <p>
     * A {@code null} {@code cs} CharSequence will return {@code false}. A {@code null} or zero
     * length search array will return {@code false}.
     * </p>
     *
     * <pre>
     * StringUtils.containsAny(null, *)            = false
     * StringUtils.containsAny("", *)              = false
     * StringUtils.containsAny(*, null)            = false
     * StringUtils.containsAny(*, [])              = false
     * StringUtils.containsAny("abcd", "ab", null) = true
     * StringUtils.containsAny("abcd", "ab", "cd") = true
     * StringUtils.containsAny("abc", "d", "abc")  = true
     * </pre>
     *
     *
     * @param cs The CharSequence to check, may be null
     * @param searchCharSequences The array of CharSequences to search for, may be null.
     * Individual CharSequences may be null as well.
     * @return {@code true} if any of the search CharSequences are found, {@code false} otherwise
     * @since 3.4
     */
    public static boolean containsAny(final CharSequence cs, final CharSequence... searchCharSequences) {
        if (isEmpty(cs) || ArrayUtils.isEmpty(searchCharSequences)) {
            return false;
        }
        for (final CharSequence searchCharSequence : searchCharSequences) {
            if (contains(cs, searchCharSequence)) {
                return true;
            }
        }
        return false;
    }

    
Checks if CharSequence contains a search CharSequence irrespective of case, handling null. Case-insensitivity is defined as by String.equalsIgnoreCase(String). 
A null CharSequence will return false.
StringUtils.containsIgnoreCase(null, *) = false
StringUtils.containsIgnoreCase(*, null) = false
StringUtils.containsIgnoreCase("", "") = true
StringUtils.containsIgnoreCase("abc", "") = true
StringUtils.containsIgnoreCase("abc", "a") = true
StringUtils.containsIgnoreCase("abc", "z") = false
StringUtils.containsIgnoreCase("abc", "A") = true
StringUtils.containsIgnoreCase("abc", "Z") = false

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
Returns:
true if the CharSequence contains the search CharSequence irrespective of case or false if not or null string input
Since:
3.0 Changed signature from containsIgnoreCase(String, String) to containsIgnoreCase(CharSequence, CharSequence)/**
     * <p>Checks if CharSequence contains a search CharSequence irrespective of case,
     * handling {@code null}. Case-insensitivity is defined as by
     * {@link String#equalsIgnoreCase(String)}.
     *
     * <p>A {@code null} CharSequence will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.containsIgnoreCase(null, *) = false
     * StringUtils.containsIgnoreCase(*, null) = false
     * StringUtils.containsIgnoreCase("", "") = true
     * StringUtils.containsIgnoreCase("abc", "") = true
     * StringUtils.containsIgnoreCase("abc", "a") = true
     * StringUtils.containsIgnoreCase("abc", "z") = false
     * StringUtils.containsIgnoreCase("abc", "A") = true
     * StringUtils.containsIgnoreCase("abc", "Z") = false
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @return true if the CharSequence contains the search CharSequence irrespective of
     * case or false if not or {@code null} string input
     * @since 3.0 Changed signature from containsIgnoreCase(String, String) to containsIgnoreCase(CharSequence, CharSequence)
     */
    public static boolean containsIgnoreCase(final CharSequence str, final CharSequence searchStr) {
        if (str == null || searchStr == null) {
            return false;
        }
        final int len = searchStr.length();
        final int max = str.length() - len;
        for (int i = 0; i <= max; i++) {
            if (CharSequenceUtils.regionMatches(str, true, i, searchStr, 0, len)) {
                return true;
            }
        }
        return false;
    }

    // ContainsNone
    //-----------------------------------------------------------------------
    
Checks that the CharSequence does not contain certain characters.
A null CharSequence will return true. A null invalid character array will return true. An empty CharSequence (length()=0) always returns true.
StringUtils.containsNone(null, *)       = true
StringUtils.containsNone(*, null)       = true
StringUtils.containsNone("", *)         = true
StringUtils.containsNone("ab", '')      = true
StringUtils.containsNone("abab", 'xyz') = true
StringUtils.containsNone("ab1", 'xyz')  = true
StringUtils.containsNone("abz", 'xyz')  = false

Params:
cs –  the CharSequence to check, may be null
searchChars –  an array of invalid chars, may be null
Returns:
true if it contains none of the invalid chars, or is null
Since:
2.0
Since:
3.0 Changed signature from containsNone(String, char[]) to containsNone(CharSequence, char...)/**
     * <p>Checks that the CharSequence does not contain certain characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code true}.
     * A {@code null} invalid character array will return {@code true}.
     * An empty CharSequence (length()=0) always returns true.</p>
     *
     * <pre>
     * StringUtils.containsNone(null, *)       = true
     * StringUtils.containsNone(*, null)       = true
     * StringUtils.containsNone("", *)         = true
     * StringUtils.containsNone("ab", '')      = true
     * StringUtils.containsNone("abab", 'xyz') = true
     * StringUtils.containsNone("ab1", 'xyz')  = true
     * StringUtils.containsNone("abz", 'xyz')  = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param searchChars  an array of invalid chars, may be null
     * @return true if it contains none of the invalid chars, or is null
     * @since 2.0
     * @since 3.0 Changed signature from containsNone(String, char[]) to containsNone(CharSequence, char...)
     */
    public static boolean containsNone(final CharSequence cs, final char... searchChars) {
        if (cs == null || searchChars == null) {
            return true;
        }
        final int csLen = cs.length();
        final int csLast = csLen - 1;
        final int searchLen = searchChars.length;
        final int searchLast = searchLen - 1;
        for (int i = 0; i < csLen; i++) {
            final char ch = cs.charAt(i);
            for (int j = 0; j < searchLen; j++) {
                if (searchChars[j] == ch) {
                    if (Character.isHighSurrogate(ch)) {
                        if (j == searchLast) {
                            // missing low surrogate, fine, like String.indexOf(String)
                            return false;
                        }
                        if (i < csLast && searchChars[j + 1] == cs.charAt(i + 1)) {
                            return false;
                        }
                    } else {
                        // ch is in the Basic Multilingual Plane
                        return false;
                    }
                }
            }
        }
        return true;
    }

    
Checks that the CharSequence does not contain certain characters.
A null CharSequence will return true. A null invalid character array will return true. An empty String ("") always returns true.
StringUtils.containsNone(null, *)       = true
StringUtils.containsNone(*, null)       = true
StringUtils.containsNone("", *)         = true
StringUtils.containsNone("ab", "")      = true
StringUtils.containsNone("abab", "xyz") = true
StringUtils.containsNone("ab1", "xyz")  = true
StringUtils.containsNone("abz", "xyz")  = false

Params:
cs –  the CharSequence to check, may be null
invalidChars –  a String of invalid chars, may be null
Returns:
true if it contains none of the invalid chars, or is null
Since:
2.0
Since:
3.0 Changed signature from containsNone(String, String) to containsNone(CharSequence, String)/**
     * <p>Checks that the CharSequence does not contain certain characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code true}.
     * A {@code null} invalid character array will return {@code true}.
     * An empty String ("") always returns true.</p>
     *
     * <pre>
     * StringUtils.containsNone(null, *)       = true
     * StringUtils.containsNone(*, null)       = true
     * StringUtils.containsNone("", *)         = true
     * StringUtils.containsNone("ab", "")      = true
     * StringUtils.containsNone("abab", "xyz") = true
     * StringUtils.containsNone("ab1", "xyz")  = true
     * StringUtils.containsNone("abz", "xyz")  = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param invalidChars  a String of invalid chars, may be null
     * @return true if it contains none of the invalid chars, or is null
     * @since 2.0
     * @since 3.0 Changed signature from containsNone(String, String) to containsNone(CharSequence, String)
     */
    public static boolean containsNone(final CharSequence cs, final String invalidChars) {
        if (cs == null || invalidChars == null) {
            return true;
        }
        return containsNone(cs, invalidChars.toCharArray());
    }

    // ContainsOnly
    //-----------------------------------------------------------------------
    
Checks if the CharSequence contains only certain characters.
A null CharSequence will return false. A null valid character array will return false. An empty CharSequence (length()=0) always returns true.
StringUtils.containsOnly(null, *)       = false
StringUtils.containsOnly(*, null)       = false
StringUtils.containsOnly("", *)         = true
StringUtils.containsOnly("ab", '')      = false
StringUtils.containsOnly("abab", 'abc') = true
StringUtils.containsOnly("ab1", 'abc')  = false
StringUtils.containsOnly("abz", 'abc')  = false

Params:
cs –  the String to check, may be null
valid –  an array of valid chars, may be null
Returns:
true if it only contains valid chars and is non-null
Since:
3.0 Changed signature from containsOnly(String, char[]) to containsOnly(CharSequence, char...)/**
     * <p>Checks if the CharSequence contains only certain characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code false}.
     * A {@code null} valid character array will return {@code false}.
     * An empty CharSequence (length()=0) always returns {@code true}.</p>
     *
     * <pre>
     * StringUtils.containsOnly(null, *)       = false
     * StringUtils.containsOnly(*, null)       = false
     * StringUtils.containsOnly("", *)         = true
     * StringUtils.containsOnly("ab", '')      = false
     * StringUtils.containsOnly("abab", 'abc') = true
     * StringUtils.containsOnly("ab1", 'abc')  = false
     * StringUtils.containsOnly("abz", 'abc')  = false
     * </pre>
     *
     * @param cs  the String to check, may be null
     * @param valid  an array of valid chars, may be null
     * @return true if it only contains valid chars and is non-null
     * @since 3.0 Changed signature from containsOnly(String, char[]) to containsOnly(CharSequence, char...)
     */
    public static boolean containsOnly(final CharSequence cs, final char... valid) {
        // All these pre-checks are to maintain API with an older version
        if (valid == null || cs == null) {
            return false;
        }
        if (cs.length() == 0) {
            return true;
        }
        if (valid.length == 0) {
            return false;
        }
        return indexOfAnyBut(cs, valid) == INDEX_NOT_FOUND;
    }

    
Checks if the CharSequence contains only certain characters.
A null CharSequence will return false. A null valid character String will return false. An empty String (length()=0) always returns true.
StringUtils.containsOnly(null, *)       = false
StringUtils.containsOnly(*, null)       = false
StringUtils.containsOnly("", *)         = true
StringUtils.containsOnly("ab", "")      = false
StringUtils.containsOnly("abab", "abc") = true
StringUtils.containsOnly("ab1", "abc")  = false
StringUtils.containsOnly("abz", "abc")  = false

Params:
cs –  the CharSequence to check, may be null
validChars –  a String of valid chars, may be null
Returns:
true if it only contains valid chars and is non-null
Since:
2.0
Since:
3.0 Changed signature from containsOnly(String, String) to containsOnly(CharSequence, String)/**
     * <p>Checks if the CharSequence contains only certain characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code false}.
     * A {@code null} valid character String will return {@code false}.
     * An empty String (length()=0) always returns {@code true}.</p>
     *
     * <pre>
     * StringUtils.containsOnly(null, *)       = false
     * StringUtils.containsOnly(*, null)       = false
     * StringUtils.containsOnly("", *)         = true
     * StringUtils.containsOnly("ab", "")      = false
     * StringUtils.containsOnly("abab", "abc") = true
     * StringUtils.containsOnly("ab1", "abc")  = false
     * StringUtils.containsOnly("abz", "abc")  = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param validChars  a String of valid chars, may be null
     * @return true if it only contains valid chars and is non-null
     * @since 2.0
     * @since 3.0 Changed signature from containsOnly(String, String) to containsOnly(CharSequence, String)
     */
    public static boolean containsOnly(final CharSequence cs, final String validChars) {
        if (cs == null || validChars == null) {
            return false;
        }
        return containsOnly(cs, validChars.toCharArray());
    }

    
Check whether the given CharSequence contains any whitespace characters.
Whitespace is defined by Character.isWhitespace(char).
Params:
seq – the CharSequence to check (may be null)
Returns:
true if the CharSequence is not empty and contains at least 1 (breaking) whitespace character
Since:
3.0/**
     * <p>Check whether the given CharSequence contains any whitespace characters.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * @param seq the CharSequence to check (may be {@code null})
     * @return {@code true} if the CharSequence is not empty and
     * contains at least 1 (breaking) whitespace character
     * @since 3.0
     */
    // From org.springframework.util.StringUtils, under Apache License 2.0
    public static boolean containsWhitespace(final CharSequence seq) {
        if (isEmpty(seq)) {
            return false;
        }
        final int strLen = seq.length();
        for (int i = 0; i < strLen; i++) {
            if (Character.isWhitespace(seq.charAt(i))) {
                return true;
            }
        }
        return false;
    }

    private static void convertRemainingAccentCharacters(final StringBuilder decomposed) {
        for (int i = 0; i < decomposed.length(); i++) {
            if (decomposed.charAt(i) == '\u0141') {
                decomposed.deleteCharAt(i);
                decomposed.insert(i, 'L');
            } else if (decomposed.charAt(i) == '\u0142') {
                decomposed.deleteCharAt(i);
                decomposed.insert(i, 'l');
            }
        }
    }

    
Counts how many times the char appears in the given string.
A null or empty ("") String input returns 0.
StringUtils.countMatches(null, *)       = 0
StringUtils.countMatches("", *)         = 0
StringUtils.countMatches("abba", 0)  = 0
StringUtils.countMatches("abba", 'a')   = 2
StringUtils.countMatches("abba", 'b')  = 2
StringUtils.countMatches("abba", 'x') = 0

Params:
str –  the CharSequence to check, may be null
ch –  the char to count
Returns:
the number of occurrences, 0 if the CharSequence is null
Since:
3.4/**
     * <p>Counts how many times the char appears in the given string.</p>
     *
     * <p>A {@code null} or empty ("") String input returns {@code 0}.</p>
     *
     * <pre>
     * StringUtils.countMatches(null, *)       = 0
     * StringUtils.countMatches("", *)         = 0
     * StringUtils.countMatches("abba", 0)  = 0
     * StringUtils.countMatches("abba", 'a')   = 2
     * StringUtils.countMatches("abba", 'b')  = 2
     * StringUtils.countMatches("abba", 'x') = 0
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param ch  the char to count
     * @return the number of occurrences, 0 if the CharSequence is {@code null}
     * @since 3.4
     */
    public static int countMatches(final CharSequence str, final char ch) {
        if (isEmpty(str)) {
            return 0;
        }
        int count = 0;
        // We could also call str.toCharArray() for faster look ups but that would generate more garbage.
        for (int i = 0; i < str.length(); i++) {
            if (ch == str.charAt(i)) {
                count++;
            }
        }
        return count;
    }

    // Count matches
    //-----------------------------------------------------------------------
    
Counts how many times the substring appears in the larger string.
A null or empty ("") String input returns 0.
StringUtils.countMatches(null, *)       = 0
StringUtils.countMatches("", *)         = 0
StringUtils.countMatches("abba", null)  = 0
StringUtils.countMatches("abba", "")    = 0
StringUtils.countMatches("abba", "a")   = 2
StringUtils.countMatches("abba", "ab")  = 1
StringUtils.countMatches("abba", "xxx") = 0

Params:
str –  the CharSequence to check, may be null
sub –  the substring to count, may be null
Returns:
the number of occurrences, 0 if either CharSequence is null
Since:
3.0 Changed signature from countMatches(String, String) to countMatches(CharSequence, CharSequence)/**
     * <p>Counts how many times the substring appears in the larger string.</p>
     *
     * <p>A {@code null} or empty ("") String input returns {@code 0}.</p>
     *
     * <pre>
     * StringUtils.countMatches(null, *)       = 0
     * StringUtils.countMatches("", *)         = 0
     * StringUtils.countMatches("abba", null)  = 0
     * StringUtils.countMatches("abba", "")    = 0
     * StringUtils.countMatches("abba", "a")   = 2
     * StringUtils.countMatches("abba", "ab")  = 1
     * StringUtils.countMatches("abba", "xxx") = 0
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param sub  the substring to count, may be null
     * @return the number of occurrences, 0 if either CharSequence is {@code null}
     * @since 3.0 Changed signature from countMatches(String, String) to countMatches(CharSequence, CharSequence)
     */
    public static int countMatches(final CharSequence str, final CharSequence sub) {
        if (isEmpty(str) || isEmpty(sub)) {
            return 0;
        }
        int count = 0;
        int idx = 0;
        while ((idx = CharSequenceUtils.indexOf(str, sub, idx)) != INDEX_NOT_FOUND) {
            count++;
            idx += sub.length();
        }
        return count;
    }

    
Returns either the passed in CharSequence, or if the CharSequence is whitespace, empty ("") or null, the value of defaultStr.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.defaultIfBlank(null, "NULL")  = "NULL"
StringUtils.defaultIfBlank("", "NULL")    = "NULL"
StringUtils.defaultIfBlank(" ", "NULL")   = "NULL"
StringUtils.defaultIfBlank("bat", "NULL") = "bat"
StringUtils.defaultIfBlank("", null)      = null

Params:
str – the CharSequence to check, may be null
defaultStr –  the default CharSequence to return if the input is whitespace, empty ("") or null, may be null
Type parameters:
<T> – the specific kind of CharSequence
See Also:
defaultString(String, String)
Returns:
the passed in CharSequence, or the default/**
     * <p>Returns either the passed in CharSequence, or if the CharSequence is
     * whitespace, empty ("") or {@code null}, the value of {@code defaultStr}.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.defaultIfBlank(null, "NULL")  = "NULL"
     * StringUtils.defaultIfBlank("", "NULL")    = "NULL"
     * StringUtils.defaultIfBlank(" ", "NULL")   = "NULL"
     * StringUtils.defaultIfBlank("bat", "NULL") = "bat"
     * StringUtils.defaultIfBlank("", null)      = null
     * </pre>
     * @param <T> the specific kind of CharSequence
     * @param str the CharSequence to check, may be null
     * @param defaultStr  the default CharSequence to return
     *  if the input is whitespace, empty ("") or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     */
    public static <T extends CharSequence> T defaultIfBlank(final T str, final T defaultStr) {
        return isBlank(str) ? defaultStr : str;
    }

    
Returns either the passed in CharSequence, or if the CharSequence is empty or null, the value of defaultStr.
StringUtils.defaultIfEmpty(null, "NULL")  = "NULL"
StringUtils.defaultIfEmpty("", "NULL")    = "NULL"
StringUtils.defaultIfEmpty(" ", "NULL")   = " "
StringUtils.defaultIfEmpty("bat", "NULL") = "bat"
StringUtils.defaultIfEmpty("", null)      = null

Params:
str –  the CharSequence to check, may be null
defaultStr –  the default CharSequence to return if the input is empty ("") or null, may be null
Type parameters:
<T> – the specific kind of CharSequence
See Also:
defaultString(String, String)
Returns:
the passed in CharSequence, or the default/**
     * <p>Returns either the passed in CharSequence, or if the CharSequence is
     * empty or {@code null}, the value of {@code defaultStr}.</p>
     *
     * <pre>
     * StringUtils.defaultIfEmpty(null, "NULL")  = "NULL"
     * StringUtils.defaultIfEmpty("", "NULL")    = "NULL"
     * StringUtils.defaultIfEmpty(" ", "NULL")   = " "
     * StringUtils.defaultIfEmpty("bat", "NULL") = "bat"
     * StringUtils.defaultIfEmpty("", null)      = null
     * </pre>
     * @param <T> the specific kind of CharSequence
     * @param str  the CharSequence to check, may be null
     * @param defaultStr  the default CharSequence to return
     *  if the input is empty ("") or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     */
    public static <T extends CharSequence> T defaultIfEmpty(final T str, final T defaultStr) {
        return isEmpty(str) ? defaultStr : str;
    }

    
Returns either the passed in String, or if the String is null, an empty String ("").
StringUtils.defaultString(null)  = ""
StringUtils.defaultString("")    = ""
StringUtils.defaultString("bat") = "bat"

Params:
str –  the String to check, may be null
See Also:
ObjectUtils.toString(Object)
String.valueOf(Object)
Returns:
the passed in String, or the empty String if it was null/**
     * <p>Returns either the passed in String,
     * or if the String is {@code null}, an empty String ("").</p>
     *
     * <pre>
     * StringUtils.defaultString(null)  = ""
     * StringUtils.defaultString("")    = ""
     * StringUtils.defaultString("bat") = "bat"
     * </pre>
     *
     * @see ObjectUtils#toString(Object)
     * @see String#valueOf(Object)
     * @param str  the String to check, may be null
     * @return the passed in String, or the empty String if it
     *  was {@code null}
     */
    public static String defaultString(final String str) {
        return defaultString(str, EMPTY);
    }

    
Returns either the passed in String, or if the String is null, the value of defaultStr.
StringUtils.defaultString(null, "NULL")  = "NULL"
StringUtils.defaultString("", "NULL")    = ""
StringUtils.defaultString("bat", "NULL") = "bat"

Params:
str –  the String to check, may be null
defaultStr –  the default String to return if the input is null, may be null
See Also:
ObjectUtils.toString(Object, String)
String.valueOf(Object)
Returns:
the passed in String, or the default if it was null/**
     * <p>Returns either the passed in String, or if the String is
     * {@code null}, the value of {@code defaultStr}.</p>
     *
     * <pre>
     * StringUtils.defaultString(null, "NULL")  = "NULL"
     * StringUtils.defaultString("", "NULL")    = ""
     * StringUtils.defaultString("bat", "NULL") = "bat"
     * </pre>
     *
     * @see ObjectUtils#toString(Object,String)
     * @see String#valueOf(Object)
     * @param str  the String to check, may be null
     * @param defaultStr  the default String to return
     *  if the input is {@code null}, may be null
     * @return the passed in String, or the default if it was {@code null}
     */
    public static String defaultString(final String str, final String defaultStr) {
        return str == null ? defaultStr : str;
    }

    // Delete
    //-----------------------------------------------------------------------
    
Deletes all whitespaces from a String as defined by Character.isWhitespace(char).
StringUtils.deleteWhitespace(null)         = null
StringUtils.deleteWhitespace("")           = ""
StringUtils.deleteWhitespace("abc")        = "abc"
StringUtils.deleteWhitespace("   ab  c  ") = "abc"

Params:
str –  the String to delete whitespace from, may be null
Returns:
the String without whitespaces, null if null String input/**
     * <p>Deletes all whitespaces from a String as defined by
     * {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.deleteWhitespace(null)         = null
     * StringUtils.deleteWhitespace("")           = ""
     * StringUtils.deleteWhitespace("abc")        = "abc"
     * StringUtils.deleteWhitespace("   ab  c  ") = "abc"
     * </pre>
     *
     * @param str  the String to delete whitespace from, may be null
     * @return the String without whitespaces, {@code null} if null String input
     */
    public static String deleteWhitespace(final String str) {
        if (isEmpty(str)) {
            return str;
        }
        final int sz = str.length();
        final char[] chs = new char[sz];
        int count = 0;
        for (int i = 0; i < sz; i++) {
            if (!Character.isWhitespace(str.charAt(i))) {
                chs[count++] = str.charAt(i);
            }
        }
        if (count == sz) {
            return str;
        }
        return new String(chs, 0, count);
    }

    // Difference
    //-----------------------------------------------------------------------
    
Compares two Strings, and returns the portion where they differ.
More precisely, return the remainder of the second String,
starting from where it's different from the first. This means that
the difference between "abc" and "ab" is the empty String and not "c". 
For example, difference("i am a machine", "i am a robot") -> "robot".
StringUtils.difference(null, null) = null
StringUtils.difference("", "") = ""
StringUtils.difference("", "abc") = "abc"
StringUtils.difference("abc", "") = ""
StringUtils.difference("abc", "abc") = ""
StringUtils.difference("abc", "ab") = ""
StringUtils.difference("ab", "abxyz") = "xyz"
StringUtils.difference("abcde", "abxyz") = "xyz"
StringUtils.difference("abcde", "xyz") = "xyz"

Params:
str1 –  the first String, may be null
str2 –  the second String, may be null
See Also:
indexOfDifference(CharSequence, CharSequence)
Returns:
the portion of str2 where it differs from str1; returns the
empty String if they are equal
Since:
2.0/**
     * <p>Compares two Strings, and returns the portion where they differ.
     * More precisely, return the remainder of the second String,
     * starting from where it's different from the first. This means that
     * the difference between "abc" and "ab" is the empty String and not "c". </p>
     *
     * <p>For example,
     * {@code difference("i am a machine", "i am a robot") -> "robot"}.</p>
     *
     * <pre>
     * StringUtils.difference(null, null) = null
     * StringUtils.difference("", "") = ""
     * StringUtils.difference("", "abc") = "abc"
     * StringUtils.difference("abc", "") = ""
     * StringUtils.difference("abc", "abc") = ""
     * StringUtils.difference("abc", "ab") = ""
     * StringUtils.difference("ab", "abxyz") = "xyz"
     * StringUtils.difference("abcde", "abxyz") = "xyz"
     * StringUtils.difference("abcde", "xyz") = "xyz"
     * </pre>
     *
     * @param str1  the first String, may be null
     * @param str2  the second String, may be null
     * @return the portion of str2 where it differs from str1; returns the
     * empty String if they are equal
     * @see #indexOfDifference(CharSequence,CharSequence)
     * @since 2.0
     */
    public static String difference(final String str1, final String str2) {
        if (str1 == null) {
            return str2;
        }
        if (str2 == null) {
            return str1;
        }
        final int at = indexOfDifference(str1, str2);
        if (at == INDEX_NOT_FOUND) {
            return EMPTY;
        }
        return str2.substring(at);
    }

    
Check if a CharSequence ends with a specified suffix.
nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.
StringUtils.endsWith(null, null)      = true
StringUtils.endsWith(null, "def")     = false
StringUtils.endsWith("abcdef", null)  = false
StringUtils.endsWith("abcdef", "def") = true
StringUtils.endsWith("ABCDEF", "def") = false
StringUtils.endsWith("ABCDEF", "cde") = false
StringUtils.endsWith("ABCDEF", "")    = true

Params:
str –  the CharSequence to check, may be null
suffix – the suffix to find, may be null
See Also:
String.endsWith(String)
Returns:
true if the CharSequence ends with the suffix, case sensitive, or both null
Since:
2.4
Since:
3.0 Changed signature from endsWith(String, String) to endsWith(CharSequence, CharSequence)/**
     * <p>Check if a CharSequence ends with a specified suffix.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is case sensitive.</p>
     *
     * <pre>
     * StringUtils.endsWith(null, null)      = true
     * StringUtils.endsWith(null, "def")     = false
     * StringUtils.endsWith("abcdef", null)  = false
     * StringUtils.endsWith("abcdef", "def") = true
     * StringUtils.endsWith("ABCDEF", "def") = false
     * StringUtils.endsWith("ABCDEF", "cde") = false
     * StringUtils.endsWith("ABCDEF", "")    = true
     * </pre>
     *
     * @see java.lang.String#endsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param suffix the suffix to find, may be null
     * @return {@code true} if the CharSequence ends with the suffix, case sensitive, or
     *  both {@code null}
     * @since 2.4
     * @since 3.0 Changed signature from endsWith(String, String) to endsWith(CharSequence, CharSequence)
     */
    public static boolean endsWith(final CharSequence str, final CharSequence suffix) {
        return endsWith(str, suffix, false);
    }

    
Check if a CharSequence ends with a specified suffix (optionally case insensitive).
Params:
str –  the CharSequence to check, may be null
suffix – the suffix to find, may be null
ignoreCase – indicates whether the compare should ignore case
 (case insensitive) or not.
See Also:
endsWith.endsWith(String)
Returns:
true if the CharSequence starts with the prefix or both null/**
     * <p>Check if a CharSequence ends with a specified suffix (optionally case insensitive).</p>
     *
     * @see java.lang.String#endsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param suffix the suffix to find, may be null
     * @param ignoreCase indicates whether the compare should ignore case
     *  (case insensitive) or not.
     * @return {@code true} if the CharSequence starts with the prefix or
     *  both {@code null}
     */
    private static boolean endsWith(final CharSequence str, final CharSequence suffix, final boolean ignoreCase) {
        if (str == null || suffix == null) {
            return str == suffix;
        }
        if (suffix.length() > str.length()) {
            return false;
        }
        final int strOffset = str.length() - suffix.length();
        return CharSequenceUtils.regionMatches(str, ignoreCase, strOffset, suffix, 0, suffix.length());
    }

    
Check if a CharSequence ends with any of the provided case-sensitive suffixes.
StringUtils.endsWithAny(null, null)      = false
StringUtils.endsWithAny(null, new String[] {"abc"})  = false
StringUtils.endsWithAny("abcxyz", null)     = false
StringUtils.endsWithAny("abcxyz", new String[] {""}) = true
StringUtils.endsWithAny("abcxyz", new String[] {"xyz"}) = true
StringUtils.endsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true
StringUtils.endsWithAny("abcXYZ", "def", "XYZ") = true
StringUtils.endsWithAny("abcXYZ", "def", "xyz") = false

Params:
sequence –  the CharSequence to check, may be null
searchStrings – the case-sensitive CharSequences to find, may be empty or contain null
See Also:
endsWith(CharSequence, CharSequence)
Returns:
true if the input sequence is null AND no searchStrings are provided, or the input sequence ends in any of the provided case-sensitive searchStrings.
Since:
3.0/**
     * <p>Check if a CharSequence ends with any of the provided case-sensitive suffixes.</p>
     *
     * <pre>
     * StringUtils.endsWithAny(null, null)      = false
     * StringUtils.endsWithAny(null, new String[] {"abc"})  = false
     * StringUtils.endsWithAny("abcxyz", null)     = false
     * StringUtils.endsWithAny("abcxyz", new String[] {""}) = true
     * StringUtils.endsWithAny("abcxyz", new String[] {"xyz"}) = true
     * StringUtils.endsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true
     * StringUtils.endsWithAny("abcXYZ", "def", "XYZ") = true
     * StringUtils.endsWithAny("abcXYZ", "def", "xyz") = false
     * </pre>
     *
     * @param sequence  the CharSequence to check, may be null
     * @param searchStrings the case-sensitive CharSequences to find, may be empty or contain {@code null}
     * @see StringUtils#endsWith(CharSequence, CharSequence)
     * @return {@code true} if the input {@code sequence} is {@code null} AND no {@code searchStrings} are provided, or
     *   the input {@code sequence} ends in any of the provided case-sensitive {@code searchStrings}.
     * @since 3.0
     */
    public static boolean endsWithAny(final CharSequence sequence, final CharSequence... searchStrings) {
        if (isEmpty(sequence) || ArrayUtils.isEmpty(searchStrings)) {
            return false;
        }
        for (final CharSequence searchString : searchStrings) {
            if (endsWith(sequence, searchString)) {
                return true;
            }
        }
        return false;
    }

    
Case insensitive check if a CharSequence ends with a specified suffix.
nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case insensitive.
StringUtils.endsWithIgnoreCase(null, null)      = true
StringUtils.endsWithIgnoreCase(null, "def")     = false
StringUtils.endsWithIgnoreCase("abcdef", null)  = false
StringUtils.endsWithIgnoreCase("abcdef", "def") = true
StringUtils.endsWithIgnoreCase("ABCDEF", "def") = true
StringUtils.endsWithIgnoreCase("ABCDEF", "cde") = false

Params:
str –  the CharSequence to check, may be null
suffix – the suffix to find, may be null
See Also:
String.endsWith(String)
Returns:
true if the CharSequence ends with the suffix, case insensitive, or both null
Since:
2.4
Since:
3.0 Changed signature from endsWithIgnoreCase(String, String) to endsWithIgnoreCase(CharSequence, CharSequence)/**
     * <p>Case insensitive check if a CharSequence ends with a specified suffix.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is case insensitive.</p>
     *
     * <pre>
     * StringUtils.endsWithIgnoreCase(null, null)      = true
     * StringUtils.endsWithIgnoreCase(null, "def")     = false
     * StringUtils.endsWithIgnoreCase("abcdef", null)  = false
     * StringUtils.endsWithIgnoreCase("abcdef", "def") = true
     * StringUtils.endsWithIgnoreCase("ABCDEF", "def") = true
     * StringUtils.endsWithIgnoreCase("ABCDEF", "cde") = false
     * </pre>
     *
     * @see java.lang.String#endsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param suffix the suffix to find, may be null
     * @return {@code true} if the CharSequence ends with the suffix, case insensitive, or
     *  both {@code null}
     * @since 2.4
     * @since 3.0 Changed signature from endsWithIgnoreCase(String, String) to endsWithIgnoreCase(CharSequence, CharSequence)
     */
    public static boolean endsWithIgnoreCase(final CharSequence str, final CharSequence suffix) {
        return endsWith(str, suffix, true);
    }

    // Equals
    //-----------------------------------------------------------------------
    
Compares two CharSequences, returning true if they represent equal sequences of characters.
nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.
StringUtils.equals(null, null)   = true
StringUtils.equals(null, "abc")  = false
StringUtils.equals("abc", null)  = false
StringUtils.equals("abc", "abc") = true
StringUtils.equals("abc", "ABC") = false

Params:
cs1 –  the first CharSequence, may be null
cs2 –  the second CharSequence, may be null
See Also:
Object.equals(Object)
equalsIgnoreCase(CharSequence, CharSequence)
Returns:
true if the CharSequences are equal (case-sensitive), or both null
Since:
3.0 Changed signature from equals(String, String) to equals(CharSequence, CharSequence)/**
     * <p>Compares two CharSequences, returning {@code true} if they represent
     * equal sequences of characters.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is <strong>case sensitive</strong>.</p>
     *
     * <pre>
     * StringUtils.equals(null, null)   = true
     * StringUtils.equals(null, "abc")  = false
     * StringUtils.equals("abc", null)  = false
     * StringUtils.equals("abc", "abc") = true
     * StringUtils.equals("abc", "ABC") = false
     * </pre>
     *
     * @param cs1  the first CharSequence, may be {@code null}
     * @param cs2  the second CharSequence, may be {@code null}
     * @return {@code true} if the CharSequences are equal (case-sensitive), or both {@code null}
     * @since 3.0 Changed signature from equals(String, String) to equals(CharSequence, CharSequence)
     * @see Object#equals(Object)
     * @see #equalsIgnoreCase(CharSequence, CharSequence)
     */
    public static boolean equals(final CharSequence cs1, final CharSequence cs2) {
        if (cs1 == cs2) {
            return true;
        }
        if (cs1 == null || cs2 == null) {
            return false;
        }
        if (cs1.length() != cs2.length()) {
            return false;
        }
        if (cs1 instanceof String && cs2 instanceof String) {
            return cs1.equals(cs2);
        }
        // Step-wise comparison
        final int length = cs1.length();
        for (int i = 0; i < length; i++) {
            if (cs1.charAt(i) != cs2.charAt(i)) {
                return false;
            }
        }
        return true;
    }

    
Compares given string to a CharSequences vararg of searchStrings, returning true if the string is equal to any of the searchStrings.
StringUtils.equalsAny(null, (CharSequence[]) null) = false
StringUtils.equalsAny(null, null, null)    = true
StringUtils.equalsAny(null, "abc", "def")  = false
StringUtils.equalsAny("abc", null, "def")  = false
StringUtils.equalsAny("abc", "abc", "def") = true
StringUtils.equalsAny("abc", "ABC", "DEF") = false

Params:
string – to compare, may be null.
searchStrings – a vararg of strings, may be null.
Returns:
true if the string is equal (case-sensitive) to any other element of searchStrings; false if searchStrings is null or contains no matches.
Since:
3.5/**
     * <p>Compares given {@code string} to a CharSequences vararg of {@code searchStrings},
     * returning {@code true} if the {@code string} is equal to any of the {@code searchStrings}.</p>
     *
     * <pre>
     * StringUtils.equalsAny(null, (CharSequence[]) null) = false
     * StringUtils.equalsAny(null, null, null)    = true
     * StringUtils.equalsAny(null, "abc", "def")  = false
     * StringUtils.equalsAny("abc", null, "def")  = false
     * StringUtils.equalsAny("abc", "abc", "def") = true
     * StringUtils.equalsAny("abc", "ABC", "DEF") = false
     * </pre>
     *
     * @param string to compare, may be {@code null}.
     * @param searchStrings a vararg of strings, may be {@code null}.
     * @return {@code true} if the string is equal (case-sensitive) to any other element of {@code searchStrings};
     * {@code false} if {@code searchStrings} is null or contains no matches.
     * @since 3.5
     */
    public static boolean equalsAny(final CharSequence string, final CharSequence... searchStrings) {
        if (ArrayUtils.isNotEmpty(searchStrings)) {
            for (final CharSequence next : searchStrings) {
                if (equals(string, next)) {
                    return true;
                }
            }
        }
        return false;
    }

    
Compares given string to a CharSequences vararg of searchStrings, returning true if the string is equal to any of the searchStrings, ignoring case.
StringUtils.equalsAnyIgnoreCase(null, (CharSequence[]) null) = false
StringUtils.equalsAnyIgnoreCase(null, null, null)    = true
StringUtils.equalsAnyIgnoreCase(null, "abc", "def")  = false
StringUtils.equalsAnyIgnoreCase("abc", null, "def")  = false
StringUtils.equalsAnyIgnoreCase("abc", "abc", "def") = true
StringUtils.equalsAnyIgnoreCase("abc", "ABC", "DEF") = true

Params:
string – to compare, may be null.
searchStrings – a vararg of strings, may be null.
Returns:
true if the string is equal (case-insensitive) to any other element of searchStrings; false if searchStrings is null or contains no matches.
Since:
3.5/**
     * <p>Compares given {@code string} to a CharSequences vararg of {@code searchStrings},
     * returning {@code true} if the {@code string} is equal to any of the {@code searchStrings}, ignoring case.</p>
     *
     * <pre>
     * StringUtils.equalsAnyIgnoreCase(null, (CharSequence[]) null) = false
     * StringUtils.equalsAnyIgnoreCase(null, null, null)    = true
     * StringUtils.equalsAnyIgnoreCase(null, "abc", "def")  = false
     * StringUtils.equalsAnyIgnoreCase("abc", null, "def")  = false
     * StringUtils.equalsAnyIgnoreCase("abc", "abc", "def") = true
     * StringUtils.equalsAnyIgnoreCase("abc", "ABC", "DEF") = true
     * </pre>
     *
     * @param string to compare, may be {@code null}.
     * @param searchStrings a vararg of strings, may be {@code null}.
     * @return {@code true} if the string is equal (case-insensitive) to any other element of {@code searchStrings};
     * {@code false} if {@code searchStrings} is null or contains no matches.
     * @since 3.5
     */
    public static boolean equalsAnyIgnoreCase(final CharSequence string, final CharSequence...searchStrings) {
        if (ArrayUtils.isNotEmpty(searchStrings)) {
            for (final CharSequence next : searchStrings) {
                if (equalsIgnoreCase(string, next)) {
                    return true;
                }
            }
        }
        return false;
    }

    
Compares two CharSequences, returning true if they represent equal sequences of characters, ignoring case.
nulls are handled without exceptions. Two null references are considered equal. The comparison is case insensitive.
StringUtils.equalsIgnoreCase(null, null)   = true
StringUtils.equalsIgnoreCase(null, "abc")  = false
StringUtils.equalsIgnoreCase("abc", null)  = false
StringUtils.equalsIgnoreCase("abc", "abc") = true
StringUtils.equalsIgnoreCase("abc", "ABC") = true

Params:
cs1 –  the first CharSequence, may be null
cs2 –  the second CharSequence, may be null
See Also:
equals(CharSequence, CharSequence)
Returns:
true if the CharSequences are equal (case-insensitive), or both null
Since:
3.0 Changed signature from equalsIgnoreCase(String, String) to equalsIgnoreCase(CharSequence, CharSequence)/**
     * <p>Compares two CharSequences, returning {@code true} if they represent
     * equal sequences of characters, ignoring case.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered equal. The comparison is <strong>case insensitive</strong>.</p>
     *
     * <pre>
     * StringUtils.equalsIgnoreCase(null, null)   = true
     * StringUtils.equalsIgnoreCase(null, "abc")  = false
     * StringUtils.equalsIgnoreCase("abc", null)  = false
     * StringUtils.equalsIgnoreCase("abc", "abc") = true
     * StringUtils.equalsIgnoreCase("abc", "ABC") = true
     * </pre>
     *
     * @param cs1  the first CharSequence, may be {@code null}
     * @param cs2  the second CharSequence, may be {@code null}
     * @return {@code true} if the CharSequences are equal (case-insensitive), or both {@code null}
     * @since 3.0 Changed signature from equalsIgnoreCase(String, String) to equalsIgnoreCase(CharSequence, CharSequence)
     * @see #equals(CharSequence, CharSequence)
     */
    public static boolean equalsIgnoreCase(final CharSequence cs1, final CharSequence cs2) {
        if (cs1 == cs2) {
            return true;
        }
        if (cs1 == null || cs2 == null) {
            return false;
        }
        if (cs1.length() != cs2.length()) {
            return false;
        }
        return CharSequenceUtils.regionMatches(cs1, true, 0, cs2, 0, cs1.length());
    }

    
Returns the first value in the array which is not empty (""), null or whitespace only.
Whitespace is defined by Character.isWhitespace(char).
If all values are blank or the array is null or empty then null is returned.
StringUtils.firstNonBlank(null, null, null)     = null
StringUtils.firstNonBlank(null, "", " ")        = null
StringUtils.firstNonBlank("abc")                = "abc"
StringUtils.firstNonBlank(null, "xyz")          = "xyz"
StringUtils.firstNonBlank(null, "", " ", "xyz") = "xyz"
StringUtils.firstNonBlank(null, "xyz", "abc")   = "xyz"
StringUtils.firstNonBlank()                     = null

Params:
values –  the values to test, may be null or empty
Type parameters:
<T> – the specific kind of CharSequence
Returns:
the first value from values which is not blank, or null if there are no non-blank values
Since:
3.8/**
     * <p>Returns the first value in the array which is not empty (""),
     * {@code null} or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>If all values are blank or the array is {@code null}
     * or empty then {@code null} is returned.</p>
     *
     * <pre>
     * StringUtils.firstNonBlank(null, null, null)     = null
     * StringUtils.firstNonBlank(null, "", " ")        = null
     * StringUtils.firstNonBlank("abc")                = "abc"
     * StringUtils.firstNonBlank(null, "xyz")          = "xyz"
     * StringUtils.firstNonBlank(null, "", " ", "xyz") = "xyz"
     * StringUtils.firstNonBlank(null, "xyz", "abc")   = "xyz"
     * StringUtils.firstNonBlank()                     = null
     * </pre>
     *
     * @param <T> the specific kind of CharSequence
     * @param values  the values to test, may be {@code null} or empty
     * @return the first value from {@code values} which is not blank,
     *  or {@code null} if there are no non-blank values
     * @since 3.8
     */
    @SafeVarargs
    public static <T extends CharSequence> T firstNonBlank(final T... values) {
        if (values != null) {
            for (final T val : values) {
                if (isNotBlank(val)) {
                    return val;
                }
            }
        }
        return null;
    }

    
Returns the first value in the array which is not empty.
If all values are empty or the array is null or empty then null is returned.
StringUtils.firstNonEmpty(null, null, null)   = null
StringUtils.firstNonEmpty(null, null, "")     = null
StringUtils.firstNonEmpty(null, "", " ")      = " "
StringUtils.firstNonEmpty("abc")              = "abc"
StringUtils.firstNonEmpty(null, "xyz")        = "xyz"
StringUtils.firstNonEmpty("", "xyz")          = "xyz"
StringUtils.firstNonEmpty(null, "xyz", "abc") = "xyz"
StringUtils.firstNonEmpty()                   = null

Params:
values –  the values to test, may be null or empty
Type parameters:
<T> – the specific kind of CharSequence
Returns:
the first value from values which is not empty, or null if there are no non-empty values
Since:
3.8/**
     * <p>Returns the first value in the array which is not empty.</p>
     *
     * <p>If all values are empty or the array is {@code null}
     * or empty then {@code null} is returned.</p>
     *
     * <pre>
     * StringUtils.firstNonEmpty(null, null, null)   = null
     * StringUtils.firstNonEmpty(null, null, "")     = null
     * StringUtils.firstNonEmpty(null, "", " ")      = " "
     * StringUtils.firstNonEmpty("abc")              = "abc"
     * StringUtils.firstNonEmpty(null, "xyz")        = "xyz"
     * StringUtils.firstNonEmpty("", "xyz")          = "xyz"
     * StringUtils.firstNonEmpty(null, "xyz", "abc") = "xyz"
     * StringUtils.firstNonEmpty()                   = null
     * </pre>
     *
     * @param <T> the specific kind of CharSequence
     * @param values  the values to test, may be {@code null} or empty
     * @return the first value from {@code values} which is not empty,
     *  or {@code null} if there are no non-empty values
     * @since 3.8
     */
    @SafeVarargs
    public static <T extends CharSequence> T firstNonEmpty(final T... values) {
        if (values != null) {
            for (final T val : values) {
                if (isNotEmpty(val)) {
                    return val;
                }
            }
        }
        return null;
    }

    
Calls String.getBytes(Charset) in a null-safe manner. 
Params:
string – input string
charset – The Charset to encode the String. If null, then use the default Charset.
See Also:
String.getBytes(Charset)
Returns:
The empty byte[] if string is null, the result of String.getBytes(Charset) otherwise.
Since:
3.10/**
     * Calls {@link String#getBytes(Charset)} in a null-safe manner.
     *
     * @param string input string
     * @param charset The {@link Charset} to encode the {@code String}. If null, then use the default Charset.
     * @return The empty byte[] if {@code string} is null, the result of {@link String#getBytes(Charset)} otherwise.
     * @see String#getBytes(Charset)
     * @since 3.10
     */
    public static byte[] getBytes(final String string, final Charset charset) {
        return string == null ? ArrayUtils.EMPTY_BYTE_ARRAY : string.getBytes(Charsets.toCharset(charset));
    }

    
Calls String.getBytes(String) in a null-safe manner. 
Params:
string – input string
charset – The Charset name to encode the String. If null, then use the default Charset.
Throws:
UnsupportedEncodingException – Thrown when the named charset is not supported.
See Also:
String.getBytes(String)
Returns:
The empty byte[] if string is null, the result of String.getBytes(String) otherwise.
Since:
3.10/**
     * Calls {@link String#getBytes(String)} in a null-safe manner.
     *
     * @param string input string
     * @param charset The {@link Charset} name to encode the {@code String}. If null, then use the default Charset.
     * @return The empty byte[] if {@code string} is null, the result of {@link String#getBytes(String)} otherwise.
     * @throws UnsupportedEncodingException Thrown when the named charset is not supported.
     * @see String#getBytes(String)
     * @since 3.10
     */
    public static byte[] getBytes(final String string, final String charset) throws UnsupportedEncodingException {
        return string == null ? ArrayUtils.EMPTY_BYTE_ARRAY : string.getBytes(Charsets.toCharsetName(charset));
    }

    
Compares all Strings in an array and returns the initial sequence of
characters that is common to all of them.
For example, getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) -&gt; "i am a "
StringUtils.getCommonPrefix(null) = ""
StringUtils.getCommonPrefix(new String[] {}) = ""
StringUtils.getCommonPrefix(new String[] {"abc"}) = "abc"
StringUtils.getCommonPrefix(new String[] {null, null}) = ""
StringUtils.getCommonPrefix(new String[] {"", ""}) = ""
StringUtils.getCommonPrefix(new String[] {"", null}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", null, null}) = ""
StringUtils.getCommonPrefix(new String[] {null, null, "abc"}) = ""
StringUtils.getCommonPrefix(new String[] {"", "abc"}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", ""}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", "abc"}) = "abc"
StringUtils.getCommonPrefix(new String[] {"abc", "a"}) = "a"
StringUtils.getCommonPrefix(new String[] {"ab", "abxyz"}) = "ab"
StringUtils.getCommonPrefix(new String[] {"abcde", "abxyz"}) = "ab"
StringUtils.getCommonPrefix(new String[] {"abcde", "xyz"}) = ""
StringUtils.getCommonPrefix(new String[] {"xyz", "abcde"}) = ""
StringUtils.getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) = "i am a "

Params:
strs –  array of String objects, entries may be null
Returns:
the initial sequence of characters that are common to all Strings
in the array; empty String if the array is null, the elements are all null
or if there is no common prefix.
Since:
2.4/**
     * <p>Compares all Strings in an array and returns the initial sequence of
     * characters that is common to all of them.</p>
     *
     * <p>For example,
     * {@code getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) -&gt; "i am a "}</p>
     *
     * <pre>
     * StringUtils.getCommonPrefix(null) = ""
     * StringUtils.getCommonPrefix(new String[] {}) = ""
     * StringUtils.getCommonPrefix(new String[] {"abc"}) = "abc"
     * StringUtils.getCommonPrefix(new String[] {null, null}) = ""
     * StringUtils.getCommonPrefix(new String[] {"", ""}) = ""
     * StringUtils.getCommonPrefix(new String[] {"", null}) = ""
     * StringUtils.getCommonPrefix(new String[] {"abc", null, null}) = ""
     * StringUtils.getCommonPrefix(new String[] {null, null, "abc"}) = ""
     * StringUtils.getCommonPrefix(new String[] {"", "abc"}) = ""
     * StringUtils.getCommonPrefix(new String[] {"abc", ""}) = ""
     * StringUtils.getCommonPrefix(new String[] {"abc", "abc"}) = "abc"
     * StringUtils.getCommonPrefix(new String[] {"abc", "a"}) = "a"
     * StringUtils.getCommonPrefix(new String[] {"ab", "abxyz"}) = "ab"
     * StringUtils.getCommonPrefix(new String[] {"abcde", "abxyz"}) = "ab"
     * StringUtils.getCommonPrefix(new String[] {"abcde", "xyz"}) = ""
     * StringUtils.getCommonPrefix(new String[] {"xyz", "abcde"}) = ""
     * StringUtils.getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) = "i am a "
     * </pre>
     *
     * @param strs  array of String objects, entries may be null
     * @return the initial sequence of characters that are common to all Strings
     * in the array; empty String if the array is null, the elements are all null
     * or if there is no common prefix.
     * @since 2.4
     */
    public static String getCommonPrefix(final String... strs) {
        if (ArrayUtils.isEmpty(strs)) {
            return EMPTY;
        }
        final int smallestIndexOfDiff = indexOfDifference(strs);
        if (smallestIndexOfDiff == INDEX_NOT_FOUND) {
            // all strings were identical
            if (strs[0] == null) {
                return EMPTY;
            }
            return strs[0];
        } else if (smallestIndexOfDiff == 0) {
            // there were no common initial characters
            return EMPTY;
        } else {
            // we found a common initial character sequence
            return strs[0].substring(0, smallestIndexOfDiff);
        }
    }

    
Checks if a String str contains Unicode digits, if yes then concatenate all the digits in str and return it as a String.
An empty ("") String will be returned if no digits found in str.
StringUtils.getDigits(null)  = null
StringUtils.getDigits("")    = ""
StringUtils.getDigits("abc") = ""
StringUtils.getDigits("1000$") = "1000"
StringUtils.getDigits("1123~45") = "112345"
StringUtils.getDigits("(541) 754-3010") = "5417543010"
StringUtils.getDigits("\u0967\u0968\u0969") = "\u0967\u0968\u0969"

Params:
str – the String to extract digits from, may be null
Returns:
String with only digits, or an empty ("") String if no digits found, or null String if str is null
Since:
3.6/**
     * <p>Checks if a String {@code str} contains Unicode digits,
     * if yes then concatenate all the digits in {@code str} and return it as a String.</p>
     *
     * <p>An empty ("") String will be returned if no digits found in {@code str}.</p>
     *
     * <pre>
     * StringUtils.getDigits(null)  = null
     * StringUtils.getDigits("")    = ""
     * StringUtils.getDigits("abc") = ""
     * StringUtils.getDigits("1000$") = "1000"
     * StringUtils.getDigits("1123~45") = "112345"
     * StringUtils.getDigits("(541) 754-3010") = "5417543010"
     * StringUtils.getDigits("\u0967\u0968\u0969") = "\u0967\u0968\u0969"
     * </pre>
     *
     * @param str the String to extract digits from, may be null
     * @return String with only digits,
     *           or an empty ("") String if no digits found,
     *           or {@code null} String if {@code str} is null
     * @since 3.6
     */
    public static String getDigits(final String str) {
        if (isEmpty(str)) {
            return str;
        }
        final int sz = str.length();
        final StringBuilder strDigits = new StringBuilder(sz);
        for (int i = 0; i < sz; i++) {
            final char tempChar = str.charAt(i);
            if (Character.isDigit(tempChar)) {
                strDigits.append(tempChar);
            }
        }
        return strDigits.toString();
    }

    
Find the Fuzzy Distance which indicates the similarity score between two Strings.
This string matching algorithm is similar to the algorithms of editors such as Sublime Text,
TextMate, Atom and others. One point is given for every matched character. Subsequent
matches yield two bonus points. A higher score indicates a higher similarity.
StringUtils.getFuzzyDistance(null, null, null)                                    = IllegalArgumentException
StringUtils.getFuzzyDistance("", "", Locale.ENGLISH)                              = 0
StringUtils.getFuzzyDistance("Workshop", "b", Locale.ENGLISH)                     = 0
StringUtils.getFuzzyDistance("Room", "o", Locale.ENGLISH)                         = 1
StringUtils.getFuzzyDistance("Workshop", "w", Locale.ENGLISH)                     = 1
StringUtils.getFuzzyDistance("Workshop", "ws", Locale.ENGLISH)                    = 2
StringUtils.getFuzzyDistance("Workshop", "wo", Locale.ENGLISH)                    = 4
StringUtils.getFuzzyDistance("Apache Software Foundation", "asf", Locale.ENGLISH) = 3

Params:
term – a full term that should be matched against, must not be null
query – the query that will be matched against a term, must not be null
locale – This string matching logic is case insensitive. A locale is necessary to normalize
 both Strings to lower case.
Throws:
IllegalArgumentException – if either String input null or Locale input null
Returns:
result score
Since:
3.4
Deprecated:
as of 3.6, use commons-text

FuzzyScore instead/**
     * <p>Find the Fuzzy Distance which indicates the similarity score between two Strings.</p>
     *
     * <p>This string matching algorithm is similar to the algorithms of editors such as Sublime Text,
     * TextMate, Atom and others. One point is given for every matched character. Subsequent
     * matches yield two bonus points. A higher score indicates a higher similarity.</p>
     *
     * <pre>
     * StringUtils.getFuzzyDistance(null, null, null)                                    = IllegalArgumentException
     * StringUtils.getFuzzyDistance("", "", Locale.ENGLISH)                              = 0
     * StringUtils.getFuzzyDistance("Workshop", "b", Locale.ENGLISH)                     = 0
     * StringUtils.getFuzzyDistance("Room", "o", Locale.ENGLISH)                         = 1
     * StringUtils.getFuzzyDistance("Workshop", "w", Locale.ENGLISH)                     = 1
     * StringUtils.getFuzzyDistance("Workshop", "ws", Locale.ENGLISH)                    = 2
     * StringUtils.getFuzzyDistance("Workshop", "wo", Locale.ENGLISH)                    = 4
     * StringUtils.getFuzzyDistance("Apache Software Foundation", "asf", Locale.ENGLISH) = 3
     * </pre>
     *
     * @param term a full term that should be matched against, must not be null
     * @param query the query that will be matched against a term, must not be null
     * @param locale This string matching logic is case insensitive. A locale is necessary to normalize
     *  both Strings to lower case.
     * @return result score
     * @throws IllegalArgumentException if either String input {@code null} or Locale input {@code null}
     * @since 3.4
     * @deprecated as of 3.6, use commons-text
     * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/similarity/FuzzyScore.html">
     * FuzzyScore</a> instead
     */
    @Deprecated
    public static int getFuzzyDistance(final CharSequence term, final CharSequence query, final Locale locale) {
        if (term == null || query == null) {
            throw new IllegalArgumentException("Strings must not be null");
        } else if (locale == null) {
            throw new IllegalArgumentException("Locale must not be null");
        }

        // fuzzy logic is case insensitive. We normalize the Strings to lower
        // case right from the start. Turning characters to lower case
        // via Character.toLowerCase(char) is unfortunately insufficient
        // as it does not accept a locale.
        final String termLowerCase = term.toString().toLowerCase(locale);
        final String queryLowerCase = query.toString().toLowerCase(locale);

        // the resulting score
        int score = 0;

        // the position in the term which will be scanned next for potential
        // query character matches
        int termIndex = 0;

        // index of the previously matched character in the term
        int previousMatchingCharacterIndex = Integer.MIN_VALUE;

        for (int queryIndex = 0; queryIndex < queryLowerCase.length(); queryIndex++) {
            final char queryChar = queryLowerCase.charAt(queryIndex);

            boolean termCharacterMatchFound = false;
            for (; termIndex < termLowerCase.length() && !termCharacterMatchFound; termIndex++) {
                final char termChar = termLowerCase.charAt(termIndex);

                if (queryChar == termChar) {
                    // simple character matches result in one point
                    score++;

                    // subsequent character matches further improve
                    // the score.
                    if (previousMatchingCharacterIndex + 1 == termIndex) {
                        score += 2;
                    }

                    previousMatchingCharacterIndex = termIndex;

                    // we can leave the nested loop. Every character in the
                    // query can match at most one character in the term.
                    termCharacterMatchFound = true;
                }
            }
        }

        return score;
    }

    
Returns either the passed in CharSequence, or if the CharSequence is whitespace, empty ("") or null, the value supplied by defaultStrSupplier.
Whitespace is defined by Character.isWhitespace(char).
Caller responsible for thread-safety and exception handling of default value supplier

StringUtils.getIfBlank(null, () -> "NULL")   = "NULL"
StringUtils.getIfBlank("", () -> "NULL")     = "NULL"
StringUtils.getIfBlank(" ", () -> "NULL")    = "NULL"
StringUtils.getIfBlank("bat", () -> "NULL")  = "bat"
StringUtils.getIfBlank("", () -> null)       = null
StringUtils.getIfBlank("", null)             = null

Params:
str – the CharSequence to check, may be null
defaultSupplier – the supplier of default CharSequence to return if the input is whitespace, empty ("") or null, may be null
Type parameters:
<T> – the specific kind of CharSequence
See Also:
defaultString(String, String)
Returns:
the passed in CharSequence, or the default
Since:
3.10/**
     * <p>Returns either the passed in CharSequence, or if the CharSequence is
     * whitespace, empty ("") or {@code null}, the value supplied by {@code defaultStrSupplier}.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>Caller responsible for thread-safety and exception handling of default value supplier</p>
     *
     * <pre>
     * {@code
     * StringUtils.getIfBlank(null, () -> "NULL")   = "NULL"
     * StringUtils.getIfBlank("", () -> "NULL")     = "NULL"
     * StringUtils.getIfBlank(" ", () -> "NULL")    = "NULL"
     * StringUtils.getIfBlank("bat", () -> "NULL")  = "bat"
     * StringUtils.getIfBlank("", () -> null)       = null
     * StringUtils.getIfBlank("", null)             = null
     * }</pre>
     * @param <T> the specific kind of CharSequence
     * @param str the CharSequence to check, may be null
     * @param defaultSupplier the supplier of default CharSequence to return
     *  if the input is whitespace, empty ("") or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     * @since 3.10
     */
    public static <T extends CharSequence> T getIfBlank(final T str, final Supplier<T> defaultSupplier) {
        return isBlank(str) ? defaultSupplier == null ? null : defaultSupplier.get() : str;
    }

    
Returns either the passed in CharSequence, or if the CharSequence is empty or null, the value supplied by defaultStrSupplier.
Caller responsible for thread-safety and exception handling of default value supplier

StringUtils.getIfEmpty(null, () -> "NULL")    = "NULL"
StringUtils.getIfEmpty("", () -> "NULL")      = "NULL"
StringUtils.getIfEmpty(" ", () -> "NULL")     = " "
StringUtils.getIfEmpty("bat", () -> "NULL")   = "bat"
StringUtils.getIfEmpty("", () -> null)        = null
StringUtils.getIfEmpty("", null)              = null
 
Params:
str –  the CharSequence to check, may be null
defaultSupplier –  the supplier of default CharSequence to return if the input is empty ("") or null, may be null
Type parameters:
<T> – the specific kind of CharSequence
See Also:
defaultString(String, String)
Returns:
the passed in CharSequence, or the default
Since:
3.10/**
     * <p>Returns either the passed in CharSequence, or if the CharSequence is
     * empty or {@code null}, the value supplied by {@code defaultStrSupplier}.</p>
     *
     * <p>Caller responsible for thread-safety and exception handling of default value supplier</p>
     *
     * <pre>
     * {@code
     * StringUtils.getIfEmpty(null, () -> "NULL")    = "NULL"
     * StringUtils.getIfEmpty("", () -> "NULL")      = "NULL"
     * StringUtils.getIfEmpty(" ", () -> "NULL")     = " "
     * StringUtils.getIfEmpty("bat", () -> "NULL")   = "bat"
     * StringUtils.getIfEmpty("", () -> null)        = null
     * StringUtils.getIfEmpty("", null)              = null
     * }
     * </pre>
     * @param <T> the specific kind of CharSequence
     * @param str  the CharSequence to check, may be null
     * @param defaultSupplier  the supplier of default CharSequence to return
     *  if the input is empty ("") or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     * @since 3.10
     */
    public static <T extends CharSequence> T getIfEmpty(final T str, final Supplier<T> defaultSupplier) {
        return isEmpty(str) ? defaultSupplier == null ? null : defaultSupplier.get() : str;
    }

    
Find the Jaro Winkler Distance which indicates the similarity score between two Strings.
The Jaro measure is the weighted sum of percentage of matched characters from each file and transposed characters.
Winkler increased this measure for matching initial characters.
This implementation is based on the Jaro Winkler similarity algorithm
from http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance.
StringUtils.getJaroWinklerDistance(null, null)          = IllegalArgumentException
StringUtils.getJaroWinklerDistance("", "")              = 0.0
StringUtils.getJaroWinklerDistance("", "a")             = 0.0
StringUtils.getJaroWinklerDistance("aaapppp", "")       = 0.0
StringUtils.getJaroWinklerDistance("frog", "fog")       = 0.93
StringUtils.getJaroWinklerDistance("fly", "ant")        = 0.0
StringUtils.getJaroWinklerDistance("elephant", "hippo") = 0.44
StringUtils.getJaroWinklerDistance("hippo", "elephant") = 0.44
StringUtils.getJaroWinklerDistance("hippo", "zzzzzzzz") = 0.0
StringUtils.getJaroWinklerDistance("hello", "hallo")    = 0.88
StringUtils.getJaroWinklerDistance("ABC Corporation", "ABC Corp") = 0.93
StringUtils.getJaroWinklerDistance("D N H Enterprises Inc", "D & H Enterprises, Inc.") = 0.95
StringUtils.getJaroWinklerDistance("My Gym Children's Fitness Center", "My Gym. Childrens Fitness") = 0.92
StringUtils.getJaroWinklerDistance("PENNSYLVANIA", "PENNCISYLVNIA") = 0.88

Params:
first – the first String, must not be null
second – the second String, must not be null
Throws:
IllegalArgumentException – if either String input null
Returns:
result distance
Since:
3.3
Deprecated:
as of 3.6, use commons-text

JaroWinklerDistance instead/**
     * <p>Find the Jaro Winkler Distance which indicates the similarity score between two Strings.</p>
     *
     * <p>The Jaro measure is the weighted sum of percentage of matched characters from each file and transposed characters.
     * Winkler increased this measure for matching initial characters.</p>
     *
     * <p>This implementation is based on the Jaro Winkler similarity algorithm
     * from <a href="http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance">http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance</a>.</p>
     *
     * <pre>
     * StringUtils.getJaroWinklerDistance(null, null)          = IllegalArgumentException
     * StringUtils.getJaroWinklerDistance("", "")              = 0.0
     * StringUtils.getJaroWinklerDistance("", "a")             = 0.0
     * StringUtils.getJaroWinklerDistance("aaapppp", "")       = 0.0
     * StringUtils.getJaroWinklerDistance("frog", "fog")       = 0.93
     * StringUtils.getJaroWinklerDistance("fly", "ant")        = 0.0
     * StringUtils.getJaroWinklerDistance("elephant", "hippo") = 0.44
     * StringUtils.getJaroWinklerDistance("hippo", "elephant") = 0.44
     * StringUtils.getJaroWinklerDistance("hippo", "zzzzzzzz") = 0.0
     * StringUtils.getJaroWinklerDistance("hello", "hallo")    = 0.88
     * StringUtils.getJaroWinklerDistance("ABC Corporation", "ABC Corp") = 0.93
     * StringUtils.getJaroWinklerDistance("D N H Enterprises Inc", "D &amp; H Enterprises, Inc.") = 0.95
     * StringUtils.getJaroWinklerDistance("My Gym Children's Fitness Center", "My Gym. Childrens Fitness") = 0.92
     * StringUtils.getJaroWinklerDistance("PENNSYLVANIA", "PENNCISYLVNIA") = 0.88
     * </pre>
     *
     * @param first the first String, must not be null
     * @param second the second String, must not be null
     * @return result distance
     * @throws IllegalArgumentException if either String input {@code null}
     * @since 3.3
     * @deprecated as of 3.6, use commons-text
     * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/similarity/JaroWinklerDistance.html">
     * JaroWinklerDistance</a> instead
     */
    @Deprecated
    public static double getJaroWinklerDistance(final CharSequence first, final CharSequence second) {
        final double DEFAULT_SCALING_FACTOR = 0.1;

        if (first == null || second == null) {
            throw new IllegalArgumentException("Strings must not be null");
        }

        final int[] mtp = matches(first, second);
        final double m = mtp[0];
        if (m == 0) {
            return 0D;
        }
        final double j = ((m / first.length() + m / second.length() + (m - mtp[1]) / m)) / 3;
        final double jw = j < 0.7D ? j : j + Math.min(DEFAULT_SCALING_FACTOR, 1D / mtp[3]) * mtp[2] * (1D - j);
        return Math.round(jw * 100.0D) / 100.0D;
    }

    // Misc
    //-----------------------------------------------------------------------
    
Find the Levenshtein distance between two Strings.
This is the number of changes needed to change one String into
another, where each change is a single character modification (deletion,
insertion or substitution).
The implementation uses a single-dimensional array of length s.length() + 1. See

http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html for details.
StringUtils.getLevenshteinDistance(null, *)             = IllegalArgumentException
StringUtils.getLevenshteinDistance(*, null)             = IllegalArgumentException
StringUtils.getLevenshteinDistance("", "")              = 0
StringUtils.getLevenshteinDistance("", "a")             = 1
StringUtils.getLevenshteinDistance("aaapppp", "")       = 7
StringUtils.getLevenshteinDistance("frog", "fog")       = 1
StringUtils.getLevenshteinDistance("fly", "ant")        = 3
StringUtils.getLevenshteinDistance("elephant", "hippo") = 7
StringUtils.getLevenshteinDistance("hippo", "elephant") = 7
StringUtils.getLevenshteinDistance("hippo", "zzzzzzzz") = 8
StringUtils.getLevenshteinDistance("hello", "hallo")    = 1

Params:
s –  the first String, must not be null
t –  the second String, must not be null
Throws:
IllegalArgumentException – if either String input null
Returns:
result distance
Since:
3.0 Changed signature from getLevenshteinDistance(String, String) to
getLevenshteinDistance(CharSequence, CharSequence)
Deprecated:
as of 3.6, use commons-text

LevenshteinDistance instead/**
     * <p>Find the Levenshtein distance between two Strings.</p>
     *
     * <p>This is the number of changes needed to change one String into
     * another, where each change is a single character modification (deletion,
     * insertion or substitution).</p>
     *
     * <p>The implementation uses a single-dimensional array of length s.length() + 1. See
     * <a href="http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html">
     * http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html</a> for details.</p>
     *
     * <pre>
     * StringUtils.getLevenshteinDistance(null, *)             = IllegalArgumentException
     * StringUtils.getLevenshteinDistance(*, null)             = IllegalArgumentException
     * StringUtils.getLevenshteinDistance("", "")              = 0
     * StringUtils.getLevenshteinDistance("", "a")             = 1
     * StringUtils.getLevenshteinDistance("aaapppp", "")       = 7
     * StringUtils.getLevenshteinDistance("frog", "fog")       = 1
     * StringUtils.getLevenshteinDistance("fly", "ant")        = 3
     * StringUtils.getLevenshteinDistance("elephant", "hippo") = 7
     * StringUtils.getLevenshteinDistance("hippo", "elephant") = 7
     * StringUtils.getLevenshteinDistance("hippo", "zzzzzzzz") = 8
     * StringUtils.getLevenshteinDistance("hello", "hallo")    = 1
     * </pre>
     *
     * @param s  the first String, must not be null
     * @param t  the second String, must not be null
     * @return result distance
     * @throws IllegalArgumentException if either String input {@code null}
     * @since 3.0 Changed signature from getLevenshteinDistance(String, String) to
     * getLevenshteinDistance(CharSequence, CharSequence)
     * @deprecated as of 3.6, use commons-text
     * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/similarity/LevenshteinDistance.html">
     * LevenshteinDistance</a> instead
     */
    @Deprecated
    public static int getLevenshteinDistance(CharSequence s, CharSequence t) {
        if (s == null || t == null) {
            throw new IllegalArgumentException("Strings must not be null");
        }

        int n = s.length();
        int m = t.length();

        if (n == 0) {
            return m;
        } else if (m == 0) {
            return n;
        }

        if (n > m) {
            // swap the input strings to consume less memory
            final CharSequence tmp = s;
            s = t;
            t = tmp;
            n = m;
            m = t.length();
        }

        final int[] p = new int[n + 1];
        // indexes into strings s and t
        int i; // iterates through s
        int j; // iterates through t
        int upper_left;
        int upper;

        char t_j; // jth character of t
        int cost;

        for (i = 0; i <= n; i++) {
            p[i] = i;
        }

        for (j = 1; j <= m; j++) {
            upper_left = p[0];
            t_j = t.charAt(j - 1);
            p[0] = j;

            for (i = 1; i <= n; i++) {
                upper = p[i];
                cost = s.charAt(i - 1) == t_j ? 0 : 1;
                // minimum of cell to the left+1, to the top+1, diagonally left and up +cost
                p[i] = Math.min(Math.min(p[i - 1] + 1, p[i] + 1), upper_left + cost);
                upper_left = upper;
            }
        }

        return p[n];
    }

    
Find the Levenshtein distance between two Strings if it's less than or equal to a given
threshold.
This is the number of changes needed to change one String into
another, where each change is a single character modification (deletion,
insertion or substitution).
This implementation follows from Algorithms on Strings, Trees and Sequences by Dan Gusfield
and Chas Emerick's implementation of the Levenshtein distance algorithm from
http://www.merriampark.com/ld.htm
StringUtils.getLevenshteinDistance(null, *, *)             = IllegalArgumentException
StringUtils.getLevenshteinDistance(*, null, *)             = IllegalArgumentException
StringUtils.getLevenshteinDistance(*, *, -1)               = IllegalArgumentException
StringUtils.getLevenshteinDistance("", "", 0)              = 0
StringUtils.getLevenshteinDistance("aaapppp", "", 8)       = 7
StringUtils.getLevenshteinDistance("aaapppp", "", 7)       = 7
StringUtils.getLevenshteinDistance("aaapppp", "", 6))      = -1
StringUtils.getLevenshteinDistance("elephant", "hippo", 7) = 7
StringUtils.getLevenshteinDistance("elephant", "hippo", 6) = -1
StringUtils.getLevenshteinDistance("hippo", "elephant", 7) = 7
StringUtils.getLevenshteinDistance("hippo", "elephant", 6) = -1

Params:
s –  the first String, must not be null
t –  the second String, must not be null
threshold – the target threshold, must not be negative
Throws:
IllegalArgumentException – if either String input null or negative threshold
Returns:
result distance, or -1 if the distance would be greater than the threshold
Deprecated:
as of 3.6, use commons-text

LevenshteinDistance instead/**
     * <p>Find the Levenshtein distance between two Strings if it's less than or equal to a given
     * threshold.</p>
     *
     * <p>This is the number of changes needed to change one String into
     * another, where each change is a single character modification (deletion,
     * insertion or substitution).</p>
     *
     * <p>This implementation follows from Algorithms on Strings, Trees and Sequences by Dan Gusfield
     * and Chas Emerick's implementation of the Levenshtein distance algorithm from
     * <a href="http://www.merriampark.com/ld.htm">http://www.merriampark.com/ld.htm</a></p>
     *
     * <pre>
     * StringUtils.getLevenshteinDistance(null, *, *)             = IllegalArgumentException
     * StringUtils.getLevenshteinDistance(*, null, *)             = IllegalArgumentException
     * StringUtils.getLevenshteinDistance(*, *, -1)               = IllegalArgumentException
     * StringUtils.getLevenshteinDistance("", "", 0)              = 0
     * StringUtils.getLevenshteinDistance("aaapppp", "", 8)       = 7
     * StringUtils.getLevenshteinDistance("aaapppp", "", 7)       = 7
     * StringUtils.getLevenshteinDistance("aaapppp", "", 6))      = -1
     * StringUtils.getLevenshteinDistance("elephant", "hippo", 7) = 7
     * StringUtils.getLevenshteinDistance("elephant", "hippo", 6) = -1
     * StringUtils.getLevenshteinDistance("hippo", "elephant", 7) = 7
     * StringUtils.getLevenshteinDistance("hippo", "elephant", 6) = -1
     * </pre>
     *
     * @param s  the first String, must not be null
     * @param t  the second String, must not be null
     * @param threshold the target threshold, must not be negative
     * @return result distance, or {@code -1} if the distance would be greater than the threshold
     * @throws IllegalArgumentException if either String input {@code null} or negative threshold
     * @deprecated as of 3.6, use commons-text
     * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/similarity/LevenshteinDistance.html">
     * LevenshteinDistance</a> instead
     */
    @Deprecated
    public static int getLevenshteinDistance(CharSequence s, CharSequence t, final int threshold) {
        if (s == null || t == null) {
            throw new IllegalArgumentException("Strings must not be null");
        }
        if (threshold < 0) {
            throw new IllegalArgumentException("Threshold must not be negative");
        }

        /*
        This implementation only computes the distance if it's less than or equal to the
        threshold value, returning -1 if it's greater.  The advantage is performance: unbounded
        distance is O(nm), but a bound of k allows us to reduce it to O(km) time by only
        computing a diagonal stripe of width 2k + 1 of the cost table.
        It is also possible to use this to compute the unbounded Levenshtein distance by starting
        the threshold at 1 and doubling each time until the distance is found; this is O(dm), where
        d is the distance.

        One subtlety comes from needing to ignore entries on the border of our stripe
        eg.
        p[] = |#|#|#|*
        d[] =  *|#|#|#|
        We must ignore the entry to the left of the leftmost member
        We must ignore the entry above the rightmost member

        Another subtlety comes from our stripe running off the matrix if the strings aren't
        of the same size.  Since string s is always swapped to be the shorter of the two,
        the stripe will always run off to the upper right instead of the lower left of the matrix.

        As a concrete example, suppose s is of length 5, t is of length 7, and our threshold is 1.
        In this case we're going to walk a stripe of length 3.  The matrix would look like so:

           1 2 3 4 5
        1 |#|#| | | |
        2 |#|#|#| | |
        3 | |#|#|#| |
        4 | | |#|#|#|
        5 | | | |#|#|
        6 | | | | |#|
        7 | | | | | |

        Note how the stripe leads off the table as there is no possible way to turn a string of length 5
        into one of length 7 in edit distance of 1.

        Additionally, this implementation decreases memory usage by using two
        single-dimensional arrays and swapping them back and forth instead of allocating
        an entire n by m matrix.  This requires a few minor changes, such as immediately returning
        when it's detected that the stripe has run off the matrix and initially filling the arrays with
        large values so that entries we don't compute are ignored.

        See Algorithms on Strings, Trees and Sequences by Dan Gusfield for some discussion.
         */

        int n = s.length(); // length of s
        int m = t.length(); // length of t

        // if one string is empty, the edit distance is necessarily the length of the other
        if (n == 0) {
            return m <= threshold ? m : -1;
        } else if (m == 0) {
            return n <= threshold ? n : -1;
        } else if (Math.abs(n - m) > threshold) {
            // no need to calculate the distance if the length difference is greater than the threshold
            return -1;
        }

        if (n > m) {
            // swap the two strings to consume less memory
            final CharSequence tmp = s;
            s = t;
            t = tmp;
            n = m;
            m = t.length();
        }

        int[] p = new int[n + 1]; // 'previous' cost array, horizontally
        int[] d = new int[n + 1]; // cost array, horizontally
        int[] _d; // placeholder to assist in swapping p and d

        // fill in starting table values
        final int boundary = Math.min(n, threshold) + 1;
        for (int i = 0; i < boundary; i++) {
            p[i] = i;
        }
        // these fills ensure that the value above the rightmost entry of our
        // stripe will be ignored in following loop iterations
        Arrays.fill(p, boundary, p.length, Integer.MAX_VALUE);
        Arrays.fill(d, Integer.MAX_VALUE);

        // iterates through t
        for (int j = 1; j <= m; j++) {
            final char t_j = t.charAt(j - 1); // jth character of t
            d[0] = j;

            // compute stripe indices, constrain to array size
            final int min = Math.max(1, j - threshold);
            final int max = j > Integer.MAX_VALUE - threshold ? n : Math.min(n, j + threshold);

            // the stripe may lead off of the table if s and t are of different sizes
            if (min > max) {
                return -1;
            }

            // ignore entry left of leftmost
            if (min > 1) {
                d[min - 1] = Integer.MAX_VALUE;
            }

            // iterates through [min, max] in s
            for (int i = min; i <= max; i++) {
                if (s.charAt(i - 1) == t_j) {
                    // diagonally left and up
                    d[i] = p[i - 1];
                } else {
                    // 1 + minimum of cell to the left, to the top, diagonally left and up
                    d[i] = 1 + Math.min(Math.min(d[i - 1], p[i]), p[i - 1]);
                }
            }

            // copy current distance counts to 'previous row' distance counts
            _d = p;
            p = d;
            d = _d;
        }

        // if p[n] is greater than the threshold, there's no guarantee on it being the correct
        // distance
        if (p[n] <= threshold) {
            return p[n];
        }
        return -1;
    }

    
Finds the first index within a CharSequence, handling null. This method uses String.indexOf(String, int) if possible.
A null CharSequence will return -1.
StringUtils.indexOf(null, *)          = -1
StringUtils.indexOf(*, null)          = -1
StringUtils.indexOf("", "")           = 0
StringUtils.indexOf("", *)            = -1 (except when * = "")
StringUtils.indexOf("aabaabaa", "a")  = 0
StringUtils.indexOf("aabaabaa", "b")  = 2
StringUtils.indexOf("aabaabaa", "ab") = 1
StringUtils.indexOf("aabaabaa", "")   = 0

Params:
seq –  the CharSequence to check, may be null
searchSeq –  the CharSequence to find, may be null
Returns:
the first index of the search CharSequence, -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from indexOf(String, String) to indexOf(CharSequence, CharSequence)/**
     * <p>Finds the first index within a CharSequence, handling {@code null}.
     * This method uses {@link String#indexOf(String, int)} if possible.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.indexOf(null, *)          = -1
     * StringUtils.indexOf(*, null)          = -1
     * StringUtils.indexOf("", "")           = 0
     * StringUtils.indexOf("", *)            = -1 (except when * = "")
     * StringUtils.indexOf("aabaabaa", "a")  = 0
     * StringUtils.indexOf("aabaabaa", "b")  = 2
     * StringUtils.indexOf("aabaabaa", "ab") = 1
     * StringUtils.indexOf("aabaabaa", "")   = 0
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchSeq  the CharSequence to find, may be null
     * @return the first index of the search CharSequence,
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from indexOf(String, String) to indexOf(CharSequence, CharSequence)
     */
    public static int indexOf(final CharSequence seq, final CharSequence searchSeq) {
        if (seq == null || searchSeq == null) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.indexOf(seq, searchSeq, 0);
    }

    
Finds the first index within a CharSequence, handling null. This method uses String.indexOf(String, int) if possible.
A null CharSequence will return -1. A negative start position is treated as zero. An empty ("") search CharSequence always matches. A start position greater than the string length only matches an empty search CharSequence.
StringUtils.indexOf(null, *, *)          = -1
StringUtils.indexOf(*, null, *)          = -1
StringUtils.indexOf("", "", 0)           = 0
StringUtils.indexOf("", *, 0)            = -1 (except when * = "")
StringUtils.indexOf("aabaabaa", "a", 0)  = 0
StringUtils.indexOf("aabaabaa", "b", 0)  = 2
StringUtils.indexOf("aabaabaa", "ab", 0) = 1
StringUtils.indexOf("aabaabaa", "b", 3)  = 5
StringUtils.indexOf("aabaabaa", "b", 9)  = -1
StringUtils.indexOf("aabaabaa", "b", -1) = 2
StringUtils.indexOf("aabaabaa", "", 2)   = 2
StringUtils.indexOf("abc", "", 9)        = 3

Params:
seq –  the CharSequence to check, may be null
searchSeq –  the CharSequence to find, may be null
startPos –  the start position, negative treated as zero
Returns:
the first index of the search CharSequence (always ≥ startPos), -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from indexOf(String, String, int) to indexOf(CharSequence, CharSequence, int)/**
     * <p>Finds the first index within a CharSequence, handling {@code null}.
     * This method uses {@link String#indexOf(String, int)} if possible.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position is treated as zero.
     * An empty ("") search CharSequence always matches.
     * A start position greater than the string length only matches
     * an empty search CharSequence.</p>
     *
     * <pre>
     * StringUtils.indexOf(null, *, *)          = -1
     * StringUtils.indexOf(*, null, *)          = -1
     * StringUtils.indexOf("", "", 0)           = 0
     * StringUtils.indexOf("", *, 0)            = -1 (except when * = "")
     * StringUtils.indexOf("aabaabaa", "a", 0)  = 0
     * StringUtils.indexOf("aabaabaa", "b", 0)  = 2
     * StringUtils.indexOf("aabaabaa", "ab", 0) = 1
     * StringUtils.indexOf("aabaabaa", "b", 3)  = 5
     * StringUtils.indexOf("aabaabaa", "b", 9)  = -1
     * StringUtils.indexOf("aabaabaa", "b", -1) = 2
     * StringUtils.indexOf("aabaabaa", "", 2)   = 2
     * StringUtils.indexOf("abc", "", 9)        = 3
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchSeq  the CharSequence to find, may be null
     * @param startPos  the start position, negative treated as zero
     * @return the first index of the search CharSequence (always &ge; startPos),
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from indexOf(String, String, int) to indexOf(CharSequence, CharSequence, int)
     */
    public static int indexOf(final CharSequence seq, final CharSequence searchSeq, final int startPos) {
        if (seq == null || searchSeq == null) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.indexOf(seq, searchSeq, startPos);
    }

    // IndexOf
    //-----------------------------------------------------------------------
    
Returns the index within seq of the first occurrence of the specified character. If a character with value searchChar occurs in the character sequence represented by seq CharSequence object, then the index (in Unicode code units) of the first such occurrence is returned. For values of searchChar in the range from 0 to 0xFFFF (inclusive), this is the smallest value k such that:
this.charAt(k) == searchChar
 is true. For other values of searchChar, it is the smallest value k such that:
this.codePointAt(k) == searchChar
 is true. In either case, if no such character occurs in seq, then INDEX_NOT_FOUND (-1) is returned. 
Furthermore, a null or empty ("") CharSequence will return INDEX_NOT_FOUND (-1).
StringUtils.indexOf(null, *)         = -1
StringUtils.indexOf("", *)           = -1
StringUtils.indexOf("aabaabaa", 'a') = 0
StringUtils.indexOf("aabaabaa", 'b') = 2

Params:
seq –  the CharSequence to check, may be null
searchChar –  the character to find
Returns:
the first index of the search character, -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from indexOf(String, int) to indexOf(CharSequence, int)
Since:
3.6 Updated CharSequenceUtils call to behave more like String/**
     * Returns the index within {@code seq} of the first occurrence of
     * the specified character. If a character with value
     * {@code searchChar} occurs in the character sequence represented by
     * {@code seq} {@code CharSequence} object, then the index (in Unicode
     * code units) of the first such occurrence is returned. For
     * values of {@code searchChar} in the range from 0 to 0xFFFF
     * (inclusive), this is the smallest value <i>k</i> such that:
     * <blockquote><pre>
     * this.charAt(<i>k</i>) == searchChar
     * </pre></blockquote>
     * is true. For other values of {@code searchChar}, it is the
     * smallest value <i>k</i> such that:
     * <blockquote><pre>
     * this.codePointAt(<i>k</i>) == searchChar
     * </pre></blockquote>
     * is true. In either case, if no such character occurs in {@code seq},
     * then {@code INDEX_NOT_FOUND (-1)} is returned.
     *
     * <p>Furthermore, a {@code null} or empty ("") CharSequence will
     * return {@code INDEX_NOT_FOUND (-1)}.</p>
     *
     * <pre>
     * StringUtils.indexOf(null, *)         = -1
     * StringUtils.indexOf("", *)           = -1
     * StringUtils.indexOf("aabaabaa", 'a') = 0
     * StringUtils.indexOf("aabaabaa", 'b') = 2
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchChar  the character to find
     * @return the first index of the search character,
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from indexOf(String, int) to indexOf(CharSequence, int)
     * @since 3.6 Updated {@link CharSequenceUtils} call to behave more like {@code String}
     */
    public static int indexOf(final CharSequence seq, final int searchChar) {
        if (isEmpty(seq)) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.indexOf(seq, searchChar, 0);
    }

    
Returns the index within seq of the first occurrence of the specified character, starting the search at the specified index. 
 If a character with value searchChar occurs in the character sequence represented by the seq CharSequence object at an index no smaller than startPos, then the index of the first such occurrence is returned. For values of searchChar in the range from 0 to 0xFFFF (inclusive), this is the smallest value k such that:
(this.charAt(k) == searchChar) && (k >= startPos)
 is true. For other values of searchChar, it is the smallest value k such that:
(this.codePointAt(k) == searchChar) && (k >= startPos)
 is true. In either case, if no such character occurs in seq at or after position startPos, then -1 is returned. 
 There is no restriction on the value of startPos. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: (INDEX_NOT_FOUND) -1 is returned. Furthermore, a null or empty ("") CharSequence will return (INDEX_NOT_FOUND) -1. 
All indices are specified in char values (Unicode code units). 
StringUtils.indexOf(null, *, *)          = -1
StringUtils.indexOf("", *, *)            = -1
StringUtils.indexOf("aabaabaa", 'b', 0)  = 2
StringUtils.indexOf("aabaabaa", 'b', 3)  = 5
StringUtils.indexOf("aabaabaa", 'b', 9)  = -1
StringUtils.indexOf("aabaabaa", 'b', -1) = 2

Params:
seq –  the CharSequence to check, may be null
searchChar –  the character to find
startPos –  the start position, negative treated as zero
Returns:
the first index of the search character (always ≥ startPos), -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from indexOf(String, int, int) to indexOf(CharSequence, int, int)
Since:
3.6 Updated CharSequenceUtils call to behave more like String/**
     *
     * Returns the index within {@code seq} of the first occurrence of the
     * specified character, starting the search at the specified index.
     * <p>
     * If a character with value {@code searchChar} occurs in the
     * character sequence represented by the {@code seq} {@code CharSequence}
     * object at an index no smaller than {@code startPos}, then
     * the index of the first such occurrence is returned. For values
     * of {@code searchChar} in the range from 0 to 0xFFFF (inclusive),
     * this is the smallest value <i>k</i> such that:
     * <blockquote><pre>
     * (this.charAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &gt;= startPos)
     * </pre></blockquote>
     * is true. For other values of {@code searchChar}, it is the
     * smallest value <i>k</i> such that:
     * <blockquote><pre>
     * (this.codePointAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &gt;= startPos)
     * </pre></blockquote>
     * is true. In either case, if no such character occurs in {@code seq}
     * at or after position {@code startPos}, then
     * {@code -1} is returned.
     *
     * <p>
     * There is no restriction on the value of {@code startPos}. If it
     * is negative, it has the same effect as if it were zero: this entire
     * string may be searched. If it is greater than the length of this
     * string, it has the same effect as if it were equal to the length of
     * this string: {@code (INDEX_NOT_FOUND) -1} is returned. Furthermore, a
     * {@code null} or empty ("") CharSequence will
     * return {@code (INDEX_NOT_FOUND) -1}.
     *
     * <p>All indices are specified in {@code char} values
     * (Unicode code units).
     *
     * <pre>
     * StringUtils.indexOf(null, *, *)          = -1
     * StringUtils.indexOf("", *, *)            = -1
     * StringUtils.indexOf("aabaabaa", 'b', 0)  = 2
     * StringUtils.indexOf("aabaabaa", 'b', 3)  = 5
     * StringUtils.indexOf("aabaabaa", 'b', 9)  = -1
     * StringUtils.indexOf("aabaabaa", 'b', -1) = 2
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchChar  the character to find
     * @param startPos  the start position, negative treated as zero
     * @return the first index of the search character (always &ge; startPos),
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from indexOf(String, int, int) to indexOf(CharSequence, int, int)
     * @since 3.6 Updated {@link CharSequenceUtils} call to behave more like {@code String}
     */
    public static int indexOf(final CharSequence seq, final int searchChar, final int startPos) {
        if (isEmpty(seq)) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.indexOf(seq, searchChar, startPos);
    }

    // IndexOfAny chars
    //-----------------------------------------------------------------------
    
Search a CharSequence to find the first index of any
character in the given set of characters.
A null String will return -1. A null or zero length search array will return -1.
StringUtils.indexOfAny(null, *)                  = -1
StringUtils.indexOfAny("", *)                    = -1
StringUtils.indexOfAny(*, null)                  = -1
StringUtils.indexOfAny(*, [])                    = -1
StringUtils.indexOfAny("zzabyycdxx", ['z', 'a']) = 0
StringUtils.indexOfAny("zzabyycdxx", ['b', 'y']) = 3
StringUtils.indexOfAny("aba", ['z'])             = -1

Params:
cs –  the CharSequence to check, may be null
searchChars –  the chars to search for, may be null
Returns:
the index of any of the chars, -1 if no match or null input
Since:
2.0
Since:
3.0 Changed signature from indexOfAny(String, char[]) to indexOfAny(CharSequence, char...)/**
     * <p>Search a CharSequence to find the first index of any
     * character in the given set of characters.</p>
     *
     * <p>A {@code null} String will return {@code -1}.
     * A {@code null} or zero length search array will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.indexOfAny(null, *)                  = -1
     * StringUtils.indexOfAny("", *)                    = -1
     * StringUtils.indexOfAny(*, null)                  = -1
     * StringUtils.indexOfAny(*, [])                    = -1
     * StringUtils.indexOfAny("zzabyycdxx", ['z', 'a']) = 0
     * StringUtils.indexOfAny("zzabyycdxx", ['b', 'y']) = 3
     * StringUtils.indexOfAny("aba", ['z'])             = -1
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param searchChars  the chars to search for, may be null
     * @return the index of any of the chars, -1 if no match or null input
     * @since 2.0
     * @since 3.0 Changed signature from indexOfAny(String, char[]) to indexOfAny(CharSequence, char...)
     */
    public static int indexOfAny(final CharSequence cs, final char... searchChars) {
        if (isEmpty(cs) || ArrayUtils.isEmpty(searchChars)) {
            return INDEX_NOT_FOUND;
        }
        final int csLen = cs.length();
        final int csLast = csLen - 1;
        final int searchLen = searchChars.length;
        final int searchLast = searchLen - 1;
        for (int i = 0; i < csLen; i++) {
            final char ch = cs.charAt(i);
            for (int j = 0; j < searchLen; j++) {
                if (searchChars[j] == ch) {
                    if (i < csLast && j < searchLast && Character.isHighSurrogate(ch)) {
                        // ch is a supplementary character
                        if (searchChars[j + 1] == cs.charAt(i + 1)) {
                            return i;
                        }
                    } else {
                        return i;
                    }
                }
            }
        }
        return INDEX_NOT_FOUND;
    }

    // IndexOfAny strings
    //-----------------------------------------------------------------------
    
Find the first index of any of a set of potential substrings.
A null CharSequence will return -1. A null or zero length search array will return -1. A null search array entry will be ignored, but a search array containing "" will return 0 if str is not null. This method uses String.indexOf(String) if possible.
StringUtils.indexOfAny(null, *)                      = -1
StringUtils.indexOfAny(*, null)                      = -1
StringUtils.indexOfAny(*, [])                        = -1
StringUtils.indexOfAny("zzabyycdxx", ["ab", "cd"])   = 2
StringUtils.indexOfAny("zzabyycdxx", ["cd", "ab"])   = 2
StringUtils.indexOfAny("zzabyycdxx", ["mn", "op"])   = -1
StringUtils.indexOfAny("zzabyycdxx", ["zab", "aby"]) = 1
StringUtils.indexOfAny("zzabyycdxx", [""])           = 0
StringUtils.indexOfAny("", [""])                     = 0
StringUtils.indexOfAny("", ["a"])                    = -1

Params:
str –  the CharSequence to check, may be null
searchStrs –  the CharSequences to search for, may be null
Returns:
the first index of any of the searchStrs in str, -1 if no match
Since:
3.0 Changed signature from indexOfAny(String, String[]) to indexOfAny(CharSequence, CharSequence...)/**
     * <p>Find the first index of any of a set of potential substrings.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A {@code null} or zero length search array will return {@code -1}.
     * A {@code null} search array entry will be ignored, but a search
     * array containing "" will return {@code 0} if {@code str} is not
     * null. This method uses {@link String#indexOf(String)} if possible.</p>
     *
     * <pre>
     * StringUtils.indexOfAny(null, *)                      = -1
     * StringUtils.indexOfAny(*, null)                      = -1
     * StringUtils.indexOfAny(*, [])                        = -1
     * StringUtils.indexOfAny("zzabyycdxx", ["ab", "cd"])   = 2
     * StringUtils.indexOfAny("zzabyycdxx", ["cd", "ab"])   = 2
     * StringUtils.indexOfAny("zzabyycdxx", ["mn", "op"])   = -1
     * StringUtils.indexOfAny("zzabyycdxx", ["zab", "aby"]) = 1
     * StringUtils.indexOfAny("zzabyycdxx", [""])           = 0
     * StringUtils.indexOfAny("", [""])                     = 0
     * StringUtils.indexOfAny("", ["a"])                    = -1
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStrs  the CharSequences to search for, may be null
     * @return the first index of any of the searchStrs in str, -1 if no match
     * @since 3.0 Changed signature from indexOfAny(String, String[]) to indexOfAny(CharSequence, CharSequence...)
     */
    public static int indexOfAny(final CharSequence str, final CharSequence... searchStrs) {
        if (str == null || searchStrs == null) {
            return INDEX_NOT_FOUND;
        }

        // String's can't have a MAX_VALUEth index.
        int ret = Integer.MAX_VALUE;

        int tmp = 0;
        for (final CharSequence search : searchStrs) {
            if (search == null) {
                continue;
            }
            tmp = CharSequenceUtils.indexOf(str, search, 0);
            if (tmp == INDEX_NOT_FOUND) {
                continue;
            }

            if (tmp < ret) {
                ret = tmp;
            }
        }

        return ret == Integer.MAX_VALUE ? INDEX_NOT_FOUND : ret;
    }

    
Search a CharSequence to find the first index of any
character in the given set of characters.
A null String will return -1. A null search string will return -1.
StringUtils.indexOfAny(null, *)            = -1
StringUtils.indexOfAny("", *)              = -1
StringUtils.indexOfAny(*, null)            = -1
StringUtils.indexOfAny(*, "")              = -1
StringUtils.indexOfAny("zzabyycdxx", "za") = 0
StringUtils.indexOfAny("zzabyycdxx", "by") = 3
StringUtils.indexOfAny("aba", "z")         = -1

Params:
cs –  the CharSequence to check, may be null
searchChars –  the chars to search for, may be null
Returns:
the index of any of the chars, -1 if no match or null input
Since:
2.0
Since:
3.0 Changed signature from indexOfAny(String, String) to indexOfAny(CharSequence, String)/**
     * <p>Search a CharSequence to find the first index of any
     * character in the given set of characters.</p>
     *
     * <p>A {@code null} String will return {@code -1}.
     * A {@code null} search string will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.indexOfAny(null, *)            = -1
     * StringUtils.indexOfAny("", *)              = -1
     * StringUtils.indexOfAny(*, null)            = -1
     * StringUtils.indexOfAny(*, "")              = -1
     * StringUtils.indexOfAny("zzabyycdxx", "za") = 0
     * StringUtils.indexOfAny("zzabyycdxx", "by") = 3
     * StringUtils.indexOfAny("aba", "z")         = -1
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param searchChars  the chars to search for, may be null
     * @return the index of any of the chars, -1 if no match or null input
     * @since 2.0
     * @since 3.0 Changed signature from indexOfAny(String, String) to indexOfAny(CharSequence, String)
     */
    public static int indexOfAny(final CharSequence cs, final String searchChars) {
        if (isEmpty(cs) || isEmpty(searchChars)) {
            return INDEX_NOT_FOUND;
        }
        return indexOfAny(cs, searchChars.toCharArray());
    }

    // IndexOfAnyBut chars
    //-----------------------------------------------------------------------
    
Searches a CharSequence to find the first index of any
character not in the given set of characters.
A null CharSequence will return -1. A null or zero length search array will return -1.
StringUtils.indexOfAnyBut(null, *)                              = -1
StringUtils.indexOfAnyBut("", *)                                = -1
StringUtils.indexOfAnyBut(*, null)                              = -1
StringUtils.indexOfAnyBut(*, [])                                = -1
StringUtils.indexOfAnyBut("zzabyycdxx", new char[] {'z', 'a'} ) = 3
StringUtils.indexOfAnyBut("aba", new char[] {'z'} )             = 0
StringUtils.indexOfAnyBut("aba", new char[] {'a', 'b'} )        = -1

Params:
cs –  the CharSequence to check, may be null
searchChars –  the chars to search for, may be null
Returns:
the index of any of the chars, -1 if no match or null input
Since:
2.0
Since:
3.0 Changed signature from indexOfAnyBut(String, char[]) to indexOfAnyBut(CharSequence, char...)/**
     * <p>Searches a CharSequence to find the first index of any
     * character not in the given set of characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A {@code null} or zero length search array will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.indexOfAnyBut(null, *)                              = -1
     * StringUtils.indexOfAnyBut("", *)                                = -1
     * StringUtils.indexOfAnyBut(*, null)                              = -1
     * StringUtils.indexOfAnyBut(*, [])                                = -1
     * StringUtils.indexOfAnyBut("zzabyycdxx", new char[] {'z', 'a'} ) = 3
     * StringUtils.indexOfAnyBut("aba", new char[] {'z'} )             = 0
     * StringUtils.indexOfAnyBut("aba", new char[] {'a', 'b'} )        = -1

     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @param searchChars  the chars to search for, may be null
     * @return the index of any of the chars, -1 if no match or null input
     * @since 2.0
     * @since 3.0 Changed signature from indexOfAnyBut(String, char[]) to indexOfAnyBut(CharSequence, char...)
     */
    public static int indexOfAnyBut(final CharSequence cs, final char... searchChars) {
        if (isEmpty(cs) || ArrayUtils.isEmpty(searchChars)) {
            return INDEX_NOT_FOUND;
        }
        final int csLen = cs.length();
        final int csLast = csLen - 1;
        final int searchLen = searchChars.length;
        final int searchLast = searchLen - 1;
        outer:
        for (int i = 0; i < csLen; i++) {
            final char ch = cs.charAt(i);
            for (int j = 0; j < searchLen; j++) {
                if (searchChars[j] == ch) {
                    if (i < csLast && j < searchLast && Character.isHighSurrogate(ch)) {
                        if (searchChars[j + 1] == cs.charAt(i + 1)) {
                            continue outer;
                        }
                    } else {
                        continue outer;
                    }
                }
            }
            return i;
        }
        return INDEX_NOT_FOUND;
    }

    
Search a CharSequence to find the first index of any
character not in the given set of characters.
A null CharSequence will return -1. A null or empty search string will return -1.
StringUtils.indexOfAnyBut(null, *)            = -1
StringUtils.indexOfAnyBut("", *)              = -1
StringUtils.indexOfAnyBut(*, null)            = -1
StringUtils.indexOfAnyBut(*, "")              = -1
StringUtils.indexOfAnyBut("zzabyycdxx", "za") = 3
StringUtils.indexOfAnyBut("zzabyycdxx", "")   = -1
StringUtils.indexOfAnyBut("aba", "ab")        = -1

Params:
seq –  the CharSequence to check, may be null
searchChars –  the chars to search for, may be null
Returns:
the index of any of the chars, -1 if no match or null input
Since:
2.0
Since:
3.0 Changed signature from indexOfAnyBut(String, String) to indexOfAnyBut(CharSequence, CharSequence)/**
     * <p>Search a CharSequence to find the first index of any
     * character not in the given set of characters.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A {@code null} or empty search string will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.indexOfAnyBut(null, *)            = -1
     * StringUtils.indexOfAnyBut("", *)              = -1
     * StringUtils.indexOfAnyBut(*, null)            = -1
     * StringUtils.indexOfAnyBut(*, "")              = -1
     * StringUtils.indexOfAnyBut("zzabyycdxx", "za") = 3
     * StringUtils.indexOfAnyBut("zzabyycdxx", "")   = -1
     * StringUtils.indexOfAnyBut("aba", "ab")        = -1
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchChars  the chars to search for, may be null
     * @return the index of any of the chars, -1 if no match or null input
     * @since 2.0
     * @since 3.0 Changed signature from indexOfAnyBut(String, String) to indexOfAnyBut(CharSequence, CharSequence)
     */
    public static int indexOfAnyBut(final CharSequence seq, final CharSequence searchChars) {
        if (isEmpty(seq) || isEmpty(searchChars)) {
            return INDEX_NOT_FOUND;
        }
        final int strLen = seq.length();
        for (int i = 0; i < strLen; i++) {
            final char ch = seq.charAt(i);
            final boolean chFound = CharSequenceUtils.indexOf(searchChars, ch, 0) >= 0;
            if (i + 1 < strLen && Character.isHighSurrogate(ch)) {
                final char ch2 = seq.charAt(i + 1);
                if (chFound && CharSequenceUtils.indexOf(searchChars, ch2, 0) < 0) {
                    return i;
                }
            } else {
                if (!chFound) {
                    return i;
                }
            }
        }
        return INDEX_NOT_FOUND;
    }

    
Compares all CharSequences in an array and returns the index at which the
CharSequences begin to differ.
For example, indexOfDifference(new String[] {"i am a machine", "i am a robot"}) -> 7
StringUtils.indexOfDifference(null) = -1
StringUtils.indexOfDifference(new String[] {}) = -1
StringUtils.indexOfDifference(new String[] {"abc"}) = -1
StringUtils.indexOfDifference(new String[] {null, null}) = -1
StringUtils.indexOfDifference(new String[] {"", ""}) = -1
StringUtils.indexOfDifference(new String[] {"", null}) = 0
StringUtils.indexOfDifference(new String[] {"abc", null, null}) = 0
StringUtils.indexOfDifference(new String[] {null, null, "abc"}) = 0
StringUtils.indexOfDifference(new String[] {"", "abc"}) = 0
StringUtils.indexOfDifference(new String[] {"abc", ""}) = 0
StringUtils.indexOfDifference(new String[] {"abc", "abc"}) = -1
StringUtils.indexOfDifference(new String[] {"abc", "a"}) = 1
StringUtils.indexOfDifference(new String[] {"ab", "abxyz"}) = 2
StringUtils.indexOfDifference(new String[] {"abcde", "abxyz"}) = 2
StringUtils.indexOfDifference(new String[] {"abcde", "xyz"}) = 0
StringUtils.indexOfDifference(new String[] {"xyz", "abcde"}) = 0
StringUtils.indexOfDifference(new String[] {"i am a machine", "i am a robot"}) = 7

Params:
css –  array of CharSequences, entries may be null
Returns:
the index where the strings begin to differ; -1 if they are all equal
Since:
2.4
Since:
3.0 Changed signature from indexOfDifference(String...) to indexOfDifference(CharSequence...)/**
     * <p>Compares all CharSequences in an array and returns the index at which the
     * CharSequences begin to differ.</p>
     *
     * <p>For example,
     * {@code indexOfDifference(new String[] {"i am a machine", "i am a robot"}) -> 7}</p>
     *
     * <pre>
     * StringUtils.indexOfDifference(null) = -1
     * StringUtils.indexOfDifference(new String[] {}) = -1
     * StringUtils.indexOfDifference(new String[] {"abc"}) = -1
     * StringUtils.indexOfDifference(new String[] {null, null}) = -1
     * StringUtils.indexOfDifference(new String[] {"", ""}) = -1
     * StringUtils.indexOfDifference(new String[] {"", null}) = 0
     * StringUtils.indexOfDifference(new String[] {"abc", null, null}) = 0
     * StringUtils.indexOfDifference(new String[] {null, null, "abc"}) = 0
     * StringUtils.indexOfDifference(new String[] {"", "abc"}) = 0
     * StringUtils.indexOfDifference(new String[] {"abc", ""}) = 0
     * StringUtils.indexOfDifference(new String[] {"abc", "abc"}) = -1
     * StringUtils.indexOfDifference(new String[] {"abc", "a"}) = 1
     * StringUtils.indexOfDifference(new String[] {"ab", "abxyz"}) = 2
     * StringUtils.indexOfDifference(new String[] {"abcde", "abxyz"}) = 2
     * StringUtils.indexOfDifference(new String[] {"abcde", "xyz"}) = 0
     * StringUtils.indexOfDifference(new String[] {"xyz", "abcde"}) = 0
     * StringUtils.indexOfDifference(new String[] {"i am a machine", "i am a robot"}) = 7
     * </pre>
     *
     * @param css  array of CharSequences, entries may be null
     * @return the index where the strings begin to differ; -1 if they are all equal
     * @since 2.4
     * @since 3.0 Changed signature from indexOfDifference(String...) to indexOfDifference(CharSequence...)
     */
    public static int indexOfDifference(final CharSequence... css) {
        if (ArrayUtils.getLength(css) <= 1) {
            return INDEX_NOT_FOUND;
        }
        boolean anyStringNull = false;
        boolean allStringsNull = true;
        final int arrayLen = css.length;
        int shortestStrLen = Integer.MAX_VALUE;
        int longestStrLen = 0;

        // find the min and max string lengths; this avoids checking to make
        // sure we are not exceeding the length of the string each time through
        // the bottom loop.
        for (final CharSequence cs : css) {
            if (cs == null) {
                anyStringNull = true;
                shortestStrLen = 0;
            } else {
                allStringsNull = false;
                shortestStrLen = Math.min(cs.length(), shortestStrLen);
                longestStrLen = Math.max(cs.length(), longestStrLen);
            }
        }

        // handle lists containing all nulls or all empty strings
        if (allStringsNull || longestStrLen == 0 && !anyStringNull) {
            return INDEX_NOT_FOUND;
        }

        // handle lists containing some nulls or some empty strings
        if (shortestStrLen == 0) {
            return 0;
        }

        // find the position with the first difference across all strings
        int firstDiff = -1;
        for (int stringPos = 0; stringPos < shortestStrLen; stringPos++) {
            final char comparisonChar = css[0].charAt(stringPos);
            for (int arrayPos = 1; arrayPos < arrayLen; arrayPos++) {
                if (css[arrayPos].charAt(stringPos) != comparisonChar) {
                    firstDiff = stringPos;
                    break;
                }
            }
            if (firstDiff != -1) {
                break;
            }
        }

        if (firstDiff == -1 && shortestStrLen != longestStrLen) {
            // we compared all of the characters up to the length of the
            // shortest string and didn't find a match, but the string lengths
            // vary, so return the length of the shortest string.
            return shortestStrLen;
        }
        return firstDiff;
    }

    
Compares two CharSequences, and returns the index at which the
CharSequences begin to differ.
For example, indexOfDifference("i am a machine", "i am a robot") -> 7
StringUtils.indexOfDifference(null, null) = -1
StringUtils.indexOfDifference("", "") = -1
StringUtils.indexOfDifference("", "abc") = 0
StringUtils.indexOfDifference("abc", "") = 0
StringUtils.indexOfDifference("abc", "abc") = -1
StringUtils.indexOfDifference("ab", "abxyz") = 2
StringUtils.indexOfDifference("abcde", "abxyz") = 2
StringUtils.indexOfDifference("abcde", "xyz") = 0

Params:
cs1 –  the first CharSequence, may be null
cs2 –  the second CharSequence, may be null
Returns:
the index where cs1 and cs2 begin to differ; -1 if they are equal
Since:
2.0
Since:
3.0 Changed signature from indexOfDifference(String, String) to
indexOfDifference(CharSequence, CharSequence)/**
     * <p>Compares two CharSequences, and returns the index at which the
     * CharSequences begin to differ.</p>
     *
     * <p>For example,
     * {@code indexOfDifference("i am a machine", "i am a robot") -> 7}</p>
     *
     * <pre>
     * StringUtils.indexOfDifference(null, null) = -1
     * StringUtils.indexOfDifference("", "") = -1
     * StringUtils.indexOfDifference("", "abc") = 0
     * StringUtils.indexOfDifference("abc", "") = 0
     * StringUtils.indexOfDifference("abc", "abc") = -1
     * StringUtils.indexOfDifference("ab", "abxyz") = 2
     * StringUtils.indexOfDifference("abcde", "abxyz") = 2
     * StringUtils.indexOfDifference("abcde", "xyz") = 0
     * </pre>
     *
     * @param cs1  the first CharSequence, may be null
     * @param cs2  the second CharSequence, may be null
     * @return the index where cs1 and cs2 begin to differ; -1 if they are equal
     * @since 2.0
     * @since 3.0 Changed signature from indexOfDifference(String, String) to
     * indexOfDifference(CharSequence, CharSequence)
     */
    public static int indexOfDifference(final CharSequence cs1, final CharSequence cs2) {
        if (cs1 == cs2) {
            return INDEX_NOT_FOUND;
        }
        if (cs1 == null || cs2 == null) {
            return 0;
        }
        int i;
        for (i = 0; i < cs1.length() && i < cs2.length(); ++i) {
            if (cs1.charAt(i) != cs2.charAt(i)) {
                break;
            }
        }
        if (i < cs2.length() || i < cs1.length()) {
            return i;
        }
        return INDEX_NOT_FOUND;
    }

    
Case in-sensitive find of the first index within a CharSequence.
A null CharSequence will return -1. A negative start position is treated as zero. An empty ("") search CharSequence always matches. A start position greater than the string length only matches an empty search CharSequence.
StringUtils.indexOfIgnoreCase(null, *)          = -1
StringUtils.indexOfIgnoreCase(*, null)          = -1
StringUtils.indexOfIgnoreCase("", "")           = 0
StringUtils.indexOfIgnoreCase("aabaabaa", "a")  = 0
StringUtils.indexOfIgnoreCase("aabaabaa", "b")  = 2
StringUtils.indexOfIgnoreCase("aabaabaa", "ab") = 1

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
Returns:
the first index of the search CharSequence, -1 if no match or null string input
Since:
2.5
Since:
3.0 Changed signature from indexOfIgnoreCase(String, String) to indexOfIgnoreCase(CharSequence, CharSequence)/**
     * <p>Case in-sensitive find of the first index within a CharSequence.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position is treated as zero.
     * An empty ("") search CharSequence always matches.
     * A start position greater than the string length only matches
     * an empty search CharSequence.</p>
     *
     * <pre>
     * StringUtils.indexOfIgnoreCase(null, *)          = -1
     * StringUtils.indexOfIgnoreCase(*, null)          = -1
     * StringUtils.indexOfIgnoreCase("", "")           = 0
     * StringUtils.indexOfIgnoreCase("aabaabaa", "a")  = 0
     * StringUtils.indexOfIgnoreCase("aabaabaa", "b")  = 2
     * StringUtils.indexOfIgnoreCase("aabaabaa", "ab") = 1
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @return the first index of the search CharSequence,
     *  -1 if no match or {@code null} string input
     * @since 2.5
     * @since 3.0 Changed signature from indexOfIgnoreCase(String, String) to indexOfIgnoreCase(CharSequence, CharSequence)
     */
    public static int indexOfIgnoreCase(final CharSequence str, final CharSequence searchStr) {
        return indexOfIgnoreCase(str, searchStr, 0);
    }

    
Case in-sensitive find of the first index within a CharSequence
from the specified position.
A null CharSequence will return -1. A negative start position is treated as zero. An empty ("") search CharSequence always matches. A start position greater than the string length only matches an empty search CharSequence.
StringUtils.indexOfIgnoreCase(null, *, *)          = -1
StringUtils.indexOfIgnoreCase(*, null, *)          = -1
StringUtils.indexOfIgnoreCase("", "", 0)           = 0
StringUtils.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
StringUtils.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
StringUtils.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
StringUtils.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
StringUtils.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
StringUtils.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
StringUtils.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
StringUtils.indexOfIgnoreCase("abc", "", 9)        = -1

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
startPos –  the start position, negative treated as zero
Returns:
the first index of the search CharSequence (always ≥ startPos), -1 if no match or null string input
Since:
2.5
Since:
3.0 Changed signature from indexOfIgnoreCase(String, String, int) to indexOfIgnoreCase(CharSequence, CharSequence, int)/**
     * <p>Case in-sensitive find of the first index within a CharSequence
     * from the specified position.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position is treated as zero.
     * An empty ("") search CharSequence always matches.
     * A start position greater than the string length only matches
     * an empty search CharSequence.</p>
     *
     * <pre>
     * StringUtils.indexOfIgnoreCase(null, *, *)          = -1
     * StringUtils.indexOfIgnoreCase(*, null, *)          = -1
     * StringUtils.indexOfIgnoreCase("", "", 0)           = 0
     * StringUtils.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
     * StringUtils.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
     * StringUtils.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
     * StringUtils.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
     * StringUtils.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
     * StringUtils.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
     * StringUtils.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
     * StringUtils.indexOfIgnoreCase("abc", "", 9)        = -1
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @param startPos  the start position, negative treated as zero
     * @return the first index of the search CharSequence (always &ge; startPos),
     *  -1 if no match or {@code null} string input
     * @since 2.5
     * @since 3.0 Changed signature from indexOfIgnoreCase(String, String, int) to indexOfIgnoreCase(CharSequence, CharSequence, int)
     */
    public static int indexOfIgnoreCase(final CharSequence str, final CharSequence searchStr, int startPos) {
        if (str == null || searchStr == null) {
            return INDEX_NOT_FOUND;
        }
        if (startPos < 0) {
            startPos = 0;
        }
        final int endLimit = str.length() - searchStr.length() + 1;
        if (startPos > endLimit) {
            return INDEX_NOT_FOUND;
        }
        if (searchStr.length() == 0) {
            return startPos;
        }
        for (int i = startPos; i < endLimit; i++) {
            if (CharSequenceUtils.regionMatches(str, true, i, searchStr, 0, searchStr.length())) {
                return i;
            }
        }
        return INDEX_NOT_FOUND;
    }

    
Checks if all of the CharSequences are empty (""), null or whitespace only.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.isAllBlank(null)             = true
StringUtils.isAllBlank(null, "foo")      = false
StringUtils.isAllBlank(null, null)       = true
StringUtils.isAllBlank("", "bar")        = false
StringUtils.isAllBlank("bob", "")        = false
StringUtils.isAllBlank("  bob  ", null)  = false
StringUtils.isAllBlank(" ", "bar")       = false
StringUtils.isAllBlank("foo", "bar")     = false
StringUtils.isAllBlank(new String[] {})  = true

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if all of the CharSequences are empty or null or whitespace only
Since:
3.6/**
     * <p>Checks if all of the CharSequences are empty (""), null or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isAllBlank(null)             = true
     * StringUtils.isAllBlank(null, "foo")      = false
     * StringUtils.isAllBlank(null, null)       = true
     * StringUtils.isAllBlank("", "bar")        = false
     * StringUtils.isAllBlank("bob", "")        = false
     * StringUtils.isAllBlank("  bob  ", null)  = false
     * StringUtils.isAllBlank(" ", "bar")       = false
     * StringUtils.isAllBlank("foo", "bar")     = false
     * StringUtils.isAllBlank(new String[] {})  = true
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if all of the CharSequences are empty or null or whitespace only
     * @since 3.6
     */
    public static boolean isAllBlank(final CharSequence... css) {
        if (ArrayUtils.isEmpty(css)) {
            return true;
        }
        for (final CharSequence cs : css) {
            if (isNotBlank(cs)) {
               return false;
            }
        }
        return true;
    }

    
Checks if all of the CharSequences are empty ("") or null.
StringUtils.isAllEmpty(null)             = true
StringUtils.isAllEmpty(null, "")         = true
StringUtils.isAllEmpty(new String[] {})  = true
StringUtils.isAllEmpty(null, "foo")      = false
StringUtils.isAllEmpty("", "bar")        = false
StringUtils.isAllEmpty("bob", "")        = false
StringUtils.isAllEmpty("  bob  ", null)  = false
StringUtils.isAllEmpty(" ", "bar")       = false
StringUtils.isAllEmpty("foo", "bar")     = false

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if all of the CharSequences are empty or null
Since:
3.6/**
     * <p>Checks if all of the CharSequences are empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isAllEmpty(null)             = true
     * StringUtils.isAllEmpty(null, "")         = true
     * StringUtils.isAllEmpty(new String[] {})  = true
     * StringUtils.isAllEmpty(null, "foo")      = false
     * StringUtils.isAllEmpty("", "bar")        = false
     * StringUtils.isAllEmpty("bob", "")        = false
     * StringUtils.isAllEmpty("  bob  ", null)  = false
     * StringUtils.isAllEmpty(" ", "bar")       = false
     * StringUtils.isAllEmpty("foo", "bar")     = false
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if all of the CharSequences are empty or null
     * @since 3.6
     */
    public static boolean isAllEmpty(final CharSequence... css) {
        if (ArrayUtils.isEmpty(css)) {
            return true;
        }
        for (final CharSequence cs : css) {
            if (isNotEmpty(cs)) {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only lowercase characters.
null will return false. An empty CharSequence (length()=0) will return false.
StringUtils.isAllLowerCase(null)   = false
StringUtils.isAllLowerCase("")     = false
StringUtils.isAllLowerCase("  ")   = false
StringUtils.isAllLowerCase("abc")  = true
StringUtils.isAllLowerCase("abC")  = false
StringUtils.isAllLowerCase("ab c") = false
StringUtils.isAllLowerCase("ab1c") = false
StringUtils.isAllLowerCase("ab/c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains lowercase characters, and is non-null
Since:
2.5
Since:
3.0 Changed signature from isAllLowerCase(String) to isAllLowerCase(CharSequence)/**
     * <p>Checks if the CharSequence contains only lowercase characters.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.isAllLowerCase(null)   = false
     * StringUtils.isAllLowerCase("")     = false
     * StringUtils.isAllLowerCase("  ")   = false
     * StringUtils.isAllLowerCase("abc")  = true
     * StringUtils.isAllLowerCase("abC")  = false
     * StringUtils.isAllLowerCase("ab c") = false
     * StringUtils.isAllLowerCase("ab1c") = false
     * StringUtils.isAllLowerCase("ab/c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains lowercase characters, and is non-null
     * @since 2.5
     * @since 3.0 Changed signature from isAllLowerCase(String) to isAllLowerCase(CharSequence)
     */
    public static boolean isAllLowerCase(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLowerCase(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only uppercase characters.
null will return false. An empty String (length()=0) will return false.
StringUtils.isAllUpperCase(null)   = false
StringUtils.isAllUpperCase("")     = false
StringUtils.isAllUpperCase("  ")   = false
StringUtils.isAllUpperCase("ABC")  = true
StringUtils.isAllUpperCase("aBC")  = false
StringUtils.isAllUpperCase("A C")  = false
StringUtils.isAllUpperCase("A1C")  = false
StringUtils.isAllUpperCase("A/C")  = false

Params:
cs – the CharSequence to check, may be null
Returns:
true if only contains uppercase characters, and is non-null
Since:
2.5
Since:
3.0 Changed signature from isAllUpperCase(String) to isAllUpperCase(CharSequence)/**
     * <p>Checks if the CharSequence contains only uppercase characters.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty String (length()=0) will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.isAllUpperCase(null)   = false
     * StringUtils.isAllUpperCase("")     = false
     * StringUtils.isAllUpperCase("  ")   = false
     * StringUtils.isAllUpperCase("ABC")  = true
     * StringUtils.isAllUpperCase("aBC")  = false
     * StringUtils.isAllUpperCase("A C")  = false
     * StringUtils.isAllUpperCase("A1C")  = false
     * StringUtils.isAllUpperCase("A/C")  = false
     * </pre>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if only contains uppercase characters, and is non-null
     * @since 2.5
     * @since 3.0 Changed signature from isAllUpperCase(String) to isAllUpperCase(CharSequence)
     */
    public static boolean isAllUpperCase(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isUpperCase(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    // Character Tests
    //-----------------------------------------------------------------------
    
Checks if the CharSequence contains only Unicode letters.
null will return false. An empty CharSequence (length()=0) will return false.
StringUtils.isAlpha(null)   = false
StringUtils.isAlpha("")     = false
StringUtils.isAlpha("  ")   = false
StringUtils.isAlpha("abc")  = true
StringUtils.isAlpha("ab2c") = false
StringUtils.isAlpha("ab-c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains letters, and is non-null
Since:
3.0 Changed signature from isAlpha(String) to isAlpha(CharSequence)
Since:
3.0 Changed "" to return false and not true/**
     * <p>Checks if the CharSequence contains only Unicode letters.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.isAlpha(null)   = false
     * StringUtils.isAlpha("")     = false
     * StringUtils.isAlpha("  ")   = false
     * StringUtils.isAlpha("abc")  = true
     * StringUtils.isAlpha("ab2c") = false
     * StringUtils.isAlpha("ab-c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains letters, and is non-null
     * @since 3.0 Changed signature from isAlpha(String) to isAlpha(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isAlpha(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetter(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only Unicode letters or digits.
null will return false. An empty CharSequence (length()=0) will return false.
StringUtils.isAlphanumeric(null)   = false
StringUtils.isAlphanumeric("")     = false
StringUtils.isAlphanumeric("  ")   = false
StringUtils.isAlphanumeric("abc")  = true
StringUtils.isAlphanumeric("ab c") = false
StringUtils.isAlphanumeric("ab2c") = true
StringUtils.isAlphanumeric("ab-c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains letters or digits, and is non-null
Since:
3.0 Changed signature from isAlphanumeric(String) to isAlphanumeric(CharSequence)
Since:
3.0 Changed "" to return false and not true/**
     * <p>Checks if the CharSequence contains only Unicode letters or digits.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code false}.</p>
     *
     * <pre>
     * StringUtils.isAlphanumeric(null)   = false
     * StringUtils.isAlphanumeric("")     = false
     * StringUtils.isAlphanumeric("  ")   = false
     * StringUtils.isAlphanumeric("abc")  = true
     * StringUtils.isAlphanumeric("ab c") = false
     * StringUtils.isAlphanumeric("ab2c") = true
     * StringUtils.isAlphanumeric("ab-c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains letters or digits,
     *  and is non-null
     * @since 3.0 Changed signature from isAlphanumeric(String) to isAlphanumeric(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isAlphanumeric(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetterOrDigit(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only Unicode letters, digits or space (' ').
null will return false. An empty CharSequence (length()=0) will return true.
StringUtils.isAlphanumericSpace(null)   = false
StringUtils.isAlphanumericSpace("")     = true
StringUtils.isAlphanumericSpace("  ")   = true
StringUtils.isAlphanumericSpace("abc")  = true
StringUtils.isAlphanumericSpace("ab c") = true
StringUtils.isAlphanumericSpace("ab2c") = true
StringUtils.isAlphanumericSpace("ab-c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains letters, digits or space, and is non-null
Since:
3.0 Changed signature from isAlphanumericSpace(String) to isAlphanumericSpace(CharSequence)/**
     * <p>Checks if the CharSequence contains only Unicode letters, digits
     * or space ({@code ' '}).</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code true}.</p>
     *
     * <pre>
     * StringUtils.isAlphanumericSpace(null)   = false
     * StringUtils.isAlphanumericSpace("")     = true
     * StringUtils.isAlphanumericSpace("  ")   = true
     * StringUtils.isAlphanumericSpace("abc")  = true
     * StringUtils.isAlphanumericSpace("ab c") = true
     * StringUtils.isAlphanumericSpace("ab2c") = true
     * StringUtils.isAlphanumericSpace("ab-c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains letters, digits or space,
     *  and is non-null
     * @since 3.0 Changed signature from isAlphanumericSpace(String) to isAlphanumericSpace(CharSequence)
     */
    public static boolean isAlphanumericSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetterOrDigit(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only Unicode letters and
space (' ').
null will return false An empty CharSequence (length()=0) will return true.
StringUtils.isAlphaSpace(null)   = false
StringUtils.isAlphaSpace("")     = true
StringUtils.isAlphaSpace("  ")   = true
StringUtils.isAlphaSpace("abc")  = true
StringUtils.isAlphaSpace("ab c") = true
StringUtils.isAlphaSpace("ab2c") = false
StringUtils.isAlphaSpace("ab-c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains letters and space, and is non-null
Since:
3.0 Changed signature from isAlphaSpace(String) to isAlphaSpace(CharSequence)/**
     * <p>Checks if the CharSequence contains only Unicode letters and
     * space (' ').</p>
     *
     * <p>{@code null} will return {@code false}
     * An empty CharSequence (length()=0) will return {@code true}.</p>
     *
     * <pre>
     * StringUtils.isAlphaSpace(null)   = false
     * StringUtils.isAlphaSpace("")     = true
     * StringUtils.isAlphaSpace("  ")   = true
     * StringUtils.isAlphaSpace("abc")  = true
     * StringUtils.isAlphaSpace("ab c") = true
     * StringUtils.isAlphaSpace("ab2c") = false
     * StringUtils.isAlphaSpace("ab-c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains letters and space,
     *  and is non-null
     * @since 3.0 Changed signature from isAlphaSpace(String) to isAlphaSpace(CharSequence)
     */
    public static boolean isAlphaSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetter(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    
Checks if any of the CharSequences are empty ("") or null or whitespace only.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.isAnyBlank((String) null)    = true
StringUtils.isAnyBlank((String[]) null)  = false
StringUtils.isAnyBlank(null, "foo")      = true
StringUtils.isAnyBlank(null, null)       = true
StringUtils.isAnyBlank("", "bar")        = true
StringUtils.isAnyBlank("bob", "")        = true
StringUtils.isAnyBlank("  bob  ", null)  = true
StringUtils.isAnyBlank(" ", "bar")       = true
StringUtils.isAnyBlank(new String[] {})  = false
StringUtils.isAnyBlank(new String[]{""}) = true
StringUtils.isAnyBlank("foo", "bar")     = false

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if any of the CharSequences are empty or null or whitespace only
Since:
3.2/**
     * <p>Checks if any of the CharSequences are empty ("") or null or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isAnyBlank((String) null)    = true
     * StringUtils.isAnyBlank((String[]) null)  = false
     * StringUtils.isAnyBlank(null, "foo")      = true
     * StringUtils.isAnyBlank(null, null)       = true
     * StringUtils.isAnyBlank("", "bar")        = true
     * StringUtils.isAnyBlank("bob", "")        = true
     * StringUtils.isAnyBlank("  bob  ", null)  = true
     * StringUtils.isAnyBlank(" ", "bar")       = true
     * StringUtils.isAnyBlank(new String[] {})  = false
     * StringUtils.isAnyBlank(new String[]{""}) = true
     * StringUtils.isAnyBlank("foo", "bar")     = false
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if any of the CharSequences are empty or null or whitespace only
     * @since 3.2
     */
    public static boolean isAnyBlank(final CharSequence... css) {
      if (ArrayUtils.isEmpty(css)) {
        return false;
      }
      for (final CharSequence cs : css) {
        if (isBlank(cs)) {
          return true;
        }
      }
      return false;
    }

    
Checks if any of the CharSequences are empty ("") or null.
StringUtils.isAnyEmpty((String) null)    = true
StringUtils.isAnyEmpty((String[]) null)  = false
StringUtils.isAnyEmpty(null, "foo")      = true
StringUtils.isAnyEmpty("", "bar")        = true
StringUtils.isAnyEmpty("bob", "")        = true
StringUtils.isAnyEmpty("  bob  ", null)  = true
StringUtils.isAnyEmpty(" ", "bar")       = false
StringUtils.isAnyEmpty("foo", "bar")     = false
StringUtils.isAnyEmpty(new String[]{})   = false
StringUtils.isAnyEmpty(new String[]{""}) = true

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if any of the CharSequences are empty or null
Since:
3.2/**
     * <p>Checks if any of the CharSequences are empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isAnyEmpty((String) null)    = true
     * StringUtils.isAnyEmpty((String[]) null)  = false
     * StringUtils.isAnyEmpty(null, "foo")      = true
     * StringUtils.isAnyEmpty("", "bar")        = true
     * StringUtils.isAnyEmpty("bob", "")        = true
     * StringUtils.isAnyEmpty("  bob  ", null)  = true
     * StringUtils.isAnyEmpty(" ", "bar")       = false
     * StringUtils.isAnyEmpty("foo", "bar")     = false
     * StringUtils.isAnyEmpty(new String[]{})   = false
     * StringUtils.isAnyEmpty(new String[]{""}) = true
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if any of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isAnyEmpty(final CharSequence... css) {
      if (ArrayUtils.isEmpty(css)) {
        return false;
      }
      for (final CharSequence cs : css) {
        if (isEmpty(cs)) {
          return true;
        }
      }
      return false;
    }

    
Checks if the CharSequence contains only ASCII printable characters.
null will return false. An empty CharSequence (length()=0) will return true.
StringUtils.isAsciiPrintable(null)     = false
StringUtils.isAsciiPrintable("")       = true
StringUtils.isAsciiPrintable(" ")      = true
StringUtils.isAsciiPrintable("Ceki")   = true
StringUtils.isAsciiPrintable("ab2c")   = true
StringUtils.isAsciiPrintable("!ab-c~") = true
StringUtils.isAsciiPrintable("\u0020") = true
StringUtils.isAsciiPrintable("\u0021") = true
StringUtils.isAsciiPrintable("\u007e") = true
StringUtils.isAsciiPrintable("\u007f") = false
StringUtils.isAsciiPrintable("Ceki G\u00fclc\u00fc") = false

Params:
cs – the CharSequence to check, may be null
Returns:
true if every character is in the range 32 thru 126
Since:
2.1
Since:
3.0 Changed signature from isAsciiPrintable(String) to isAsciiPrintable(CharSequence)/**
     * <p>Checks if the CharSequence contains only ASCII printable characters.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code true}.</p>
     *
     * <pre>
     * StringUtils.isAsciiPrintable(null)     = false
     * StringUtils.isAsciiPrintable("")       = true
     * StringUtils.isAsciiPrintable(" ")      = true
     * StringUtils.isAsciiPrintable("Ceki")   = true
     * StringUtils.isAsciiPrintable("ab2c")   = true
     * StringUtils.isAsciiPrintable("!ab-c~") = true
     * StringUtils.isAsciiPrintable("\u0020") = true
     * StringUtils.isAsciiPrintable("\u0021") = true
     * StringUtils.isAsciiPrintable("\u007e") = true
     * StringUtils.isAsciiPrintable("\u007f") = false
     * StringUtils.isAsciiPrintable("Ceki G\u00fclc\u00fc") = false
     * </pre>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if every character is in the range
     *  32 thru 126
     * @since 2.1
     * @since 3.0 Changed signature from isAsciiPrintable(String) to isAsciiPrintable(CharSequence)
     */
    public static boolean isAsciiPrintable(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!CharUtils.isAsciiPrintable(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    // Nested extraction
    //-----------------------------------------------------------------------

    
Checks if a CharSequence is empty (""), null or whitespace only.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.isBlank(null)      = true
StringUtils.isBlank("")        = true
StringUtils.isBlank(" ")       = true
StringUtils.isBlank("bob")     = false
StringUtils.isBlank("  bob  ") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if the CharSequence is null, empty or whitespace only
Since:
2.0
Since:
3.0 Changed signature from isBlank(String) to isBlank(CharSequence)/**
     * <p>Checks if a CharSequence is empty (""), null or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isBlank(null)      = true
     * StringUtils.isBlank("")        = true
     * StringUtils.isBlank(" ")       = true
     * StringUtils.isBlank("bob")     = false
     * StringUtils.isBlank("  bob  ") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is null, empty or whitespace only
     * @since 2.0
     * @since 3.0 Changed signature from isBlank(String) to isBlank(CharSequence)
     */
    public static boolean isBlank(final CharSequence cs) {
        final int strLen = length(cs);
        if (strLen == 0) {
            return true;
        }
        for (int i = 0; i < strLen; i++) {
            if (!Character.isWhitespace(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    // Empty checks
    //-----------------------------------------------------------------------
    
Checks if a CharSequence is empty ("") or null.
StringUtils.isEmpty(null)      = true
StringUtils.isEmpty("")        = true
StringUtils.isEmpty(" ")       = false
StringUtils.isEmpty("bob")     = false
StringUtils.isEmpty("  bob  ") = false

NOTE: This method changed in Lang version 2.0.
It no longer trims the CharSequence.
That functionality is available in isBlank().
Params:
cs –  the CharSequence to check, may be null
Returns:
true if the CharSequence is empty or null
Since:
3.0 Changed signature from isEmpty(String) to isEmpty(CharSequence)/**
     * <p>Checks if a CharSequence is empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the CharSequence.
     * That functionality is available in isBlank().</p>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is empty or null
     * @since 3.0 Changed signature from isEmpty(String) to isEmpty(CharSequence)
     */
    public static boolean isEmpty(final CharSequence cs) {
        return cs == null || cs.length() == 0;
    }

    
Checks if the CharSequence contains mixed casing of both uppercase and lowercase characters.
null will return false. An empty CharSequence (length()=0) will return false.
StringUtils.isMixedCase(null)    = false
StringUtils.isMixedCase("")      = false
StringUtils.isMixedCase("ABC")   = false
StringUtils.isMixedCase("abc")   = false
StringUtils.isMixedCase("aBc")   = true
StringUtils.isMixedCase("A c")   = true
StringUtils.isMixedCase("A1c")   = true
StringUtils.isMixedCase("a/C")   = true
StringUtils.isMixedCase("aC\t")  = true

Params:
cs – the CharSequence to check, may be null
Returns:
true if the CharSequence contains both uppercase and lowercase characters
Since:
3.5/**
     * <p>Checks if the CharSequence contains mixed casing of both uppercase and lowercase characters.</p>
     *
     * <p>{@code null} will return {@code false}. An empty CharSequence ({@code length()=0}) will return
     * {@code false}.</p>
     *
     * <pre>
     * StringUtils.isMixedCase(null)    = false
     * StringUtils.isMixedCase("")      = false
     * StringUtils.isMixedCase("ABC")   = false
     * StringUtils.isMixedCase("abc")   = false
     * StringUtils.isMixedCase("aBc")   = true
     * StringUtils.isMixedCase("A c")   = true
     * StringUtils.isMixedCase("A1c")   = true
     * StringUtils.isMixedCase("a/C")   = true
     * StringUtils.isMixedCase("aC\t")  = true
     * </pre>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if the CharSequence contains both uppercase and lowercase characters
     * @since 3.5
     */
    public static boolean isMixedCase(final CharSequence cs) {
        if (isEmpty(cs) || cs.length() == 1) {
            return false;
        }
        boolean containsUppercase = false;
        boolean containsLowercase = false;
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (containsUppercase && containsLowercase) {
                return true;
            } else if (Character.isUpperCase(cs.charAt(i))) {
                containsUppercase = true;
            } else if (Character.isLowerCase(cs.charAt(i))) {
                containsLowercase = true;
            }
        }
        return containsUppercase && containsLowercase;
    }

    
Checks if none of the CharSequences are empty (""), null or whitespace only.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.isNoneBlank((String) null)    = false
StringUtils.isNoneBlank((String[]) null)  = true
StringUtils.isNoneBlank(null, "foo")      = false
StringUtils.isNoneBlank(null, null)       = false
StringUtils.isNoneBlank("", "bar")        = false
StringUtils.isNoneBlank("bob", "")        = false
StringUtils.isNoneBlank("  bob  ", null)  = false
StringUtils.isNoneBlank(" ", "bar")       = false
StringUtils.isNoneBlank(new String[] {})  = true
StringUtils.isNoneBlank(new String[]{""}) = false
StringUtils.isNoneBlank("foo", "bar")     = true

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if none of the CharSequences are empty or null or whitespace only
Since:
3.2/**
     * <p>Checks if none of the CharSequences are empty (""), null or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isNoneBlank((String) null)    = false
     * StringUtils.isNoneBlank((String[]) null)  = true
     * StringUtils.isNoneBlank(null, "foo")      = false
     * StringUtils.isNoneBlank(null, null)       = false
     * StringUtils.isNoneBlank("", "bar")        = false
     * StringUtils.isNoneBlank("bob", "")        = false
     * StringUtils.isNoneBlank("  bob  ", null)  = false
     * StringUtils.isNoneBlank(" ", "bar")       = false
     * StringUtils.isNoneBlank(new String[] {})  = true
     * StringUtils.isNoneBlank(new String[]{""}) = false
     * StringUtils.isNoneBlank("foo", "bar")     = true
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if none of the CharSequences are empty or null or whitespace only
     * @since 3.2
     */
    public static boolean isNoneBlank(final CharSequence... css) {
      return !isAnyBlank(css);
    }

    
Checks if none of the CharSequences are empty ("") or null.
StringUtils.isNoneEmpty((String) null)    = false
StringUtils.isNoneEmpty((String[]) null)  = true
StringUtils.isNoneEmpty(null, "foo")      = false
StringUtils.isNoneEmpty("", "bar")        = false
StringUtils.isNoneEmpty("bob", "")        = false
StringUtils.isNoneEmpty("  bob  ", null)  = false
StringUtils.isNoneEmpty(new String[] {})  = true
StringUtils.isNoneEmpty(new String[]{""}) = false
StringUtils.isNoneEmpty(" ", "bar")       = true
StringUtils.isNoneEmpty("foo", "bar")     = true

Params:
css –  the CharSequences to check, may be null or empty
Returns:
true if none of the CharSequences are empty or null
Since:
3.2/**
     * <p>Checks if none of the CharSequences are empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isNoneEmpty((String) null)    = false
     * StringUtils.isNoneEmpty((String[]) null)  = true
     * StringUtils.isNoneEmpty(null, "foo")      = false
     * StringUtils.isNoneEmpty("", "bar")        = false
     * StringUtils.isNoneEmpty("bob", "")        = false
     * StringUtils.isNoneEmpty("  bob  ", null)  = false
     * StringUtils.isNoneEmpty(new String[] {})  = true
     * StringUtils.isNoneEmpty(new String[]{""}) = false
     * StringUtils.isNoneEmpty(" ", "bar")       = true
     * StringUtils.isNoneEmpty("foo", "bar")     = true
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if none of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isNoneEmpty(final CharSequence... css) {
      return !isAnyEmpty(css);
    }

    
Checks if a CharSequence is not empty (""), not null and not whitespace only.
Whitespace is defined by Character.isWhitespace(char).
StringUtils.isNotBlank(null)      = false
StringUtils.isNotBlank("")        = false
StringUtils.isNotBlank(" ")       = false
StringUtils.isNotBlank("bob")     = true
StringUtils.isNotBlank("  bob  ") = true

Params:
cs –  the CharSequence to check, may be null
Returns:
true if the CharSequence is not empty and not null and not whitespace only
Since:
2.0
Since:
3.0 Changed signature from isNotBlank(String) to isNotBlank(CharSequence)/**
     * <p>Checks if a CharSequence is not empty (""), not null and not whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isNotBlank(null)      = false
     * StringUtils.isNotBlank("")        = false
     * StringUtils.isNotBlank(" ")       = false
     * StringUtils.isNotBlank("bob")     = true
     * StringUtils.isNotBlank("  bob  ") = true
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is
     *  not empty and not null and not whitespace only
     * @since 2.0
     * @since 3.0 Changed signature from isNotBlank(String) to isNotBlank(CharSequence)
     */
    public static boolean isNotBlank(final CharSequence cs) {
        return !isBlank(cs);
    }

    
Checks if a CharSequence is not empty ("") and not null.
StringUtils.isNotEmpty(null)      = false
StringUtils.isNotEmpty("")        = false
StringUtils.isNotEmpty(" ")       = true
StringUtils.isNotEmpty("bob")     = true
StringUtils.isNotEmpty("  bob  ") = true

Params:
cs –  the CharSequence to check, may be null
Returns:
true if the CharSequence is not empty and not null
Since:
3.0 Changed signature from isNotEmpty(String) to isNotEmpty(CharSequence)/**
     * <p>Checks if a CharSequence is not empty ("") and not null.</p>
     *
     * <pre>
     * StringUtils.isNotEmpty(null)      = false
     * StringUtils.isNotEmpty("")        = false
     * StringUtils.isNotEmpty(" ")       = true
     * StringUtils.isNotEmpty("bob")     = true
     * StringUtils.isNotEmpty("  bob  ") = true
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is not empty and not null
     * @since 3.0 Changed signature from isNotEmpty(String) to isNotEmpty(CharSequence)
     */
    public static boolean isNotEmpty(final CharSequence cs) {
        return !isEmpty(cs);
    }

    
Checks if the CharSequence contains only Unicode digits.
A decimal point is not a Unicode digit and returns false.
null will return false. An empty CharSequence (length()=0) will return false.
Note that the method does not allow for a leading sign, either positive or negative.
Also, if a String passes the numeric test, it may still generate a NumberFormatException
when parsed by Integer.parseInt or Long.parseLong, e.g. if the value is outside the range
for int or long respectively.
StringUtils.isNumeric(null)   = false
StringUtils.isNumeric("")     = false
StringUtils.isNumeric("  ")   = false
StringUtils.isNumeric("123")  = true
StringUtils.isNumeric("\u0967\u0968\u0969")  = true
StringUtils.isNumeric("12 3") = false
StringUtils.isNumeric("ab2c") = false
StringUtils.isNumeric("12-3") = false
StringUtils.isNumeric("12.3") = false
StringUtils.isNumeric("-123") = false
StringUtils.isNumeric("+123") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains digits, and is non-null
Since:
3.0 Changed signature from isNumeric(String) to isNumeric(CharSequence)
Since:
3.0 Changed "" to return false and not true/**
     * <p>Checks if the CharSequence contains only Unicode digits.
     * A decimal point is not a Unicode digit and returns false.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code false}.</p>
     *
     * <p>Note that the method does not allow for a leading sign, either positive or negative.
     * Also, if a String passes the numeric test, it may still generate a NumberFormatException
     * when parsed by Integer.parseInt or Long.parseLong, e.g. if the value is outside the range
     * for int or long respectively.</p>
     *
     * <pre>
     * StringUtils.isNumeric(null)   = false
     * StringUtils.isNumeric("")     = false
     * StringUtils.isNumeric("  ")   = false
     * StringUtils.isNumeric("123")  = true
     * StringUtils.isNumeric("\u0967\u0968\u0969")  = true
     * StringUtils.isNumeric("12 3") = false
     * StringUtils.isNumeric("ab2c") = false
     * StringUtils.isNumeric("12-3") = false
     * StringUtils.isNumeric("12.3") = false
     * StringUtils.isNumeric("-123") = false
     * StringUtils.isNumeric("+123") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains digits, and is non-null
     * @since 3.0 Changed signature from isNumeric(String) to isNumeric(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isNumeric(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isDigit(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only Unicode digits or space (' '). A decimal point is not a Unicode digit and returns false.
null will return false. An empty CharSequence (length()=0) will return true.
StringUtils.isNumericSpace(null)   = false
StringUtils.isNumericSpace("")     = true
StringUtils.isNumericSpace("  ")   = true
StringUtils.isNumericSpace("123")  = true
StringUtils.isNumericSpace("12 3") = true
StringUtils.isNumeric("\u0967\u0968\u0969")  = true
StringUtils.isNumeric("\u0967\u0968 \u0969")  = true
StringUtils.isNumericSpace("ab2c") = false
StringUtils.isNumericSpace("12-3") = false
StringUtils.isNumericSpace("12.3") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains digits or space, and is non-null
Since:
3.0 Changed signature from isNumericSpace(String) to isNumericSpace(CharSequence)/**
     * <p>Checks if the CharSequence contains only Unicode digits or space
     * ({@code ' '}).
     * A decimal point is not a Unicode digit and returns false.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code true}.</p>
     *
     * <pre>
     * StringUtils.isNumericSpace(null)   = false
     * StringUtils.isNumericSpace("")     = true
     * StringUtils.isNumericSpace("  ")   = true
     * StringUtils.isNumericSpace("123")  = true
     * StringUtils.isNumericSpace("12 3") = true
     * StringUtils.isNumeric("\u0967\u0968\u0969")  = true
     * StringUtils.isNumeric("\u0967\u0968 \u0969")  = true
     * StringUtils.isNumericSpace("ab2c") = false
     * StringUtils.isNumericSpace("12-3") = false
     * StringUtils.isNumericSpace("12.3") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains digits or space,
     *  and is non-null
     * @since 3.0 Changed signature from isNumericSpace(String) to isNumericSpace(CharSequence)
     */
    public static boolean isNumericSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isDigit(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    
Checks if the CharSequence contains only whitespace.
Whitespace is defined by Character.isWhitespace(char).
null will return false. An empty CharSequence (length()=0) will return true.
StringUtils.isWhitespace(null)   = false
StringUtils.isWhitespace("")     = true
StringUtils.isWhitespace("  ")   = true
StringUtils.isWhitespace("abc")  = false
StringUtils.isWhitespace("ab2c") = false
StringUtils.isWhitespace("ab-c") = false

Params:
cs –  the CharSequence to check, may be null
Returns:
true if only contains whitespace, and is non-null
Since:
2.0
Since:
3.0 Changed signature from isWhitespace(String) to isWhitespace(CharSequence)/**
     * <p>Checks if the CharSequence contains only whitespace.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code true}.</p>
     *
     * <pre>
     * StringUtils.isWhitespace(null)   = false
     * StringUtils.isWhitespace("")     = true
     * StringUtils.isWhitespace("  ")   = true
     * StringUtils.isWhitespace("abc")  = false
     * StringUtils.isWhitespace("ab2c") = false
     * StringUtils.isWhitespace("ab-c") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains whitespace, and is non-null
     * @since 2.0
     * @since 3.0 Changed signature from isWhitespace(String) to isWhitespace(CharSequence)
     */
    public static boolean isWhitespace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isWhitespace(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final byte[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final byte[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final char[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final char[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final double[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final double[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final float[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final float[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final int[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final int[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    
Joins the elements of the provided Iterable into a single String containing the provided elements.
No delimiter is added before or after the list. Null objects or empty
strings within the iteration are represented by empty strings.
See the examples here: join(Object[], char). 
Params:
iterable –  the Iterable providing the values to join together, may be null
separator –  the separator character to use
Returns:
the joined String, null if null iterator input
Since:
2.3/**
     * <p>Joins the elements of the provided {@code Iterable} into
     * a single String containing the provided elements.</p>
     *
     * <p>No delimiter is added before or after the list. Null objects or empty
     * strings within the iteration are represented by empty strings.</p>
     *
     * <p>See the examples here: {@link #join(Object[],char)}. </p>
     *
     * @param iterable  the {@code Iterable} providing the values to join together, may be null
     * @param separator  the separator character to use
     * @return the joined String, {@code null} if null iterator input
     * @since 2.3
     */
    public static String join(final Iterable<?> iterable, final char separator) {
        if (iterable == null) {
            return null;
        }
        return join(iterable.iterator(), separator);
    }

    
Joins the elements of the provided Iterable into a single String containing the provided elements.
No delimiter is added before or after the list. A null separator is the same as an empty String ("").
See the examples here: join(Object[], String). 
Params:
iterable –  the Iterable providing the values to join together, may be null
separator –  the separator character to use, null treated as ""
Returns:
the joined String, null if null iterator input
Since:
2.3/**
     * <p>Joins the elements of the provided {@code Iterable} into
     * a single String containing the provided elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A {@code null} separator is the same as an empty String ("").</p>
     *
     * <p>See the examples here: {@link #join(Object[],String)}. </p>
     *
     * @param iterable  the {@code Iterable} providing the values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, {@code null} if null iterator input
     * @since 2.3
     */
    public static String join(final Iterable<?> iterable, final String separator) {
        if (iterable == null) {
            return null;
        }
        return join(iterable.iterator(), separator);
    }

    
Joins the elements of the provided Iterator into a single String containing the provided elements.
No delimiter is added before or after the list. Null objects or empty
strings within the iteration are represented by empty strings.
See the examples here: join(Object[], char). 
Params:
iterator –  the Iterator of values to join together, may be null
separator –  the separator character to use
Returns:
the joined String, null if null iterator input
Since:
2.0/**
     * <p>Joins the elements of the provided {@code Iterator} into
     * a single String containing the provided elements.</p>
     *
     * <p>No delimiter is added before or after the list. Null objects or empty
     * strings within the iteration are represented by empty strings.</p>
     *
     * <p>See the examples here: {@link #join(Object[],char)}. </p>
     *
     * @param iterator  the {@code Iterator} of values to join together, may be null
     * @param separator  the separator character to use
     * @return the joined String, {@code null} if null iterator input
     * @since 2.0
     */
    public static String join(final Iterator<?> iterator, final char separator) {

        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        final Object first = iterator.next();
        if (!iterator.hasNext()) {
            return Objects.toString(first, EMPTY);
        }

        // two or more elements
        final StringBuilder buf = new StringBuilder(STRING_BUILDER_SIZE); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }

        while (iterator.hasNext()) {
            buf.append(separator);
            final Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }

        return buf.toString();
    }

    
Joins the elements of the provided Iterator into a single String containing the provided elements.
No delimiter is added before or after the list. A null separator is the same as an empty String ("").
See the examples here: join(Object[], String). 
Params:
iterator –  the Iterator of values to join together, may be null
separator –  the separator character to use, null treated as ""
Returns:
the joined String, null if null iterator input/**
     * <p>Joins the elements of the provided {@code Iterator} into
     * a single String containing the provided elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A {@code null} separator is the same as an empty String ("").</p>
     *
     * <p>See the examples here: {@link #join(Object[],String)}. </p>
     *
     * @param iterator  the {@code Iterator} of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, {@code null} if null iterator input
     */
    public static String join(final Iterator<?> iterator, final String separator) {

        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        final Object first = iterator.next();
        if (!iterator.hasNext()) {
            return Objects.toString(first, "");
        }

        // two or more elements
        final StringBuilder buf = new StringBuilder(STRING_BUILDER_SIZE); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }

        while (iterator.hasNext()) {
            if (separator != null) {
                buf.append(separator);
            }
            final Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }
        return buf.toString();
    }

    
Joins the elements of the provided List into a single String containing the provided list of elements.
No delimiter is added before or after the list.
Null objects or empty strings within the array are represented by
empty strings.
StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';')  = ";;a"

Params:
list –  the List of values to join together, may be null
separator –  the separator character to use
startIndex – the first index to start joining from.  It is
an error to pass in a start index past the end of the list
endIndex – the index to stop joining from (exclusive). It is
an error to pass in an end index past the end of the list
Returns:
the joined String, null if null list input
Since:
3.8/**
     * <p>Joins the elements of the provided {@code List} into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param list  the {@code List} of values to join together, may be null
     * @param separator  the separator character to use
     * @param startIndex the first index to start joining from.  It is
     * an error to pass in a start index past the end of the list
     * @param endIndex the index to stop joining from (exclusive). It is
     * an error to pass in an end index past the end of the list
     * @return the joined String, {@code null} if null list input
     * @since 3.8
     */
    public static String join(final List<?> list, final char separator, final int startIndex, final int endIndex) {
        if (list == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final List<?> subList = list.subList(startIndex, endIndex);
        return join(subList.iterator(), separator);
    }

    
Joins the elements of the provided List into a single String containing the provided list of elements.
No delimiter is added before or after the list.
Null objects or empty strings within the array are represented by
empty strings.
StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';')  = ";;a"

Params:
list –  the List of values to join together, may be null
separator –  the separator character to use
startIndex – the first index to start joining from.  It is
an error to pass in a start index past the end of the list
endIndex – the index to stop joining from (exclusive). It is
an error to pass in an end index past the end of the list
Returns:
the joined String, null if null list input
Since:
3.8/**
     * <p>Joins the elements of the provided {@code List} into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param list  the {@code List} of values to join together, may be null
     * @param separator  the separator character to use
     * @param startIndex the first index to start joining from.  It is
     * an error to pass in a start index past the end of the list
     * @param endIndex the index to stop joining from (exclusive). It is
     * an error to pass in an end index past the end of the list
     * @return the joined String, {@code null} if null list input
     * @since 3.8
     */
    public static String join(final List<?> list, final String separator, final int startIndex, final int endIndex) {
        if (list == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final List<?> subList = list.subList(startIndex, endIndex);
        return join(subList.iterator(), separator);
    }


    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final long[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final long[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }

    
Joins the elements of the provided array into a single String
containing the provided list of elements.
No delimiter is added before or after the list.
Null objects or empty strings within the array are represented by
empty strings.
StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';')  = ";;a"

Params:
array –  the array of values to join together, may be null
separator –  the separator character to use
Returns:
the joined String, null if null array input
Since:
2.0/**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 2.0
     */
    public static String join(final Object[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    
Joins the elements of the provided array into a single String
containing the provided list of elements.
No delimiter is added before or after the list.
Null objects or empty strings within the array are represented by
empty strings.
StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';')  = ";;a"

Params:
array –  the array of values to join together, may be null
separator –  the separator character to use
startIndex – the first index to start joining from.  It is
an error to pass in a start index past the end of the array
endIndex – the index to stop joining from (exclusive). It is
an error to pass in an end index past the end of the array
Returns:
the joined String, null if null array input
Since:
2.0/**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use
     * @param startIndex the first index to start joining from.  It is
     * an error to pass in a start index past the end of the array
     * @param endIndex the index to stop joining from (exclusive). It is
     * an error to pass in an end index past the end of the array
     * @return the joined String, {@code null} if null array input
     * @since 2.0
     */
    public static String join(final Object[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        if (array[startIndex] != null) {
            buf.append(array[startIndex]);
        }
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

    
Joins the elements of the provided array into a single String
containing the provided list of elements.
No delimiter is added before or after the list. A null separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.
StringUtils.join(null, *)                = null
StringUtils.join([], *)                  = ""
StringUtils.join([null], *)              = ""
StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
StringUtils.join(["a", "b", "c"], null)  = "abc"
StringUtils.join(["a", "b", "c"], "")    = "abc"
StringUtils.join([null, "", "a"], ',')   = ",,a"

Params:
array –  the array of values to join together, may be null
separator –  the separator character to use, null treated as ""
Returns:
the joined String, null if null array input/**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A {@code null} separator is the same as an empty String ("").
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)                = null
     * StringUtils.join([], *)                  = ""
     * StringUtils.join([null], *)              = ""
     * StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
     * StringUtils.join(["a", "b", "c"], null)  = "abc"
     * StringUtils.join(["a", "b", "c"], "")    = "abc"
     * StringUtils.join([null, "", "a"], ',')   = ",,a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, {@code null} if null array input
     */
    public static String join(final Object[] array, final String separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    
Joins the elements of the provided array into a single String
containing the provided list of elements.
No delimiter is added before or after the list. A null separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.
StringUtils.join(null, *, *, *)                = null
StringUtils.join([], *, *, *)                  = ""
StringUtils.join([null], *, *, *)              = ""
StringUtils.join(["a", "b", "c"], "--", 0, 3)  = "a--b--c"
StringUtils.join(["a", "b", "c"], "--", 1, 3)  = "b--c"
StringUtils.join(["a", "b", "c"], "--", 2, 3)  = "c"
StringUtils.join(["a", "b", "c"], "--", 2, 2)  = ""
StringUtils.join(["a", "b", "c"], null, 0, 3)  = "abc"
StringUtils.join(["a", "b", "c"], "", 0, 3)    = "abc"
StringUtils.join([null, "", "a"], ',', 0, 3)   = ",,a"

Params:
array –  the array of values to join together, may be null
separator –  the separator character to use, null treated as ""
startIndex – the first index to start joining from.
endIndex – the index to stop joining from (exclusive).
Throws:
ArrayIndexOutOfBoundsException – ife
 startIndex < 0 or 
 startIndex >= array.length() or 
 endIndex < 0 or 
 endIndex > array.length()
Returns:
the joined String, null if null array input; or the empty string if endIndex - startIndex <= 0. The number of joined entries is given by endIndex - startIndex/**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A {@code null} separator is the same as an empty String ("").
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *, *, *)                = null
     * StringUtils.join([], *, *, *)                  = ""
     * StringUtils.join([null], *, *, *)              = ""
     * StringUtils.join(["a", "b", "c"], "--", 0, 3)  = "a--b--c"
     * StringUtils.join(["a", "b", "c"], "--", 1, 3)  = "b--c"
     * StringUtils.join(["a", "b", "c"], "--", 2, 3)  = "c"
     * StringUtils.join(["a", "b", "c"], "--", 2, 2)  = ""
     * StringUtils.join(["a", "b", "c"], null, 0, 3)  = "abc"
     * StringUtils.join(["a", "b", "c"], "", 0, 3)    = "abc"
     * StringUtils.join([null, "", "a"], ',', 0, 3)   = ",,a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @param startIndex the first index to start joining from.
     * @param endIndex the index to stop joining from (exclusive).
     * @return the joined String, {@code null} if null array input; or the empty string
     * if {@code endIndex - startIndex <= 0}. The number of joined entries is given by
     * {@code endIndex - startIndex}
     * @throws ArrayIndexOutOfBoundsException ife<br>
     * {@code startIndex < 0} or <br>
     * {@code startIndex >= array.length()} or <br>
     * {@code endIndex < 0} or <br>
     * {@code endIndex > array.length()}
     */
    public static String join(final Object[] array, String separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        if (separator == null) {
            separator = EMPTY;
        }

        // endIndex - startIndex > 0:   Len = NofStrings *(len(firstString) + len(separator))
        //           (Assuming that all Strings are roughly equally long)
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }

        final StringBuilder buf = newStringBuilder(noOfItems);

        if (array[startIndex] != null) {
            buf.append(array[startIndex]);
        }

        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);

            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final short[] array, final char separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    

Joins the elements of the provided array into a single String containing the provided list of elements.


No delimiter is added before or after the list. Null objects or empty strings within the array are represented
by empty strings.

StringUtils.join(null, *)               = null
StringUtils.join([], *)                 = ""
StringUtils.join([null], *)             = ""
StringUtils.join([1, 2, 3], ';')  = "1;2;3"
StringUtils.join([1, 2, 3], null) = "123"

Params:
array – 
           the array of values to join together, may be null
separator – 
           the separator character to use
startIndex – 
           the first index to start joining from. It is an error to pass in a start index past the end of the
           array
endIndex – 
           the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
           the array
Returns:
the joined String, null if null array input
Since:
3.2/**
     * <p>
     * Joins the elements of the provided array into a single String containing the provided list of elements.
     * </p>
     *
     * <p>
     * No delimiter is added before or after the list. Null objects or empty strings within the array are represented
     * by empty strings.
     * </p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join([1, 2, 3], ';')  = "1;2;3"
     * StringUtils.join([1, 2, 3], null) = "123"
     * </pre>
     *
     * @param array
     *            the array of values to join together, may be null
     * @param separator
     *            the separator character to use
     * @param startIndex
     *            the first index to start joining from. It is an error to pass in a start index past the end of the
     *            array
     * @param endIndex
     *            the index to stop joining from (exclusive). It is an error to pass in an end index past the end of
     *            the array
     * @return the joined String, {@code null} if null array input
     * @since 3.2
     */
    public static String join(final short[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = newStringBuilder(noOfItems);
        buf.append(array[startIndex]);
        for (int i = startIndex + 1; i < endIndex; i++) {
            buf.append(separator);
            buf.append(array[i]);
        }
        return buf.toString();
    }


    // Joining
    //-----------------------------------------------------------------------
    
Joins the elements of the provided array into a single String
containing the provided list of elements.
No separator is added to the joined String.
Null objects or empty strings within the array are represented by
empty strings.
StringUtils.join(null)            = null
StringUtils.join([])              = ""
StringUtils.join([null])          = ""
StringUtils.join(["a", "b", "c"]) = "abc"
StringUtils.join([null, "", "a"]) = "a"

Params:
elements –  the values to join together, may be null
Type parameters:
<T> – the specific type of values to join together
Returns:
the joined String, null if null array input
Since:
2.0
Since:
3.0 Changed signature to use varargs/**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No separator is added to the joined String.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null)            = null
     * StringUtils.join([])              = ""
     * StringUtils.join([null])          = ""
     * StringUtils.join(["a", "b", "c"]) = "abc"
     * StringUtils.join([null, "", "a"]) = "a"
     * </pre>
     *
     * @param <T> the specific type of values to join together
     * @param elements  the values to join together, may be null
     * @return the joined String, {@code null} if null array input
     * @since 2.0
     * @since 3.0 Changed signature to use varargs
     */
    @SafeVarargs
    public static <T> String join(final T... elements) {
        return join(elements, null);
    }

    
Joins the elements of the provided varargs into a
single String containing the provided elements.
No delimiter is added before or after the list. null elements and separator are treated as empty Strings ("").
StringUtils.joinWith(",", {"a", "b"})        = "a,b"
StringUtils.joinWith(",", {"a", "b",""})     = "a,b,"
StringUtils.joinWith(",", {"a", null, "b"})  = "a,,b"
StringUtils.joinWith(null, {"a", "b"})       = "ab"

Params:
separator – the separator character to use, null treated as ""
objects – the varargs providing the values to join together. null elements are treated as ""
Throws:
IllegalArgumentException – if a null varargs is provided
Returns:
the joined String.
Since:
3.5/**
     * <p>Joins the elements of the provided varargs into a
     * single String containing the provided elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * {@code null} elements and separator are treated as empty Strings ("").</p>
     *
     * <pre>
     * StringUtils.joinWith(",", {"a", "b"})        = "a,b"
     * StringUtils.joinWith(",", {"a", "b",""})     = "a,b,"
     * StringUtils.joinWith(",", {"a", null, "b"})  = "a,,b"
     * StringUtils.joinWith(null, {"a", "b"})       = "ab"
     * </pre>
     *
     * @param separator the separator character to use, null treated as ""
     * @param objects the varargs providing the values to join together. {@code null} elements are treated as ""
     * @return the joined String.
     * @throws java.lang.IllegalArgumentException if a null varargs is provided
     * @since 3.5
     */
    public static String joinWith(final String separator, final Object... objects) {
        if (objects == null) {
            throw new IllegalArgumentException("Object varargs must not be null");
        }

        final String sanitizedSeparator = defaultString(separator);

        final StringBuilder result = new StringBuilder();

        final Iterator<Object> iterator = Arrays.asList(objects).iterator();
        while (iterator.hasNext()) {
            final String value = Objects.toString(iterator.next(), "");
            result.append(value);

            if (iterator.hasNext()) {
                result.append(sanitizedSeparator);
            }
        }

        return result.toString();
    }

    
Finds the last index within a CharSequence, handling null. This method uses String.lastIndexOf(String) if possible.
A null CharSequence will return -1.
StringUtils.lastIndexOf(null, *)          = -1
StringUtils.lastIndexOf(*, null)          = -1
StringUtils.lastIndexOf("", "")           = 0
StringUtils.lastIndexOf("aabaabaa", "a")  = 7
StringUtils.lastIndexOf("aabaabaa", "b")  = 5
StringUtils.lastIndexOf("aabaabaa", "ab") = 4
StringUtils.lastIndexOf("aabaabaa", "")   = 8

Params:
seq –  the CharSequence to check, may be null
searchSeq –  the CharSequence to find, may be null
Returns:
the last index of the search String, -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from lastIndexOf(String, String) to lastIndexOf(CharSequence, CharSequence)/**
     * <p>Finds the last index within a CharSequence, handling {@code null}.
     * This method uses {@link String#lastIndexOf(String)} if possible.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.lastIndexOf(null, *)          = -1
     * StringUtils.lastIndexOf(*, null)          = -1
     * StringUtils.lastIndexOf("", "")           = 0
     * StringUtils.lastIndexOf("aabaabaa", "a")  = 7
     * StringUtils.lastIndexOf("aabaabaa", "b")  = 5
     * StringUtils.lastIndexOf("aabaabaa", "ab") = 4
     * StringUtils.lastIndexOf("aabaabaa", "")   = 8
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchSeq  the CharSequence to find, may be null
     * @return the last index of the search String,
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from lastIndexOf(String, String) to lastIndexOf(CharSequence, CharSequence)
     */
    public static int lastIndexOf(final CharSequence seq, final CharSequence searchSeq) {
        if (seq == null || searchSeq == null) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.lastIndexOf(seq, searchSeq, seq.length());
    }

    
Finds the last index within a CharSequence, handling null. This method uses String.lastIndexOf(String, int) if possible.
A null CharSequence will return -1. A negative start position returns -1. An empty ("") search CharSequence always matches unless the start position is negative. A start position greater than the string length searches the whole string. The search starts at the startPos and works backwards; matches starting after the start position are ignored. 
StringUtils.lastIndexOf(null, *, *)          = -1
StringUtils.lastIndexOf(*, null, *)          = -1
StringUtils.lastIndexOf("aabaabaa", "a", 8)  = 7
StringUtils.lastIndexOf("aabaabaa", "b", 8)  = 5
StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
StringUtils.lastIndexOf("aabaabaa", "b", 9)  = 5
StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
StringUtils.lastIndexOf("aabaabaa", "a", 0)  = 0
StringUtils.lastIndexOf("aabaabaa", "b", 0)  = -1
StringUtils.lastIndexOf("aabaabaa", "b", 1)  = -1
StringUtils.lastIndexOf("aabaabaa", "b", 2)  = 2
StringUtils.lastIndexOf("aabaabaa", "ba", 2)  = 2

Params:
seq –  the CharSequence to check, may be null
searchSeq –  the CharSequence to find, may be null
startPos –  the start position, negative treated as zero
Returns:
the last index of the search CharSequence (always ≤ startPos), -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from lastIndexOf(String, String, int) to lastIndexOf(CharSequence, CharSequence, int)/**
     * <p>Finds the last index within a CharSequence, handling {@code null}.
     * This method uses {@link String#lastIndexOf(String, int)} if possible.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position returns {@code -1}.
     * An empty ("") search CharSequence always matches unless the start position is negative.
     * A start position greater than the string length searches the whole string.
     * The search starts at the startPos and works backwards; matches starting after the start
     * position are ignored.
     * </p>
     *
     * <pre>
     * StringUtils.lastIndexOf(null, *, *)          = -1
     * StringUtils.lastIndexOf(*, null, *)          = -1
     * StringUtils.lastIndexOf("aabaabaa", "a", 8)  = 7
     * StringUtils.lastIndexOf("aabaabaa", "b", 8)  = 5
     * StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
     * StringUtils.lastIndexOf("aabaabaa", "b", 9)  = 5
     * StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
     * StringUtils.lastIndexOf("aabaabaa", "a", 0)  = 0
     * StringUtils.lastIndexOf("aabaabaa", "b", 0)  = -1
     * StringUtils.lastIndexOf("aabaabaa", "b", 1)  = -1
     * StringUtils.lastIndexOf("aabaabaa", "b", 2)  = 2
     * StringUtils.lastIndexOf("aabaabaa", "ba", 2)  = 2
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchSeq  the CharSequence to find, may be null
     * @param startPos  the start position, negative treated as zero
     * @return the last index of the search CharSequence (always &le; startPos),
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from lastIndexOf(String, String, int) to lastIndexOf(CharSequence, CharSequence, int)
     */
    public static int lastIndexOf(final CharSequence seq, final CharSequence searchSeq, final int startPos) {
        if (seq == null || searchSeq == null) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.lastIndexOf(seq, searchSeq, startPos);
    }

    // LastIndexOf
    //-----------------------------------------------------------------------
    
Returns the index within seq of the last occurrence of the specified character. For values of searchChar in the range from 0 to 0xFFFF (inclusive), the index (in Unicode code units) returned is the largest value k such that:
this.charAt(k) == searchChar
 is true. For other values of searchChar, it is the largest value k such that:
this.codePointAt(k) == searchChar
 is true. In either case, if no such character occurs in this string, then -1 is returned. Furthermore, a null or empty ("") CharSequence will return -1. The seq CharSequence object is searched backwards starting at the last character. 
StringUtils.lastIndexOf(null, *)         = -1
StringUtils.lastIndexOf("", *)           = -1
StringUtils.lastIndexOf("aabaabaa", 'a') = 7
StringUtils.lastIndexOf("aabaabaa", 'b') = 5

Params:
seq –  the CharSequence to check, may be null
searchChar –  the character to find
Returns:
the last index of the search character, -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from lastIndexOf(String, int) to lastIndexOf(CharSequence, int)
Since:
3.6 Updated CharSequenceUtils call to behave more like String/**
     * Returns the index within {@code seq} of the last occurrence of
     * the specified character. For values of {@code searchChar} in the
     * range from 0 to 0xFFFF (inclusive), the index (in Unicode code
     * units) returned is the largest value <i>k</i> such that:
     * <blockquote><pre>
     * this.charAt(<i>k</i>) == searchChar
     * </pre></blockquote>
     * is true. For other values of {@code searchChar}, it is the
     * largest value <i>k</i> such that:
     * <blockquote><pre>
     * this.codePointAt(<i>k</i>) == searchChar
     * </pre></blockquote>
     * is true.  In either case, if no such character occurs in this
     * string, then {@code -1} is returned. Furthermore, a {@code null} or empty ("")
     * {@code CharSequence} will return {@code -1}. The
     * {@code seq} {@code CharSequence} object is searched backwards
     * starting at the last character.
     *
     * <pre>
     * StringUtils.lastIndexOf(null, *)         = -1
     * StringUtils.lastIndexOf("", *)           = -1
     * StringUtils.lastIndexOf("aabaabaa", 'a') = 7
     * StringUtils.lastIndexOf("aabaabaa", 'b') = 5
     * </pre>
     *
     * @param seq  the {@code CharSequence} to check, may be null
     * @param searchChar  the character to find
     * @return the last index of the search character,
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from lastIndexOf(String, int) to lastIndexOf(CharSequence, int)
     * @since 3.6 Updated {@link CharSequenceUtils} call to behave more like {@code String}
     */
    public static int lastIndexOf(final CharSequence seq, final int searchChar) {
        if (isEmpty(seq)) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.lastIndexOf(seq, searchChar, seq.length());
    }

    
Returns the index within seq of the last occurrence of the specified character, searching backward starting at the specified index. For values of searchChar in the range from 0 to 0xFFFF (inclusive), the index returned is the largest value k such that:
(this.charAt(k) == searchChar) && (k <= startPos)
 is true. For other values of searchChar, it is the largest value k such that:
(this.codePointAt(k) == searchChar) && (k <= startPos)
 is true. In either case, if no such character occurs in seq at or before position startPos, then -1 is returned. Furthermore, a null or empty ("") CharSequence will return -1. A start position greater than the string length searches the whole string. The search starts at the startPos and works backwards; matches starting after the start position are ignored. 
All indices are specified in char values (Unicode code units). 
StringUtils.lastIndexOf(null, *, *)          = -1
StringUtils.lastIndexOf("", *,  *)           = -1
StringUtils.lastIndexOf("aabaabaa", 'b', 8)  = 5
StringUtils.lastIndexOf("aabaabaa", 'b', 4)  = 2
StringUtils.lastIndexOf("aabaabaa", 'b', 0)  = -1
StringUtils.lastIndexOf("aabaabaa", 'b', 9)  = 5
StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1
StringUtils.lastIndexOf("aabaabaa", 'a', 0)  = 0

Params:
seq –  the CharSequence to check, may be null
searchChar –  the character to find
startPos –  the start position
Returns:
the last index of the search character (always ≤ startPos), -1 if no match or null string input
Since:
2.0
Since:
3.0 Changed signature from lastIndexOf(String, int, int) to lastIndexOf(CharSequence, int, int)/**
     * Returns the index within {@code seq} of the last occurrence of
     * the specified character, searching backward starting at the
     * specified index. For values of {@code searchChar} in the range
     * from 0 to 0xFFFF (inclusive), the index returned is the largest
     * value <i>k</i> such that:
     * <blockquote><pre>
     * (this.charAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &lt;= startPos)
     * </pre></blockquote>
     * is true. For other values of {@code searchChar}, it is the
     * largest value <i>k</i> such that:
     * <blockquote><pre>
     * (this.codePointAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &lt;= startPos)
     * </pre></blockquote>
     * is true. In either case, if no such character occurs in {@code seq}
     * at or before position {@code startPos}, then
     * {@code -1} is returned. Furthermore, a {@code null} or empty ("")
     * {@code CharSequence} will return {@code -1}. A start position greater
     * than the string length searches the whole string.
     * The search starts at the {@code startPos} and works backwards;
     * matches starting after the start position are ignored.
     *
     * <p>All indices are specified in {@code char} values
     * (Unicode code units).
     *
     * <pre>
     * StringUtils.lastIndexOf(null, *, *)          = -1
     * StringUtils.lastIndexOf("", *,  *)           = -1
     * StringUtils.lastIndexOf("aabaabaa", 'b', 8)  = 5
     * StringUtils.lastIndexOf("aabaabaa", 'b', 4)  = 2
     * StringUtils.lastIndexOf("aabaabaa", 'b', 0)  = -1
     * StringUtils.lastIndexOf("aabaabaa", 'b', 9)  = 5
     * StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1
     * StringUtils.lastIndexOf("aabaabaa", 'a', 0)  = 0
     * </pre>
     *
     * @param seq  the CharSequence to check, may be null
     * @param searchChar  the character to find
     * @param startPos  the start position
     * @return the last index of the search character (always &le; startPos),
     *  -1 if no match or {@code null} string input
     * @since 2.0
     * @since 3.0 Changed signature from lastIndexOf(String, int, int) to lastIndexOf(CharSequence, int, int)
     */
    public static int lastIndexOf(final CharSequence seq, final int searchChar, final int startPos) {
        if (isEmpty(seq)) {
            return INDEX_NOT_FOUND;
        }
        return CharSequenceUtils.lastIndexOf(seq, searchChar, startPos);
    }

    
Find the latest index of any substring in a set of potential substrings.
A null CharSequence will return -1. A null search array will return -1. A null or zero length search array entry will be ignored, but a search array containing "" will return the length of str if str is not null. This method uses String.indexOf(String) if possible
StringUtils.lastIndexOfAny(null, *)                    = -1
StringUtils.lastIndexOfAny(*, null)                    = -1
StringUtils.lastIndexOfAny(*, [])                      = -1
StringUtils.lastIndexOfAny(*, [null])                  = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["ab", "cd"]) = 6
StringUtils.lastIndexOfAny("zzabyycdxx", ["cd", "ab"]) = 6
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", "op"]) = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", "op"]) = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", ""])   = 10

Params:
str –  the CharSequence to check, may be null
searchStrs –  the CharSequences to search for, may be null
Returns:
the last index of any of the CharSequences, -1 if no match
Since:
3.0 Changed signature from lastIndexOfAny(String, String[]) to lastIndexOfAny(CharSequence, CharSequence)/**
     * <p>Find the latest index of any substring in a set of potential substrings.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A {@code null} search array will return {@code -1}.
     * A {@code null} or zero length search array entry will be ignored,
     * but a search array containing "" will return the length of {@code str}
     * if {@code str} is not null. This method uses {@link String#indexOf(String)} if possible</p>
     *
     * <pre>
     * StringUtils.lastIndexOfAny(null, *)                    = -1
     * StringUtils.lastIndexOfAny(*, null)                    = -1
     * StringUtils.lastIndexOfAny(*, [])                      = -1
     * StringUtils.lastIndexOfAny(*, [null])                  = -1
     * StringUtils.lastIndexOfAny("zzabyycdxx", ["ab", "cd"]) = 6
     * StringUtils.lastIndexOfAny("zzabyycdxx", ["cd", "ab"]) = 6
     * StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", "op"]) = -1
     * StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", "op"]) = -1
     * StringUtils.lastIndexOfAny("zzabyycdxx", ["mn", ""])   = 10
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStrs  the CharSequences to search for, may be null
     * @return the last index of any of the CharSequences, -1 if no match
     * @since 3.0 Changed signature from lastIndexOfAny(String, String[]) to lastIndexOfAny(CharSequence, CharSequence)
     */
    public static int lastIndexOfAny(final CharSequence str, final CharSequence... searchStrs) {
        if (str == null || searchStrs == null) {
            return INDEX_NOT_FOUND;
        }
        int ret = INDEX_NOT_FOUND;
        int tmp = 0;
        for (final CharSequence search : searchStrs) {
            if (search == null) {
                continue;
            }
            tmp = CharSequenceUtils.lastIndexOf(str, search, str.length());
            if (tmp > ret) {
                ret = tmp;
            }
        }
        return ret;
    }

    
Case in-sensitive find of the last index within a CharSequence.
A null CharSequence will return -1. A negative start position returns -1. An empty ("") search CharSequence always matches unless the start position is negative. A start position greater than the string length searches the whole string.
StringUtils.lastIndexOfIgnoreCase(null, *)          = -1
StringUtils.lastIndexOfIgnoreCase(*, null)          = -1
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A")  = 7
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B")  = 5
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB") = 4

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
Returns:
the first index of the search CharSequence, -1 if no match or null string input
Since:
2.5
Since:
3.0 Changed signature from lastIndexOfIgnoreCase(String, String) to lastIndexOfIgnoreCase(CharSequence, CharSequence)/**
     * <p>Case in-sensitive find of the last index within a CharSequence.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position returns {@code -1}.
     * An empty ("") search CharSequence always matches unless the start position is negative.
     * A start position greater than the string length searches the whole string.</p>
     *
     * <pre>
     * StringUtils.lastIndexOfIgnoreCase(null, *)          = -1
     * StringUtils.lastIndexOfIgnoreCase(*, null)          = -1
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A")  = 7
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B")  = 5
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB") = 4
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @return the first index of the search CharSequence,
     *  -1 if no match or {@code null} string input
     * @since 2.5
     * @since 3.0 Changed signature from lastIndexOfIgnoreCase(String, String) to lastIndexOfIgnoreCase(CharSequence, CharSequence)
     */
    public static int lastIndexOfIgnoreCase(final CharSequence str, final CharSequence searchStr) {
        if (str == null || searchStr == null) {
            return INDEX_NOT_FOUND;
        }
        return lastIndexOfIgnoreCase(str, searchStr, str.length());
    }

    
Case in-sensitive find of the last index within a CharSequence
from the specified position.
A null CharSequence will return -1. A negative start position returns -1. An empty ("") search CharSequence always matches unless the start position is negative. A start position greater than the string length searches the whole string. The search starts at the startPos and works backwards; matches starting after the start position are ignored. 
StringUtils.lastIndexOfIgnoreCase(null, *, *)          = -1
StringUtils.lastIndexOfIgnoreCase(*, null, *)          = -1
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 8)  = 7
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 8)  = 5
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB", 8) = 4
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 9)  = 5
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", -1) = -1
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 0)  = 0
StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 0)  = -1

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
startPos –  the start position
Returns:
the last index of the search CharSequence (always ≤ startPos), -1 if no match or null input
Since:
2.5
Since:
3.0 Changed signature from lastIndexOfIgnoreCase(String, String, int) to lastIndexOfIgnoreCase(CharSequence, CharSequence, int)/**
     * <p>Case in-sensitive find of the last index within a CharSequence
     * from the specified position.</p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.
     * A negative start position returns {@code -1}.
     * An empty ("") search CharSequence always matches unless the start position is negative.
     * A start position greater than the string length searches the whole string.
     * The search starts at the startPos and works backwards; matches starting after the start
     * position are ignored.
     * </p>
     *
     * <pre>
     * StringUtils.lastIndexOfIgnoreCase(null, *, *)          = -1
     * StringUtils.lastIndexOfIgnoreCase(*, null, *)          = -1
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 8)  = 7
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 8)  = 5
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB", 8) = 4
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 9)  = 5
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", -1) = -1
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 0)  = 0
     * StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 0)  = -1
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @param startPos  the start position
     * @return the last index of the search CharSequence (always &le; startPos),
     *  -1 if no match or {@code null} input
     * @since 2.5
     * @since 3.0 Changed signature from lastIndexOfIgnoreCase(String, String, int) to lastIndexOfIgnoreCase(CharSequence, CharSequence, int)
     */
    public static int lastIndexOfIgnoreCase(final CharSequence str, final CharSequence searchStr, int startPos) {
        if (str == null || searchStr == null) {
            return INDEX_NOT_FOUND;
        }
        if (startPos > str.length() - searchStr.length()) {
            startPos = str.length() - searchStr.length();
        }
        if (startPos < 0) {
            return INDEX_NOT_FOUND;
        }
        if (searchStr.length() == 0) {
            return startPos;
        }

        for (int i = startPos; i >= 0; i--) {
            if (CharSequenceUtils.regionMatches(str, true, i, searchStr, 0, searchStr.length())) {
                return i;
            }
        }
        return INDEX_NOT_FOUND;
    }

    
Finds the n-th last index within a String, handling null. This method uses String.lastIndexOf(String).
A null String will return -1.
StringUtils.lastOrdinalIndexOf(null, *, *)          = -1
StringUtils.lastOrdinalIndexOf(*, null, *)          = -1
StringUtils.lastOrdinalIndexOf("", "", *)           = 0
StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1)  = 7
StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2)  = 6
StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1)  = 5
StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2)  = 2
StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4
StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1
StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1)   = 8
StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2)   = 8

Note that 'tail(CharSequence str, int n)' may be implemented as: 
  str.substring(lastOrdinalIndexOf(str, "\n", n) + 1)

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
ordinal –  the n-th last searchStr to find
Returns:
the n-th last index of the search CharSequence, -1 (INDEX_NOT_FOUND) if no match or null string input
Since:
2.5
Since:
3.0 Changed signature from lastOrdinalIndexOf(String, String, int) to lastOrdinalIndexOf(CharSequence, CharSequence, int)/**
     * <p>Finds the n-th last index within a String, handling {@code null}.
     * This method uses {@link String#lastIndexOf(String)}.</p>
     *
     * <p>A {@code null} String will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.lastOrdinalIndexOf(null, *, *)          = -1
     * StringUtils.lastOrdinalIndexOf(*, null, *)          = -1
     * StringUtils.lastOrdinalIndexOf("", "", *)           = 0
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1)  = 7
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2)  = 6
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1)  = 5
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2)  = 2
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1)   = 8
     * StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2)   = 8
     * </pre>
     *
     * <p>Note that 'tail(CharSequence str, int n)' may be implemented as: </p>
     *
     * <pre>
     *   str.substring(lastOrdinalIndexOf(str, "\n", n) + 1)
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @param ordinal  the n-th last {@code searchStr} to find
     * @return the n-th last index of the search CharSequence,
     *  {@code -1} ({@code INDEX_NOT_FOUND}) if no match or {@code null} string input
     * @since 2.5
     * @since 3.0 Changed signature from lastOrdinalIndexOf(String, String, int) to lastOrdinalIndexOf(CharSequence, CharSequence, int)
     */
    public static int lastOrdinalIndexOf(final CharSequence str, final CharSequence searchStr, final int ordinal) {
        return ordinalIndexOf(str, searchStr, ordinal, true);
    }

    // Left/Right/Mid
    //-----------------------------------------------------------------------
    
Gets the leftmost len characters of a String.
If len characters are not available, or the String is null, the String will be returned without an exception. An empty String is returned if len is negative.
StringUtils.left(null, *)    = null
StringUtils.left(*, -ve)     = ""
StringUtils.left("", *)      = ""
StringUtils.left("abc", 0)   = ""
StringUtils.left("abc", 2)   = "ab"
StringUtils.left("abc", 4)   = "abc"

Params:
str –  the String to get the leftmost characters from, may be null
len –  the length of the required String
Returns:
the leftmost characters, null if null String input/**
     * <p>Gets the leftmost {@code len} characters of a String.</p>
     *
     * <p>If {@code len} characters are not available, or the
     * String is {@code null}, the String will be returned without
     * an exception. An empty String is returned if len is negative.</p>
     *
     * <pre>
     * StringUtils.left(null, *)    = null
     * StringUtils.left(*, -ve)     = ""
     * StringUtils.left("", *)      = ""
     * StringUtils.left("abc", 0)   = ""
     * StringUtils.left("abc", 2)   = "ab"
     * StringUtils.left("abc", 4)   = "abc"
     * </pre>
     *
     * @param str  the String to get the leftmost characters from, may be null
     * @param len  the length of the required String
     * @return the leftmost characters, {@code null} if null String input
     */
    public static String left(final String str, final int len) {
        if (str == null) {
            return null;
        }
        if (len < 0) {
            return EMPTY;
        }
        if (str.length() <= len) {
            return str;
        }
        return str.substring(0, len);
    }

    
Left pad a String with spaces (' ').
The String is padded to the size of size.
StringUtils.leftPad(null, *)   = null
StringUtils.leftPad("", 3)     = "   "
StringUtils.leftPad("bat", 3)  = "bat"
StringUtils.leftPad("bat", 5)  = "  bat"
StringUtils.leftPad("bat", 1)  = "bat"
StringUtils.leftPad("bat", -1) = "bat"

Params:
str –  the String to pad out, may be null
size –  the size to pad to
Returns:
left padded String or original String if no padding is necessary, null if null String input/**
     * <p>Left pad a String with spaces (' ').</p>
     *
     * <p>The String is padded to the size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.leftPad(null, *)   = null
     * StringUtils.leftPad("", 3)     = "   "
     * StringUtils.leftPad("bat", 3)  = "bat"
     * StringUtils.leftPad("bat", 5)  = "  bat"
     * StringUtils.leftPad("bat", 1)  = "bat"
     * StringUtils.leftPad("bat", -1) = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @return left padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     */
    public static String leftPad(final String str, final int size) {
        return leftPad(str, size, ' ');
    }

    
Left pad a String with a specified character.
Pad to a size of size.
StringUtils.leftPad(null, *, *)     = null
StringUtils.leftPad("", 3, 'z')     = "zzz"
StringUtils.leftPad("bat", 3, 'z')  = "bat"
StringUtils.leftPad("bat", 5, 'z')  = "zzbat"
StringUtils.leftPad("bat", 1, 'z')  = "bat"
StringUtils.leftPad("bat", -1, 'z') = "bat"

Params:
str –  the String to pad out, may be null
size –  the size to pad to
padChar –  the character to pad with
Returns:
left padded String or original String if no padding is necessary, null if null String input
Since:
2.0/**
     * <p>Left pad a String with a specified character.</p>
     *
     * <p>Pad to a size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.leftPad(null, *, *)     = null
     * StringUtils.leftPad("", 3, 'z')     = "zzz"
     * StringUtils.leftPad("bat", 3, 'z')  = "bat"
     * StringUtils.leftPad("bat", 5, 'z')  = "zzbat"
     * StringUtils.leftPad("bat", 1, 'z')  = "bat"
     * StringUtils.leftPad("bat", -1, 'z') = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padChar  the character to pad with
     * @return left padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String leftPad(final String str, final int size, final char padChar) {
        if (str == null) {
            return null;
        }
        final int pads = size - str.length();
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (pads > PAD_LIMIT) {
            return leftPad(str, size, String.valueOf(padChar));
        }
        return repeat(padChar, pads).concat(str);
    }

    
Left pad a String with a specified String.
Pad to a size of size.
StringUtils.leftPad(null, *, *)      = null
StringUtils.leftPad("", 3, "z")      = "zzz"
StringUtils.leftPad("bat", 3, "yz")  = "bat"
StringUtils.leftPad("bat", 5, "yz")  = "yzbat"
StringUtils.leftPad("bat", 8, "yz")  = "yzyzybat"
StringUtils.leftPad("bat", 1, "yz")  = "bat"
StringUtils.leftPad("bat", -1, "yz") = "bat"
StringUtils.leftPad("bat", 5, null)  = "  bat"
StringUtils.leftPad("bat", 5, "")    = "  bat"

Params:
str –  the String to pad out, may be null
size –  the size to pad to
padStr –  the String to pad with, null or empty treated as single space
Returns:
left padded String or original String if no padding is necessary, null if null String input/**
     * <p>Left pad a String with a specified String.</p>
     *
     * <p>Pad to a size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.leftPad(null, *, *)      = null
     * StringUtils.leftPad("", 3, "z")      = "zzz"
     * StringUtils.leftPad("bat", 3, "yz")  = "bat"
     * StringUtils.leftPad("bat", 5, "yz")  = "yzbat"
     * StringUtils.leftPad("bat", 8, "yz")  = "yzyzybat"
     * StringUtils.leftPad("bat", 1, "yz")  = "bat"
     * StringUtils.leftPad("bat", -1, "yz") = "bat"
     * StringUtils.leftPad("bat", 5, null)  = "  bat"
     * StringUtils.leftPad("bat", 5, "")    = "  bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padStr  the String to pad with, null or empty treated as single space
     * @return left padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     */
    public static String leftPad(final String str, final int size, String padStr) {
        if (str == null) {
            return null;
        }
        if (isEmpty(padStr)) {
            padStr = SPACE;
        }
        final int padLen = padStr.length();
        final int strLen = str.length();
        final int pads = size - strLen;
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (padLen == 1 && pads <= PAD_LIMIT) {
            return leftPad(str, size, padStr.charAt(0));
        }

        if (pads == padLen) {
            return padStr.concat(str);
        } else if (pads < padLen) {
            return padStr.substring(0, pads).concat(str);
        } else {
            final char[] padding = new char[pads];
            final char[] padChars = padStr.toCharArray();
            for (int i = 0; i < pads; i++) {
                padding[i] = padChars[i % padLen];
            }
            return new String(padding).concat(str);
        }
    }

    
Gets a CharSequence length or 0 if the CharSequence is null. 
Params:
cs –  a CharSequence or null
Returns:
CharSequence length or 0 if the CharSequence is null.
Since:
2.4
Since:
3.0 Changed signature from length(String) to length(CharSequence)/**
     * Gets a CharSequence length or {@code 0} if the CharSequence is
     * {@code null}.
     *
     * @param cs
     *            a CharSequence or {@code null}
     * @return CharSequence length or {@code 0} if the CharSequence is
     *         {@code null}.
     * @since 2.4
     * @since 3.0 Changed signature from length(String) to length(CharSequence)
     */
    public static int length(final CharSequence cs) {
        return cs == null ? 0 : cs.length();
    }

    
Converts a String to lower case as per String.toLowerCase().
A null input String returns null.
StringUtils.lowerCase(null)  = null
StringUtils.lowerCase("")    = ""
StringUtils.lowerCase("aBc") = "abc"

Note: As described in the documentation for String.toLowerCase(), the result of this method is affected by the current locale. For platform-independent case transformations, the method lowerCase(String, Locale) should be used with a specific locale (e.g. Locale.ENGLISH).
Params:
str –  the String to lower case, may be null
Returns:
the lower cased String, null if null String input/**
     * <p>Converts a String to lower case as per {@link String#toLowerCase()}.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.lowerCase(null)  = null
     * StringUtils.lowerCase("")    = ""
     * StringUtils.lowerCase("aBc") = "abc"
     * </pre>
     *
     * <p><strong>Note:</strong> As described in the documentation for {@link String#toLowerCase()},
     * the result of this method is affected by the current locale.
     * For platform-independent case transformations, the method {@link #lowerCase(String, Locale)}
     * should be used with a specific locale (e.g. {@link Locale#ENGLISH}).</p>
     *
     * @param str  the String to lower case, may be null
     * @return the lower cased String, {@code null} if null String input
     */
    public static String lowerCase(final String str) {
        if (str == null) {
            return null;
        }
        return str.toLowerCase();
    }

    
Converts a String to lower case as per String.toLowerCase(Locale).
A null input String returns null.
StringUtils.lowerCase(null, Locale.ENGLISH)  = null
StringUtils.lowerCase("", Locale.ENGLISH)    = ""
StringUtils.lowerCase("aBc", Locale.ENGLISH) = "abc"

Params:
str –  the String to lower case, may be null
locale –  the locale that defines the case transformation rules, must not be null
Returns:
the lower cased String, null if null String input
Since:
2.5/**
     * <p>Converts a String to lower case as per {@link String#toLowerCase(Locale)}.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.lowerCase(null, Locale.ENGLISH)  = null
     * StringUtils.lowerCase("", Locale.ENGLISH)    = ""
     * StringUtils.lowerCase("aBc", Locale.ENGLISH) = "abc"
     * </pre>
     *
     * @param str  the String to lower case, may be null
     * @param locale  the locale that defines the case transformation rules, must not be null
     * @return the lower cased String, {@code null} if null String input
     * @since 2.5
     */
    public static String lowerCase(final String str, final Locale locale) {
        if (str == null) {
            return null;
        }
        return str.toLowerCase(locale);
    }

    private static int[] matches(final CharSequence first, final CharSequence second) {
        CharSequence max, min;
        if (first.length() > second.length()) {
            max = first;
            min = second;
        } else {
            max = second;
            min = first;
        }
        final int range = Math.max(max.length() / 2 - 1, 0);
        final int[] matchIndexes = new int[min.length()];
        Arrays.fill(matchIndexes, -1);
        final boolean[] matchFlags = new boolean[max.length()];
        int matches = 0;
        for (int mi = 0; mi < min.length(); mi++) {
            final char c1 = min.charAt(mi);
            for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max.length()); xi < xn; xi++) {
                if (!matchFlags[xi] && c1 == max.charAt(xi)) {
                    matchIndexes[mi] = xi;
                    matchFlags[xi] = true;
                    matches++;
                    break;
                }
            }
        }
        final char[] ms1 = new char[matches];
        final char[] ms2 = new char[matches];
        for (int i = 0, si = 0; i < min.length(); i++) {
            if (matchIndexes[i] != -1) {
                ms1[si] = min.charAt(i);
                si++;
            }
        }
        for (int i = 0, si = 0; i < max.length(); i++) {
            if (matchFlags[i]) {
                ms2[si] = max.charAt(i);
                si++;
            }
        }
        int transpositions = 0;
        for (int mi = 0; mi < ms1.length; mi++) {
            if (ms1[mi] != ms2[mi]) {
                transpositions++;
            }
        }
        int prefix = 0;
        for (int mi = 0; mi < min.length(); mi++) {
            if (first.charAt(mi) == second.charAt(mi)) {
                prefix++;
            } else {
                break;
            }
        }
        return new int[] { matches, transpositions / 2, prefix, max.length() };
    }

    
Gets len characters from the middle of a String.
If len characters are not available, the remainder of the String will be returned without an exception. If the String is null, null will be returned. An empty String is returned if len is negative or exceeds the length of str.
StringUtils.mid(null, *, *)    = null
StringUtils.mid(*, *, -ve)     = ""
StringUtils.mid("", 0, *)      = ""
StringUtils.mid("abc", 0, 2)   = "ab"
StringUtils.mid("abc", 0, 4)   = "abc"
StringUtils.mid("abc", 2, 4)   = "c"
StringUtils.mid("abc", 4, 2)   = ""
StringUtils.mid("abc", -2, 2)  = "ab"

Params:
str –  the String to get the characters from, may be null
pos –  the position to start from, negative treated as zero
len –  the length of the required String
Returns:
the middle characters, null if null String input/**
     * <p>Gets {@code len} characters from the middle of a String.</p>
     *
     * <p>If {@code len} characters are not available, the remainder
     * of the String will be returned without an exception. If the
     * String is {@code null}, {@code null} will be returned.
     * An empty String is returned if len is negative or exceeds the
     * length of {@code str}.</p>
     *
     * <pre>
     * StringUtils.mid(null, *, *)    = null
     * StringUtils.mid(*, *, -ve)     = ""
     * StringUtils.mid("", 0, *)      = ""
     * StringUtils.mid("abc", 0, 2)   = "ab"
     * StringUtils.mid("abc", 0, 4)   = "abc"
     * StringUtils.mid("abc", 2, 4)   = "c"
     * StringUtils.mid("abc", 4, 2)   = ""
     * StringUtils.mid("abc", -2, 2)  = "ab"
     * </pre>
     *
     * @param str  the String to get the characters from, may be null
     * @param pos  the position to start from, negative treated as zero
     * @param len  the length of the required String
     * @return the middle characters, {@code null} if null String input
     */
    public static String mid(final String str, int pos, final int len) {
        if (str == null) {
            return null;
        }
        if (len < 0 || pos > str.length()) {
            return EMPTY;
        }
        if (pos < 0) {
            pos = 0;
        }
        if (str.length() <= pos + len) {
            return str.substring(pos);
        }
        return str.substring(pos, pos + len);
    }

    private static StringBuilder newStringBuilder(final int noOfItems) {
        return new StringBuilder(noOfItems * 16);
    }

    

Similar to http://www.w3.org/TR/xpath/#function-normalize
-space

 The function returns the argument string with whitespace normalized by using {@link #trim(String)} to remove leading and trailing whitespace and then replacing sequences of whitespace characters by a single space. 
In XML Whitespace characters are the same as those allowed by the S production, which is S ::= (#x20 | #x9 | #xD | #xA)+

Java's regexp pattern \s defines whitespace as [ \t\n\x0B\f\r]
For reference:

\x0B = vertical tab
\f = #xC = form feed
#x20 = space
#x9 = \t
#xA = \n
#xD = \r

 The difference is that Java's whitespace includes vertical tab and form feed, which this functional will also normalize. Additionally {@link #trim(String)} removes control characters (char <= 32) from both ends of this String. 
Params:
str – the source String to normalize whitespaces from, may be null
See Also:
Pattern
trim(String)
http://www.w3.org/TR/xpath/#function-normalize-space
Returns:
the modified string with whitespace normalized, null if null String input
Since:
3.0/**
     * <p>
     * Similar to <a
     * href="http://www.w3.org/TR/xpath/#function-normalize-space">http://www.w3.org/TR/xpath/#function-normalize
     * -space</a>
     * </p>
     * <p>
     * The function returns the argument string with whitespace normalized by using
     * {@code {@link #trim(String)}} to remove leading and trailing whitespace
     * and then replacing sequences of whitespace characters by a single space.
     * </p>
     * In XML Whitespace characters are the same as those allowed by the <a
     * href="http://www.w3.org/TR/REC-xml/#NT-S">S</a> production, which is S ::= (#x20 | #x9 | #xD | #xA)+
     * <p>
     * Java's regexp pattern \s defines whitespace as [ \t\n\x0B\f\r]
     *
     * <p>For reference:</p>
     * <ul>
     * <li>\x0B = vertical tab</li>
     * <li>\f = #xC = form feed</li>
     * <li>#x20 = space</li>
     * <li>#x9 = \t</li>
     * <li>#xA = \n</li>
     * <li>#xD = \r</li>
     * </ul>
     *
     * <p>
     * The difference is that Java's whitespace includes vertical tab and form feed, which this functional will also
     * normalize. Additionally {@code {@link #trim(String)}} removes control characters (char &lt;= 32) from both
     * ends of this String.
     * </p>
     *
     * @see Pattern
     * @see #trim(String)
     * @see <a
     *      href="http://www.w3.org/TR/xpath/#function-normalize-space">http://www.w3.org/TR/xpath/#function-normalize-space</a>
     * @param str the source String to normalize whitespaces from, may be null
     * @return the modified string with whitespace normalized, {@code null} if null String input
     *
     * @since 3.0
     */
    public static String normalizeSpace(final String str) {
        // LANG-1020: Improved performance significantly by normalizing manually instead of using regex
        // See https://github.com/librucha/commons-lang-normalizespaces-benchmark for performance test
        if (isEmpty(str)) {
            return str;
        }
        final int size = str.length();
        final char[] newChars = new char[size];
        int count = 0;
        int whitespacesCount = 0;
        boolean startWhitespaces = true;
        for (int i = 0; i < size; i++) {
            final char actualChar = str.charAt(i);
            final boolean isWhitespace = Character.isWhitespace(actualChar);
            if (isWhitespace) {
                if (whitespacesCount == 0 && !startWhitespaces) {
                    newChars[count++] = SPACE.charAt(0);
                }
                whitespacesCount++;
            } else {
                startWhitespaces = false;
                newChars[count++] = (actualChar == 160 ? 32 : actualChar);
                whitespacesCount = 0;
            }
        }
        if (startWhitespaces) {
            return EMPTY;
        }
        return new String(newChars, 0, count - (whitespacesCount > 0 ? 1 : 0)).trim();
    }

    
Finds the n-th index within a CharSequence, handling null. This method uses String.indexOf(String) if possible.
Note: The code starts looking for a match at the start of the target, incrementing the starting index by one after each successful match (unless searchStr is an empty string in which case the position is never incremented and 0 is returned immediately). This means that matches may overlap.
A null CharSequence will return -1.
StringUtils.ordinalIndexOf(null, *, *)          = -1
StringUtils.ordinalIndexOf(*, null, *)          = -1
StringUtils.ordinalIndexOf("", "", *)           = 0
StringUtils.ordinalIndexOf("aabaabaa", "a", 1)  = 0
StringUtils.ordinalIndexOf("aabaabaa", "a", 2)  = 1
StringUtils.ordinalIndexOf("aabaabaa", "b", 1)  = 2
StringUtils.ordinalIndexOf("aabaabaa", "b", 2)  = 5
StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1
StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4
StringUtils.ordinalIndexOf("aabaabaa", "", 1)   = 0
StringUtils.ordinalIndexOf("aabaabaa", "", 2)   = 0

Matches may overlap:
StringUtils.ordinalIndexOf("ababab", "aba", 1)   = 0
StringUtils.ordinalIndexOf("ababab", "aba", 2)   = 2
StringUtils.ordinalIndexOf("ababab", "aba", 3)   = -1
StringUtils.ordinalIndexOf("abababab", "abab", 1) = 0
StringUtils.ordinalIndexOf("abababab", "abab", 2) = 2
StringUtils.ordinalIndexOf("abababab", "abab", 3) = 4
StringUtils.ordinalIndexOf("abababab", "abab", 4) = -1

Note that 'head(CharSequence str, int n)' may be implemented as: 
  str.substring(0, lastOrdinalIndexOf(str, "\n", n))

Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
ordinal –  the n-th searchStr to find
Returns:
the n-th index of the search CharSequence, -1 (INDEX_NOT_FOUND) if no match or null string input
Since:
2.1
Since:
3.0 Changed signature from ordinalIndexOf(String, String, int) to ordinalIndexOf(CharSequence, CharSequence, int)/**
     * <p>Finds the n-th index within a CharSequence, handling {@code null}.
     * This method uses {@link String#indexOf(String)} if possible.</p>
     * <p><b>Note:</b> The code starts looking for a match at the start of the target,
     * incrementing the starting index by one after each successful match
     * (unless {@code searchStr} is an empty string in which case the position
     * is never incremented and {@code 0} is returned immediately).
     * This means that matches may overlap.</p>
     * <p>A {@code null} CharSequence will return {@code -1}.</p>
     *
     * <pre>
     * StringUtils.ordinalIndexOf(null, *, *)          = -1
     * StringUtils.ordinalIndexOf(*, null, *)          = -1
     * StringUtils.ordinalIndexOf("", "", *)           = 0
     * StringUtils.ordinalIndexOf("aabaabaa", "a", 1)  = 0
     * StringUtils.ordinalIndexOf("aabaabaa", "a", 2)  = 1
     * StringUtils.ordinalIndexOf("aabaabaa", "b", 1)  = 2
     * StringUtils.ordinalIndexOf("aabaabaa", "b", 2)  = 5
     * StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1
     * StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4
     * StringUtils.ordinalIndexOf("aabaabaa", "", 1)   = 0
     * StringUtils.ordinalIndexOf("aabaabaa", "", 2)   = 0
     * </pre>
     *
     * <p>Matches may overlap:</p>
     * <pre>
     * StringUtils.ordinalIndexOf("ababab", "aba", 1)   = 0
     * StringUtils.ordinalIndexOf("ababab", "aba", 2)   = 2
     * StringUtils.ordinalIndexOf("ababab", "aba", 3)   = -1
     *
     * StringUtils.ordinalIndexOf("abababab", "abab", 1) = 0
     * StringUtils.ordinalIndexOf("abababab", "abab", 2) = 2
     * StringUtils.ordinalIndexOf("abababab", "abab", 3) = 4
     * StringUtils.ordinalIndexOf("abababab", "abab", 4) = -1
     * </pre>
     *
     * <p>Note that 'head(CharSequence str, int n)' may be implemented as: </p>
     *
     * <pre>
     *   str.substring(0, lastOrdinalIndexOf(str, "\n", n))
     * </pre>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @param ordinal  the n-th {@code searchStr} to find
     * @return the n-th index of the search CharSequence,
     *  {@code -1} ({@code INDEX_NOT_FOUND}) if no match or {@code null} string input
     * @since 2.1
     * @since 3.0 Changed signature from ordinalIndexOf(String, String, int) to ordinalIndexOf(CharSequence, CharSequence, int)
     */
    public static int ordinalIndexOf(final CharSequence str, final CharSequence searchStr, final int ordinal) {
        return ordinalIndexOf(str, searchStr, ordinal, false);
    }

    
Finds the n-th index within a String, handling null. This method uses String.indexOf(String) if possible.
Note that matches may overlap

A null CharSequence will return -1.
Params:
str –  the CharSequence to check, may be null
searchStr –  the CharSequence to find, may be null
ordinal –  the n-th searchStr to find, overlapping matches are allowed.
lastIndex – true if lastOrdinalIndexOf() otherwise false if ordinalIndexOf()
Returns:
the n-th index of the search CharSequence, -1 (INDEX_NOT_FOUND) if no match or null string input/**
     * <p>Finds the n-th index within a String, handling {@code null}.
     * This method uses {@link String#indexOf(String)} if possible.</p>
     * <p>Note that matches may overlap<p>
     *
     * <p>A {@code null} CharSequence will return {@code -1}.</p>
     *
     * @param str  the CharSequence to check, may be null
     * @param searchStr  the CharSequence to find, may be null
     * @param ordinal  the n-th {@code searchStr} to find, overlapping matches are allowed.
     * @param lastIndex true if lastOrdinalIndexOf() otherwise false if ordinalIndexOf()
     * @return the n-th index of the search CharSequence,
     *  {@code -1} ({@code INDEX_NOT_FOUND}) if no match or {@code null} string input
     */
    // Shared code between ordinalIndexOf(String, String, int) and lastOrdinalIndexOf(String, String, int)
    private static int ordinalIndexOf(final CharSequence str, final CharSequence searchStr, final int ordinal, final boolean lastIndex) {
        if (str == null || searchStr == null || ordinal <= 0) {
            return INDEX_NOT_FOUND;
        }
        if (searchStr.length() == 0) {
            return lastIndex ? str.length() : 0;
        }
        int found = 0;
        // set the initial index beyond the end of the string
        // this is to allow for the initial index decrement/increment
        int index = lastIndex ? str.length() : INDEX_NOT_FOUND;
        do {
            if (lastIndex) {
                index = CharSequenceUtils.lastIndexOf(str, searchStr, index - 1); // step backwards thru string
            } else {
                index = CharSequenceUtils.indexOf(str, searchStr, index + 1); // step forwards through string
            }
            if (index < 0) {
                return index;
            }
            found++;
        } while (found < ordinal);
        return index;
    }

    // Overlay
    //-----------------------------------------------------------------------
    
Overlays part of a String with another String.
A null string input returns null. A negative index is treated as zero. An index greater than the string length is treated as the string length. The start index is always the smaller of the two indices.
StringUtils.overlay(null, *, *, *)            = null
StringUtils.overlay("", "abc", 0, 0)          = "abc"
StringUtils.overlay("abcdef", null, 2, 4)     = "abef"
StringUtils.overlay("abcdef", "", 2, 4)       = "abef"
StringUtils.overlay("abcdef", "", 4, 2)       = "abef"
StringUtils.overlay("abcdef", "zzzz", 2, 4)   = "abzzzzef"
StringUtils.overlay("abcdef", "zzzz", 4, 2)   = "abzzzzef"
StringUtils.overlay("abcdef", "zzzz", -1, 4)  = "zzzzef"
StringUtils.overlay("abcdef", "zzzz", 2, 8)   = "abzzzz"
StringUtils.overlay("abcdef", "zzzz", -2, -3) = "zzzzabcdef"
StringUtils.overlay("abcdef", "zzzz", 8, 10)  = "abcdefzzzz"

Params:
str –  the String to do overlaying in, may be null
overlay –  the String to overlay, may be null
start –  the position to start overlaying at
end –  the position to stop overlaying before
Returns:
overlayed String, null if null String input
Since:
2.0/**
     * <p>Overlays part of a String with another String.</p>
     *
     * <p>A {@code null} string input returns {@code null}.
     * A negative index is treated as zero.
     * An index greater than the string length is treated as the string length.
     * The start index is always the smaller of the two indices.</p>
     *
     * <pre>
     * StringUtils.overlay(null, *, *, *)            = null
     * StringUtils.overlay("", "abc", 0, 0)          = "abc"
     * StringUtils.overlay("abcdef", null, 2, 4)     = "abef"
     * StringUtils.overlay("abcdef", "", 2, 4)       = "abef"
     * StringUtils.overlay("abcdef", "", 4, 2)       = "abef"
     * StringUtils.overlay("abcdef", "zzzz", 2, 4)   = "abzzzzef"
     * StringUtils.overlay("abcdef", "zzzz", 4, 2)   = "abzzzzef"
     * StringUtils.overlay("abcdef", "zzzz", -1, 4)  = "zzzzef"
     * StringUtils.overlay("abcdef", "zzzz", 2, 8)   = "abzzzz"
     * StringUtils.overlay("abcdef", "zzzz", -2, -3) = "zzzzabcdef"
     * StringUtils.overlay("abcdef", "zzzz", 8, 10)  = "abcdefzzzz"
     * </pre>
     *
     * @param str  the String to do overlaying in, may be null
     * @param overlay  the String to overlay, may be null
     * @param start  the position to start overlaying at
     * @param end  the position to stop overlaying before
     * @return overlayed String, {@code null} if null String input
     * @since 2.0
     */
    public static String overlay(final String str, String overlay, int start, int end) {
        if (str == null) {
            return null;
        }
        if (overlay == null) {
            overlay = EMPTY;
        }
        final int len = str.length();
        if (start < 0) {
            start = 0;
        }
        if (start > len) {
            start = len;
        }
        if (end < 0) {
            end = 0;
        }
        if (end > len) {
            end = len;
        }
        if (start > end) {
            final int temp = start;
            start = end;
            end = temp;
        }
        return str.substring(0, start) +
            overlay +
            str.substring(end);
    }

    
Prepends the prefix to the start of the string if the string does not
already start with any of the prefixes.
Params:
str – The string.
prefix – The prefix to prepend to the start of the string.
ignoreCase – Indicates whether the compare should ignore case.
prefixes – Additional prefixes that are valid (optional).
Returns:
A new String if prefix was prepended, the same string otherwise./**
     * Prepends the prefix to the start of the string if the string does not
     * already start with any of the prefixes.
     *
     * @param str The string.
     * @param prefix The prefix to prepend to the start of the string.
     * @param ignoreCase Indicates whether the compare should ignore case.
     * @param prefixes Additional prefixes that are valid (optional).
     *
     * @return A new String if prefix was prepended, the same string otherwise.
     */
    private static String prependIfMissing(final String str, final CharSequence prefix, final boolean ignoreCase, final CharSequence... prefixes) {
        if (str == null || isEmpty(prefix) || startsWith(str, prefix, ignoreCase)) {
            return str;
        }
        if (ArrayUtils.isNotEmpty(prefixes)) {
            for (final CharSequence p : prefixes) {
                if (startsWith(str, p, ignoreCase)) {
                    return str;
                }
            }
        }
        return prefix.toString() + str;
    }

    
Prepends the prefix to the start of the string if the string does not
already start with any of the prefixes.
StringUtils.prependIfMissing(null, null) = null
StringUtils.prependIfMissing("abc", null) = "abc"
StringUtils.prependIfMissing("", "xyz") = "xyz"
StringUtils.prependIfMissing("abc", "xyz") = "xyzabc"
StringUtils.prependIfMissing("xyzabc", "xyz") = "xyzabc"
StringUtils.prependIfMissing("XYZabc", "xyz") = "xyzXYZabc"

With additional prefixes,
StringUtils.prependIfMissing(null, null, null) = null
StringUtils.prependIfMissing("abc", null, null) = "abc"
StringUtils.prependIfMissing("", "xyz", null) = "xyz"
StringUtils.prependIfMissing("abc", "xyz", new CharSequence[]{null}) = "xyzabc"
StringUtils.prependIfMissing("abc", "xyz", "") = "abc"
StringUtils.prependIfMissing("abc", "xyz", "mno") = "xyzabc"
StringUtils.prependIfMissing("xyzabc", "xyz", "mno") = "xyzabc"
StringUtils.prependIfMissing("mnoabc", "xyz", "mno") = "mnoabc"
StringUtils.prependIfMissing("XYZabc", "xyz", "mno") = "xyzXYZabc"
StringUtils.prependIfMissing("MNOabc", "xyz", "mno") = "xyzMNOabc"

Params:
str – The string.
prefix – The prefix to prepend to the start of the string.
prefixes – Additional prefixes that are valid.
Returns:
A new String if prefix was prepended, the same string otherwise.
Since:
3.2/**
     * Prepends the prefix to the start of the string if the string does not
     * already start with any of the prefixes.
     *
     * <pre>
     * StringUtils.prependIfMissing(null, null) = null
     * StringUtils.prependIfMissing("abc", null) = "abc"
     * StringUtils.prependIfMissing("", "xyz") = "xyz"
     * StringUtils.prependIfMissing("abc", "xyz") = "xyzabc"
     * StringUtils.prependIfMissing("xyzabc", "xyz") = "xyzabc"
     * StringUtils.prependIfMissing("XYZabc", "xyz") = "xyzXYZabc"
     * </pre>
     * <p>With additional prefixes,</p>
     * <pre>
     * StringUtils.prependIfMissing(null, null, null) = null
     * StringUtils.prependIfMissing("abc", null, null) = "abc"
     * StringUtils.prependIfMissing("", "xyz", null) = "xyz"
     * StringUtils.prependIfMissing("abc", "xyz", new CharSequence[]{null}) = "xyzabc"
     * StringUtils.prependIfMissing("abc", "xyz", "") = "abc"
     * StringUtils.prependIfMissing("abc", "xyz", "mno") = "xyzabc"
     * StringUtils.prependIfMissing("xyzabc", "xyz", "mno") = "xyzabc"
     * StringUtils.prependIfMissing("mnoabc", "xyz", "mno") = "mnoabc"
     * StringUtils.prependIfMissing("XYZabc", "xyz", "mno") = "xyzXYZabc"
     * StringUtils.prependIfMissing("MNOabc", "xyz", "mno") = "xyzMNOabc"
     * </pre>
     *
     * @param str The string.
     * @param prefix The prefix to prepend to the start of the string.
     * @param prefixes Additional prefixes that are valid.
     *
     * @return A new String if prefix was prepended, the same string otherwise.
     *
     * @since 3.2
     */
    public static String prependIfMissing(final String str, final CharSequence prefix, final CharSequence... prefixes) {
        return prependIfMissing(str, prefix, false, prefixes);
    }

    
Prepends the prefix to the start of the string if the string does not
already start, case insensitive, with any of the prefixes.
StringUtils.prependIfMissingIgnoreCase(null, null) = null
StringUtils.prependIfMissingIgnoreCase("abc", null) = "abc"
StringUtils.prependIfMissingIgnoreCase("", "xyz") = "xyz"
StringUtils.prependIfMissingIgnoreCase("abc", "xyz") = "xyzabc"
StringUtils.prependIfMissingIgnoreCase("xyzabc", "xyz") = "xyzabc"
StringUtils.prependIfMissingIgnoreCase("XYZabc", "xyz") = "XYZabc"

With additional prefixes,
StringUtils.prependIfMissingIgnoreCase(null, null, null) = null
StringUtils.prependIfMissingIgnoreCase("abc", null, null) = "abc"
StringUtils.prependIfMissingIgnoreCase("", "xyz", null) = "xyz"
StringUtils.prependIfMissingIgnoreCase("abc", "xyz", new CharSequence[]{null}) = "xyzabc"
StringUtils.prependIfMissingIgnoreCase("abc", "xyz", "") = "abc"
StringUtils.prependIfMissingIgnoreCase("abc", "xyz", "mno") = "xyzabc"
StringUtils.prependIfMissingIgnoreCase("xyzabc", "xyz", "mno") = "xyzabc"
StringUtils.prependIfMissingIgnoreCase("mnoabc", "xyz", "mno") = "mnoabc"
StringUtils.prependIfMissingIgnoreCase("XYZabc", "xyz", "mno") = "XYZabc"
StringUtils.prependIfMissingIgnoreCase("MNOabc", "xyz", "mno") = "MNOabc"

Params:
str – The string.
prefix – The prefix to prepend to the start of the string.
prefixes – Additional prefixes that are valid (optional).
Returns:
A new String if prefix was prepended, the same string otherwise.
Since:
3.2/**
     * Prepends the prefix to the start of the string if the string does not
     * already start, case insensitive, with any of the prefixes.
     *
     * <pre>
     * StringUtils.prependIfMissingIgnoreCase(null, null) = null
     * StringUtils.prependIfMissingIgnoreCase("abc", null) = "abc"
     * StringUtils.prependIfMissingIgnoreCase("", "xyz") = "xyz"
     * StringUtils.prependIfMissingIgnoreCase("abc", "xyz") = "xyzabc"
     * StringUtils.prependIfMissingIgnoreCase("xyzabc", "xyz") = "xyzabc"
     * StringUtils.prependIfMissingIgnoreCase("XYZabc", "xyz") = "XYZabc"
     * </pre>
     * <p>With additional prefixes,</p>
     * <pre>
     * StringUtils.prependIfMissingIgnoreCase(null, null, null) = null
     * StringUtils.prependIfMissingIgnoreCase("abc", null, null) = "abc"
     * StringUtils.prependIfMissingIgnoreCase("", "xyz", null) = "xyz"
     * StringUtils.prependIfMissingIgnoreCase("abc", "xyz", new CharSequence[]{null}) = "xyzabc"
     * StringUtils.prependIfMissingIgnoreCase("abc", "xyz", "") = "abc"
     * StringUtils.prependIfMissingIgnoreCase("abc", "xyz", "mno") = "xyzabc"
     * StringUtils.prependIfMissingIgnoreCase("xyzabc", "xyz", "mno") = "xyzabc"
     * StringUtils.prependIfMissingIgnoreCase("mnoabc", "xyz", "mno") = "mnoabc"
     * StringUtils.prependIfMissingIgnoreCase("XYZabc", "xyz", "mno") = "XYZabc"
     * StringUtils.prependIfMissingIgnoreCase("MNOabc", "xyz", "mno") = "MNOabc"
     * </pre>
     *
     * @param str The string.
     * @param prefix The prefix to prepend to the start of the string.
     * @param prefixes Additional prefixes that are valid (optional).
     *
     * @return A new String if prefix was prepended, the same string otherwise.
     *
     * @since 3.2
     */
    public static String prependIfMissingIgnoreCase(final String str, final CharSequence prefix, final CharSequence... prefixes) {
        return prependIfMissing(str, prefix, true, prefixes);
    }

    
Removes all occurrences of a character from within the source string.
A null source string will return null. An empty ("") source string will return the empty string.
StringUtils.remove(null, *)       = null
StringUtils.remove("", *)         = ""
StringUtils.remove("queued", 'u') = "qeed"
StringUtils.remove("queued", 'z') = "queued"

Params:
str –  the source String to search, may be null
remove –  the char to search for and remove, may be null
Returns:
the substring with the char removed if found, null if null String input
Since:
2.1/**
     * <p>Removes all occurrences of a character from within the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.</p>
     *
     * <pre>
     * StringUtils.remove(null, *)       = null
     * StringUtils.remove("", *)         = ""
     * StringUtils.remove("queued", 'u') = "qeed"
     * StringUtils.remove("queued", 'z') = "queued"
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the char to search for and remove, may be null
     * @return the substring with the char removed if found,
     *  {@code null} if null String input
     * @since 2.1
     */
    public static String remove(final String str, final char remove) {
        if (isEmpty(str) || str.indexOf(remove) == INDEX_NOT_FOUND) {
            return str;
        }
        final char[] chars = str.toCharArray();
        int pos = 0;
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] != remove) {
                chars[pos++] = chars[i];
            }
        }
        return new String(chars, 0, pos);
    }

    
Removes all occurrences of a substring from within the source string.
A null source string will return null. An empty ("") source string will return the empty string. A null remove string will return the source string. An empty ("") remove string will return the source string.
StringUtils.remove(null, *)        = null
StringUtils.remove("", *)          = ""
StringUtils.remove(*, null)        = *
StringUtils.remove(*, "")          = *
StringUtils.remove("queued", "ue") = "qd"
StringUtils.remove("queued", "zz") = "queued"

Params:
str –  the source String to search, may be null
remove –  the String to search for and remove, may be null
Returns:
the substring with the string removed if found, null if null String input
Since:
2.1/**
     * <p>Removes all occurrences of a substring from within the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.
     * A {@code null} remove string will return the source string.
     * An empty ("") remove string will return the source string.</p>
     *
     * <pre>
     * StringUtils.remove(null, *)        = null
     * StringUtils.remove("", *)          = ""
     * StringUtils.remove(*, null)        = *
     * StringUtils.remove(*, "")          = *
     * StringUtils.remove("queued", "ue") = "qd"
     * StringUtils.remove("queued", "zz") = "queued"
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the String to search for and remove, may be null
     * @return the substring with the string removed if found,
     *  {@code null} if null String input
     * @since 2.1
     */
    public static String remove(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        return replace(str, remove, EMPTY, -1);
    }

    
Removes each substring of the text String that matches the given regular expression.
 This method is a null safe equivalent to: 

 
text.replaceAll(regex, StringUtils.EMPTY)
 
Pattern.compile(regex).matcher(text).replaceAll(StringUtils.EMPTY)

A null reference passed to this method is a no-op.
Unlike in the removePattern(String, String) method, the Pattern.DOTALL option is NOT automatically added. To use the DOTALL option prepend "(?s)" to the regex. DOTALL is also known as single-line mode in Perl.
StringUtils.removeAll(null, *)      = null
StringUtils.removeAll("any", (String) null)  = "any"
StringUtils.removeAll("any", "")    = "any"
StringUtils.removeAll("any", ".*")  = ""
StringUtils.removeAll("any", ".+")  = ""
StringUtils.removeAll("abc", ".?")  = ""
StringUtils.removeAll("A<__>\n<__>B", "<.*>")      = "A\nB"
StringUtils.removeAll("A<__>\n<__>B", "(?s)<.*>")  = "AB"
StringUtils.removeAll("ABCabc123abc", "[a-z]")     = "ABC123"

Params:
text –  text to remove from, may be null
regex –  the regular expression to which this string is to be matched
Throws:
PatternSyntaxException – 
             if the regular expression's syntax is invalid
See Also:
replaceAll(String, String, String)
removePattern(String, String)
String.replaceAll(String, String)
Pattern
Pattern.DOTALL
Returns:
 the text with any removes processed, null if null String input
Since:
3.5
Deprecated:
Moved to RegExUtils./**
     * <p>Removes each substring of the text String that matches the given regular expression.</p>
     *
     * This method is a {@code null} safe equivalent to:
     * <ul>
     *  <li>{@code text.replaceAll(regex, StringUtils.EMPTY)}</li>
     *  <li>{@code Pattern.compile(regex).matcher(text).replaceAll(StringUtils.EMPTY)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <p>Unlike in the {@link #removePattern(String, String)} method, the {@link Pattern#DOTALL} option
     * is NOT automatically added.
     * To use the DOTALL option prepend {@code "(?s)"} to the regex.
     * DOTALL is also known as single-line mode in Perl.</p>
     *
     * <pre>
     * StringUtils.removeAll(null, *)      = null
     * StringUtils.removeAll("any", (String) null)  = "any"
     * StringUtils.removeAll("any", "")    = "any"
     * StringUtils.removeAll("any", ".*")  = ""
     * StringUtils.removeAll("any", ".+")  = ""
     * StringUtils.removeAll("abc", ".?")  = ""
     * StringUtils.removeAll("A&lt;__&gt;\n&lt;__&gt;B", "&lt;.*&gt;")      = "A\nB"
     * StringUtils.removeAll("A&lt;__&gt;\n&lt;__&gt;B", "(?s)&lt;.*&gt;")  = "AB"
     * StringUtils.removeAll("ABCabc123abc", "[a-z]")     = "ABC123"
     * </pre>
     *
     * @param text  text to remove from, may be null
     * @param regex  the regular expression to which this string is to be matched
     * @return  the text with any removes processed,
     *              {@code null} if null String input
     *
     * @throws  java.util.regex.PatternSyntaxException
     *              if the regular expression's syntax is invalid
     *
     * @see #replaceAll(String, String, String)
     * @see #removePattern(String, String)
     * @see String#replaceAll(String, String)
     * @see java.util.regex.Pattern
     * @see java.util.regex.Pattern#DOTALL
     * @since 3.5
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String removeAll(final String text, final String regex) {
        return RegExUtils.removeAll(text, regex);
    }

    
Removes a substring only if it is at the end of a source string,
otherwise returns the source string.
A null source string will return null. An empty ("") source string will return the empty string. A null search string will return the source string.
StringUtils.removeEnd(null, *)      = null
StringUtils.removeEnd("", *)        = ""
StringUtils.removeEnd(*, null)      = *
StringUtils.removeEnd("www.domain.com", ".com.")  = "www.domain.com"
StringUtils.removeEnd("www.domain.com", ".com")   = "www.domain"
StringUtils.removeEnd("www.domain.com", "domain") = "www.domain.com"
StringUtils.removeEnd("abc", "")    = "abc"

Params:
str –  the source String to search, may be null
remove –  the String to search for and remove, may be null
Returns:
the substring with the string removed if found, null if null String input
Since:
2.1/**
     * <p>Removes a substring only if it is at the end of a source string,
     * otherwise returns the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.
     * A {@code null} search string will return the source string.</p>
     *
     * <pre>
     * StringUtils.removeEnd(null, *)      = null
     * StringUtils.removeEnd("", *)        = ""
     * StringUtils.removeEnd(*, null)      = *
     * StringUtils.removeEnd("www.domain.com", ".com.")  = "www.domain.com"
     * StringUtils.removeEnd("www.domain.com", ".com")   = "www.domain"
     * StringUtils.removeEnd("www.domain.com", "domain") = "www.domain.com"
     * StringUtils.removeEnd("abc", "")    = "abc"
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the String to search for and remove, may be null
     * @return the substring with the string removed if found,
     *  {@code null} if null String input
     * @since 2.1
     */
    public static String removeEnd(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        if (str.endsWith(remove)) {
            return str.substring(0, str.length() - remove.length());
        }
        return str;
    }

    
Case insensitive removal of a substring if it is at the end of a source string,
otherwise returns the source string.
A null source string will return null. An empty ("") source string will return the empty string. A null search string will return the source string.
StringUtils.removeEndIgnoreCase(null, *)      = null
StringUtils.removeEndIgnoreCase("", *)        = ""
StringUtils.removeEndIgnoreCase(*, null)      = *
StringUtils.removeEndIgnoreCase("www.domain.com", ".com.")  = "www.domain.com"
StringUtils.removeEndIgnoreCase("www.domain.com", ".com")   = "www.domain"
StringUtils.removeEndIgnoreCase("www.domain.com", "domain") = "www.domain.com"
StringUtils.removeEndIgnoreCase("abc", "")    = "abc"
StringUtils.removeEndIgnoreCase("www.domain.com", ".COM") = "www.domain")
StringUtils.removeEndIgnoreCase("www.domain.COM", ".com") = "www.domain")

Params:
str –  the source String to search, may be null
remove –  the String to search for (case insensitive) and remove, may be null
Returns:
the substring with the string removed if found, null if null String input
Since:
2.4/**
     * <p>Case insensitive removal of a substring if it is at the end of a source string,
     * otherwise returns the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.
     * A {@code null} search string will return the source string.</p>
     *
     * <pre>
     * StringUtils.removeEndIgnoreCase(null, *)      = null
     * StringUtils.removeEndIgnoreCase("", *)        = ""
     * StringUtils.removeEndIgnoreCase(*, null)      = *
     * StringUtils.removeEndIgnoreCase("www.domain.com", ".com.")  = "www.domain.com"
     * StringUtils.removeEndIgnoreCase("www.domain.com", ".com")   = "www.domain"
     * StringUtils.removeEndIgnoreCase("www.domain.com", "domain") = "www.domain.com"
     * StringUtils.removeEndIgnoreCase("abc", "")    = "abc"
     * StringUtils.removeEndIgnoreCase("www.domain.com", ".COM") = "www.domain")
     * StringUtils.removeEndIgnoreCase("www.domain.COM", ".com") = "www.domain")
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the String to search for (case insensitive) and remove, may be null
     * @return the substring with the string removed if found,
     *  {@code null} if null String input
     * @since 2.4
     */
    public static String removeEndIgnoreCase(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        if (endsWithIgnoreCase(str, remove)) {
            return str.substring(0, str.length() - remove.length());
        }
        return str;
    }

    
Removes the first substring of the text string that matches the given regular expression.
 This method is a null safe equivalent to: 

 
text.replaceFirst(regex, StringUtils.EMPTY)
 
Pattern.compile(regex).matcher(text).replaceFirst(StringUtils.EMPTY)

A null reference passed to this method is a no-op.
The Pattern.DOTALL option is NOT automatically added. To use the DOTALL option prepend "(?s)" to the regex. DOTALL is also known as single-line mode in Perl.
StringUtils.removeFirst(null, *)      = null
StringUtils.removeFirst("any", (String) null)  = "any"
StringUtils.removeFirst("any", "")    = "any"
StringUtils.removeFirst("any", ".*")  = ""
StringUtils.removeFirst("any", ".+")  = ""
StringUtils.removeFirst("abc", ".?")  = "bc"
StringUtils.removeFirst("A<__>\n<__>B", "<.*>")      = "A\n<__>B"
StringUtils.removeFirst("A<__>\n<__>B", "(?s)<.*>")  = "AB"
StringUtils.removeFirst("ABCabc123", "[a-z]")          = "ABCbc123"
StringUtils.removeFirst("ABCabc123abc", "[a-z]+")      = "ABC123abc"

Params:
text –  text to remove from, may be null
regex –  the regular expression to which this string is to be matched
Throws:
PatternSyntaxException – 
             if the regular expression's syntax is invalid
See Also:
replaceFirst(String, String, String)
String.replaceFirst(String, String)
Pattern
Pattern.DOTALL
Returns:
 the text with the first replacement processed, null if null String input
Since:
3.5
Deprecated:
Moved to RegExUtils./**
     * <p>Removes the first substring of the text string that matches the given regular expression.</p>
     *
     * This method is a {@code null} safe equivalent to:
     * <ul>
     *  <li>{@code text.replaceFirst(regex, StringUtils.EMPTY)}</li>
     *  <li>{@code Pattern.compile(regex).matcher(text).replaceFirst(StringUtils.EMPTY)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <p>The {@link Pattern#DOTALL} option is NOT automatically added.
     * To use the DOTALL option prepend {@code "(?s)"} to the regex.
     * DOTALL is also known as single-line mode in Perl.</p>
     *
     * <pre>
     * StringUtils.removeFirst(null, *)      = null
     * StringUtils.removeFirst("any", (String) null)  = "any"
     * StringUtils.removeFirst("any", "")    = "any"
     * StringUtils.removeFirst("any", ".*")  = ""
     * StringUtils.removeFirst("any", ".+")  = ""
     * StringUtils.removeFirst("abc", ".?")  = "bc"
     * StringUtils.removeFirst("A&lt;__&gt;\n&lt;__&gt;B", "&lt;.*&gt;")      = "A\n&lt;__&gt;B"
     * StringUtils.removeFirst("A&lt;__&gt;\n&lt;__&gt;B", "(?s)&lt;.*&gt;")  = "AB"
     * StringUtils.removeFirst("ABCabc123", "[a-z]")          = "ABCbc123"
     * StringUtils.removeFirst("ABCabc123abc", "[a-z]+")      = "ABC123abc"
     * </pre>
     *
     * @param text  text to remove from, may be null
     * @param regex  the regular expression to which this string is to be matched
     * @return  the text with the first replacement processed,
     *              {@code null} if null String input
     *
     * @throws  java.util.regex.PatternSyntaxException
     *              if the regular expression's syntax is invalid
     *
     * @see #replaceFirst(String, String, String)
     * @see String#replaceFirst(String, String)
     * @see java.util.regex.Pattern
     * @see java.util.regex.Pattern#DOTALL
     * @since 3.5
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String removeFirst(final String text, final String regex) {
        return replaceFirst(text, regex, EMPTY);
    }

    

Case insensitive removal of all occurrences of a substring from within
the source string.

 A null source string will return null. An empty ("") source string will return the empty string. A null remove string will return the source string. An empty ("") remove string will return the source string. 
StringUtils.removeIgnoreCase(null, *)        = null
StringUtils.removeIgnoreCase("", *)          = ""
StringUtils.removeIgnoreCase(*, null)        = *
StringUtils.removeIgnoreCase(*, "")          = *
StringUtils.removeIgnoreCase("queued", "ue") = "qd"
StringUtils.removeIgnoreCase("queued", "zz") = "queued"
StringUtils.removeIgnoreCase("quEUed", "UE") = "qd"
StringUtils.removeIgnoreCase("queued", "zZ") = "queued"

Params:
str – 
           the source String to search, may be null
remove – 
           the String to search for (case insensitive) and remove, may be
           null
Returns:
the substring with the string removed if found, null if null String input
Since:
3.5/**
     * <p>
     * Case insensitive removal of all occurrences of a substring from within
     * the source string.
     * </p>
     *
     * <p>
     * A {@code null} source string will return {@code null}. An empty ("")
     * source string will return the empty string. A {@code null} remove string
     * will return the source string. An empty ("") remove string will return
     * the source string.
     * </p>
     *
     * <pre>
     * StringUtils.removeIgnoreCase(null, *)        = null
     * StringUtils.removeIgnoreCase("", *)          = ""
     * StringUtils.removeIgnoreCase(*, null)        = *
     * StringUtils.removeIgnoreCase(*, "")          = *
     * StringUtils.removeIgnoreCase("queued", "ue") = "qd"
     * StringUtils.removeIgnoreCase("queued", "zz") = "queued"
     * StringUtils.removeIgnoreCase("quEUed", "UE") = "qd"
     * StringUtils.removeIgnoreCase("queued", "zZ") = "queued"
     * </pre>
     *
     * @param str
     *            the source String to search, may be null
     * @param remove
     *            the String to search for (case insensitive) and remove, may be
     *            null
     * @return the substring with the string removed if found, {@code null} if
     *         null String input
     * @since 3.5
     */
    public static String removeIgnoreCase(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        return replaceIgnoreCase(str, remove, EMPTY, -1);
    }

    
Removes each substring of the source String that matches the given regular expression using the DOTALL option.
 This call is a null safe equivalent to: 

source.replaceAll(&quot;(?s)&quot; + regex, StringUtils.EMPTY)
Pattern.compile(regex, Pattern.DOTALL).matcher(source).replaceAll(StringUtils.EMPTY)

A null reference passed to this method is a no-op.
StringUtils.removePattern(null, *)       = null
StringUtils.removePattern("any", (String) null)   = "any"
StringUtils.removePattern("A<__>\n<__>B", "<.*>")  = "AB"
StringUtils.removePattern("ABCabc123", "[a-z]")    = "ABC123"

Params:
source – 
           the source string
regex – 
           the regular expression to which this string is to be matched
See Also:
replacePattern(String, String, String)
String.replaceAll(String, String)
Pattern.DOTALL
Returns:
The resulting String
Since:
3.2
Since:
3.5 Changed null reference passed to this method is a no-op.
Deprecated:
Moved to RegExUtils./**
     * <p>Removes each substring of the source String that matches the given regular expression using the DOTALL option.
     * </p>
     *
     * This call is a {@code null} safe equivalent to:
     * <ul>
     * <li>{@code source.replaceAll(&quot;(?s)&quot; + regex, StringUtils.EMPTY)}</li>
     * <li>{@code Pattern.compile(regex, Pattern.DOTALL).matcher(source).replaceAll(StringUtils.EMPTY)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.removePattern(null, *)       = null
     * StringUtils.removePattern("any", (String) null)   = "any"
     * StringUtils.removePattern("A&lt;__&gt;\n&lt;__&gt;B", "&lt;.*&gt;")  = "AB"
     * StringUtils.removePattern("ABCabc123", "[a-z]")    = "ABC123"
     * </pre>
     *
     * @param source
     *            the source string
     * @param regex
     *            the regular expression to which this string is to be matched
     * @return The resulting {@code String}
     * @see #replacePattern(String, String, String)
     * @see String#replaceAll(String, String)
     * @see Pattern#DOTALL
     * @since 3.2
     * @since 3.5 Changed {@code null} reference passed to this method is a no-op.
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String removePattern(final String source, final String regex) {
        return RegExUtils.removePattern(source, regex);
    }

    // Remove
    //-----------------------------------------------------------------------
    
Removes a substring only if it is at the beginning of a source string,
otherwise returns the source string.
A null source string will return null. An empty ("") source string will return the empty string. A null search string will return the source string.
StringUtils.removeStart(null, *)      = null
StringUtils.removeStart("", *)        = ""
StringUtils.removeStart(*, null)      = *
StringUtils.removeStart("www.domain.com", "www.")   = "domain.com"
StringUtils.removeStart("domain.com", "www.")       = "domain.com"
StringUtils.removeStart("www.domain.com", "domain") = "www.domain.com"
StringUtils.removeStart("abc", "")    = "abc"

Params:
str –  the source String to search, may be null
remove –  the String to search for and remove, may be null
Returns:
the substring with the string removed if found, null if null String input
Since:
2.1/**
     * <p>Removes a substring only if it is at the beginning of a source string,
     * otherwise returns the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.
     * A {@code null} search string will return the source string.</p>
     *
     * <pre>
     * StringUtils.removeStart(null, *)      = null
     * StringUtils.removeStart("", *)        = ""
     * StringUtils.removeStart(*, null)      = *
     * StringUtils.removeStart("www.domain.com", "www.")   = "domain.com"
     * StringUtils.removeStart("domain.com", "www.")       = "domain.com"
     * StringUtils.removeStart("www.domain.com", "domain") = "www.domain.com"
     * StringUtils.removeStart("abc", "")    = "abc"
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the String to search for and remove, may be null
     * @return the substring with the string removed if found,
     *  {@code null} if null String input
     * @since 2.1
     */
    public static String removeStart(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        if (str.startsWith(remove)) {
            return str.substring(remove.length());
        }
        return str;
    }

    
Case insensitive removal of a substring if it is at the beginning of a source string,
otherwise returns the source string.
A null source string will return null. An empty ("") source string will return the empty string. A null search string will return the source string.
StringUtils.removeStartIgnoreCase(null, *)      = null
StringUtils.removeStartIgnoreCase("", *)        = ""
StringUtils.removeStartIgnoreCase(*, null)      = *
StringUtils.removeStartIgnoreCase("www.domain.com", "www.")   = "domain.com"
StringUtils.removeStartIgnoreCase("www.domain.com", "WWW.")   = "domain.com"
StringUtils.removeStartIgnoreCase("domain.com", "www.")       = "domain.com"
StringUtils.removeStartIgnoreCase("www.domain.com", "domain") = "www.domain.com"
StringUtils.removeStartIgnoreCase("abc", "")    = "abc"

Params:
str –  the source String to search, may be null
remove –  the String to search for (case insensitive) and remove, may be null
Returns:
the substring with the string removed if found, null if null String input
Since:
2.4/**
     * <p>Case insensitive removal of a substring if it is at the beginning of a source string,
     * otherwise returns the source string.</p>
     *
     * <p>A {@code null} source string will return {@code null}.
     * An empty ("") source string will return the empty string.
     * A {@code null} search string will return the source string.</p>
     *
     * <pre>
     * StringUtils.removeStartIgnoreCase(null, *)      = null
     * StringUtils.removeStartIgnoreCase("", *)        = ""
     * StringUtils.removeStartIgnoreCase(*, null)      = *
     * StringUtils.removeStartIgnoreCase("www.domain.com", "www.")   = "domain.com"
     * StringUtils.removeStartIgnoreCase("www.domain.com", "WWW.")   = "domain.com"
     * StringUtils.removeStartIgnoreCase("domain.com", "www.")       = "domain.com"
     * StringUtils.removeStartIgnoreCase("www.domain.com", "domain") = "www.domain.com"
     * StringUtils.removeStartIgnoreCase("abc", "")    = "abc"
     * </pre>
     *
     * @param str  the source String to search, may be null
     * @param remove  the String to search for (case insensitive) and remove, may be null
     * @return the substring with the string removed if found,
     *  {@code null} if null String input
     * @since 2.4
     */
    public static String removeStartIgnoreCase(final String str, final String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }
        if (startsWithIgnoreCase(str, remove)) {
            return str.substring(remove.length());
        }
        return str;
    }

    
Returns padding using the specified delimiter repeated
to a given length.
StringUtils.repeat('e', 0)  = ""
StringUtils.repeat('e', 3)  = "eee"
StringUtils.repeat('e', -2) = ""

Note: this method does not support padding with
Unicode Supplementary Characters as they require a pair of chars to be represented. If you are needing to support full I18N of your applications consider using repeat(String, int) instead. 
Params:
ch –  character to repeat
repeat –  number of times to repeat char, negative treated as zero
See Also:
repeat(String, int)
Returns:
String with repeated character/**
     * <p>Returns padding using the specified delimiter repeated
     * to a given length.</p>
     *
     * <pre>
     * StringUtils.repeat('e', 0)  = ""
     * StringUtils.repeat('e', 3)  = "eee"
     * StringUtils.repeat('e', -2) = ""
     * </pre>
     *
     * <p>Note: this method does not support padding with
     * <a href="http://www.unicode.org/glossary/#supplementary_character">Unicode Supplementary Characters</a>
     * as they require a pair of {@code char}s to be represented.
     * If you are needing to support full I18N of your applications
     * consider using {@link #repeat(String, int)} instead.
     * </p>
     *
     * @param ch  character to repeat
     * @param repeat  number of times to repeat char, negative treated as zero
     * @return String with repeated character
     * @see #repeat(String, int)
     */
    public static String repeat(final char ch, final int repeat) {
        if (repeat <= 0) {
            return EMPTY;
        }
        final char[] buf = new char[repeat];
        for (int i = repeat - 1; i >= 0; i--) {
            buf[i] = ch;
        }
        return new String(buf);
    }

    // Padding
    //-----------------------------------------------------------------------
    
Repeat a String repeat times to form a new String.
StringUtils.repeat(null, 2) = null
StringUtils.repeat("", 0)   = ""
StringUtils.repeat("", 2)   = ""
StringUtils.repeat("a", 3)  = "aaa"
StringUtils.repeat("ab", 2) = "abab"
StringUtils.repeat("a", -2) = ""

Params:
str –  the String to repeat, may be null
repeat –  number of times to repeat str, negative treated as zero
Returns:
a new String consisting of the original String repeated, null if null String input/**
     * <p>Repeat a String {@code repeat} times to form a
     * new String.</p>
     *
     * <pre>
     * StringUtils.repeat(null, 2) = null
     * StringUtils.repeat("", 0)   = ""
     * StringUtils.repeat("", 2)   = ""
     * StringUtils.repeat("a", 3)  = "aaa"
     * StringUtils.repeat("ab", 2) = "abab"
     * StringUtils.repeat("a", -2) = ""
     * </pre>
     *
     * @param str  the String to repeat, may be null
     * @param repeat  number of times to repeat str, negative treated as zero
     * @return a new String consisting of the original String repeated,
     *  {@code null} if null String input
     */
    public static String repeat(final String str, final int repeat) {
        // Performance tuned for 2.0 (JDK1.4)

        if (str == null) {
            return null;
        }
        if (repeat <= 0) {
            return EMPTY;
        }
        final int inputLength = str.length();
        if (repeat == 1 || inputLength == 0) {
            return str;
        }
        if (inputLength == 1 && repeat <= PAD_LIMIT) {
            return repeat(str.charAt(0), repeat);
        }

        final int outputLength = inputLength * repeat;
        switch (inputLength) {
            case 1 :
                return repeat(str.charAt(0), repeat);
            case 2 :
                final char ch0 = str.charAt(0);
                final char ch1 = str.charAt(1);
                final char[] output2 = new char[outputLength];
                for (int i = repeat * 2 - 2; i >= 0; i--, i--) {
                    output2[i] = ch0;
                    output2[i + 1] = ch1;
                }
                return new String(output2);
            default :
                final StringBuilder buf = new StringBuilder(outputLength);
                for (int i = 0; i < repeat; i++) {
                    buf.append(str);
                }
                return buf.toString();
        }
    }

    // Conversion
    //-----------------------------------------------------------------------

    
Repeat a String repeat times to form a new String, with a String separator injected each time. 
StringUtils.repeat(null, null, 2) = null
StringUtils.repeat(null, "x", 2)  = null
StringUtils.repeat("", null, 0)   = ""
StringUtils.repeat("", "", 2)     = ""
StringUtils.repeat("", "x", 3)    = "xxx"
StringUtils.repeat("?", ", ", 3)  = "?, ?, ?"

Params:
str –        the String to repeat, may be null
separator –  the String to inject, may be null
repeat –     number of times to repeat str, negative treated as zero
Returns:
a new String consisting of the original String repeated, null if null String input
Since:
2.5/**
     * <p>Repeat a String {@code repeat} times to form a
     * new String, with a String separator injected each time. </p>
     *
     * <pre>
     * StringUtils.repeat(null, null, 2) = null
     * StringUtils.repeat(null, "x", 2)  = null
     * StringUtils.repeat("", null, 0)   = ""
     * StringUtils.repeat("", "", 2)     = ""
     * StringUtils.repeat("", "x", 3)    = "xxx"
     * StringUtils.repeat("?", ", ", 3)  = "?, ?, ?"
     * </pre>
     *
     * @param str        the String to repeat, may be null
     * @param separator  the String to inject, may be null
     * @param repeat     number of times to repeat str, negative treated as zero
     * @return a new String consisting of the original String repeated,
     *  {@code null} if null String input
     * @since 2.5
     */
    public static String repeat(final String str, final String separator, final int repeat) {
        if (str == null || separator == null) {
            return repeat(str, repeat);
        }
        // given that repeat(String, int) is quite optimized, better to rely on it than try and splice this into it
        final String result = repeat(str + separator, repeat);
        return removeEnd(result, separator);
    }

    
Replaces all occurrences of a String within another String.
A null reference passed to this method is a no-op.
StringUtils.replace(null, *, *)        = null
StringUtils.replace("", *, *)          = ""
StringUtils.replace("any", null, *)    = "any"
StringUtils.replace("any", *, null)    = "any"
StringUtils.replace("any", "", *)      = "any"
StringUtils.replace("aba", "a", null)  = "aba"
StringUtils.replace("aba", "a", "")    = "b"
StringUtils.replace("aba", "a", "z")   = "zbz"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for, may be null
replacement –  the String to replace it with, may be null
See Also:
replace(String text, String searchString, String replacement, int max)
Returns:
the text with any replacements processed, null if null String input/**
     * <p>Replaces all occurrences of a String within another String.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replace(null, *, *)        = null
     * StringUtils.replace("", *, *)          = ""
     * StringUtils.replace("any", null, *)    = "any"
     * StringUtils.replace("any", *, null)    = "any"
     * StringUtils.replace("any", "", *)      = "any"
     * StringUtils.replace("aba", "a", null)  = "aba"
     * StringUtils.replace("aba", "a", "")    = "b"
     * StringUtils.replace("aba", "a", "z")   = "zbz"
     * </pre>
     *
     * @see #replace(String text, String searchString, String replacement, int max)
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for, may be null
     * @param replacement  the String to replace it with, may be null
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     */
    public static String replace(final String text, final String searchString, final String replacement) {
        return replace(text, searchString, replacement, -1);
    }

    
Replaces a String with another String inside a larger String, for the first max values of the search String.
A null reference passed to this method is a no-op.
StringUtils.replace(null, *, *, *)         = null
StringUtils.replace("", *, *, *)           = ""
StringUtils.replace("any", null, *, *)     = "any"
StringUtils.replace("any", *, null, *)     = "any"
StringUtils.replace("any", "", *, *)       = "any"
StringUtils.replace("any", *, *, 0)        = "any"
StringUtils.replace("abaa", "a", null, -1) = "abaa"
StringUtils.replace("abaa", "a", "", -1)   = "b"
StringUtils.replace("abaa", "a", "z", 0)   = "abaa"
StringUtils.replace("abaa", "a", "z", 1)   = "zbaa"
StringUtils.replace("abaa", "a", "z", 2)   = "zbza"
StringUtils.replace("abaa", "a", "z", -1)  = "zbzz"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for, may be null
replacement –  the String to replace it with, may be null
max –  maximum number of values to replace, or -1 if no maximum
Returns:
the text with any replacements processed, null if null String input/**
     * <p>Replaces a String with another String inside a larger String,
     * for the first {@code max} values of the search String.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replace(null, *, *, *)         = null
     * StringUtils.replace("", *, *, *)           = ""
     * StringUtils.replace("any", null, *, *)     = "any"
     * StringUtils.replace("any", *, null, *)     = "any"
     * StringUtils.replace("any", "", *, *)       = "any"
     * StringUtils.replace("any", *, *, 0)        = "any"
     * StringUtils.replace("abaa", "a", null, -1) = "abaa"
     * StringUtils.replace("abaa", "a", "", -1)   = "b"
     * StringUtils.replace("abaa", "a", "z", 0)   = "abaa"
     * StringUtils.replace("abaa", "a", "z", 1)   = "zbaa"
     * StringUtils.replace("abaa", "a", "z", 2)   = "zbza"
     * StringUtils.replace("abaa", "a", "z", -1)  = "zbzz"
     * </pre>
     *
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for, may be null
     * @param replacement  the String to replace it with, may be null
     * @param max  maximum number of values to replace, or {@code -1} if no maximum
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     */
    public static String replace(final String text, final String searchString, final String replacement, final int max) {
        return replace(text, searchString, replacement, max, false);
    }

    
Replaces a String with another String inside a larger String, for the first max values of the search String, case sensitively/insensitively based on ignoreCase value.
A null reference passed to this method is a no-op.
StringUtils.replace(null, *, *, *, false)         = null
StringUtils.replace("", *, *, *, false)           = ""
StringUtils.replace("any", null, *, *, false)     = "any"
StringUtils.replace("any", *, null, *, false)     = "any"
StringUtils.replace("any", "", *, *, false)       = "any"
StringUtils.replace("any", *, *, 0, false)        = "any"
StringUtils.replace("abaa", "a", null, -1, false) = "abaa"
StringUtils.replace("abaa", "a", "", -1, false)   = "b"
StringUtils.replace("abaa", "a", "z", 0, false)   = "abaa"
StringUtils.replace("abaa", "A", "z", 1, false)   = "abaa"
StringUtils.replace("abaa", "A", "z", 1, true)   = "zbaa"
StringUtils.replace("abAa", "a", "z", 2, true)   = "zbza"
StringUtils.replace("abAa", "a", "z", -1, true)  = "zbzz"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for (case insensitive), may be null
replacement –  the String to replace it with, may be null
max –  maximum number of values to replace, or -1 if no maximum
ignoreCase – if true replace is case insensitive, otherwise case sensitive
Returns:
the text with any replacements processed, null if null String input/**
     * <p>Replaces a String with another String inside a larger String,
     * for the first {@code max} values of the search String,
     * case sensitively/insensitively based on {@code ignoreCase} value.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replace(null, *, *, *, false)         = null
     * StringUtils.replace("", *, *, *, false)           = ""
     * StringUtils.replace("any", null, *, *, false)     = "any"
     * StringUtils.replace("any", *, null, *, false)     = "any"
     * StringUtils.replace("any", "", *, *, false)       = "any"
     * StringUtils.replace("any", *, *, 0, false)        = "any"
     * StringUtils.replace("abaa", "a", null, -1, false) = "abaa"
     * StringUtils.replace("abaa", "a", "", -1, false)   = "b"
     * StringUtils.replace("abaa", "a", "z", 0, false)   = "abaa"
     * StringUtils.replace("abaa", "A", "z", 1, false)   = "abaa"
     * StringUtils.replace("abaa", "A", "z", 1, true)   = "zbaa"
     * StringUtils.replace("abAa", "a", "z", 2, true)   = "zbza"
     * StringUtils.replace("abAa", "a", "z", -1, true)  = "zbzz"
     * </pre>
     *
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for (case insensitive), may be null
     * @param replacement  the String to replace it with, may be null
     * @param max  maximum number of values to replace, or {@code -1} if no maximum
     * @param ignoreCase if true replace is case insensitive, otherwise case sensitive
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     */
     private static String replace(final String text, String searchString, final String replacement, int max, final boolean ignoreCase) {
         if (isEmpty(text) || isEmpty(searchString) || replacement == null || max == 0) {
             return text;
         }
         if (ignoreCase) {
             searchString = searchString.toLowerCase();
         }
         int start = 0;
         int end = ignoreCase ? indexOfIgnoreCase(text, searchString, start) : indexOf(text, searchString, start);
         if (end == INDEX_NOT_FOUND) {
             return text;
         }
         final int replLength = searchString.length();
         int increase = Math.max(replacement.length() - replLength, 0);
         increase *= max < 0 ? 16 : Math.min(max, 64);
         final StringBuilder buf = new StringBuilder(text.length() + increase);
         while (end != INDEX_NOT_FOUND) {
             buf.append(text, start, end).append(replacement);
             start = end + replLength;
             if (--max == 0) {
                 break;
             }
             end = ignoreCase ? indexOfIgnoreCase(text, searchString, start) : indexOf(text, searchString, start);
         }
         buf.append(text, start, text.length());
         return buf.toString();
     }

    
Replaces each substring of the text String that matches the given regular expression
with the given replacement.
 This method is a null safe equivalent to: 

 
text.replaceAll(regex, replacement)
 
Pattern.compile(regex).matcher(text).replaceAll(replacement)

A null reference passed to this method is a no-op.
Unlike in the replacePattern(String, String, String) method, the Pattern.DOTALL option is NOT automatically added. To use the DOTALL option prepend "(?s)" to the regex. DOTALL is also known as single-line mode in Perl.
StringUtils.replaceAll(null, *, *)       = null
StringUtils.replaceAll("any", (String) null, *)   = "any"
StringUtils.replaceAll("any", *, null)   = "any"
StringUtils.replaceAll("", "", "zzz")    = "zzz"
StringUtils.replaceAll("", ".*", "zzz")  = "zzz"
StringUtils.replaceAll("", ".+", "zzz")  = ""
StringUtils.replaceAll("abc", "", "ZZ")  = "ZZaZZbZZcZZ"
StringUtils.replaceAll("<__>\n<__>", "<.*>", "z")      = "z\nz"
StringUtils.replaceAll("<__>\n<__>", "(?s)<.*>", "z")  = "z"
StringUtils.replaceAll("ABCabc123", "[a-z]", "_")       = "ABC___123"
StringUtils.replaceAll("ABCabc123", "[^A-Z0-9]+", "_")  = "ABC_123"
StringUtils.replaceAll("ABCabc123", "[^A-Z0-9]+", "")   = "ABC123"
StringUtils.replaceAll("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum_dolor_sit"

Params:
text –  text to search and replace in, may be null
regex –  the regular expression to which this string is to be matched
replacement –  the string to be substituted for each match
Throws:
PatternSyntaxException – 
             if the regular expression's syntax is invalid
See Also:
replacePattern(String, String, String)
String.replaceAll(String, String)
Pattern
Pattern.DOTALL
Returns:
 the text with any replacements processed, null if null String input
Since:
3.5
Deprecated:
Moved to RegExUtils./**
     * <p>Replaces each substring of the text String that matches the given regular expression
     * with the given replacement.</p>
     *
     * This method is a {@code null} safe equivalent to:
     * <ul>
     *  <li>{@code text.replaceAll(regex, replacement)}</li>
     *  <li>{@code Pattern.compile(regex).matcher(text).replaceAll(replacement)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <p>Unlike in the {@link #replacePattern(String, String, String)} method, the {@link Pattern#DOTALL} option
     * is NOT automatically added.
     * To use the DOTALL option prepend {@code "(?s)"} to the regex.
     * DOTALL is also known as single-line mode in Perl.</p>
     *
     * <pre>
     * StringUtils.replaceAll(null, *, *)       = null
     * StringUtils.replaceAll("any", (String) null, *)   = "any"
     * StringUtils.replaceAll("any", *, null)   = "any"
     * StringUtils.replaceAll("", "", "zzz")    = "zzz"
     * StringUtils.replaceAll("", ".*", "zzz")  = "zzz"
     * StringUtils.replaceAll("", ".+", "zzz")  = ""
     * StringUtils.replaceAll("abc", "", "ZZ")  = "ZZaZZbZZcZZ"
     * StringUtils.replaceAll("&lt;__&gt;\n&lt;__&gt;", "&lt;.*&gt;", "z")      = "z\nz"
     * StringUtils.replaceAll("&lt;__&gt;\n&lt;__&gt;", "(?s)&lt;.*&gt;", "z")  = "z"
     * StringUtils.replaceAll("ABCabc123", "[a-z]", "_")       = "ABC___123"
     * StringUtils.replaceAll("ABCabc123", "[^A-Z0-9]+", "_")  = "ABC_123"
     * StringUtils.replaceAll("ABCabc123", "[^A-Z0-9]+", "")   = "ABC123"
     * StringUtils.replaceAll("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum_dolor_sit"
     * </pre>
     *
     * @param text  text to search and replace in, may be null
     * @param regex  the regular expression to which this string is to be matched
     * @param replacement  the string to be substituted for each match
     * @return  the text with any replacements processed,
     *              {@code null} if null String input
     *
     * @throws  java.util.regex.PatternSyntaxException
     *              if the regular expression's syntax is invalid
     *
     * @see #replacePattern(String, String, String)
     * @see String#replaceAll(String, String)
     * @see java.util.regex.Pattern
     * @see java.util.regex.Pattern#DOTALL
     * @since 3.5
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String replaceAll(final String text, final String regex, final String replacement) {
        return RegExUtils.replaceAll(text, regex, replacement);
    }

    // Replace, character based
    //-----------------------------------------------------------------------
    
Replaces all occurrences of a character in a String with another. This is a null-safe version of String.replace(char, char).
A null string input returns null. An empty ("") string input returns an empty string.
StringUtils.replaceChars(null, *, *)        = null
StringUtils.replaceChars("", *, *)          = ""
StringUtils.replaceChars("abcba", 'b', 'y') = "aycya"
StringUtils.replaceChars("abcba", 'z', 'y') = "abcba"

Params:
str –  String to replace characters in, may be null
searchChar –  the character to search for, may be null
replaceChar –  the character to replace, may be null
Returns:
modified String, null if null string input
Since:
2.0/**
     * <p>Replaces all occurrences of a character in a String with another.
     * This is a null-safe version of {@link String#replace(char, char)}.</p>
     *
     * <p>A {@code null} string input returns {@code null}.
     * An empty ("") string input returns an empty string.</p>
     *
     * <pre>
     * StringUtils.replaceChars(null, *, *)        = null
     * StringUtils.replaceChars("", *, *)          = ""
     * StringUtils.replaceChars("abcba", 'b', 'y') = "aycya"
     * StringUtils.replaceChars("abcba", 'z', 'y') = "abcba"
     * </pre>
     *
     * @param str  String to replace characters in, may be null
     * @param searchChar  the character to search for, may be null
     * @param replaceChar  the character to replace, may be null
     * @return modified String, {@code null} if null string input
     * @since 2.0
     */
    public static String replaceChars(final String str, final char searchChar, final char replaceChar) {
        if (str == null) {
            return null;
        }
        return str.replace(searchChar, replaceChar);
    }

    
Replaces multiple characters in a String in one go.
This method can also be used to delete characters.
For example:
 replaceChars(&quot;hello&quot;, &quot;ho&quot;, &quot;jy&quot;) = jelly.
A null string input returns null. An empty ("") string input returns an empty string. A null or empty set of search characters returns the input string.
The length of the search characters should normally equal the length
of the replace characters.
If the search characters is longer, then the extra search characters
are deleted.
If the search characters is shorter, then the extra replace characters
are ignored.
StringUtils.replaceChars(null, *, *)           = null
StringUtils.replaceChars("", *, *)             = ""
StringUtils.replaceChars("abc", null, *)       = "abc"
StringUtils.replaceChars("abc", "", *)         = "abc"
StringUtils.replaceChars("abc", "b", null)     = "ac"
StringUtils.replaceChars("abc", "b", "")       = "ac"
StringUtils.replaceChars("abcba", "bc", "yz")  = "ayzya"
StringUtils.replaceChars("abcba", "bc", "y")   = "ayya"
StringUtils.replaceChars("abcba", "bc", "yzx") = "ayzya"

Params:
str –  String to replace characters in, may be null
searchChars –  a set of characters to search for, may be null
replaceChars –  a set of characters to replace, may be null
Returns:
modified String, null if null string input
Since:
2.0/**
     * <p>Replaces multiple characters in a String in one go.
     * This method can also be used to delete characters.</p>
     *
     * <p>For example:<br>
     * {@code replaceChars(&quot;hello&quot;, &quot;ho&quot;, &quot;jy&quot;) = jelly}.</p>
     *
     * <p>A {@code null} string input returns {@code null}.
     * An empty ("") string input returns an empty string.
     * A null or empty set of search characters returns the input string.</p>
     *
     * <p>The length of the search characters should normally equal the length
     * of the replace characters.
     * If the search characters is longer, then the extra search characters
     * are deleted.
     * If the search characters is shorter, then the extra replace characters
     * are ignored.</p>
     *
     * <pre>
     * StringUtils.replaceChars(null, *, *)           = null
     * StringUtils.replaceChars("", *, *)             = ""
     * StringUtils.replaceChars("abc", null, *)       = "abc"
     * StringUtils.replaceChars("abc", "", *)         = "abc"
     * StringUtils.replaceChars("abc", "b", null)     = "ac"
     * StringUtils.replaceChars("abc", "b", "")       = "ac"
     * StringUtils.replaceChars("abcba", "bc", "yz")  = "ayzya"
     * StringUtils.replaceChars("abcba", "bc", "y")   = "ayya"
     * StringUtils.replaceChars("abcba", "bc", "yzx") = "ayzya"
     * </pre>
     *
     * @param str  String to replace characters in, may be null
     * @param searchChars  a set of characters to search for, may be null
     * @param replaceChars  a set of characters to replace, may be null
     * @return modified String, {@code null} if null string input
     * @since 2.0
     */
    public static String replaceChars(final String str, final String searchChars, String replaceChars) {
        if (isEmpty(str) || isEmpty(searchChars)) {
            return str;
        }
        if (replaceChars == null) {
            replaceChars = EMPTY;
        }
        boolean modified = false;
        final int replaceCharsLength = replaceChars.length();
        final int strLength = str.length();
        final StringBuilder buf = new StringBuilder(strLength);
        for (int i = 0; i < strLength; i++) {
            final char ch = str.charAt(i);
            final int index = searchChars.indexOf(ch);
            if (index >= 0) {
                modified = true;
                if (index < replaceCharsLength) {
                    buf.append(replaceChars.charAt(index));
                }
            } else {
                buf.append(ch);
            }
        }
        if (modified) {
            return buf.toString();
        }
        return str;
    }

    

Replaces all occurrences of Strings within another String.

 A null reference passed to this method is a no-op, or if any "search string" or "string to replace" is null, that replace will be ignored. This will not repeat. For repeating replaces, call the overloaded method. 
 StringUtils.replaceEach(null, *, *)        = null
 StringUtils.replaceEach("", *, *)          = ""
 StringUtils.replaceEach("aba", null, null) = "aba"
 StringUtils.replaceEach("aba", new String[0], null) = "aba"
 StringUtils.replaceEach("aba", null, new String[0]) = "aba"
 StringUtils.replaceEach("aba", new String[]{"a"}, null)  = "aba"
 StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""})  = "b"
 StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"})  = "aba"
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"})  = "wcte"
 (example of how it does not repeat)
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"})  = "dcte"

Params:
text – 
           text to search and replace in, no-op if null
searchList – 
           the Strings to search for, no-op if null
replacementList – 
           the Strings to replace them with, no-op if null
Throws:
IllegalArgumentException – 
            if the lengths of the arrays are not the same (null is ok,
            and/or size 0)
Returns:
the text with any replacements processed, null if null String input
Since:
2.4/**
     * <p>
     * Replaces all occurrences of Strings within another String.
     * </p>
     *
     * <p>
     * A {@code null} reference passed to this method is a no-op, or if
     * any "search string" or "string to replace" is null, that replace will be
     * ignored. This will not repeat. For repeating replaces, call the
     * overloaded method.
     * </p>
     *
     * <pre>
     *  StringUtils.replaceEach(null, *, *)        = null
     *  StringUtils.replaceEach("", *, *)          = ""
     *  StringUtils.replaceEach("aba", null, null) = "aba"
     *  StringUtils.replaceEach("aba", new String[0], null) = "aba"
     *  StringUtils.replaceEach("aba", null, new String[0]) = "aba"
     *  StringUtils.replaceEach("aba", new String[]{"a"}, null)  = "aba"
     *  StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""})  = "b"
     *  StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"})  = "aba"
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"})  = "wcte"
     *  (example of how it does not repeat)
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"})  = "dcte"
     * </pre>
     *
     * @param text
     *            text to search and replace in, no-op if null
     * @param searchList
     *            the Strings to search for, no-op if null
     * @param replacementList
     *            the Strings to replace them with, no-op if null
     * @return the text with any replacements processed, {@code null} if
     *         null String input
     * @throws IllegalArgumentException
     *             if the lengths of the arrays are not the same (null is ok,
     *             and/or size 0)
     * @since 2.4
     */
    public static String replaceEach(final String text, final String[] searchList, final String[] replacementList) {
        return replaceEach(text, searchList, replacementList, false, 0);
    }

    
 Replace all occurrences of Strings within another String. This is a private recursive helper method for replaceEachRepeatedly(String, String[], String[]) and replaceEach(String, String[], String[]) 
 A null reference passed to this method is a no-op, or if any "search string" or "string to replace" is null, that replace will be ignored. 
 StringUtils.replaceEach(null, *, *, *, *) = null
 StringUtils.replaceEach("", *, *, *, *) = ""
 StringUtils.replaceEach("aba", null, null, *, *) = "aba"
 StringUtils.replaceEach("aba", new String[0], null, *, *) = "aba"
 StringUtils.replaceEach("aba", null, new String[0], *, *) = "aba"
 StringUtils.replaceEach("aba", new String[]{"a"}, null, *, *) = "aba"
 StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""}, *, >=0) = "b"
 StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"}, *, >=0) = "aba"
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"}, *, >=0) = "wcte"
 (example of how it repeats)
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, false, >=0) = "dcte"
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, true, >=2) = "tcte"
 StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}, *, *) = IllegalStateException

Params:
text – 
           text to search and replace in, no-op if null
searchList – 
           the Strings to search for, no-op if null
replacementList – 
           the Strings to replace them with, no-op if null
repeat – if true, then replace repeatedly
      until there are no more possible replacements or timeToLive < 0
timeToLive – 
           if less than 0 then there is a circular reference and endless
           loop
Throws:
IllegalStateException – 
            if the search is repeating and there is an endless loop due
            to outputs of one being inputs to another
IllegalArgumentException – 
            if the lengths of the arrays are not the same (null is ok,
            and/or size 0)
Returns:
the text with any replacements processed, null if null String input
Since:
2.4/**
     * <p>
     * Replace all occurrences of Strings within another String.
     * This is a private recursive helper method for {@link #replaceEachRepeatedly(String, String[], String[])} and
     * {@link #replaceEach(String, String[], String[])}
     * </p>
     *
     * <p>
     * A {@code null} reference passed to this method is a no-op, or if
     * any "search string" or "string to replace" is null, that replace will be
     * ignored.
     * </p>
     *
     * <pre>
     *  StringUtils.replaceEach(null, *, *, *, *) = null
     *  StringUtils.replaceEach("", *, *, *, *) = ""
     *  StringUtils.replaceEach("aba", null, null, *, *) = "aba"
     *  StringUtils.replaceEach("aba", new String[0], null, *, *) = "aba"
     *  StringUtils.replaceEach("aba", null, new String[0], *, *) = "aba"
     *  StringUtils.replaceEach("aba", new String[]{"a"}, null, *, *) = "aba"
     *  StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""}, *, >=0) = "b"
     *  StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"}, *, >=0) = "aba"
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"}, *, >=0) = "wcte"
     *  (example of how it repeats)
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, false, >=0) = "dcte"
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, true, >=2) = "tcte"
     *  StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}, *, *) = IllegalStateException
     * </pre>
     *
     * @param text
     *            text to search and replace in, no-op if null
     * @param searchList
     *            the Strings to search for, no-op if null
     * @param replacementList
     *            the Strings to replace them with, no-op if null
     * @param repeat if true, then replace repeatedly
     *       until there are no more possible replacements or timeToLive < 0
     * @param timeToLive
     *            if less than 0 then there is a circular reference and endless
     *            loop
     * @return the text with any replacements processed, {@code null} if
     *         null String input
     * @throws IllegalStateException
     *             if the search is repeating and there is an endless loop due
     *             to outputs of one being inputs to another
     * @throws IllegalArgumentException
     *             if the lengths of the arrays are not the same (null is ok,
     *             and/or size 0)
     * @since 2.4
     */
    private static String replaceEach(
            final String text, final String[] searchList, final String[] replacementList, final boolean repeat, final int timeToLive) {

        // mchyzer Performance note: This creates very few new objects (one major goal)
        // let me know if there are performance requests, we can create a harness to measure

        // if recursing, this shouldn't be less than 0
        if (timeToLive < 0) {
            final Set<String> searchSet = new HashSet<>(Arrays.asList(searchList));
            final Set<String> replacementSet = new HashSet<>(Arrays.asList(replacementList));
            searchSet.retainAll(replacementSet);
            if (searchSet.size() > 0) {
                throw new IllegalStateException("Aborting to protect against StackOverflowError - " +
                        "output of one loop is the input of another");
            }
        }

        if (isEmpty(text) || ArrayUtils.isEmpty(searchList) || ArrayUtils.isEmpty(replacementList) || (ArrayUtils.isNotEmpty(searchList) && timeToLive == -1)) {
            return text;
        }

        final int searchLength = searchList.length;
        final int replacementLength = replacementList.length;

        // make sure lengths are ok, these need to be equal
        if (searchLength != replacementLength) {
            throw new IllegalArgumentException("Search and Replace array lengths don't match: "
                + searchLength
                + " vs "
                + replacementLength);
        }

        // keep track of which still have matches
        final boolean[] noMoreMatchesForReplIndex = new boolean[searchLength];

        // index on index that the match was found
        int textIndex = -1;
        int replaceIndex = -1;
        int tempIndex = -1;

        // index of replace array that will replace the search string found
        // NOTE: logic duplicated below START
        for (int i = 0; i < searchLength; i++) {
            if (noMoreMatchesForReplIndex[i] || isEmpty(searchList[i]) || replacementList[i] == null) {
                continue;
            }
            tempIndex = text.indexOf(searchList[i]);

            // see if we need to keep searching for this
            if (tempIndex == -1) {
                noMoreMatchesForReplIndex[i] = true;
            } else {
                if (textIndex == -1 || tempIndex < textIndex) {
                    textIndex = tempIndex;
                    replaceIndex = i;
                }
            }
        }
        // NOTE: logic mostly below END

        // no search strings found, we are done
        if (textIndex == -1) {
            return text;
        }

        int start = 0;

        // get a good guess on the size of the result buffer so it doesn't have to double if it goes over a bit
        int increase = 0;

        // count the replacement text elements that are larger than their corresponding text being replaced
        for (int i = 0; i < searchList.length; i++) {
            if (searchList[i] == null || replacementList[i] == null) {
                continue;
            }
            final int greater = replacementList[i].length() - searchList[i].length();
            if (greater > 0) {
                increase += 3 * greater; // assume 3 matches
            }
        }
        // have upper-bound at 20% increase, then let Java take over
        increase = Math.min(increase, text.length() / 5);

        final StringBuilder buf = new StringBuilder(text.length() + increase);

        while (textIndex != -1) {

            for (int i = start; i < textIndex; i++) {
                buf.append(text.charAt(i));
            }
            buf.append(replacementList[replaceIndex]);

            start = textIndex + searchList[replaceIndex].length();

            textIndex = -1;
            replaceIndex = -1;
            tempIndex = -1;
            // find the next earliest match
            // NOTE: logic mostly duplicated above START
            for (int i = 0; i < searchLength; i++) {
                if (noMoreMatchesForReplIndex[i] || searchList[i] == null ||
                        searchList[i].isEmpty() || replacementList[i] == null) {
                    continue;
                }
                tempIndex = text.indexOf(searchList[i], start);

                // see if we need to keep searching for this
                if (tempIndex == -1) {
                    noMoreMatchesForReplIndex[i] = true;
                } else {
                    if (textIndex == -1 || tempIndex < textIndex) {
                        textIndex = tempIndex;
                        replaceIndex = i;
                    }
                }
            }
            // NOTE: logic duplicated above END

        }
        final int textLength = text.length();
        for (int i = start; i < textLength; i++) {
            buf.append(text.charAt(i));
        }
        final String result = buf.toString();
        if (!repeat) {
            return result;
        }

        return replaceEach(result, searchList, replacementList, repeat, timeToLive - 1);
    }

    

Replaces all occurrences of Strings within another String.

 A null reference passed to this method is a no-op, or if any "search string" or "string to replace" is null, that replace will be ignored. 
 StringUtils.replaceEachRepeatedly(null, *, *) = null
 StringUtils.replaceEachRepeatedly("", *, *) = ""
 StringUtils.replaceEachRepeatedly("aba", null, null) = "aba"
 StringUtils.replaceEachRepeatedly("aba", new String[0], null) = "aba"
 StringUtils.replaceEachRepeatedly("aba", null, new String[0]) = "aba"
 StringUtils.replaceEachRepeatedly("aba", new String[]{"a"}, null) = "aba"
 StringUtils.replaceEachRepeatedly("aba", new String[]{"a"}, new String[]{""}) = "b"
 StringUtils.replaceEachRepeatedly("aba", new String[]{null}, new String[]{"a"}) = "aba"
 StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"}) = "wcte"
 (example of how it repeats)
 StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}) = "tcte"
 StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}) = IllegalStateException

Params:
text – 
           text to search and replace in, no-op if null
searchList – 
           the Strings to search for, no-op if null
replacementList – 
           the Strings to replace them with, no-op if null
Throws:
IllegalStateException – 
            if the search is repeating and there is an endless loop due
            to outputs of one being inputs to another
IllegalArgumentException – 
            if the lengths of the arrays are not the same (null is ok,
            and/or size 0)
Returns:
the text with any replacements processed, null if null String input
Since:
2.4/**
     * <p>
     * Replaces all occurrences of Strings within another String.
     * </p>
     *
     * <p>
     * A {@code null} reference passed to this method is a no-op, or if
     * any "search string" or "string to replace" is null, that replace will be
     * ignored.
     * </p>
     *
     * <pre>
     *  StringUtils.replaceEachRepeatedly(null, *, *) = null
     *  StringUtils.replaceEachRepeatedly("", *, *) = ""
     *  StringUtils.replaceEachRepeatedly("aba", null, null) = "aba"
     *  StringUtils.replaceEachRepeatedly("aba", new String[0], null) = "aba"
     *  StringUtils.replaceEachRepeatedly("aba", null, new String[0]) = "aba"
     *  StringUtils.replaceEachRepeatedly("aba", new String[]{"a"}, null) = "aba"
     *  StringUtils.replaceEachRepeatedly("aba", new String[]{"a"}, new String[]{""}) = "b"
     *  StringUtils.replaceEachRepeatedly("aba", new String[]{null}, new String[]{"a"}) = "aba"
     *  StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"}) = "wcte"
     *  (example of how it repeats)
     *  StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}) = "tcte"
     *  StringUtils.replaceEachRepeatedly("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}) = IllegalStateException
     * </pre>
     *
     * @param text
     *            text to search and replace in, no-op if null
     * @param searchList
     *            the Strings to search for, no-op if null
     * @param replacementList
     *            the Strings to replace them with, no-op if null
     * @return the text with any replacements processed, {@code null} if
     *         null String input
     * @throws IllegalStateException
     *             if the search is repeating and there is an endless loop due
     *             to outputs of one being inputs to another
     * @throws IllegalArgumentException
     *             if the lengths of the arrays are not the same (null is ok,
     *             and/or size 0)
     * @since 2.4
     */
    public static String replaceEachRepeatedly(final String text, final String[] searchList, final String[] replacementList) {
        // timeToLive should be 0 if not used or nothing to replace, else it's
        // the length of the replace array
        final int timeToLive = searchList == null ? 0 : searchList.length;
        return replaceEach(text, searchList, replacementList, true, timeToLive);
    }

    
Replaces the first substring of the text string that matches the given regular expression
with the given replacement.
 This method is a null safe equivalent to: 

 
text.replaceFirst(regex, replacement)
 
Pattern.compile(regex).matcher(text).replaceFirst(replacement)

A null reference passed to this method is a no-op.
The Pattern.DOTALL option is NOT automatically added. To use the DOTALL option prepend "(?s)" to the regex. DOTALL is also known as single-line mode in Perl.
StringUtils.replaceFirst(null, *, *)       = null
StringUtils.replaceFirst("any", (String) null, *)   = "any"
StringUtils.replaceFirst("any", *, null)   = "any"
StringUtils.replaceFirst("", "", "zzz")    = "zzz"
StringUtils.replaceFirst("", ".*", "zzz")  = "zzz"
StringUtils.replaceFirst("", ".+", "zzz")  = ""
StringUtils.replaceFirst("abc", "", "ZZ")  = "ZZabc"
StringUtils.replaceFirst("<__>\n<__>", "<.*>", "z")      = "z\n<__>"
StringUtils.replaceFirst("<__>\n<__>", "(?s)<.*>", "z")  = "z"
StringUtils.replaceFirst("ABCabc123", "[a-z]", "_")          = "ABC_bc123"
StringUtils.replaceFirst("ABCabc123abc", "[^A-Z0-9]+", "_")  = "ABC_123abc"
StringUtils.replaceFirst("ABCabc123abc", "[^A-Z0-9]+", "")   = "ABC123abc"
StringUtils.replaceFirst("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum  dolor   sit"

Params:
text –  text to search and replace in, may be null
regex –  the regular expression to which this string is to be matched
replacement –  the string to be substituted for the first match
Throws:
PatternSyntaxException – 
             if the regular expression's syntax is invalid
See Also:
String.replaceFirst(String, String)
Pattern
Pattern.DOTALL
Returns:
 the text with the first replacement processed, null if null String input
Since:
3.5
Deprecated:
Moved to RegExUtils./**
     * <p>Replaces the first substring of the text string that matches the given regular expression
     * with the given replacement.</p>
     *
     * This method is a {@code null} safe equivalent to:
     * <ul>
     *  <li>{@code text.replaceFirst(regex, replacement)}</li>
     *  <li>{@code Pattern.compile(regex).matcher(text).replaceFirst(replacement)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <p>The {@link Pattern#DOTALL} option is NOT automatically added.
     * To use the DOTALL option prepend {@code "(?s)"} to the regex.
     * DOTALL is also known as single-line mode in Perl.</p>
     *
     * <pre>
     * StringUtils.replaceFirst(null, *, *)       = null
     * StringUtils.replaceFirst("any", (String) null, *)   = "any"
     * StringUtils.replaceFirst("any", *, null)   = "any"
     * StringUtils.replaceFirst("", "", "zzz")    = "zzz"
     * StringUtils.replaceFirst("", ".*", "zzz")  = "zzz"
     * StringUtils.replaceFirst("", ".+", "zzz")  = ""
     * StringUtils.replaceFirst("abc", "", "ZZ")  = "ZZabc"
     * StringUtils.replaceFirst("&lt;__&gt;\n&lt;__&gt;", "&lt;.*&gt;", "z")      = "z\n&lt;__&gt;"
     * StringUtils.replaceFirst("&lt;__&gt;\n&lt;__&gt;", "(?s)&lt;.*&gt;", "z")  = "z"
     * StringUtils.replaceFirst("ABCabc123", "[a-z]", "_")          = "ABC_bc123"
     * StringUtils.replaceFirst("ABCabc123abc", "[^A-Z0-9]+", "_")  = "ABC_123abc"
     * StringUtils.replaceFirst("ABCabc123abc", "[^A-Z0-9]+", "")   = "ABC123abc"
     * StringUtils.replaceFirst("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum  dolor   sit"
     * </pre>
     *
     * @param text  text to search and replace in, may be null
     * @param regex  the regular expression to which this string is to be matched
     * @param replacement  the string to be substituted for the first match
     * @return  the text with the first replacement processed,
     *              {@code null} if null String input
     *
     * @throws  java.util.regex.PatternSyntaxException
     *              if the regular expression's syntax is invalid
     *
     * @see String#replaceFirst(String, String)
     * @see java.util.regex.Pattern
     * @see java.util.regex.Pattern#DOTALL
     * @since 3.5
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String replaceFirst(final String text, final String regex, final String replacement) {
        return RegExUtils.replaceFirst(text, regex, replacement);
    }

    
Case insensitively replaces all occurrences of a String within another String.
A null reference passed to this method is a no-op.
StringUtils.replaceIgnoreCase(null, *, *)        = null
StringUtils.replaceIgnoreCase("", *, *)          = ""
StringUtils.replaceIgnoreCase("any", null, *)    = "any"
StringUtils.replaceIgnoreCase("any", *, null)    = "any"
StringUtils.replaceIgnoreCase("any", "", *)      = "any"
StringUtils.replaceIgnoreCase("aba", "a", null)  = "aba"
StringUtils.replaceIgnoreCase("abA", "A", "")    = "b"
StringUtils.replaceIgnoreCase("aba", "A", "z")   = "zbz"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for (case insensitive), may be null
replacement –  the String to replace it with, may be null
See Also:
replaceIgnoreCase(String text, String searchString, String replacement, int max)
Returns:
the text with any replacements processed, null if null String input
Since:
3.5/**
    * <p>Case insensitively replaces all occurrences of a String within another String.</p>
    *
    * <p>A {@code null} reference passed to this method is a no-op.</p>
    *
    * <pre>
    * StringUtils.replaceIgnoreCase(null, *, *)        = null
    * StringUtils.replaceIgnoreCase("", *, *)          = ""
    * StringUtils.replaceIgnoreCase("any", null, *)    = "any"
    * StringUtils.replaceIgnoreCase("any", *, null)    = "any"
    * StringUtils.replaceIgnoreCase("any", "", *)      = "any"
    * StringUtils.replaceIgnoreCase("aba", "a", null)  = "aba"
    * StringUtils.replaceIgnoreCase("abA", "A", "")    = "b"
    * StringUtils.replaceIgnoreCase("aba", "A", "z")   = "zbz"
    * </pre>
    *
    * @see #replaceIgnoreCase(String text, String searchString, String replacement, int max)
    * @param text  text to search and replace in, may be null
    * @param searchString  the String to search for (case insensitive), may be null
    * @param replacement  the String to replace it with, may be null
    * @return the text with any replacements processed,
    *  {@code null} if null String input
    * @since 3.5
    */
   public static String replaceIgnoreCase(final String text, final String searchString, final String replacement) {
       return replaceIgnoreCase(text, searchString, replacement, -1);
   }

    
Case insensitively replaces a String with another String inside a larger String, for the first max values of the search String.
A null reference passed to this method is a no-op.
StringUtils.replaceIgnoreCase(null, *, *, *)         = null
StringUtils.replaceIgnoreCase("", *, *, *)           = ""
StringUtils.replaceIgnoreCase("any", null, *, *)     = "any"
StringUtils.replaceIgnoreCase("any", *, null, *)     = "any"
StringUtils.replaceIgnoreCase("any", "", *, *)       = "any"
StringUtils.replaceIgnoreCase("any", *, *, 0)        = "any"
StringUtils.replaceIgnoreCase("abaa", "a", null, -1) = "abaa"
StringUtils.replaceIgnoreCase("abaa", "a", "", -1)   = "b"
StringUtils.replaceIgnoreCase("abaa", "a", "z", 0)   = "abaa"
StringUtils.replaceIgnoreCase("abaa", "A", "z", 1)   = "zbaa"
StringUtils.replaceIgnoreCase("abAa", "a", "z", 2)   = "zbza"
StringUtils.replaceIgnoreCase("abAa", "a", "z", -1)  = "zbzz"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for (case insensitive), may be null
replacement –  the String to replace it with, may be null
max –  maximum number of values to replace, or -1 if no maximum
Returns:
the text with any replacements processed, null if null String input
Since:
3.5/**
     * <p>Case insensitively replaces a String with another String inside a larger String,
     * for the first {@code max} values of the search String.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replaceIgnoreCase(null, *, *, *)         = null
     * StringUtils.replaceIgnoreCase("", *, *, *)           = ""
     * StringUtils.replaceIgnoreCase("any", null, *, *)     = "any"
     * StringUtils.replaceIgnoreCase("any", *, null, *)     = "any"
     * StringUtils.replaceIgnoreCase("any", "", *, *)       = "any"
     * StringUtils.replaceIgnoreCase("any", *, *, 0)        = "any"
     * StringUtils.replaceIgnoreCase("abaa", "a", null, -1) = "abaa"
     * StringUtils.replaceIgnoreCase("abaa", "a", "", -1)   = "b"
     * StringUtils.replaceIgnoreCase("abaa", "a", "z", 0)   = "abaa"
     * StringUtils.replaceIgnoreCase("abaa", "A", "z", 1)   = "zbaa"
     * StringUtils.replaceIgnoreCase("abAa", "a", "z", 2)   = "zbza"
     * StringUtils.replaceIgnoreCase("abAa", "a", "z", -1)  = "zbzz"
     * </pre>
     *
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for (case insensitive), may be null
     * @param replacement  the String to replace it with, may be null
     * @param max  maximum number of values to replace, or {@code -1} if no maximum
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     * @since 3.5
     */
    public static String replaceIgnoreCase(final String text, final String searchString, final String replacement, final int max) {
        return replace(text, searchString, replacement, max, true);
    }

    // Replacing
    //-----------------------------------------------------------------------
    
Replaces a String with another String inside a larger String, once.
A null reference passed to this method is a no-op.
StringUtils.replaceOnce(null, *, *)        = null
StringUtils.replaceOnce("", *, *)          = ""
StringUtils.replaceOnce("any", null, *)    = "any"
StringUtils.replaceOnce("any", *, null)    = "any"
StringUtils.replaceOnce("any", "", *)      = "any"
StringUtils.replaceOnce("aba", "a", null)  = "aba"
StringUtils.replaceOnce("aba", "a", "")    = "ba"
StringUtils.replaceOnce("aba", "a", "z")   = "zba"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for, may be null
replacement –  the String to replace with, may be null
See Also:
replace(String text, String searchString, String replacement, int max)
Returns:
the text with any replacements processed, null if null String input/**
     * <p>Replaces a String with another String inside a larger String, once.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replaceOnce(null, *, *)        = null
     * StringUtils.replaceOnce("", *, *)          = ""
     * StringUtils.replaceOnce("any", null, *)    = "any"
     * StringUtils.replaceOnce("any", *, null)    = "any"
     * StringUtils.replaceOnce("any", "", *)      = "any"
     * StringUtils.replaceOnce("aba", "a", null)  = "aba"
     * StringUtils.replaceOnce("aba", "a", "")    = "ba"
     * StringUtils.replaceOnce("aba", "a", "z")   = "zba"
     * </pre>
     *
     * @see #replace(String text, String searchString, String replacement, int max)
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for, may be null
     * @param replacement  the String to replace with, may be null
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     */
    public static String replaceOnce(final String text, final String searchString, final String replacement) {
        return replace(text, searchString, replacement, 1);
    }

    
Case insensitively replaces a String with another String inside a larger String, once.
A null reference passed to this method is a no-op.
StringUtils.replaceOnceIgnoreCase(null, *, *)        = null
StringUtils.replaceOnceIgnoreCase("", *, *)          = ""
StringUtils.replaceOnceIgnoreCase("any", null, *)    = "any"
StringUtils.replaceOnceIgnoreCase("any", *, null)    = "any"
StringUtils.replaceOnceIgnoreCase("any", "", *)      = "any"
StringUtils.replaceOnceIgnoreCase("aba", "a", null)  = "aba"
StringUtils.replaceOnceIgnoreCase("aba", "a", "")    = "ba"
StringUtils.replaceOnceIgnoreCase("aba", "a", "z")   = "zba"
StringUtils.replaceOnceIgnoreCase("FoOFoofoo", "foo", "") = "Foofoo"

Params:
text –  text to search and replace in, may be null
searchString –  the String to search for (case insensitive), may be null
replacement –  the String to replace with, may be null
See Also:
replaceIgnoreCase(String text, String searchString, String replacement, int max)
Returns:
the text with any replacements processed, null if null String input
Since:
3.5/**
     * <p>Case insensitively replaces a String with another String inside a larger String, once.</p>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replaceOnceIgnoreCase(null, *, *)        = null
     * StringUtils.replaceOnceIgnoreCase("", *, *)          = ""
     * StringUtils.replaceOnceIgnoreCase("any", null, *)    = "any"
     * StringUtils.replaceOnceIgnoreCase("any", *, null)    = "any"
     * StringUtils.replaceOnceIgnoreCase("any", "", *)      = "any"
     * StringUtils.replaceOnceIgnoreCase("aba", "a", null)  = "aba"
     * StringUtils.replaceOnceIgnoreCase("aba", "a", "")    = "ba"
     * StringUtils.replaceOnceIgnoreCase("aba", "a", "z")   = "zba"
     * StringUtils.replaceOnceIgnoreCase("FoOFoofoo", "foo", "") = "Foofoo"
     * </pre>
     *
     * @see #replaceIgnoreCase(String text, String searchString, String replacement, int max)
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for (case insensitive), may be null
     * @param replacement  the String to replace with, may be null
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     * @since 3.5
     */
    public static String replaceOnceIgnoreCase(final String text, final String searchString, final String replacement) {
        return replaceIgnoreCase(text, searchString, replacement, 1);
    }

    
Replaces each substring of the source String that matches the given regular expression with the given replacement using the Pattern.DOTALL option. DOTALL is also known as single-line mode in Perl.
 This call is a null safe equivalent to: 

source.replaceAll(&quot;(?s)&quot; + regex, replacement)
Pattern.compile(regex, Pattern.DOTALL).matcher(source).replaceAll(replacement)

A null reference passed to this method is a no-op.
StringUtils.replacePattern(null, *, *)       = null
StringUtils.replacePattern("any", (String) null, *)   = "any"
StringUtils.replacePattern("any", *, null)   = "any"
StringUtils.replacePattern("", "", "zzz")    = "zzz"
StringUtils.replacePattern("", ".*", "zzz")  = "zzz"
StringUtils.replacePattern("", ".+", "zzz")  = ""
StringUtils.replacePattern("<__>\n<__>", "<.*>", "z")       = "z"
StringUtils.replacePattern("ABCabc123", "[a-z]", "_")       = "ABC___123"
StringUtils.replacePattern("ABCabc123", "[^A-Z0-9]+", "_")  = "ABC_123"
StringUtils.replacePattern("ABCabc123", "[^A-Z0-9]+", "")   = "ABC123"
StringUtils.replacePattern("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum_dolor_sit"

Params:
source – 
           the source string
regex – 
           the regular expression to which this string is to be matched
replacement – 
           the string to be substituted for each match
See Also:
replaceAll(String, String, String)
String.replaceAll(String, String)
Pattern.DOTALL
Returns:
The resulting String
Since:
3.2
Since:
3.5 Changed null reference passed to this method is a no-op.
Deprecated:
Moved to RegExUtils./**
     * <p>Replaces each substring of the source String that matches the given regular expression with the given
     * replacement using the {@link Pattern#DOTALL} option. DOTALL is also known as single-line mode in Perl.</p>
     *
     * This call is a {@code null} safe equivalent to:
     * <ul>
     * <li>{@code source.replaceAll(&quot;(?s)&quot; + regex, replacement)}</li>
     * <li>{@code Pattern.compile(regex, Pattern.DOTALL).matcher(source).replaceAll(replacement)}</li>
     * </ul>
     *
     * <p>A {@code null} reference passed to this method is a no-op.</p>
     *
     * <pre>
     * StringUtils.replacePattern(null, *, *)       = null
     * StringUtils.replacePattern("any", (String) null, *)   = "any"
     * StringUtils.replacePattern("any", *, null)   = "any"
     * StringUtils.replacePattern("", "", "zzz")    = "zzz"
     * StringUtils.replacePattern("", ".*", "zzz")  = "zzz"
     * StringUtils.replacePattern("", ".+", "zzz")  = ""
     * StringUtils.replacePattern("&lt;__&gt;\n&lt;__&gt;", "&lt;.*&gt;", "z")       = "z"
     * StringUtils.replacePattern("ABCabc123", "[a-z]", "_")       = "ABC___123"
     * StringUtils.replacePattern("ABCabc123", "[^A-Z0-9]+", "_")  = "ABC_123"
     * StringUtils.replacePattern("ABCabc123", "[^A-Z0-9]+", "")   = "ABC123"
     * StringUtils.replacePattern("Lorem ipsum  dolor   sit", "( +)([a-z]+)", "_$2")  = "Lorem_ipsum_dolor_sit"
     * </pre>
     *
     * @param source
     *            the source string
     * @param regex
     *            the regular expression to which this string is to be matched
     * @param replacement
     *            the string to be substituted for each match
     * @return The resulting {@code String}
     * @see #replaceAll(String, String, String)
     * @see String#replaceAll(String, String)
     * @see Pattern#DOTALL
     * @since 3.2
     * @since 3.5 Changed {@code null} reference passed to this method is a no-op.
     *
     * @deprecated Moved to RegExUtils.
     */
    @Deprecated
    public static String replacePattern(final String source, final String regex, final String replacement) {
        return RegExUtils.replacePattern(source, regex, replacement);
    }

    // Reversing
    //-----------------------------------------------------------------------
    
Reverses a String as per StringBuilder.reverse().
A null String returns null.
StringUtils.reverse(null)  = null
StringUtils.reverse("")    = ""
StringUtils.reverse("bat") = "tab"

Params:
str –  the String to reverse, may be null
Returns:
the reversed String, null if null String input/**
     * <p>Reverses a String as per {@link StringBuilder#reverse()}.</p>
     *
     * <p>A {@code null} String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.reverse(null)  = null
     * StringUtils.reverse("")    = ""
     * StringUtils.reverse("bat") = "tab"
     * </pre>
     *
     * @param str  the String to reverse, may be null
     * @return the reversed String, {@code null} if null String input
     */
    public static String reverse(final String str) {
        if (str == null) {
            return null;
        }
        return new StringBuilder(str).reverse().toString();
    }

    
Reverses a String that is delimited by a specific character.
The Strings between the delimiters are not reversed. Thus java.lang.String becomes String.lang.java (if the delimiter is '.').
StringUtils.reverseDelimited(null, *)      = null
StringUtils.reverseDelimited("", *)        = ""
StringUtils.reverseDelimited("a.b.c", 'x') = "a.b.c"
StringUtils.reverseDelimited("a.b.c", ".") = "c.b.a"

Params:
str –  the String to reverse, may be null
separatorChar –  the separator character to use
Returns:
the reversed String, null if null String input
Since:
2.0/**
     * <p>Reverses a String that is delimited by a specific character.</p>
     *
     * <p>The Strings between the delimiters are not reversed.
     * Thus java.lang.String becomes String.lang.java (if the delimiter
     * is {@code '.'}).</p>
     *
     * <pre>
     * StringUtils.reverseDelimited(null, *)      = null
     * StringUtils.reverseDelimited("", *)        = ""
     * StringUtils.reverseDelimited("a.b.c", 'x') = "a.b.c"
     * StringUtils.reverseDelimited("a.b.c", ".") = "c.b.a"
     * </pre>
     *
     * @param str  the String to reverse, may be null
     * @param separatorChar  the separator character to use
     * @return the reversed String, {@code null} if null String input
     * @since 2.0
     */
    public static String reverseDelimited(final String str, final char separatorChar) {
        if (str == null) {
            return null;
        }
        // could implement manually, but simple way is to reuse other,
        // probably slower, methods.
        final String[] strs = split(str, separatorChar);
        ArrayUtils.reverse(strs);
        return join(strs, separatorChar);
    }

    
Gets the rightmost len characters of a String.
If len characters are not available, or the String is null, the String will be returned without an an exception. An empty String is returned if len is negative.
StringUtils.right(null, *)    = null
StringUtils.right(*, -ve)     = ""
StringUtils.right("", *)      = ""
StringUtils.right("abc", 0)   = ""
StringUtils.right("abc", 2)   = "bc"
StringUtils.right("abc", 4)   = "abc"

Params:
str –  the String to get the rightmost characters from, may be null
len –  the length of the required String
Returns:
the rightmost characters, null if null String input/**
     * <p>Gets the rightmost {@code len} characters of a String.</p>
     *
     * <p>If {@code len} characters are not available, or the String
     * is {@code null}, the String will be returned without an
     * an exception. An empty String is returned if len is negative.</p>
     *
     * <pre>
     * StringUtils.right(null, *)    = null
     * StringUtils.right(*, -ve)     = ""
     * StringUtils.right("", *)      = ""
     * StringUtils.right("abc", 0)   = ""
     * StringUtils.right("abc", 2)   = "bc"
     * StringUtils.right("abc", 4)   = "abc"
     * </pre>
     *
     * @param str  the String to get the rightmost characters from, may be null
     * @param len  the length of the required String
     * @return the rightmost characters, {@code null} if null String input
     */
    public static String right(final String str, final int len) {
        if (str == null) {
            return null;
        }
        if (len < 0) {
            return EMPTY;
        }
        if (str.length() <= len) {
            return str;
        }
        return str.substring(str.length() - len);
    }

    
Right pad a String with spaces (' ').
The String is padded to the size of size.
StringUtils.rightPad(null, *)   = null
StringUtils.rightPad("", 3)     = "   "
StringUtils.rightPad("bat", 3)  = "bat"
StringUtils.rightPad("bat", 5)  = "bat  "
StringUtils.rightPad("bat", 1)  = "bat"
StringUtils.rightPad("bat", -1) = "bat"

Params:
str –  the String to pad out, may be null
size –  the size to pad to
Returns:
right padded String or original String if no padding is necessary, null if null String input/**
     * <p>Right pad a String with spaces (' ').</p>
     *
     * <p>The String is padded to the size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.rightPad(null, *)   = null
     * StringUtils.rightPad("", 3)     = "   "
     * StringUtils.rightPad("bat", 3)  = "bat"
     * StringUtils.rightPad("bat", 5)  = "bat  "
     * StringUtils.rightPad("bat", 1)  = "bat"
     * StringUtils.rightPad("bat", -1) = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @return right padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     */
    public static String rightPad(final String str, final int size) {
        return rightPad(str, size, ' ');
    }

    
Right pad a String with a specified character.
The String is padded to the size of size.
StringUtils.rightPad(null, *, *)     = null
StringUtils.rightPad("", 3, 'z')     = "zzz"
StringUtils.rightPad("bat", 3, 'z')  = "bat"
StringUtils.rightPad("bat", 5, 'z')  = "batzz"
StringUtils.rightPad("bat", 1, 'z')  = "bat"
StringUtils.rightPad("bat", -1, 'z') = "bat"

Params:
str –  the String to pad out, may be null
size –  the size to pad to
padChar –  the character to pad with
Returns:
right padded String or original String if no padding is necessary, null if null String input
Since:
2.0/**
     * <p>Right pad a String with a specified character.</p>
     *
     * <p>The String is padded to the size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.rightPad(null, *, *)     = null
     * StringUtils.rightPad("", 3, 'z')     = "zzz"
     * StringUtils.rightPad("bat", 3, 'z')  = "bat"
     * StringUtils.rightPad("bat", 5, 'z')  = "batzz"
     * StringUtils.rightPad("bat", 1, 'z')  = "bat"
     * StringUtils.rightPad("bat", -1, 'z') = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padChar  the character to pad with
     * @return right padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String rightPad(final String str, final int size, final char padChar) {
        if (str == null) {
            return null;
        }
        final int pads = size - str.length();
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (pads > PAD_LIMIT) {
            return rightPad(str, size, String.valueOf(padChar));
        }
        return str.concat(repeat(padChar, pads));
    }

    
Right pad a String with a specified String.
The String is padded to the size of size.
StringUtils.rightPad(null, *, *)      = null
StringUtils.rightPad("", 3, "z")      = "zzz"
StringUtils.rightPad("bat", 3, "yz")  = "bat"
StringUtils.rightPad("bat", 5, "yz")  = "batyz"
StringUtils.rightPad("bat", 8, "yz")  = "batyzyzy"
StringUtils.rightPad("bat", 1, "yz")  = "bat"
StringUtils.rightPad("bat", -1, "yz") = "bat"
StringUtils.rightPad("bat", 5, null)  = "bat  "
StringUtils.rightPad("bat", 5, "")    = "bat  "

Params:
str –  the String to pad out, may be null
size –  the size to pad to
padStr –  the String to pad with, null or empty treated as single space
Returns:
right padded String or original String if no padding is necessary, null if null String input/**
     * <p>Right pad a String with a specified String.</p>
     *
     * <p>The String is padded to the size of {@code size}.</p>
     *
     * <pre>
     * StringUtils.rightPad(null, *, *)      = null
     * StringUtils.rightPad("", 3, "z")      = "zzz"
     * StringUtils.rightPad("bat", 3, "yz")  = "bat"
     * StringUtils.rightPad("bat", 5, "yz")  = "batyz"
     * StringUtils.rightPad("bat", 8, "yz")  = "batyzyzy"
     * StringUtils.rightPad("bat", 1, "yz")  = "bat"
     * StringUtils.rightPad("bat", -1, "yz") = "bat"
     * StringUtils.rightPad("bat", 5, null)  = "bat  "
     * StringUtils.rightPad("bat", 5, "")    = "bat  "
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padStr  the String to pad with, null or empty treated as single space
     * @return right padded String or original String if no padding is necessary,
     *  {@code null} if null String input
     */
    public static String rightPad(final String str, final int size, String padStr) {
        if (str == null) {
            return null;
        }
        if (isEmpty(padStr)) {
            padStr = SPACE;
        }
        final int padLen = padStr.length();
        final int strLen = str.length();
        final int pads = size - strLen;
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (padLen == 1 && pads <= PAD_LIMIT) {
            return rightPad(str, size, padStr.charAt(0));
        }

        if (pads == padLen) {
            return str.concat(padStr);
        } else if (pads < padLen) {
            return str.concat(padStr.substring(0, pads));
        } else {
            final char[] padding = new char[pads];
            final char[] padChars = padStr.toCharArray();
            for (int i = 0; i < pads; i++) {
                padding[i] = padChars[i % padLen];
            }
            return str.concat(new String(padding));
        }
    }

    // Rotating (circular shift)
    //-----------------------------------------------------------------------
    
Rotate (circular shift) a String of shift characters.

 
If shift > 0, right circular shift (ex : ABCDEF => FABCDE)
 
If shift < 0, left circular shift (ex : ABCDEF => BCDEFA)

StringUtils.rotate(null, *)        = null
StringUtils.rotate("", *)          = ""
StringUtils.rotate("abcdefg", 0)   = "abcdefg"
StringUtils.rotate("abcdefg", 2)   = "fgabcde"
StringUtils.rotate("abcdefg", -2)  = "cdefgab"
StringUtils.rotate("abcdefg", 7)   = "abcdefg"
StringUtils.rotate("abcdefg", -7)  = "abcdefg"
StringUtils.rotate("abcdefg", 9)   = "fgabcde"
StringUtils.rotate("abcdefg", -9)  = "cdefgab"

Params:
str –  the String to rotate, may be null
shift –  number of time to shift (positive : right shift, negative : left shift)
Returns:
the rotated String, or the original String if shift == 0, or null if null String input
Since:
3.5/**
     * <p>Rotate (circular shift) a String of {@code shift} characters.</p>
     * <ul>
     *  <li>If {@code shift > 0}, right circular shift (ex : ABCDEF =&gt; FABCDE)</li>
     *  <li>If {@code shift < 0}, left circular shift (ex : ABCDEF =&gt; BCDEFA)</li>
     * </ul>
     *
     * <pre>
     * StringUtils.rotate(null, *)        = null
     * StringUtils.rotate("", *)          = ""
     * StringUtils.rotate("abcdefg", 0)   = "abcdefg"
     * StringUtils.rotate("abcdefg", 2)   = "fgabcde"
     * StringUtils.rotate("abcdefg", -2)  = "cdefgab"
     * StringUtils.rotate("abcdefg", 7)   = "abcdefg"
     * StringUtils.rotate("abcdefg", -7)  = "abcdefg"
     * StringUtils.rotate("abcdefg", 9)   = "fgabcde"
     * StringUtils.rotate("abcdefg", -9)  = "cdefgab"
     * </pre>
     *
     * @param str  the String to rotate, may be null
     * @param shift  number of time to shift (positive : right shift, negative : left shift)
     * @return the rotated String,
     *          or the original String if {@code shift == 0},
     *          or {@code null} if null String input
     * @since 3.5
     */
    public static String rotate(final String str, final int shift) {
        if (str == null) {
            return null;
        }

        final int strLen = str.length();
        if (shift == 0 || strLen == 0 || shift % strLen == 0) {
            return str;
        }

        final StringBuilder builder = new StringBuilder(strLen);
        final int offset = - (shift % strLen);
        builder.append(substring(str, offset));
        builder.append(substring(str, 0, offset));
        return builder.toString();
    }

    // Splitting
    //-----------------------------------------------------------------------
    
Splits the provided text into an array, using whitespace as the separator. Whitespace is defined by Character.isWhitespace(char).
The separator is not included in the returned String array.
Adjacent separators are treated as one separator.
For more control over the split use the StrTokenizer class.
A null input String returns null.
StringUtils.split(null)       = null
StringUtils.split("")         = []
StringUtils.split("abc def")  = ["abc", "def"]
StringUtils.split("abc  def") = ["abc", "def"]
StringUtils.split(" abc ")    = ["abc"]

Params:
str –  the String to parse, may be null
Returns:
an array of parsed Strings, null if null String input/**
     * <p>Splits the provided text into an array, using whitespace as the
     * separator.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.split(null)       = null
     * StringUtils.split("")         = []
     * StringUtils.split("abc def")  = ["abc", "def"]
     * StringUtils.split("abc  def") = ["abc", "def"]
     * StringUtils.split(" abc ")    = ["abc"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @return an array of parsed Strings, {@code null} if null String input
     */
    public static String[] split(final String str) {
        return split(str, null, -1);
    }

    
Splits the provided text into an array, separator specified.
This is an alternative to using StringTokenizer.
The separator is not included in the returned String array.
Adjacent separators are treated as one separator.
For more control over the split use the StrTokenizer class.
A null input String returns null.
StringUtils.split(null, *)         = null
StringUtils.split("", *)           = []
StringUtils.split("a.b.c", '.')    = ["a", "b", "c"]
StringUtils.split("a..b.c", '.')   = ["a", "b", "c"]
StringUtils.split("a:b:c", '.')    = ["a:b:c"]
StringUtils.split("a b c", ' ')    = ["a", "b", "c"]

Params:
str –  the String to parse, may be null
separatorChar –  the character used as the delimiter
Returns:
an array of parsed Strings, null if null String input
Since:
2.0/**
     * <p>Splits the provided text into an array, separator specified.
     * This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.split(null, *)         = null
     * StringUtils.split("", *)           = []
     * StringUtils.split("a.b.c", '.')    = ["a", "b", "c"]
     * StringUtils.split("a..b.c", '.')   = ["a", "b", "c"]
     * StringUtils.split("a:b:c", '.')    = ["a:b:c"]
     * StringUtils.split("a b c", ' ')    = ["a", "b", "c"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separatorChar  the character used as the delimiter
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.0
     */
    public static String[] split(final String str, final char separatorChar) {
        return splitWorker(str, separatorChar, false);
    }

    
Splits the provided text into an array, separators specified.
This is an alternative to using StringTokenizer.
The separator is not included in the returned String array.
Adjacent separators are treated as one separator.
For more control over the split use the StrTokenizer class.
A null input String returns null. A null separatorChars splits on whitespace.
StringUtils.split(null, *)         = null
StringUtils.split("", *)           = []
StringUtils.split("abc def", null) = ["abc", "def"]
StringUtils.split("abc def", " ")  = ["abc", "def"]
StringUtils.split("abc  def", " ") = ["abc", "def"]
StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"]

Params:
str –  the String to parse, may be null
separatorChars –  the characters used as the delimiters, null splits on whitespace
Returns:
an array of parsed Strings, null if null String input/**
     * <p>Splits the provided text into an array, separators specified.
     * This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separatorChars splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.split(null, *)         = null
     * StringUtils.split("", *)           = []
     * StringUtils.split("abc def", null) = ["abc", "def"]
     * StringUtils.split("abc def", " ")  = ["abc", "def"]
     * StringUtils.split("abc  def", " ") = ["abc", "def"]
     * StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separatorChars  the characters used as the delimiters,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String input
     */
    public static String[] split(final String str, final String separatorChars) {
        return splitWorker(str, separatorChars, -1, false);
    }

    
Splits the provided text into an array with a maximum length,
separators specified.
The separator is not included in the returned String array.
Adjacent separators are treated as one separator.
A null input String returns null. A null separatorChars splits on whitespace.
If more than max delimited substrings are found, the last returned string includes all characters after the first max - 1 returned strings (including separator characters).
StringUtils.split(null, *, *)            = null
StringUtils.split("", *, *)              = []
StringUtils.split("ab cd ef", null, 0)   = ["ab", "cd", "ef"]
StringUtils.split("ab   cd ef", null, 0) = ["ab", "cd", "ef"]
StringUtils.split("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
StringUtils.split("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]

Params:
str –  the String to parse, may be null
separatorChars –  the characters used as the delimiters, null splits on whitespace
max –  the maximum number of elements to include in the
 array. A zero or negative value implies no limit
Returns:
an array of parsed Strings, null if null String input/**
     * <p>Splits the provided text into an array with a maximum length,
     * separators specified.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separatorChars splits on whitespace.</p>
     *
     * <p>If more than {@code max} delimited substrings are found, the last
     * returned string includes all characters after the first {@code max - 1}
     * returned strings (including separator characters).</p>
     *
     * <pre>
     * StringUtils.split(null, *, *)            = null
     * StringUtils.split("", *, *)              = []
     * StringUtils.split("ab cd ef", null, 0)   = ["ab", "cd", "ef"]
     * StringUtils.split("ab   cd ef", null, 0) = ["ab", "cd", "ef"]
     * StringUtils.split("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
     * StringUtils.split("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separatorChars  the characters used as the delimiters,
     *  {@code null} splits on whitespace
     * @param max  the maximum number of elements to include in the
     *  array. A zero or negative value implies no limit
     * @return an array of parsed Strings, {@code null} if null String input
     */
    public static String[] split(final String str, final String separatorChars, final int max) {
        return splitWorker(str, separatorChars, max, false);
    }

    
Splits a String by Character type as returned by java.lang.Character.getType(char). Groups of contiguous characters of the same type are returned as complete tokens. 
StringUtils.splitByCharacterType(null)         = null
StringUtils.splitByCharacterType("")           = []
StringUtils.splitByCharacterType("ab de fg")   = ["ab", " ", "de", " ", "fg"]
StringUtils.splitByCharacterType("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
StringUtils.splitByCharacterType("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
StringUtils.splitByCharacterType("number5")    = ["number", "5"]
StringUtils.splitByCharacterType("fooBar")     = ["foo", "B", "ar"]
StringUtils.splitByCharacterType("foo200Bar")  = ["foo", "200", "B", "ar"]
StringUtils.splitByCharacterType("ASFRules")   = ["ASFR", "ules"]

Params:
str – the String to split, may be null
Returns:
an array of parsed Strings, null if null String input
Since:
2.4/**
     * <p>Splits a String by Character type as returned by
     * {@code java.lang.Character.getType(char)}. Groups of contiguous
     * characters of the same type are returned as complete tokens.
     * <pre>
     * StringUtils.splitByCharacterType(null)         = null
     * StringUtils.splitByCharacterType("")           = []
     * StringUtils.splitByCharacterType("ab de fg")   = ["ab", " ", "de", " ", "fg"]
     * StringUtils.splitByCharacterType("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
     * StringUtils.splitByCharacterType("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
     * StringUtils.splitByCharacterType("number5")    = ["number", "5"]
     * StringUtils.splitByCharacterType("fooBar")     = ["foo", "B", "ar"]
     * StringUtils.splitByCharacterType("foo200Bar")  = ["foo", "200", "B", "ar"]
     * StringUtils.splitByCharacterType("ASFRules")   = ["ASFR", "ules"]
     * </pre>
     * @param str the String to split, may be {@code null}
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.4
     */
    public static String[] splitByCharacterType(final String str) {
        return splitByCharacterType(str, false);
    }

    
Splits a String by Character type as returned by java.lang.Character.getType(char). Groups of contiguous characters of the same type are returned as complete tokens, with the following exception: if camelCase is true, the character of type Character.UPPERCASE_LETTER, if any, immediately preceding a token of type Character.LOWERCASE_LETTER will belong to the following token rather than to the preceding, if any, Character.UPPERCASE_LETTER token. 
Params:
str – the String to split, may be null
camelCase – whether to use so-called "camel-case" for letter types
Returns:
an array of parsed Strings, null if null String input
Since:
2.4/**
     * <p>Splits a String by Character type as returned by
     * {@code java.lang.Character.getType(char)}. Groups of contiguous
     * characters of the same type are returned as complete tokens, with the
     * following exception: if {@code camelCase} is {@code true},
     * the character of type {@code Character.UPPERCASE_LETTER}, if any,
     * immediately preceding a token of type {@code Character.LOWERCASE_LETTER}
     * will belong to the following token rather than to the preceding, if any,
     * {@code Character.UPPERCASE_LETTER} token.
     * @param str the String to split, may be {@code null}
     * @param camelCase whether to use so-called "camel-case" for letter types
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.4
     */
    private static String[] splitByCharacterType(final String str, final boolean camelCase) {
        if (str == null) {
            return null;
        }
        if (str.isEmpty()) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final char[] c = str.toCharArray();
        final List<String> list = new ArrayList<>();
        int tokenStart = 0;
        int currentType = Character.getType(c[tokenStart]);
        for (int pos = tokenStart + 1; pos < c.length; pos++) {
            final int type = Character.getType(c[pos]);
            if (type == currentType) {
                continue;
            }
            if (camelCase && type == Character.LOWERCASE_LETTER && currentType == Character.UPPERCASE_LETTER) {
                final int newTokenStart = pos - 1;
                if (newTokenStart != tokenStart) {
                    list.add(new String(c, tokenStart, newTokenStart - tokenStart));
                    tokenStart = newTokenStart;
                }
            } else {
                list.add(new String(c, tokenStart, pos - tokenStart));
                tokenStart = pos;
            }
            currentType = type;
        }
        list.add(new String(c, tokenStart, c.length - tokenStart));
        return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    
Splits a String by Character type as returned by java.lang.Character.getType(char). Groups of contiguous characters of the same type are returned as complete tokens, with the following exception: the character of type Character.UPPERCASE_LETTER, if any, immediately preceding a token of type Character.LOWERCASE_LETTER will belong to the following token rather than to the preceding, if any, Character.UPPERCASE_LETTER token. 
StringUtils.splitByCharacterTypeCamelCase(null)         = null
StringUtils.splitByCharacterTypeCamelCase("")           = []
StringUtils.splitByCharacterTypeCamelCase("ab de fg")   = ["ab", " ", "de", " ", "fg"]
StringUtils.splitByCharacterTypeCamelCase("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
StringUtils.splitByCharacterTypeCamelCase("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
StringUtils.splitByCharacterTypeCamelCase("number5")    = ["number", "5"]
StringUtils.splitByCharacterTypeCamelCase("fooBar")     = ["foo", "Bar"]
StringUtils.splitByCharacterTypeCamelCase("foo200Bar")  = ["foo", "200", "Bar"]
StringUtils.splitByCharacterTypeCamelCase("ASFRules")   = ["ASF", "Rules"]

Params:
str – the String to split, may be null
Returns:
an array of parsed Strings, null if null String input
Since:
2.4/**
     * <p>Splits a String by Character type as returned by
     * {@code java.lang.Character.getType(char)}. Groups of contiguous
     * characters of the same type are returned as complete tokens, with the
     * following exception: the character of type
     * {@code Character.UPPERCASE_LETTER}, if any, immediately
     * preceding a token of type {@code Character.LOWERCASE_LETTER}
     * will belong to the following token rather than to the preceding, if any,
     * {@code Character.UPPERCASE_LETTER} token.
     * <pre>
     * StringUtils.splitByCharacterTypeCamelCase(null)         = null
     * StringUtils.splitByCharacterTypeCamelCase("")           = []
     * StringUtils.splitByCharacterTypeCamelCase("ab de fg")   = ["ab", " ", "de", " ", "fg"]
     * StringUtils.splitByCharacterTypeCamelCase("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
     * StringUtils.splitByCharacterTypeCamelCase("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
     * StringUtils.splitByCharacterTypeCamelCase("number5")    = ["number", "5"]
     * StringUtils.splitByCharacterTypeCamelCase("fooBar")     = ["foo", "Bar"]
     * StringUtils.splitByCharacterTypeCamelCase("foo200Bar")  = ["foo", "200", "Bar"]
     * StringUtils.splitByCharacterTypeCamelCase("ASFRules")   = ["ASF", "Rules"]
     * </pre>
     * @param str the String to split, may be {@code null}
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.4
     */
    public static String[] splitByCharacterTypeCamelCase(final String str) {
        return splitByCharacterType(str, true);
    }

    
Splits the provided text into an array, separator string specified.
The separator(s) will not be included in the returned String array.
Adjacent separators are treated as one separator.
A null input String returns null. A null separator splits on whitespace.
StringUtils.splitByWholeSeparator(null, *)               = null
StringUtils.splitByWholeSeparator("", *)                 = []
StringUtils.splitByWholeSeparator("ab de fg", null)      = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparator("ab   de fg", null)    = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparator("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]

Params:
str –  the String to parse, may be null
separator –  String containing the String to be used as a delimiter, null splits on whitespace
Returns:
an array of parsed Strings, null if null String was input/**
     * <p>Splits the provided text into an array, separator string specified.</p>
     *
     * <p>The separator(s) will not be included in the returned String array.
     * Adjacent separators are treated as one separator.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separator splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.splitByWholeSeparator(null, *)               = null
     * StringUtils.splitByWholeSeparator("", *)                 = []
     * StringUtils.splitByWholeSeparator("ab de fg", null)      = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparator("ab   de fg", null)    = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparator("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
     * StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separator  String containing the String to be used as a delimiter,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String was input
     */
    public static String[] splitByWholeSeparator(final String str, final String separator) {
        return splitByWholeSeparatorWorker(str, separator, -1, false);
    }

    
Splits the provided text into an array, separator string specified. Returns a maximum of max substrings.
The separator(s) will not be included in the returned String array.
Adjacent separators are treated as one separator.
A null input String returns null. A null separator splits on whitespace.
StringUtils.splitByWholeSeparator(null, *, *)               = null
StringUtils.splitByWholeSeparator("", *, *)                 = []
StringUtils.splitByWholeSeparator("ab de fg", null, 0)      = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparator("ab   de fg", null, 0)    = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparator("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]

Params:
str –  the String to parse, may be null
separator –  String containing the String to be used as a delimiter, null splits on whitespace
max –  the maximum number of elements to include in the returned
 array. A zero or negative value implies no limit.
Returns:
an array of parsed Strings, null if null String was input/**
     * <p>Splits the provided text into an array, separator string specified.
     * Returns a maximum of {@code max} substrings.</p>
     *
     * <p>The separator(s) will not be included in the returned String array.
     * Adjacent separators are treated as one separator.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separator splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.splitByWholeSeparator(null, *, *)               = null
     * StringUtils.splitByWholeSeparator("", *, *)                 = []
     * StringUtils.splitByWholeSeparator("ab de fg", null, 0)      = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparator("ab   de fg", null, 0)    = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparator("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
     * StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
     * StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separator  String containing the String to be used as a delimiter,
     *  {@code null} splits on whitespace
     * @param max  the maximum number of elements to include in the returned
     *  array. A zero or negative value implies no limit.
     * @return an array of parsed Strings, {@code null} if null String was input
     */
    public static String[] splitByWholeSeparator( final String str, final String separator, final int max) {
        return splitByWholeSeparatorWorker(str, separator, max, false);
    }

    
Splits the provided text into an array, separator string specified. 
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
For more control over the split use the StrTokenizer class.
A null input String returns null. A null separator splits on whitespace.
StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *)               = null
StringUtils.splitByWholeSeparatorPreserveAllTokens("", *)                 = []
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null)      = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null)    = ["ab", "", "", "de", "fg"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]

Params:
str –  the String to parse, may be null
separator –  String containing the String to be used as a delimiter, null splits on whitespace
Returns:
an array of parsed Strings, null if null String was input
Since:
2.4/**
     * <p>Splits the provided text into an array, separator string specified. </p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separator splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *)               = null
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("", *)                 = []
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null)      = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null)    = ["ab", "", "", "de", "fg"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separator  String containing the String to be used as a delimiter,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String was input
     * @since 2.4
     */
    public static String[] splitByWholeSeparatorPreserveAllTokens(final String str, final String separator) {
        return splitByWholeSeparatorWorker(str, separator, -1, true);
    }

    
Splits the provided text into an array, separator string specified. Returns a maximum of max substrings.
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
For more control over the split use the StrTokenizer class.
A null input String returns null. A null separator splits on whitespace.
StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *, *)               = null
StringUtils.splitByWholeSeparatorPreserveAllTokens("", *, *)                 = []
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null, 0)      = ["ab", "de", "fg"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null, 0)    = ["ab", "", "", "de", "fg"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]

Params:
str –  the String to parse, may be null
separator –  String containing the String to be used as a delimiter, null splits on whitespace
max –  the maximum number of elements to include in the returned
 array. A zero or negative value implies no limit.
Returns:
an array of parsed Strings, null if null String was input
Since:
2.4/**
     * <p>Splits the provided text into an array, separator string specified.
     * Returns a maximum of {@code max} substrings.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separator splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *, *)               = null
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("", *, *)                 = []
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null, 0)      = ["ab", "de", "fg"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null, 0)    = ["ab", "", "", "de", "fg"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
     * StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separator  String containing the String to be used as a delimiter,
     *  {@code null} splits on whitespace
     * @param max  the maximum number of elements to include in the returned
     *  array. A zero or negative value implies no limit.
     * @return an array of parsed Strings, {@code null} if null String was input
     * @since 2.4
     */
    public static String[] splitByWholeSeparatorPreserveAllTokens(final String str, final String separator, final int max) {
        return splitByWholeSeparatorWorker(str, separator, max, true);
    }

    
Performs the logic for the splitByWholeSeparatorPreserveAllTokens methods. 
Params:
str –  the String to parse, may be null
separator –  String containing the String to be used as a delimiter, null splits on whitespace
max –  the maximum number of elements to include in the returned
 array. A zero or negative value implies no limit.
preserveAllTokens – if true, adjacent separators are treated as empty token separators; if false, adjacent separators are treated as one separator.
Returns:
an array of parsed Strings, null if null String input
Since:
2.4/**
     * Performs the logic for the {@code splitByWholeSeparatorPreserveAllTokens} methods.
     *
     * @param str  the String to parse, may be {@code null}
     * @param separator  String containing the String to be used as a delimiter,
     *  {@code null} splits on whitespace
     * @param max  the maximum number of elements to include in the returned
     *  array. A zero or negative value implies no limit.
     * @param preserveAllTokens if {@code true}, adjacent separators are
     * treated as empty token separators; if {@code false}, adjacent
     * separators are treated as one separator.
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.4
     */
    private static String[] splitByWholeSeparatorWorker(
            final String str, final String separator, final int max, final boolean preserveAllTokens) {
        if (str == null) {
            return null;
        }

        final int len = str.length();

        if (len == 0) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }

        if (separator == null || EMPTY.equals(separator)) {
            // Split on whitespace.
            return splitWorker(str, null, max, preserveAllTokens);
        }

        final int separatorLength = separator.length();

        final ArrayList<String> substrings = new ArrayList<>();
        int numberOfSubstrings = 0;
        int beg = 0;
        int end = 0;
        while (end < len) {
            end = str.indexOf(separator, beg);

            if (end > -1) {
                if (end > beg) {
                    numberOfSubstrings += 1;

                    if (numberOfSubstrings == max) {
                        end = len;
                        substrings.add(str.substring(beg));
                    } else {
                        // The following is OK, because String.substring( beg, end ) excludes
                        // the character at the position 'end'.
                        substrings.add(str.substring(beg, end));

                        // Set the starting point for the next search.
                        // The following is equivalent to beg = end + (separatorLength - 1) + 1,
                        // which is the right calculation:
                        beg = end + separatorLength;
                    }
                } else {
                    // We found a consecutive occurrence of the separator, so skip it.
                    if (preserveAllTokens) {
                        numberOfSubstrings += 1;
                        if (numberOfSubstrings == max) {
                            end = len;
                            substrings.add(str.substring(beg));
                        } else {
                            substrings.add(EMPTY);
                        }
                    }
                    beg = end + separatorLength;
                }
            } else {
                // String.substring( beg ) goes from 'beg' to the end of the String.
                substrings.add(str.substring(beg));
                end = len;
            }
        }

        return substrings.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    // -----------------------------------------------------------------------
    
Splits the provided text into an array, using whitespace as the separator, preserving all tokens, including empty tokens created by adjacent separators. This is an alternative to using StringTokenizer. Whitespace is defined by Character.isWhitespace(char).
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
For more control over the split use the StrTokenizer class.
A null input String returns null.
StringUtils.splitPreserveAllTokens(null)       = null
StringUtils.splitPreserveAllTokens("")         = []
StringUtils.splitPreserveAllTokens("abc def")  = ["abc", "def"]
StringUtils.splitPreserveAllTokens("abc  def") = ["abc", "", "def"]
StringUtils.splitPreserveAllTokens(" abc ")    = ["", "abc", ""]

Params:
str –  the String to parse, may be null
Returns:
an array of parsed Strings, null if null String input
Since:
2.1/**
     * <p>Splits the provided text into an array, using whitespace as the
     * separator, preserving all tokens, including empty tokens created by
     * adjacent separators. This is an alternative to using StringTokenizer.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.splitPreserveAllTokens(null)       = null
     * StringUtils.splitPreserveAllTokens("")         = []
     * StringUtils.splitPreserveAllTokens("abc def")  = ["abc", "def"]
     * StringUtils.splitPreserveAllTokens("abc  def") = ["abc", "", "def"]
     * StringUtils.splitPreserveAllTokens(" abc ")    = ["", "abc", ""]
     * </pre>
     *
     * @param str  the String to parse, may be {@code null}
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.1
     */
    public static String[] splitPreserveAllTokens(final String str) {
        return splitWorker(str, null, -1, true);
    }

    
Splits the provided text into an array, separator specified,
preserving all tokens, including empty tokens created by adjacent
separators. This is an alternative to using StringTokenizer.
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
For more control over the split use the StrTokenizer class.
A null input String returns null.
StringUtils.splitPreserveAllTokens(null, *)         = null
StringUtils.splitPreserveAllTokens("", *)           = []
StringUtils.splitPreserveAllTokens("a.b.c", '.')    = ["a", "b", "c"]
StringUtils.splitPreserveAllTokens("a..b.c", '.')   = ["a", "", "b", "c"]
StringUtils.splitPreserveAllTokens("a:b:c", '.')    = ["a:b:c"]
StringUtils.splitPreserveAllTokens("a\tb\nc", null) = ["a", "b", "c"]
StringUtils.splitPreserveAllTokens("a b c", ' ')    = ["a", "b", "c"]
StringUtils.splitPreserveAllTokens("a b c ", ' ')   = ["a", "b", "c", ""]
StringUtils.splitPreserveAllTokens("a b c  ", ' ')   = ["a", "b", "c", "", ""]
StringUtils.splitPreserveAllTokens(" a b c", ' ')   = ["", a", "b", "c"]
StringUtils.splitPreserveAllTokens("  a b c", ' ')  = ["", "", a", "b", "c"]
StringUtils.splitPreserveAllTokens(" a b c ", ' ')  = ["", a", "b", "c", ""]

Params:
str –  the String to parse, may be null
separatorChar –  the character used as the delimiter, null splits on whitespace
Returns:
an array of parsed Strings, null if null String input
Since:
2.1/**
     * <p>Splits the provided text into an array, separator specified,
     * preserving all tokens, including empty tokens created by adjacent
     * separators. This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.splitPreserveAllTokens(null, *)         = null
     * StringUtils.splitPreserveAllTokens("", *)           = []
     * StringUtils.splitPreserveAllTokens("a.b.c", '.')    = ["a", "b", "c"]
     * StringUtils.splitPreserveAllTokens("a..b.c", '.')   = ["a", "", "b", "c"]
     * StringUtils.splitPreserveAllTokens("a:b:c", '.')    = ["a:b:c"]
     * StringUtils.splitPreserveAllTokens("a\tb\nc", null) = ["a", "b", "c"]
     * StringUtils.splitPreserveAllTokens("a b c", ' ')    = ["a", "b", "c"]
     * StringUtils.splitPreserveAllTokens("a b c ", ' ')   = ["a", "b", "c", ""]
     * StringUtils.splitPreserveAllTokens("a b c  ", ' ')   = ["a", "b", "c", "", ""]
     * StringUtils.splitPreserveAllTokens(" a b c", ' ')   = ["", a", "b", "c"]
     * StringUtils.splitPreserveAllTokens("  a b c", ' ')  = ["", "", a", "b", "c"]
     * StringUtils.splitPreserveAllTokens(" a b c ", ' ')  = ["", a", "b", "c", ""]
     * </pre>
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChar  the character used as the delimiter,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.1
     */
    public static String[] splitPreserveAllTokens(final String str, final char separatorChar) {
        return splitWorker(str, separatorChar, true);
    }

    
Splits the provided text into an array, separators specified,
preserving all tokens, including empty tokens created by adjacent
separators. This is an alternative to using StringTokenizer.
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
For more control over the split use the StrTokenizer class.
A null input String returns null. A null separatorChars splits on whitespace.
StringUtils.splitPreserveAllTokens(null, *)           = null
StringUtils.splitPreserveAllTokens("", *)             = []
StringUtils.splitPreserveAllTokens("abc def", null)   = ["abc", "def"]
StringUtils.splitPreserveAllTokens("abc def", " ")    = ["abc", "def"]
StringUtils.splitPreserveAllTokens("abc  def", " ")   = ["abc", "", def"]
StringUtils.splitPreserveAllTokens("ab:cd:ef", ":")   = ["ab", "cd", "ef"]
StringUtils.splitPreserveAllTokens("ab:cd:ef:", ":")  = ["ab", "cd", "ef", ""]
StringUtils.splitPreserveAllTokens("ab:cd:ef::", ":") = ["ab", "cd", "ef", "", ""]
StringUtils.splitPreserveAllTokens("ab::cd:ef", ":")  = ["ab", "", cd", "ef"]
StringUtils.splitPreserveAllTokens(":cd:ef", ":")     = ["", cd", "ef"]
StringUtils.splitPreserveAllTokens("::cd:ef", ":")    = ["", "", cd", "ef"]
StringUtils.splitPreserveAllTokens(":cd:ef:", ":")    = ["", cd", "ef", ""]

Params:
str –  the String to parse, may be null
separatorChars –  the characters used as the delimiters, null splits on whitespace
Returns:
an array of parsed Strings, null if null String input
Since:
2.1/**
     * <p>Splits the provided text into an array, separators specified,
     * preserving all tokens, including empty tokens created by adjacent
     * separators. This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separatorChars splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.splitPreserveAllTokens(null, *)           = null
     * StringUtils.splitPreserveAllTokens("", *)             = []
     * StringUtils.splitPreserveAllTokens("abc def", null)   = ["abc", "def"]
     * StringUtils.splitPreserveAllTokens("abc def", " ")    = ["abc", "def"]
     * StringUtils.splitPreserveAllTokens("abc  def", " ")   = ["abc", "", def"]
     * StringUtils.splitPreserveAllTokens("ab:cd:ef", ":")   = ["ab", "cd", "ef"]
     * StringUtils.splitPreserveAllTokens("ab:cd:ef:", ":")  = ["ab", "cd", "ef", ""]
     * StringUtils.splitPreserveAllTokens("ab:cd:ef::", ":") = ["ab", "cd", "ef", "", ""]
     * StringUtils.splitPreserveAllTokens("ab::cd:ef", ":")  = ["ab", "", cd", "ef"]
     * StringUtils.splitPreserveAllTokens(":cd:ef", ":")     = ["", cd", "ef"]
     * StringUtils.splitPreserveAllTokens("::cd:ef", ":")    = ["", "", cd", "ef"]
     * StringUtils.splitPreserveAllTokens(":cd:ef:", ":")    = ["", cd", "ef", ""]
     * </pre>
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChars  the characters used as the delimiters,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.1
     */
    public static String[] splitPreserveAllTokens(final String str, final String separatorChars) {
        return splitWorker(str, separatorChars, -1, true);
    }

    
Splits the provided text into an array with a maximum length,
separators specified, preserving all tokens, including empty tokens
created by adjacent separators.
The separator is not included in the returned String array.
Adjacent separators are treated as separators for empty tokens.
Adjacent separators are treated as one separator.
A null input String returns null. A null separatorChars splits on whitespace.
If more than max delimited substrings are found, the last returned string includes all characters after the first max - 1 returned strings (including separator characters).
StringUtils.splitPreserveAllTokens(null, *, *)            = null
StringUtils.splitPreserveAllTokens("", *, *)              = []
StringUtils.splitPreserveAllTokens("ab de fg", null, 0)   = ["ab", "de", "fg"]
StringUtils.splitPreserveAllTokens("ab   de fg", null, 0) = ["ab", "", "", "de", "fg"]
StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]
StringUtils.splitPreserveAllTokens("ab   de fg", null, 2) = ["ab", "  de fg"]
StringUtils.splitPreserveAllTokens("ab   de fg", null, 3) = ["ab", "", " de fg"]
StringUtils.splitPreserveAllTokens("ab   de fg", null, 4) = ["ab", "", "", "de fg"]

Params:
str –  the String to parse, may be null
separatorChars –  the characters used as the delimiters, null splits on whitespace
max –  the maximum number of elements to include in the
 array. A zero or negative value implies no limit
Returns:
an array of parsed Strings, null if null String input
Since:
2.1/**
     * <p>Splits the provided text into an array with a maximum length,
     * separators specified, preserving all tokens, including empty tokens
     * created by adjacent separators.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as separators for empty tokens.
     * Adjacent separators are treated as one separator.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separatorChars splits on whitespace.</p>
     *
     * <p>If more than {@code max} delimited substrings are found, the last
     * returned string includes all characters after the first {@code max - 1}
     * returned strings (including separator characters).</p>
     *
     * <pre>
     * StringUtils.splitPreserveAllTokens(null, *, *)            = null
     * StringUtils.splitPreserveAllTokens("", *, *)              = []
     * StringUtils.splitPreserveAllTokens("ab de fg", null, 0)   = ["ab", "de", "fg"]
     * StringUtils.splitPreserveAllTokens("ab   de fg", null, 0) = ["ab", "", "", "de", "fg"]
     * StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
     * StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]
     * StringUtils.splitPreserveAllTokens("ab   de fg", null, 2) = ["ab", "  de fg"]
     * StringUtils.splitPreserveAllTokens("ab   de fg", null, 3) = ["ab", "", " de fg"]
     * StringUtils.splitPreserveAllTokens("ab   de fg", null, 4) = ["ab", "", "", "de fg"]
     * </pre>
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChars  the characters used as the delimiters,
     *  {@code null} splits on whitespace
     * @param max  the maximum number of elements to include in the
     *  array. A zero or negative value implies no limit
     * @return an array of parsed Strings, {@code null} if null String input
     * @since 2.1
     */
    public static String[] splitPreserveAllTokens(final String str, final String separatorChars, final int max) {
        return splitWorker(str, separatorChars, max, true);
    }

    
Performs the logic for the split and splitPreserveAllTokens methods that do not return a maximum array length. 
Params:
str –  the String to parse, may be null
separatorChar – the separate character
preserveAllTokens – if true, adjacent separators are treated as empty token separators; if false, adjacent separators are treated as one separator.
Returns:
an array of parsed Strings, null if null String input/**
     * Performs the logic for the {@code split} and
     * {@code splitPreserveAllTokens} methods that do not return a
     * maximum array length.
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChar the separate character
     * @param preserveAllTokens if {@code true}, adjacent separators are
     * treated as empty token separators; if {@code false}, adjacent
     * separators are treated as one separator.
     * @return an array of parsed Strings, {@code null} if null String input
     */
    private static String[] splitWorker(final String str, final char separatorChar, final boolean preserveAllTokens) {
        // Performance tuned for 2.0 (JDK1.4)

        if (str == null) {
            return null;
        }
        final int len = str.length();
        if (len == 0) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final List<String> list = new ArrayList<>();
        int i = 0, start = 0;
        boolean match = false;
        boolean lastMatch = false;
        while (i < len) {
            if (str.charAt(i) == separatorChar) {
                if (match || preserveAllTokens) {
                    list.add(str.substring(start, i));
                    match = false;
                    lastMatch = true;
                }
                start = ++i;
                continue;
            }
            lastMatch = false;
            match = true;
            i++;
        }
        if (match || preserveAllTokens && lastMatch) {
            list.add(str.substring(start, i));
        }
        return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    
Performs the logic for the split and splitPreserveAllTokens methods that return a maximum array length. 
Params:
str –  the String to parse, may be null
separatorChars – the separate character
max –  the maximum number of elements to include in the
 array. A zero or negative value implies no limit.
preserveAllTokens – if true, adjacent separators are treated as empty token separators; if false, adjacent separators are treated as one separator.
Returns:
an array of parsed Strings, null if null String input/**
     * Performs the logic for the {@code split} and
     * {@code splitPreserveAllTokens} methods that return a maximum array
     * length.
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChars the separate character
     * @param max  the maximum number of elements to include in the
     *  array. A zero or negative value implies no limit.
     * @param preserveAllTokens if {@code true}, adjacent separators are
     * treated as empty token separators; if {@code false}, adjacent
     * separators are treated as one separator.
     * @return an array of parsed Strings, {@code null} if null String input
     */
    private static String[] splitWorker(final String str, final String separatorChars, final int max, final boolean preserveAllTokens) {
        // Performance tuned for 2.0 (JDK1.4)
        // Direct code is quicker than StringTokenizer.
        // Also, StringTokenizer uses isSpace() not isWhitespace()

        if (str == null) {
            return null;
        }
        final int len = str.length();
        if (len == 0) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final List<String> list = new ArrayList<>();
        int sizePlus1 = 1;
        int i = 0, start = 0;
        boolean match = false;
        boolean lastMatch = false;
        if (separatorChars == null) {
            // Null separator means use whitespace
            while (i < len) {
                if (Character.isWhitespace(str.charAt(i))) {
                    if (match || preserveAllTokens) {
                        lastMatch = true;
                        if (sizePlus1++ == max) {
                            i = len;
                            lastMatch = false;
                        }
                        list.add(str.substring(start, i));
                        match = false;
                    }
                    start = ++i;
                    continue;
                }
                lastMatch = false;
                match = true;
                i++;
            }
        } else if (separatorChars.length() == 1) {
            // Optimise 1 character case
            final char sep = separatorChars.charAt(0);
            while (i < len) {
                if (str.charAt(i) == sep) {
                    if (match || preserveAllTokens) {
                        lastMatch = true;
                        if (sizePlus1++ == max) {
                            i = len;
                            lastMatch = false;
                        }
                        list.add(str.substring(start, i));
                        match = false;
                    }
                    start = ++i;
                    continue;
                }
                lastMatch = false;
                match = true;
                i++;
            }
        } else {
            // standard case
            while (i < len) {
                if (separatorChars.indexOf(str.charAt(i)) >= 0) {
                    if (match || preserveAllTokens) {
                        lastMatch = true;
                        if (sizePlus1++ == max) {
                            i = len;
                            lastMatch = false;
                        }
                        list.add(str.substring(start, i));
                        match = false;
                    }
                    start = ++i;
                    continue;
                }
                lastMatch = false;
                match = true;
                i++;
            }
        }
        if (match || preserveAllTokens && lastMatch) {
            list.add(str.substring(start, i));
        }
        return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    
Check if a CharSequence starts with a specified prefix.
nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.
StringUtils.startsWith(null, null)      = true
StringUtils.startsWith(null, "abc")     = false
StringUtils.startsWith("abcdef", null)  = false
StringUtils.startsWith("abcdef", "abc") = true
StringUtils.startsWith("ABCDEF", "abc") = false

Params:
str –  the CharSequence to check, may be null
prefix – the prefix to find, may be null
See Also:
String.startsWith(String)
Returns:
true if the CharSequence starts with the prefix, case sensitive, or both null
Since:
2.4
Since:
3.0 Changed signature from startsWith(String, String) to startsWith(CharSequence, CharSequence)/**
     * <p>Check if a CharSequence starts with a specified prefix.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is case sensitive.</p>
     *
     * <pre>
     * StringUtils.startsWith(null, null)      = true
     * StringUtils.startsWith(null, "abc")     = false
     * StringUtils.startsWith("abcdef", null)  = false
     * StringUtils.startsWith("abcdef", "abc") = true
     * StringUtils.startsWith("ABCDEF", "abc") = false
     * </pre>
     *
     * @see java.lang.String#startsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param prefix the prefix to find, may be null
     * @return {@code true} if the CharSequence starts with the prefix, case sensitive, or
     *  both {@code null}
     * @since 2.4
     * @since 3.0 Changed signature from startsWith(String, String) to startsWith(CharSequence, CharSequence)
     */
    public static boolean startsWith(final CharSequence str, final CharSequence prefix) {
        return startsWith(str, prefix, false);
    }

    
Check if a CharSequence starts with a specified prefix (optionally case insensitive).
Params:
str –  the CharSequence to check, may be null
prefix – the prefix to find, may be null
ignoreCase – indicates whether the compare should ignore case
 (case insensitive) or not.
See Also:
startsWith.startsWith(String)
Returns:
true if the CharSequence starts with the prefix or both null/**
     * <p>Check if a CharSequence starts with a specified prefix (optionally case insensitive).</p>
     *
     * @see java.lang.String#startsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param prefix the prefix to find, may be null
     * @param ignoreCase indicates whether the compare should ignore case
     *  (case insensitive) or not.
     * @return {@code true} if the CharSequence starts with the prefix or
     *  both {@code null}
     */
    private static boolean startsWith(final CharSequence str, final CharSequence prefix, final boolean ignoreCase) {
        if (str == null || prefix == null) {
            return str == prefix;
        }
        if (prefix.length() > str.length()) {
            return false;
        }
        return CharSequenceUtils.regionMatches(str, ignoreCase, 0, prefix, 0, prefix.length());
    }

    
Check if a CharSequence starts with any of the provided case-sensitive prefixes.
StringUtils.startsWithAny(null, null)      = false
StringUtils.startsWithAny(null, new String[] {"abc"})  = false
StringUtils.startsWithAny("abcxyz", null)     = false
StringUtils.startsWithAny("abcxyz", new String[] {""}) = true
StringUtils.startsWithAny("abcxyz", new String[] {"abc"}) = true
StringUtils.startsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true
StringUtils.startsWithAny("abcxyz", null, "xyz", "ABCX") = false
StringUtils.startsWithAny("ABCXYZ", null, "xyz", "abc") = false

Params:
sequence – the CharSequence to check, may be null
searchStrings – the case-sensitive CharSequence prefixes, may be empty or contain null
See Also:
startsWith(CharSequence, CharSequence)
Returns:
true if the input sequence is null AND no searchStrings are provided, or the input sequence begins with any of the provided case-sensitive searchStrings.
Since:
2.5
Since:
3.0 Changed signature from startsWithAny(String, String[]) to startsWithAny(CharSequence, CharSequence...)/**
     * <p>Check if a CharSequence starts with any of the provided case-sensitive prefixes.</p>
     *
     * <pre>
     * StringUtils.startsWithAny(null, null)      = false
     * StringUtils.startsWithAny(null, new String[] {"abc"})  = false
     * StringUtils.startsWithAny("abcxyz", null)     = false
     * StringUtils.startsWithAny("abcxyz", new String[] {""}) = true
     * StringUtils.startsWithAny("abcxyz", new String[] {"abc"}) = true
     * StringUtils.startsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true
     * StringUtils.startsWithAny("abcxyz", null, "xyz", "ABCX") = false
     * StringUtils.startsWithAny("ABCXYZ", null, "xyz", "abc") = false
     * </pre>
     *
     * @param sequence the CharSequence to check, may be null
     * @param searchStrings the case-sensitive CharSequence prefixes, may be empty or contain {@code null}
     * @see StringUtils#startsWith(CharSequence, CharSequence)
     * @return {@code true} if the input {@code sequence} is {@code null} AND no {@code searchStrings} are provided, or
     *   the input {@code sequence} begins with any of the provided case-sensitive {@code searchStrings}.
     * @since 2.5
     * @since 3.0 Changed signature from startsWithAny(String, String[]) to startsWithAny(CharSequence, CharSequence...)
     */
    public static boolean startsWithAny(final CharSequence sequence, final CharSequence... searchStrings) {
        if (isEmpty(sequence) || ArrayUtils.isEmpty(searchStrings)) {
            return false;
        }
        for (final CharSequence searchString : searchStrings) {
            if (startsWith(sequence, searchString)) {
                return true;
            }
        }
        return false;
    }

    
Case insensitive check if a CharSequence starts with a specified prefix.
nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case insensitive.
StringUtils.startsWithIgnoreCase(null, null)      = true
StringUtils.startsWithIgnoreCase(null, "abc")     = false
StringUtils.startsWithIgnoreCase("abcdef", null)  = false
StringUtils.startsWithIgnoreCase("abcdef", "abc") = true
StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true

Params:
str –  the CharSequence to check, may be null
prefix – the prefix to find, may be null
See Also:
String.startsWith(String)
Returns:
true if the CharSequence starts with the prefix, case insensitive, or both null
Since:
2.4
Since:
3.0 Changed signature from startsWithIgnoreCase(String, String) to startsWithIgnoreCase(CharSequence, CharSequence)/**
     * <p>Case insensitive check if a CharSequence starts with a specified prefix.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is case insensitive.</p>
     *
     * <pre>
     * StringUtils.startsWithIgnoreCase(null, null)      = true
     * StringUtils.startsWithIgnoreCase(null, "abc")     = false
     * StringUtils.startsWithIgnoreCase("abcdef", null)  = false
     * StringUtils.startsWithIgnoreCase("abcdef", "abc") = true
     * StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true
     * </pre>
     *
     * @see java.lang.String#startsWith(String)
     * @param str  the CharSequence to check, may be null
     * @param prefix the prefix to find, may be null
     * @return {@code true} if the CharSequence starts with the prefix, case insensitive, or
     *  both {@code null}
     * @since 2.4
     * @since 3.0 Changed signature from startsWithIgnoreCase(String, String) to startsWithIgnoreCase(CharSequence, CharSequence)
     */
    public static boolean startsWithIgnoreCase(final CharSequence str, final CharSequence prefix) {
        return startsWith(str, prefix, true);
    }

    // Stripping
    //-----------------------------------------------------------------------
    
Strips whitespace from the start and end of a String.
This is similar to trim(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).
A null input String returns null.
StringUtils.strip(null)     = null
StringUtils.strip("")       = ""
StringUtils.strip("   ")    = ""
StringUtils.strip("abc")    = "abc"
StringUtils.strip("  abc")  = "abc"
StringUtils.strip("abc  ")  = "abc"
StringUtils.strip(" abc ")  = "abc"
StringUtils.strip(" ab c ") = "ab c"

Params:
str –  the String to remove whitespace from, may be null
Returns:
the stripped String, null if null String input/**
     * <p>Strips whitespace from the start and end of a String.</p>
     *
     * <p>This is similar to {@link #trim(String)} but removes whitespace.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.strip(null)     = null
     * StringUtils.strip("")       = ""
     * StringUtils.strip("   ")    = ""
     * StringUtils.strip("abc")    = "abc"
     * StringUtils.strip("  abc")  = "abc"
     * StringUtils.strip("abc  ")  = "abc"
     * StringUtils.strip(" abc ")  = "abc"
     * StringUtils.strip(" ab c ") = "ab c"
     * </pre>
     *
     * @param str  the String to remove whitespace from, may be null
     * @return the stripped String, {@code null} if null String input
     */
    public static String strip(final String str) {
        return strip(str, null);
    }

    
Strips any of a set of characters from the start and end of a String. This is similar to String.trim() but allows the characters to be stripped to be controlled.
A null input String returns null. An empty string ("") input returns the empty string.
If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char). Alternatively use strip(String).
StringUtils.strip(null, *)          = null
StringUtils.strip("", *)            = ""
StringUtils.strip("abc", null)      = "abc"
StringUtils.strip("  abc", null)    = "abc"
StringUtils.strip("abc  ", null)    = "abc"
StringUtils.strip(" abc ", null)    = "abc"
StringUtils.strip("  abcyx", "xyz") = "  abc"

Params:
str –  the String to remove characters from, may be null
stripChars –  the characters to remove, null treated as whitespace
Returns:
the stripped String, null if null String input/**
     * <p>Strips any of a set of characters from the start and end of a String.
     * This is similar to {@link String#trim()} but allows the characters
     * to be stripped to be controlled.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is {@code null}, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.
     * Alternatively use {@link #strip(String)}.</p>
     *
     * <pre>
     * StringUtils.strip(null, *)          = null
     * StringUtils.strip("", *)            = ""
     * StringUtils.strip("abc", null)      = "abc"
     * StringUtils.strip("  abc", null)    = "abc"
     * StringUtils.strip("abc  ", null)    = "abc"
     * StringUtils.strip(" abc ", null)    = "abc"
     * StringUtils.strip("  abcyx", "xyz") = "  abc"
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, {@code null} if null String input
     */
    public static String strip(String str, final String stripChars) {
        if (isEmpty(str)) {
            return str;
        }
        str = stripStart(str, stripChars);
        return stripEnd(str, stripChars);
    }

    
Removes diacritics (~= accents) from a string. The case will not be altered.
For instance, 'à' will be replaced by 'a'.
Note that ligatures will be left as is.
StringUtils.stripAccents(null)                = null
StringUtils.stripAccents("")                  = ""
StringUtils.stripAccents("control")           = "control"
StringUtils.stripAccents("éclair")     = "eclair"

Params:
input – String to be stripped
Returns:
input text with diacritics removed
Since:
3.0/**
     * <p>Removes diacritics (~= accents) from a string. The case will not be altered.</p>
     * <p>For instance, '&agrave;' will be replaced by 'a'.</p>
     * <p>Note that ligatures will be left as is.</p>
     *
     * <pre>
     * StringUtils.stripAccents(null)                = null
     * StringUtils.stripAccents("")                  = ""
     * StringUtils.stripAccents("control")           = "control"
     * StringUtils.stripAccents("&eacute;clair")     = "eclair"
     * </pre>
     *
     * @param input String to be stripped
     * @return input text with diacritics removed
     *
     * @since 3.0
     */
    // See also Lucene's ASCIIFoldingFilter (Lucene 2.9) that replaces accented characters by their unaccented equivalent (and uncommitted bug fix: https://issues.apache.org/jira/browse/LUCENE-1343?focusedCommentId=12858907&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12858907).
    public static String stripAccents(final String input) {
        if (input == null) {
            return null;
        }
        final StringBuilder decomposed = new StringBuilder(Normalizer.normalize(input, Normalizer.Form.NFD));
        convertRemainingAccentCharacters(decomposed);
        // Note that this doesn't correctly remove ligatures...
        return STRIP_ACCENTS_PATTERN.matcher(decomposed).replaceAll(EMPTY);
    }

    // StripAll
    //-----------------------------------------------------------------------
    
Strips whitespace from the start and end of every String in an array. Whitespace is defined by Character.isWhitespace(char).
A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored.
StringUtils.stripAll(null)             = null
StringUtils.stripAll([])               = []
StringUtils.stripAll(["abc", "  abc"]) = ["abc", "abc"]
StringUtils.stripAll(["abc  ", null])  = ["abc", null]

Params:
strs –  the array to remove whitespace from, may be null
Returns:
the stripped Strings, null if null array input/**
     * <p>Strips whitespace from the start and end of every String in an array.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>A new array is returned each time, except for length zero.
     * A {@code null} array will return {@code null}.
     * An empty array will return itself.
     * A {@code null} array entry will be ignored.</p>
     *
     * <pre>
     * StringUtils.stripAll(null)             = null
     * StringUtils.stripAll([])               = []
     * StringUtils.stripAll(["abc", "  abc"]) = ["abc", "abc"]
     * StringUtils.stripAll(["abc  ", null])  = ["abc", null]
     * </pre>
     *
     * @param strs  the array to remove whitespace from, may be null
     * @return the stripped Strings, {@code null} if null array input
     */
    public static String[] stripAll(final String... strs) {
        return stripAll(strs, null);
    }

    
Strips any of a set of characters from the start and end of every
String in an array.
Whitespace is defined by Character.isWhitespace(char).
A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored. A null stripChars will strip whitespace as defined by Character.isWhitespace(char).
StringUtils.stripAll(null, *)                = null
StringUtils.stripAll([], *)                  = []
StringUtils.stripAll(["abc", "  abc"], null) = ["abc", "abc"]
StringUtils.stripAll(["abc  ", null], null)  = ["abc", null]
StringUtils.stripAll(["abc  ", null], "yz")  = ["abc  ", null]
StringUtils.stripAll(["yabcz", null], "yz")  = ["abc", null]

Params:
strs –  the array to remove characters from, may be null
stripChars –  the characters to remove, null treated as whitespace
Returns:
the stripped Strings, null if null array input/**
     * <p>Strips any of a set of characters from the start and end of every
     * String in an array.</p>
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <p>A new array is returned each time, except for length zero.
     * A {@code null} array will return {@code null}.
     * An empty array will return itself.
     * A {@code null} array entry will be ignored.
     * A {@code null} stripChars will strip whitespace as defined by
     * {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripAll(null, *)                = null
     * StringUtils.stripAll([], *)                  = []
     * StringUtils.stripAll(["abc", "  abc"], null) = ["abc", "abc"]
     * StringUtils.stripAll(["abc  ", null], null)  = ["abc", null]
     * StringUtils.stripAll(["abc  ", null], "yz")  = ["abc  ", null]
     * StringUtils.stripAll(["yabcz", null], "yz")  = ["abc", null]
     * </pre>
     *
     * @param strs  the array to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped Strings, {@code null} if null array input
     */
    public static String[] stripAll(final String[] strs, final String stripChars) {
        final int strsLen = ArrayUtils.getLength(strs);
        if (strsLen == 0) {
            return strs;
        }
        final String[] newArr = new String[strsLen];
        for (int i = 0; i < strsLen; i++) {
            newArr[i] = strip(strs[i], stripChars);
        }
        return newArr;
    }

    
Strips any of a set of characters from the end of a String.
A null input String returns null. An empty string ("") input returns the empty string.
If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char).
StringUtils.stripEnd(null, *)          = null
StringUtils.stripEnd("", *)            = ""
StringUtils.stripEnd("abc", "")        = "abc"
StringUtils.stripEnd("abc", null)      = "abc"
StringUtils.stripEnd("  abc", null)    = "  abc"
StringUtils.stripEnd("abc  ", null)    = "abc"
StringUtils.stripEnd(" abc ", null)    = " abc"
StringUtils.stripEnd("  abcyx", "xyz") = "  abc"
StringUtils.stripEnd("120.00", ".0")   = "12"

Params:
str –  the String to remove characters from, may be null
stripChars –  the set of characters to remove, null treated as whitespace
Returns:
the stripped String, null if null String input/**
     * <p>Strips any of a set of characters from the end of a String.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is {@code null}, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripEnd(null, *)          = null
     * StringUtils.stripEnd("", *)            = ""
     * StringUtils.stripEnd("abc", "")        = "abc"
     * StringUtils.stripEnd("abc", null)      = "abc"
     * StringUtils.stripEnd("  abc", null)    = "  abc"
     * StringUtils.stripEnd("abc  ", null)    = "abc"
     * StringUtils.stripEnd(" abc ", null)    = " abc"
     * StringUtils.stripEnd("  abcyx", "xyz") = "  abc"
     * StringUtils.stripEnd("120.00", ".0")   = "12"
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the set of characters to remove, null treated as whitespace
     * @return the stripped String, {@code null} if null String input
     */
    public static String stripEnd(final String str, final String stripChars) {
        int end = length(str);
        if (end == 0) {
            return str;
        }

        if (stripChars == null) {
            while (end != 0 && Character.isWhitespace(str.charAt(end - 1))) {
                end--;
            }
        } else if (stripChars.isEmpty()) {
            return str;
        } else {
            while (end != 0 && stripChars.indexOf(str.charAt(end - 1)) != INDEX_NOT_FOUND) {
                end--;
            }
        }
        return str.substring(0, end);
    }

    
Strips any of a set of characters from the start of a String.
A null input String returns null. An empty string ("") input returns the empty string.
If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char).
StringUtils.stripStart(null, *)          = null
StringUtils.stripStart("", *)            = ""
StringUtils.stripStart("abc", "")        = "abc"
StringUtils.stripStart("abc", null)      = "abc"
StringUtils.stripStart("  abc", null)    = "abc"
StringUtils.stripStart("abc  ", null)    = "abc  "
StringUtils.stripStart(" abc ", null)    = "abc "
StringUtils.stripStart("yxabc  ", "xyz") = "abc  "

Params:
str –  the String to remove characters from, may be null
stripChars –  the characters to remove, null treated as whitespace
Returns:
the stripped String, null if null String input/**
     * <p>Strips any of a set of characters from the start of a String.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is {@code null}, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripStart(null, *)          = null
     * StringUtils.stripStart("", *)            = ""
     * StringUtils.stripStart("abc", "")        = "abc"
     * StringUtils.stripStart("abc", null)      = "abc"
     * StringUtils.stripStart("  abc", null)    = "abc"
     * StringUtils.stripStart("abc  ", null)    = "abc  "
     * StringUtils.stripStart(" abc ", null)    = "abc "
     * StringUtils.stripStart("yxabc  ", "xyz") = "abc  "
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, {@code null} if null String input
     */
    public static String stripStart(final String str, final String stripChars) {
        final int strLen = length(str);
        if (strLen == 0) {
            return str;
        }
        int start = 0;
        if (stripChars == null) {
            while (start != strLen && Character.isWhitespace(str.charAt(start))) {
                start++;
            }
        } else if (stripChars.isEmpty()) {
            return str;
        } else {
            while (start != strLen && stripChars.indexOf(str.charAt(start)) != INDEX_NOT_FOUND) {
                start++;
            }
        }
        return str.substring(start);
    }

    
Strips whitespace from the start and end of a String returning an empty String if null input.
This is similar to trimToEmpty(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).
StringUtils.stripToEmpty(null)     = ""
StringUtils.stripToEmpty("")       = ""
StringUtils.stripToEmpty("   ")    = ""
StringUtils.stripToEmpty("abc")    = "abc"
StringUtils.stripToEmpty("  abc")  = "abc"
StringUtils.stripToEmpty("abc  ")  = "abc"
StringUtils.stripToEmpty(" abc ")  = "abc"
StringUtils.stripToEmpty(" ab c ") = "ab c"

Params:
str –  the String to be stripped, may be null
Returns:
the trimmed String, or an empty String if null input
Since:
2.0/**
     * <p>Strips whitespace from the start and end of a String  returning
     * an empty String if {@code null} input.</p>
     *
     * <p>This is similar to {@link #trimToEmpty(String)} but removes whitespace.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripToEmpty(null)     = ""
     * StringUtils.stripToEmpty("")       = ""
     * StringUtils.stripToEmpty("   ")    = ""
     * StringUtils.stripToEmpty("abc")    = "abc"
     * StringUtils.stripToEmpty("  abc")  = "abc"
     * StringUtils.stripToEmpty("abc  ")  = "abc"
     * StringUtils.stripToEmpty(" abc ")  = "abc"
     * StringUtils.stripToEmpty(" ab c ") = "ab c"
     * </pre>
     *
     * @param str  the String to be stripped, may be null
     * @return the trimmed String, or an empty String if {@code null} input
     * @since 2.0
     */
    public static String stripToEmpty(final String str) {
        return str == null ? EMPTY : strip(str, null);
    }

    
Strips whitespace from the start and end of a String returning null if the String is empty ("") after the strip.
This is similar to trimToNull(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char).
StringUtils.stripToNull(null)     = null
StringUtils.stripToNull("")       = null
StringUtils.stripToNull("   ")    = null
StringUtils.stripToNull("abc")    = "abc"
StringUtils.stripToNull("  abc")  = "abc"
StringUtils.stripToNull("abc  ")  = "abc"
StringUtils.stripToNull(" abc ")  = "abc"
StringUtils.stripToNull(" ab c ") = "ab c"

Params:
str –  the String to be stripped, may be null
Returns:
the stripped String, null if whitespace, empty or null String input
Since:
2.0/**
     * <p>Strips whitespace from the start and end of a String  returning
     * {@code null} if the String is empty ("") after the strip.</p>
     *
     * <p>This is similar to {@link #trimToNull(String)} but removes whitespace.
     * Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripToNull(null)     = null
     * StringUtils.stripToNull("")       = null
     * StringUtils.stripToNull("   ")    = null
     * StringUtils.stripToNull("abc")    = "abc"
     * StringUtils.stripToNull("  abc")  = "abc"
     * StringUtils.stripToNull("abc  ")  = "abc"
     * StringUtils.stripToNull(" abc ")  = "abc"
     * StringUtils.stripToNull(" ab c ") = "ab c"
     * </pre>
     *
     * @param str  the String to be stripped, may be null
     * @return the stripped String,
     *  {@code null} if whitespace, empty or null String input
     * @since 2.0
     */
    public static String stripToNull(String str) {
        if (str == null) {
            return null;
        }
        str = strip(str, null);
        return str.isEmpty() ? null : str;
    }

    // Substring
    //-----------------------------------------------------------------------
    
Gets a substring from the specified String avoiding exceptions.
A negative start position can be used to start n characters from the end of the String.
A null String will return null. An empty ("") String will return "".
StringUtils.substring(null, *)   = null
StringUtils.substring("", *)     = ""
StringUtils.substring("abc", 0)  = "abc"
StringUtils.substring("abc", 2)  = "c"
StringUtils.substring("abc", 4)  = ""
StringUtils.substring("abc", -2) = "bc"
StringUtils.substring("abc", -4) = "abc"

Params:
str –  the String to get the substring from, may be null
start –  the position to start from, negative means
 count back from the end of the String by this many characters
Returns:
substring from start position, null if null String input/**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start {@code n}
     * characters from the end of the String.</p>
     *
     * <p>A {@code null} String will return {@code null}.
     * An empty ("") String will return "".</p>
     *
     * <pre>
     * StringUtils.substring(null, *)   = null
     * StringUtils.substring("", *)     = ""
     * StringUtils.substring("abc", 0)  = "abc"
     * StringUtils.substring("abc", 2)  = "c"
     * StringUtils.substring("abc", 4)  = ""
     * StringUtils.substring("abc", -2) = "bc"
     * StringUtils.substring("abc", -4) = "abc"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position, {@code null} if null String input
     */
    public static String substring(final String str, int start) {
        if (str == null) {
            return null;
        }

        // handle negatives, which means last n characters
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        if (start < 0) {
            start = 0;
        }
        if (start > str.length()) {
            return EMPTY;
        }

        return str.substring(start);
    }

    
Gets a substring from the specified String avoiding exceptions.
A negative start position can be used to start/end n characters from the end of the String.
The returned substring starts with the character in the start position and ends before the end position. All position counting is zero-based -- i.e., to start at the beginning of the string use start = 0. Negative start and end positions can be used to specify offsets relative to the end of the String.
If start is not strictly to the left of end, "" is returned.
StringUtils.substring(null, *, *)    = null
StringUtils.substring("", * ,  *)    = "";
StringUtils.substring("abc", 0, 2)   = "ab"
StringUtils.substring("abc", 2, 0)   = ""
StringUtils.substring("abc", 2, 4)   = "c"
StringUtils.substring("abc", 4, 6)   = ""
StringUtils.substring("abc", 2, 2)   = ""
StringUtils.substring("abc", -2, -1) = "b"
StringUtils.substring("abc", -4, 2)  = "ab"

Params:
str –  the String to get the substring from, may be null
start –  the position to start from, negative means
 count back from the end of the String by this many characters
end –  the position to end at (exclusive), negative means
 count back from the end of the String by this many characters
Returns:
substring from start position to end position, null if null String input/**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start/end {@code n}
     * characters from the end of the String.</p>
     *
     * <p>The returned substring starts with the character in the {@code start}
     * position and ends before the {@code end} position. All position counting is
     * zero-based -- i.e., to start at the beginning of the string use
     * {@code start = 0}. Negative start and end positions can be used to
     * specify offsets relative to the end of the String.</p>
     *
     * <p>If {@code start} is not strictly to the left of {@code end}, ""
     * is returned.</p>
     *
     * <pre>
     * StringUtils.substring(null, *, *)    = null
     * StringUtils.substring("", * ,  *)    = "";
     * StringUtils.substring("abc", 0, 2)   = "ab"
     * StringUtils.substring("abc", 2, 0)   = ""
     * StringUtils.substring("abc", 2, 4)   = "c"
     * StringUtils.substring("abc", 4, 6)   = ""
     * StringUtils.substring("abc", 2, 2)   = ""
     * StringUtils.substring("abc", -2, -1) = "b"
     * StringUtils.substring("abc", -4, 2)  = "ab"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @param end  the position to end at (exclusive), negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position to end position,
     *  {@code null} if null String input
     */
    public static String substring(final String str, int start, int end) {
        if (str == null) {
            return null;
        }

        // handle negatives
        if (end < 0) {
            end = str.length() + end; // remember end is negative
        }
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        // check length next
        if (end > str.length()) {
            end = str.length();
        }

        // if start is greater than end, return ""
        if (start > end) {
            return EMPTY;
        }

        if (start < 0) {
            start = 0;
        }
        if (end < 0) {
            end = 0;
        }

        return str.substring(start, end);
    }

    
Gets the substring after the first occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. 
If nothing is found, the empty string is returned.
StringUtils.substringAfter(null, *)      = null
StringUtils.substringAfter("", *)        = ""
StringUtils.substringAfter("abc", 'a')   = "bc"
StringUtils.substringAfter("abcba", 'b') = "cba"
StringUtils.substringAfter("abc", 'c')   = ""
StringUtils.substringAfter("abc", 'd')   = ""
StringUtils.substringAfter(" abc", 32)   = "abc"

Params:
str –  the String to get a substring from, may be null
separator –  the character to search.
Returns:
the substring after the first occurrence of the separator, null if null String input
Since:
3.11/**
     * <p>Gets the substring after the first occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     *
     * <p>If nothing is found, the empty string is returned.</p>
     *
     * <pre>
     * StringUtils.substringAfter(null, *)      = null
     * StringUtils.substringAfter("", *)        = ""
     * StringUtils.substringAfter("abc", 'a')   = "bc"
     * StringUtils.substringAfter("abcba", 'b') = "cba"
     * StringUtils.substringAfter("abc", 'c')   = ""
     * StringUtils.substringAfter("abc", 'd')   = ""
     * StringUtils.substringAfter(" abc", 32)   = "abc"
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the character to search.
     * @return the substring after the first occurrence of the separator,
     *  {@code null} if null String input
     * @since 3.11
     */
    public static String substringAfter(final String str, final int separator) {
        if (isEmpty(str)) {
            return str;
        }
        final int pos = str.indexOf(separator);
        if (pos == INDEX_NOT_FOUND) {
            return EMPTY;
        }
        return str.substring(pos + 1);
    }

    
Gets the substring after the first occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. A null separator will return the empty string if the input string is not null.
If nothing is found, the empty string is returned.
StringUtils.substringAfter(null, *)      = null
StringUtils.substringAfter("", *)        = ""
StringUtils.substringAfter(*, null)      = ""
StringUtils.substringAfter("abc", "a")   = "bc"
StringUtils.substringAfter("abcba", "b") = "cba"
StringUtils.substringAfter("abc", "c")   = ""
StringUtils.substringAfter("abc", "d")   = ""
StringUtils.substringAfter("abc", "")    = "abc"

Params:
str –  the String to get a substring from, may be null
separator –  the String to search for, may be null
Returns:
the substring after the first occurrence of the separator, null if null String input
Since:
2.0/**
     * <p>Gets the substring after the first occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     * A {@code null} separator will return the empty string if the
     * input string is not {@code null}.</p>
     *
     * <p>If nothing is found, the empty string is returned.</p>
     *
     * <pre>
     * StringUtils.substringAfter(null, *)      = null
     * StringUtils.substringAfter("", *)        = ""
     * StringUtils.substringAfter(*, null)      = ""
     * StringUtils.substringAfter("abc", "a")   = "bc"
     * StringUtils.substringAfter("abcba", "b") = "cba"
     * StringUtils.substringAfter("abc", "c")   = ""
     * StringUtils.substringAfter("abc", "d")   = ""
     * StringUtils.substringAfter("abc", "")    = "abc"
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the String to search for, may be null
     * @return the substring after the first occurrence of the separator,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String substringAfter(final String str, final String separator) {
        if (isEmpty(str)) {
            return str;
        }
        if (separator == null) {
            return EMPTY;
        }
        final int pos = str.indexOf(separator);
        if (pos == INDEX_NOT_FOUND) {
            return EMPTY;
        }
        return str.substring(pos + separator.length());
    }

    // startsWith
    //-----------------------------------------------------------------------

    
Gets the substring after the last occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. 
If nothing is found, the empty string is returned.
StringUtils.substringAfterLast(null, *)      = null
StringUtils.substringAfterLast("", *)        = ""
StringUtils.substringAfterLast("abc", 'a')   = "bc"
StringUtils.substringAfterLast(" bc", 32)    = "bc"
StringUtils.substringAfterLast("abcba", 'b') = "a"
StringUtils.substringAfterLast("abc", 'c')   = ""
StringUtils.substringAfterLast("a", 'a')     = ""
StringUtils.substringAfterLast("a", 'z')     = ""

Params:
str –  the String to get a substring from, may be null
separator –  the String to search for, may be null
Returns:
the substring after the last occurrence of the separator, null if null String input
Since:
3.11/**
     * <p>Gets the substring after the last occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     *
     * <p>If nothing is found, the empty string is returned.</p>
     *
     * <pre>
     * StringUtils.substringAfterLast(null, *)      = null
     * StringUtils.substringAfterLast("", *)        = ""
     * StringUtils.substringAfterLast("abc", 'a')   = "bc"
     * StringUtils.substringAfterLast(" bc", 32)    = "bc"
     * StringUtils.substringAfterLast("abcba", 'b') = "a"
     * StringUtils.substringAfterLast("abc", 'c')   = ""
     * StringUtils.substringAfterLast("a", 'a')     = ""
     * StringUtils.substringAfterLast("a", 'z')     = ""
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the String to search for, may be null
     * @return the substring after the last occurrence of the separator,
     *  {@code null} if null String input
     * @since 3.11
     */
    public static String substringAfterLast(final String str, final int separator) {
        if (isEmpty(str)) {
            return str;
        }
        final int pos = str.lastIndexOf(separator);
        if (pos == INDEX_NOT_FOUND || pos == str.length() - 1) {
            return EMPTY;
        }
        return str.substring(pos + 1);
    }

    
Gets the substring after the last occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. An empty or null separator will return the empty string if the input string is not null.
If nothing is found, the empty string is returned.
StringUtils.substringAfterLast(null, *)      = null
StringUtils.substringAfterLast("", *)        = ""
StringUtils.substringAfterLast(*, "")        = ""
StringUtils.substringAfterLast(*, null)      = ""
StringUtils.substringAfterLast("abc", "a")   = "bc"
StringUtils.substringAfterLast("abcba", "b") = "a"
StringUtils.substringAfterLast("abc", "c")   = ""
StringUtils.substringAfterLast("a", "a")     = ""
StringUtils.substringAfterLast("a", "z")     = ""

Params:
str –  the String to get a substring from, may be null
separator –  the String to search for, may be null
Returns:
the substring after the last occurrence of the separator, null if null String input
Since:
2.0/**
     * <p>Gets the substring after the last occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     * An empty or {@code null} separator will return the empty string if
     * the input string is not {@code null}.</p>
     *
     * <p>If nothing is found, the empty string is returned.</p>
     *
     * <pre>
     * StringUtils.substringAfterLast(null, *)      = null
     * StringUtils.substringAfterLast("", *)        = ""
     * StringUtils.substringAfterLast(*, "")        = ""
     * StringUtils.substringAfterLast(*, null)      = ""
     * StringUtils.substringAfterLast("abc", "a")   = "bc"
     * StringUtils.substringAfterLast("abcba", "b") = "a"
     * StringUtils.substringAfterLast("abc", "c")   = ""
     * StringUtils.substringAfterLast("a", "a")     = ""
     * StringUtils.substringAfterLast("a", "z")     = ""
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the String to search for, may be null
     * @return the substring after the last occurrence of the separator,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String substringAfterLast(final String str, final String separator) {
        if (isEmpty(str)) {
            return str;
        }
        if (isEmpty(separator)) {
            return EMPTY;
        }
        final int pos = str.lastIndexOf(separator);
        if (pos == INDEX_NOT_FOUND || pos == str.length() - separator.length()) {
            return EMPTY;
        }
        return str.substring(pos + separator.length());
    }

    // SubStringAfter/SubStringBefore
    //-----------------------------------------------------------------------
    
Gets the substring before the first occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. A null separator will return the input string.
If nothing is found, the string input is returned.
StringUtils.substringBefore(null, *)      = null
StringUtils.substringBefore("", *)        = ""
StringUtils.substringBefore("abc", "a")   = ""
StringUtils.substringBefore("abcba", "b") = "a"
StringUtils.substringBefore("abc", "c")   = "ab"
StringUtils.substringBefore("abc", "d")   = "abc"
StringUtils.substringBefore("abc", "")    = ""
StringUtils.substringBefore("abc", null)  = "abc"

Params:
str –  the String to get a substring from, may be null
separator –  the String to search for, may be null
Returns:
the substring before the first occurrence of the separator, null if null String input
Since:
2.0/**
     * <p>Gets the substring before the first occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     * A {@code null} separator will return the input string.</p>
     *
     * <p>If nothing is found, the string input is returned.</p>
     *
     * <pre>
     * StringUtils.substringBefore(null, *)      = null
     * StringUtils.substringBefore("", *)        = ""
     * StringUtils.substringBefore("abc", "a")   = ""
     * StringUtils.substringBefore("abcba", "b") = "a"
     * StringUtils.substringBefore("abc", "c")   = "ab"
     * StringUtils.substringBefore("abc", "d")   = "abc"
     * StringUtils.substringBefore("abc", "")    = ""
     * StringUtils.substringBefore("abc", null)  = "abc"
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the String to search for, may be null
     * @return the substring before the first occurrence of the separator,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String substringBefore(final String str, final String separator) {
        if (isEmpty(str) || separator == null) {
            return str;
        }
        if (separator.isEmpty()) {
            return EMPTY;
        }
        final int pos = str.indexOf(separator);
        if (pos == INDEX_NOT_FOUND) {
            return str;
        }
        return str.substring(0, pos);
    }

    
Gets the substring before the last occurrence of a separator.
The separator is not returned.
A null string input will return null. An empty ("") string input will return the empty string. An empty or null separator will return the input string.
If nothing is found, the string input is returned.
StringUtils.substringBeforeLast(null, *)      = null
StringUtils.substringBeforeLast("", *)        = ""
StringUtils.substringBeforeLast("abcba", "b") = "abc"
StringUtils.substringBeforeLast("abc", "c")   = "ab"
StringUtils.substringBeforeLast("a", "a")     = ""
StringUtils.substringBeforeLast("a", "z")     = "a"
StringUtils.substringBeforeLast("a", null)    = "a"
StringUtils.substringBeforeLast("a", "")      = "a"

Params:
str –  the String to get a substring from, may be null
separator –  the String to search for, may be null
Returns:
the substring before the last occurrence of the separator, null if null String input
Since:
2.0/**
     * <p>Gets the substring before the last occurrence of a separator.
     * The separator is not returned.</p>
     *
     * <p>A {@code null} string input will return {@code null}.
     * An empty ("") string input will return the empty string.
     * An empty or {@code null} separator will return the input string.</p>
     *
     * <p>If nothing is found, the string input is returned.</p>
     *
     * <pre>
     * StringUtils.substringBeforeLast(null, *)      = null
     * StringUtils.substringBeforeLast("", *)        = ""
     * StringUtils.substringBeforeLast("abcba", "b") = "abc"
     * StringUtils.substringBeforeLast("abc", "c")   = "ab"
     * StringUtils.substringBeforeLast("a", "a")     = ""
     * StringUtils.substringBeforeLast("a", "z")     = "a"
     * StringUtils.substringBeforeLast("a", null)    = "a"
     * StringUtils.substringBeforeLast("a", "")      = "a"
     * </pre>
     *
     * @param str  the String to get a substring from, may be null
     * @param separator  the String to search for, may be null
     * @return the substring before the last occurrence of the separator,
     *  {@code null} if null String input
     * @since 2.0
     */
    public static String substringBeforeLast(final String str, final String separator) {
        if (isEmpty(str) || isEmpty(separator)) {
            return str;
        }
        final int pos = str.lastIndexOf(separator);
        if (pos == INDEX_NOT_FOUND) {
            return str;
        }
        return str.substring(0, pos);
    }

    // Substring between
    //-----------------------------------------------------------------------
    
Gets the String that is nested in between two instances of the
same String.
A null input String returns null. A null tag returns null.
StringUtils.substringBetween(null, *)            = null
StringUtils.substringBetween("", "")             = ""
StringUtils.substringBetween("", "tag")          = null
StringUtils.substringBetween("tagabctag", null)  = null
StringUtils.substringBetween("tagabctag", "")    = ""
StringUtils.substringBetween("tagabctag", "tag") = "abc"

Params:
str –  the String containing the substring, may be null
tag –  the String before and after the substring, may be null
Returns:
the substring, null if no match
Since:
2.0/**
     * <p>Gets the String that is nested in between two instances of the
     * same String.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} tag returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.substringBetween(null, *)            = null
     * StringUtils.substringBetween("", "")             = ""
     * StringUtils.substringBetween("", "tag")          = null
     * StringUtils.substringBetween("tagabctag", null)  = null
     * StringUtils.substringBetween("tagabctag", "")    = ""
     * StringUtils.substringBetween("tagabctag", "tag") = "abc"
     * </pre>
     *
     * @param str  the String containing the substring, may be null
     * @param tag  the String before and after the substring, may be null
     * @return the substring, {@code null} if no match
     * @since 2.0
     */
    public static String substringBetween(final String str, final String tag) {
        return substringBetween(str, tag, tag);
    }

    // endsWith
    //-----------------------------------------------------------------------

    
Gets the String that is nested in between two Strings.
Only the first match is returned.
A null input String returns null. A null open/close returns null (no match). An empty ("") open and close returns an empty string.
StringUtils.substringBetween("wx[b]yz", "[", "]") = "b"
StringUtils.substringBetween(null, *, *)          = null
StringUtils.substringBetween(*, null, *)          = null
StringUtils.substringBetween(*, *, null)          = null
StringUtils.substringBetween("", "", "")          = ""
StringUtils.substringBetween("", "", "]")         = null
StringUtils.substringBetween("", "[", "]")        = null
StringUtils.substringBetween("yabcz", "", "")     = ""
StringUtils.substringBetween("yabcz", "y", "z")   = "abc"
StringUtils.substringBetween("yabczyabcz", "y", "z")   = "abc"

Params:
str –  the String containing the substring, may be null
open –  the String before the substring, may be null
close –  the String after the substring, may be null
Returns:
the substring, null if no match
Since:
2.0/**
     * <p>Gets the String that is nested in between two Strings.
     * Only the first match is returned.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} open/close returns {@code null} (no match).
     * An empty ("") open and close returns an empty string.</p>
     *
     * <pre>
     * StringUtils.substringBetween("wx[b]yz", "[", "]") = "b"
     * StringUtils.substringBetween(null, *, *)          = null
     * StringUtils.substringBetween(*, null, *)          = null
     * StringUtils.substringBetween(*, *, null)          = null
     * StringUtils.substringBetween("", "", "")          = ""
     * StringUtils.substringBetween("", "", "]")         = null
     * StringUtils.substringBetween("", "[", "]")        = null
     * StringUtils.substringBetween("yabcz", "", "")     = ""
     * StringUtils.substringBetween("yabcz", "y", "z")   = "abc"
     * StringUtils.substringBetween("yabczyabcz", "y", "z")   = "abc"
     * </pre>
     *
     * @param str  the String containing the substring, may be null
     * @param open  the String before the substring, may be null
     * @param close  the String after the substring, may be null
     * @return the substring, {@code null} if no match
     * @since 2.0
     */
    public static String substringBetween(final String str, final String open, final String close) {
        if (!ObjectUtils.allNotNull(str, open, close)) {
            return null;
        }
        final int start = str.indexOf(open);
        if (start != INDEX_NOT_FOUND) {
            final int end = str.indexOf(close, start + open.length());
            if (end != INDEX_NOT_FOUND) {
                return str.substring(start + open.length(), end);
            }
        }
        return null;
    }

    
Searches a String for substrings delimited by a start and end tag,
returning all matching substrings in an array.
A null input String returns null. A null open/close returns null (no match). An empty ("") open/close returns null (no match).
StringUtils.substringsBetween("[a][b][c]", "[", "]") = ["a","b","c"]
StringUtils.substringsBetween(null, *, *)            = null
StringUtils.substringsBetween(*, null, *)            = null
StringUtils.substringsBetween(*, *, null)            = null
StringUtils.substringsBetween("", "[", "]")          = []

Params:
str –  the String containing the substrings, null returns null, empty returns empty
open –  the String identifying the start of the substring, empty returns null
close –  the String identifying the end of the substring, empty returns null
Returns:
a String Array of substrings, or null if no match
Since:
2.3/**
     * <p>Searches a String for substrings delimited by a start and end tag,
     * returning all matching substrings in an array.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} open/close returns {@code null} (no match).
     * An empty ("") open/close returns {@code null} (no match).</p>
     *
     * <pre>
     * StringUtils.substringsBetween("[a][b][c]", "[", "]") = ["a","b","c"]
     * StringUtils.substringsBetween(null, *, *)            = null
     * StringUtils.substringsBetween(*, null, *)            = null
     * StringUtils.substringsBetween(*, *, null)            = null
     * StringUtils.substringsBetween("", "[", "]")          = []
     * </pre>
     *
     * @param str  the String containing the substrings, null returns null, empty returns empty
     * @param open  the String identifying the start of the substring, empty returns null
     * @param close  the String identifying the end of the substring, empty returns null
     * @return a String Array of substrings, or {@code null} if no match
     * @since 2.3
     */
    public static String[] substringsBetween(final String str, final String open, final String close) {
        if (str == null || isEmpty(open) || isEmpty(close)) {
            return null;
        }
        final int strLen = str.length();
        if (strLen == 0) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final int closeLen = close.length();
        final int openLen = open.length();
        final List<String> list = new ArrayList<>();
        int pos = 0;
        while (pos < strLen - closeLen) {
            int start = str.indexOf(open, pos);
            if (start < 0) {
                break;
            }
            start += openLen;
            final int end = str.indexOf(close, start);
            if (end < 0) {
                break;
            }
            list.add(str.substring(start, end));
            pos = end + closeLen;
        }
        if (list.isEmpty()) {
            return null;
        }
        return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    
Swaps the case of a String changing upper and title case to
lower case, and lower case to upper case.

 
Upper case character converts to Lower case
 
Title case character converts to Lower case
 
Lower case character converts to Upper case

For a word based algorithm, see WordUtils.swapCase(String). A null input String returns null.
StringUtils.swapCase(null)                 = null
StringUtils.swapCase("")                   = ""
StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"

NOTE: This method changed in Lang version 2.0.
It no longer performs a word based algorithm.
If you only use ASCII, you will notice no change.
That functionality is available in org.apache.commons.lang3.text.WordUtils.
Params:
str –  the String to swap case, may be null
Returns:
the changed String, null if null String input/**
     * <p>Swaps the case of a String changing upper and title case to
     * lower case, and lower case to upper case.</p>
     *
     * <ul>
     *  <li>Upper case character converts to Lower case</li>
     *  <li>Title case character converts to Lower case</li>
     *  <li>Lower case character converts to Upper case</li>
     * </ul>
     *
     * <p>For a word based algorithm, see {@link org.apache.commons.lang3.text.WordUtils#swapCase(String)}.
     * A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.swapCase(null)                 = null
     * StringUtils.swapCase("")                   = ""
     * StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer performs a word based algorithm.
     * If you only use ASCII, you will notice no change.
     * That functionality is available in org.apache.commons.lang3.text.WordUtils.</p>
     *
     * @param str  the String to swap case, may be null
     * @return the changed String, {@code null} if null String input
     */
    public static String swapCase(final String str) {
        if (isEmpty(str)) {
            return str;
        }

        final int strLen = str.length();
        final int[] newCodePoints = new int[strLen]; // cannot be longer than the char array
        int outOffset = 0;
        for (int i = 0; i < strLen; ) {
            final int oldCodepoint = str.codePointAt(i);
            final int newCodePoint;
            if (Character.isUpperCase(oldCodepoint) || Character.isTitleCase(oldCodepoint)) {
                newCodePoint = Character.toLowerCase(oldCodepoint);
            } else if (Character.isLowerCase(oldCodepoint)) {
                newCodePoint = Character.toUpperCase(oldCodepoint);
            } else {
                newCodePoint = oldCodepoint;
            }
            newCodePoints[outOffset++] = newCodePoint;
            i += Character.charCount(newCodePoint);
         }
        return new String(newCodePoints, 0, outOffset);
    }

    
Converts a CharSequence into an array of code points.
Valid pairs of surrogate code units will be converted into a single supplementary
code point. Isolated surrogate code units (i.e. a high surrogate not followed by a low surrogate or
a low surrogate not preceded by a high surrogate) will be returned as-is.
StringUtils.toCodePoints(null)   =  null
StringUtils.toCodePoints("")     =  []  // empty array

Params:
str – the character sequence to convert
Returns:
an array of code points
Since:
3.6/**
     * <p>Converts a {@code CharSequence} into an array of code points.</p>
     *
     * <p>Valid pairs of surrogate code units will be converted into a single supplementary
     * code point. Isolated surrogate code units (i.e. a high surrogate not followed by a low surrogate or
     * a low surrogate not preceded by a high surrogate) will be returned as-is.</p>
     *
     * <pre>
     * StringUtils.toCodePoints(null)   =  null
     * StringUtils.toCodePoints("")     =  []  // empty array
     * </pre>
     *
     * @param str the character sequence to convert
     * @return an array of code points
     * @since 3.6
     */
    public static int[] toCodePoints(final CharSequence str) {
        if (str == null) {
            return null;
        }
        if (str.length() == 0) {
            return ArrayUtils.EMPTY_INT_ARRAY;
        }

        final String s = str.toString();
        final int[] result = new int[s.codePointCount(0, s.length())];
        int index = 0;
        for (int i = 0; i < result.length; i++) {
            result[i] = s.codePointAt(index);
            index += Character.charCount(result[i]);
        }
        return result;
    }

    
Converts a byte[] to a String using the specified character encoding. 
Params:
bytes – 
           the byte array to read from
charset – 
           the encoding to use, if null then use the platform default
Throws:
NullPointerException –  if bytes is null
Returns:
a new String
Since:
3.2
Since:
3.3 No longer throws UnsupportedEncodingException./**
     * Converts a {@code byte[]} to a String using the specified character encoding.
     *
     * @param bytes
     *            the byte array to read from
     * @param charset
     *            the encoding to use, if null then use the platform default
     * @return a new String
     * @throws NullPointerException
     *             if {@code bytes} is null
     * @since 3.2
     * @since 3.3 No longer throws {@link UnsupportedEncodingException}.
     */
    public static String toEncodedString(final byte[] bytes, final Charset charset) {
        return new String(bytes, Charsets.toCharset(charset));
    }

    
Converts the given source String as a lower-case using the Locale.ROOT locale in a null-safe manner. 
Params:
source – A source String or null.
Returns:
the given source String as a lower-case using the Locale.ROOT locale or null.
Since:
3.10/**
     * Converts the given source String as a lower-case using the {@link Locale#ROOT} locale in a null-safe manner.
     *
     * @param source A source String or null.
     * @return the given source String as a lower-case using the {@link Locale#ROOT} locale or null.
     * @since 3.10
     */
    public static String toRootLowerCase(final String source) {
        return source == null ? null : source.toLowerCase(Locale.ROOT);
    }

    
Converts the given source String as a upper-case using the Locale.ROOT locale in a null-safe manner. 
Params:
source – A source String or null.
Returns:
the given source String as a upper-case using the Locale.ROOT locale or null.
Since:
3.10/**
     * Converts the given source String as a upper-case using the {@link Locale#ROOT} locale in a null-safe manner.
     *
     * @param source A source String or null.
     * @return the given source String as a upper-case using the {@link Locale#ROOT} locale or null.
     * @since 3.10
     */
    public static String toRootUpperCase(final String source) {
        return source == null ? null : source.toUpperCase(Locale.ROOT);
    }

    
Converts a byte[] to a String using the specified character encoding. 
Params:
bytes – 
           the byte array to read from
charsetName – 
           the encoding to use, if null then use the platform default
Throws:
UnsupportedEncodingException – 
            If the named charset is not supported
NullPointerException – 
            if the input is null
Returns:
a new String
Deprecated:
use toEncodedString(byte[], Charset) instead of String constants in your code
Since:
3.1/**
     * Converts a {@code byte[]} to a String using the specified character encoding.
     *
     * @param bytes
     *            the byte array to read from
     * @param charsetName
     *            the encoding to use, if null then use the platform default
     * @return a new String
     * @throws UnsupportedEncodingException
     *             If the named charset is not supported
     * @throws NullPointerException
     *             if the input is null
     * @deprecated use {@link StringUtils#toEncodedString(byte[], Charset)} instead of String constants in your code
     * @since 3.1
     */
    @Deprecated
    public static String toString(final byte[] bytes, final String charsetName) throws UnsupportedEncodingException {
        return charsetName != null ? new String(bytes, charsetName) : new String(bytes, Charset.defaultCharset());
    }

    // Trim
    //-----------------------------------------------------------------------
    
Removes control characters (char <= 32) from both ends of this String, handling null by returning null.
The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use strip(String).
To trim your choice of characters, use the strip(String, String) methods.
StringUtils.trim(null)          = null
StringUtils.trim("")            = ""
StringUtils.trim("     ")       = ""
StringUtils.trim("abc")         = "abc"
StringUtils.trim("    abc    ") = "abc"

Params:
str –  the String to be trimmed, may be null
Returns:
the trimmed string, null if null String input/**
     * <p>Removes control characters (char &lt;= 32) from both
     * ends of this String, handling {@code null} by returning
     * {@code null}.</p>
     *
     * <p>The String is trimmed using {@link String#trim()}.
     * Trim removes start and end characters &lt;= 32.
     * To strip whitespace use {@link #strip(String)}.</p>
     *
     * <p>To trim your choice of characters, use the
     * {@link #strip(String, String)} methods.</p>
     *
     * <pre>
     * StringUtils.trim(null)          = null
     * StringUtils.trim("")            = ""
     * StringUtils.trim("     ")       = ""
     * StringUtils.trim("abc")         = "abc"
     * StringUtils.trim("    abc    ") = "abc"
     * </pre>
     *
     * @param str  the String to be trimmed, may be null
     * @return the trimmed string, {@code null} if null String input
     */
    public static String trim(final String str) {
        return str == null ? null : str.trim();
    }

    
Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty ("") after the trim or if it is null. 
The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToEmpty(String).
StringUtils.trimToEmpty(null)          = ""
StringUtils.trimToEmpty("")            = ""
StringUtils.trimToEmpty("     ")       = ""
StringUtils.trimToEmpty("abc")         = "abc"
StringUtils.trimToEmpty("    abc    ") = "abc"

Params:
str –  the String to be trimmed, may be null
Returns:
the trimmed String, or an empty String if null input
Since:
2.0/**
     * <p>Removes control characters (char &lt;= 32) from both
     * ends of this String returning an empty String ("") if the String
     * is empty ("") after the trim or if it is {@code null}.
     *
     * <p>The String is trimmed using {@link String#trim()}.
     * Trim removes start and end characters &lt;= 32.
     * To strip whitespace use {@link #stripToEmpty(String)}.</p>
     *
     * <pre>
     * StringUtils.trimToEmpty(null)          = ""
     * StringUtils.trimToEmpty("")            = ""
     * StringUtils.trimToEmpty("     ")       = ""
     * StringUtils.trimToEmpty("abc")         = "abc"
     * StringUtils.trimToEmpty("    abc    ") = "abc"
     * </pre>
     *
     * @param str  the String to be trimmed, may be null
     * @return the trimmed String, or an empty String if {@code null} input
     * @since 2.0
     */
    public static String trimToEmpty(final String str) {
        return str == null ? EMPTY : str.trim();
    }

    
Removes control characters (char <= 32) from both ends of this String returning null if the String is empty ("") after the trim or if it is null. 
The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToNull(String).
StringUtils.trimToNull(null)          = null
StringUtils.trimToNull("")            = null
StringUtils.trimToNull("     ")       = null
StringUtils.trimToNull("abc")         = "abc"
StringUtils.trimToNull("    abc    ") = "abc"

Params:
str –  the String to be trimmed, may be null
Returns:
the trimmed String, null if only chars <= 32, empty or null String input
Since:
2.0/**
     * <p>Removes control characters (char &lt;= 32) from both
     * ends of this String returning {@code null} if the String is
     * empty ("") after the trim or if it is {@code null}.
     *
     * <p>The String is trimmed using {@link String#trim()}.
     * Trim removes start and end characters &lt;= 32.
     * To strip whitespace use {@link #stripToNull(String)}.</p>
     *
     * <pre>
     * StringUtils.trimToNull(null)          = null
     * StringUtils.trimToNull("")            = null
     * StringUtils.trimToNull("     ")       = null
     * StringUtils.trimToNull("abc")         = "abc"
     * StringUtils.trimToNull("    abc    ") = "abc"
     * </pre>
     *
     * @param str  the String to be trimmed, may be null
     * @return the trimmed String,
     *  {@code null} if only chars &lt;= 32, empty or null String input
     * @since 2.0
     */
    public static String trimToNull(final String str) {
        final String ts = trim(str);
        return isEmpty(ts) ? null : ts;
    }

    
Truncates a String. This will turn
"Now is the time for all good men" into "Now is the time for".
Specifically:

  
If str is less than maxWidth characters long, return it.
  
Else truncate it to substring(str, 0, maxWidth).
  
If maxWidth is less than 0, throw an IllegalArgumentException.
  
In no case will it return a String of length greater than maxWidth.

StringUtils.truncate(null, 0)       = null
StringUtils.truncate(null, 2)       = null
StringUtils.truncate("", 4)         = ""
StringUtils.truncate("abcdefg", 4)  = "abcd"
StringUtils.truncate("abcdefg", 6)  = "abcdef"
StringUtils.truncate("abcdefg", 7)  = "abcdefg"
StringUtils.truncate("abcdefg", 8)  = "abcdefg"
StringUtils.truncate("abcdefg", -1) = throws an IllegalArgumentException

Params:
str –  the String to truncate, may be null
maxWidth –  maximum length of result String, must be positive
Throws:
IllegalArgumentException – If maxWidth is less than 0
Returns:
truncated String, null if null String input
Since:
3.5/**
     * <p>Truncates a String. This will turn
     * "Now is the time for all good men" into "Now is the time for".</p>
     *
     * <p>Specifically:</p>
     * <ul>
     *   <li>If {@code str} is less than {@code maxWidth} characters
     *       long, return it.</li>
     *   <li>Else truncate it to {@code substring(str, 0, maxWidth)}.</li>
     *   <li>If {@code maxWidth} is less than {@code 0}, throw an
     *       {@code IllegalArgumentException}.</li>
     *   <li>In no case will it return a String of length greater than
     *       {@code maxWidth}.</li>
     * </ul>
     *
     * <pre>
     * StringUtils.truncate(null, 0)       = null
     * StringUtils.truncate(null, 2)       = null
     * StringUtils.truncate("", 4)         = ""
     * StringUtils.truncate("abcdefg", 4)  = "abcd"
     * StringUtils.truncate("abcdefg", 6)  = "abcdef"
     * StringUtils.truncate("abcdefg", 7)  = "abcdefg"
     * StringUtils.truncate("abcdefg", 8)  = "abcdefg"
     * StringUtils.truncate("abcdefg", -1) = throws an IllegalArgumentException
     * </pre>
     *
     * @param str  the String to truncate, may be null
     * @param maxWidth  maximum length of result String, must be positive
     * @return truncated String, {@code null} if null String input
     * @throws IllegalArgumentException If {@code maxWidth} is less than {@code 0}
     * @since 3.5
     */
    public static String truncate(final String str, final int maxWidth) {
        return truncate(str, 0, maxWidth);
    }

    
Truncates a String. This will turn
"Now is the time for all good men" into "is the time for all".
Works like truncate(String, int), but allows you to specify a "left edge" offset. 
Specifically:

  
If str is less than maxWidth characters long, return it.
  
Else truncate it to substring(str, offset, maxWidth).
  
If maxWidth is less than 0, throw an IllegalArgumentException.
  
If offset is less than 0, throw an IllegalArgumentException.
  
In no case will it return a String of length greater than maxWidth.

StringUtils.truncate(null, 0, 0) = null
StringUtils.truncate(null, 2, 4) = null
StringUtils.truncate("", 0, 10) = ""
StringUtils.truncate("", 2, 10) = ""
StringUtils.truncate("abcdefghij", 0, 3) = "abc"
StringUtils.truncate("abcdefghij", 5, 6) = "fghij"
StringUtils.truncate("raspberry peach", 10, 15) = "peach"
StringUtils.truncate("abcdefghijklmno", 0, 10) = "abcdefghij"
StringUtils.truncate("abcdefghijklmno", -1, 10) = throws an IllegalArgumentException
StringUtils.truncate("abcdefghijklmno", Integer.MIN_VALUE, 10) = throws an IllegalArgumentException
StringUtils.truncate("abcdefghijklmno", Integer.MIN_VALUE, Integer.MAX_VALUE) = throws an IllegalArgumentException
StringUtils.truncate("abcdefghijklmno", 0, Integer.MAX_VALUE) = "abcdefghijklmno"
StringUtils.truncate("abcdefghijklmno", 1, 10) = "bcdefghijk"
StringUtils.truncate("abcdefghijklmno", 2, 10) = "cdefghijkl"
StringUtils.truncate("abcdefghijklmno", 3, 10) = "defghijklm"
StringUtils.truncate("abcdefghijklmno", 4, 10) = "efghijklmn"
StringUtils.truncate("abcdefghijklmno", 5, 10) = "fghijklmno"
StringUtils.truncate("abcdefghijklmno", 5, 5) = "fghij"
StringUtils.truncate("abcdefghijklmno", 5, 3) = "fgh"
StringUtils.truncate("abcdefghijklmno", 10, 3) = "klm"
StringUtils.truncate("abcdefghijklmno", 10, Integer.MAX_VALUE) = "klmno"
StringUtils.truncate("abcdefghijklmno", 13, 1) = "n"
StringUtils.truncate("abcdefghijklmno", 13, Integer.MAX_VALUE) = "no"
StringUtils.truncate("abcdefghijklmno", 14, 1) = "o"
StringUtils.truncate("abcdefghijklmno", 14, Integer.MAX_VALUE) = "o"
StringUtils.truncate("abcdefghijklmno", 15, 1) = ""
StringUtils.truncate("abcdefghijklmno", 15, Integer.MAX_VALUE) = ""
StringUtils.truncate("abcdefghijklmno", Integer.MAX_VALUE, Integer.MAX_VALUE) = ""
StringUtils.truncate("abcdefghij", 3, -1) = throws an IllegalArgumentException
StringUtils.truncate("abcdefghij", -2, 4) = throws an IllegalArgumentException

Params:
str –  the String to truncate, may be null
offset –  left edge of source String
maxWidth –  maximum length of result String, must be positive
Throws:
IllegalArgumentException – If offset or maxWidth is less than 0
Returns:
truncated String, null if null String input
Since:
3.5/**
     * <p>Truncates a String. This will turn
     * "Now is the time for all good men" into "is the time for all".</p>
     *
     * <p>Works like {@code truncate(String, int)}, but allows you to specify
     * a "left edge" offset.
     *
     * <p>Specifically:</p>
     * <ul>
     *   <li>If {@code str} is less than {@code maxWidth} characters
     *       long, return it.</li>
     *   <li>Else truncate it to {@code substring(str, offset, maxWidth)}.</li>
     *   <li>If {@code maxWidth} is less than {@code 0}, throw an
     *       {@code IllegalArgumentException}.</li>
     *   <li>If {@code offset} is less than {@code 0}, throw an
     *       {@code IllegalArgumentException}.</li>
     *   <li>In no case will it return a String of length greater than
     *       {@code maxWidth}.</li>
     * </ul>
     *
     * <pre>
     * StringUtils.truncate(null, 0, 0) = null
     * StringUtils.truncate(null, 2, 4) = null
     * StringUtils.truncate("", 0, 10) = ""
     * StringUtils.truncate("", 2, 10) = ""
     * StringUtils.truncate("abcdefghij", 0, 3) = "abc"
     * StringUtils.truncate("abcdefghij", 5, 6) = "fghij"
     * StringUtils.truncate("raspberry peach", 10, 15) = "peach"
     * StringUtils.truncate("abcdefghijklmno", 0, 10) = "abcdefghij"
     * StringUtils.truncate("abcdefghijklmno", -1, 10) = throws an IllegalArgumentException
     * StringUtils.truncate("abcdefghijklmno", Integer.MIN_VALUE, 10) = throws an IllegalArgumentException
     * StringUtils.truncate("abcdefghijklmno", Integer.MIN_VALUE, Integer.MAX_VALUE) = throws an IllegalArgumentException
     * StringUtils.truncate("abcdefghijklmno", 0, Integer.MAX_VALUE) = "abcdefghijklmno"
     * StringUtils.truncate("abcdefghijklmno", 1, 10) = "bcdefghijk"
     * StringUtils.truncate("abcdefghijklmno", 2, 10) = "cdefghijkl"
     * StringUtils.truncate("abcdefghijklmno", 3, 10) = "defghijklm"
     * StringUtils.truncate("abcdefghijklmno", 4, 10) = "efghijklmn"
     * StringUtils.truncate("abcdefghijklmno", 5, 10) = "fghijklmno"
     * StringUtils.truncate("abcdefghijklmno", 5, 5) = "fghij"
     * StringUtils.truncate("abcdefghijklmno", 5, 3) = "fgh"
     * StringUtils.truncate("abcdefghijklmno", 10, 3) = "klm"
     * StringUtils.truncate("abcdefghijklmno", 10, Integer.MAX_VALUE) = "klmno"
     * StringUtils.truncate("abcdefghijklmno", 13, 1) = "n"
     * StringUtils.truncate("abcdefghijklmno", 13, Integer.MAX_VALUE) = "no"
     * StringUtils.truncate("abcdefghijklmno", 14, 1) = "o"
     * StringUtils.truncate("abcdefghijklmno", 14, Integer.MAX_VALUE) = "o"
     * StringUtils.truncate("abcdefghijklmno", 15, 1) = ""
     * StringUtils.truncate("abcdefghijklmno", 15, Integer.MAX_VALUE) = ""
     * StringUtils.truncate("abcdefghijklmno", Integer.MAX_VALUE, Integer.MAX_VALUE) = ""
     * StringUtils.truncate("abcdefghij", 3, -1) = throws an IllegalArgumentException
     * StringUtils.truncate("abcdefghij", -2, 4) = throws an IllegalArgumentException
     * </pre>
     *
     * @param str  the String to truncate, may be null
     * @param offset  left edge of source String
     * @param maxWidth  maximum length of result String, must be positive
     * @return truncated String, {@code null} if null String input
     * @throws IllegalArgumentException If {@code offset} or {@code maxWidth} is less than {@code 0}
     * @since 3.5
     */
    public static String truncate(final String str, final int offset, final int maxWidth) {
        if (offset < 0) {
            throw new IllegalArgumentException("offset cannot be negative");
        }
        if (maxWidth < 0) {
            throw new IllegalArgumentException("maxWith cannot be negative");
        }
        if (str == null) {
            return null;
        }
        if (offset > str.length()) {
            return EMPTY;
        }
        if (str.length() > maxWidth) {
            final int ix = Math.min(offset + maxWidth, str.length());
            return str.substring(offset, ix);
        }
        return str.substring(offset);
    }

    
Uncapitalizes a String, changing the first character to lower case as per Character.toLowerCase(int). No other characters are changed.
For a word based algorithm, see WordUtils.uncapitalize(String). A null input String returns null.
StringUtils.uncapitalize(null)  = null
StringUtils.uncapitalize("")    = ""
StringUtils.uncapitalize("cat") = "cat"
StringUtils.uncapitalize("Cat") = "cat"
StringUtils.uncapitalize("CAT") = "cAT"

Params:
str – the String to uncapitalize, may be null
See Also:
WordUtils.uncapitalize(String)
capitalize(String)
Returns:
the uncapitalized String, null if null String input
Since:
2.0/**
     * <p>Uncapitalizes a String, changing the first character to lower case as
     * per {@link Character#toLowerCase(int)}. No other characters are changed.</p>
     *
     * <p>For a word based algorithm, see {@link org.apache.commons.lang3.text.WordUtils#uncapitalize(String)}.
     * A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.uncapitalize(null)  = null
     * StringUtils.uncapitalize("")    = ""
     * StringUtils.uncapitalize("cat") = "cat"
     * StringUtils.uncapitalize("Cat") = "cat"
     * StringUtils.uncapitalize("CAT") = "cAT"
     * </pre>
     *
     * @param str the String to uncapitalize, may be null
     * @return the uncapitalized String, {@code null} if null String input
     * @see org.apache.commons.lang3.text.WordUtils#uncapitalize(String)
     * @see #capitalize(String)
     * @since 2.0
     */
    public static String uncapitalize(final String str) {
        final int strLen = length(str);
        if (strLen == 0) {
            return str;
        }

        final int firstCodepoint = str.codePointAt(0);
        final int newCodePoint = Character.toLowerCase(firstCodepoint);
        if (firstCodepoint == newCodePoint) {
            // already capitalized
            return str;
        }

        final int[] newCodePoints = new int[strLen]; // cannot be longer than the char array
        int outOffset = 0;
        newCodePoints[outOffset++] = newCodePoint; // copy the first codepoint
        for (int inOffset = Character.charCount(firstCodepoint); inOffset < strLen; ) {
            final int codepoint = str.codePointAt(inOffset);
            newCodePoints[outOffset++] = codepoint; // copy the remaining ones
            inOffset += Character.charCount(codepoint);
         }
        return new String(newCodePoints, 0, outOffset);
    }

    

Unwraps a given string from a character.

StringUtils.unwrap(null, null)         = null
StringUtils.unwrap(null, '\0')         = null
StringUtils.unwrap(null, '1')          = null
StringUtils.unwrap("a", 'a')           = "a"
StringUtils.unwrap("aa", 'a')           = ""
StringUtils.unwrap("\'abc\'", '\'')    = "abc"
StringUtils.unwrap("AABabcBAA", 'A')   = "ABabcBA"
StringUtils.unwrap("A", '#')           = "A"
StringUtils.unwrap("#A", '#')          = "#A"
StringUtils.unwrap("A#", '#')          = "A#"

Params:
str – 
         the String to be unwrapped, can be null
wrapChar – 
         the character used to unwrap
Returns:
unwrapped String or the original string
         if it is not quoted properly with the wrapChar
Since:
3.6/**
     * <p>
     * Unwraps a given string from a character.
     * </p>
     *
     * <pre>
     * StringUtils.unwrap(null, null)         = null
     * StringUtils.unwrap(null, '\0')         = null
     * StringUtils.unwrap(null, '1')          = null
     * StringUtils.unwrap("a", 'a')           = "a"
     * StringUtils.unwrap("aa", 'a')           = ""
     * StringUtils.unwrap("\'abc\'", '\'')    = "abc"
     * StringUtils.unwrap("AABabcBAA", 'A')   = "ABabcBA"
     * StringUtils.unwrap("A", '#')           = "A"
     * StringUtils.unwrap("#A", '#')          = "#A"
     * StringUtils.unwrap("A#", '#')          = "A#"
     * </pre>
     *
     * @param str
     *          the String to be unwrapped, can be null
     * @param wrapChar
     *          the character used to unwrap
     * @return unwrapped String or the original string
     *          if it is not quoted properly with the wrapChar
     * @since 3.6
     */
    public static String unwrap(final String str, final char wrapChar) {
        if (isEmpty(str) || wrapChar == CharUtils.NUL || str.length() == 1) {
            return str;
        }

        if (str.charAt(0) == wrapChar && str.charAt(str.length() - 1) == wrapChar) {
            final int startIndex = 0;
            final int endIndex = str.length() - 1;

            return str.substring(startIndex + 1, endIndex);
        }

        return str;
    }

    

Unwraps a given string from anther string.

StringUtils.unwrap(null, null)         = null
StringUtils.unwrap(null, "")           = null
StringUtils.unwrap(null, "1")          = null
StringUtils.unwrap("a", "a")           = "a"
StringUtils.unwrap("aa", "a")          = ""
StringUtils.unwrap("\'abc\'", "\'")    = "abc"
StringUtils.unwrap("\"abc\"", "\"")    = "abc"
StringUtils.unwrap("AABabcBAA", "AA")  = "BabcB"
StringUtils.unwrap("A", "#")           = "A"
StringUtils.unwrap("#A", "#")          = "#A"
StringUtils.unwrap("A#", "#")          = "A#"

Params:
str – 
         the String to be unwrapped, can be null
wrapToken – 
         the String used to unwrap
Returns:
unwrapped String or the original string
         if it is not quoted properly with the wrapToken
Since:
3.6/**
     * <p>
     * Unwraps a given string from anther string.
     * </p>
     *
     * <pre>
     * StringUtils.unwrap(null, null)         = null
     * StringUtils.unwrap(null, "")           = null
     * StringUtils.unwrap(null, "1")          = null
     * StringUtils.unwrap("a", "a")           = "a"
     * StringUtils.unwrap("aa", "a")          = ""
     * StringUtils.unwrap("\'abc\'", "\'")    = "abc"
     * StringUtils.unwrap("\"abc\"", "\"")    = "abc"
     * StringUtils.unwrap("AABabcBAA", "AA")  = "BabcB"
     * StringUtils.unwrap("A", "#")           = "A"
     * StringUtils.unwrap("#A", "#")          = "#A"
     * StringUtils.unwrap("A#", "#")          = "A#"
     * </pre>
     *
     * @param str
     *          the String to be unwrapped, can be null
     * @param wrapToken
     *          the String used to unwrap
     * @return unwrapped String or the original string
     *          if it is not quoted properly with the wrapToken
     * @since 3.6
     */
    public static String unwrap(final String str, final String wrapToken) {
        if (isEmpty(str) || isEmpty(wrapToken) || str.length() == 1) {
            return str;
        }

        if (startsWith(str, wrapToken) && endsWith(str, wrapToken)) {
            final int startIndex = str.indexOf(wrapToken);
            final int endIndex = str.lastIndexOf(wrapToken);
            final int wrapLength = wrapToken.length();

            if (startIndex != -1 && endIndex != -1) {
                return str.substring(startIndex + wrapLength, endIndex);
            }
        }

        return str;
    }

    // Case conversion
    //-----------------------------------------------------------------------
    
Converts a String to upper case as per String.toUpperCase().
A null input String returns null.
StringUtils.upperCase(null)  = null
StringUtils.upperCase("")    = ""
StringUtils.upperCase("aBc") = "ABC"

Note: As described in the documentation for String.toUpperCase(), the result of this method is affected by the current locale. For platform-independent case transformations, the method lowerCase(String, Locale) should be used with a specific locale (e.g. Locale.ENGLISH).
Params:
str –  the String to upper case, may be null
Returns:
the upper cased String, null if null String input/**
     * <p>Converts a String to upper case as per {@link String#toUpperCase()}.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.upperCase(null)  = null
     * StringUtils.upperCase("")    = ""
     * StringUtils.upperCase("aBc") = "ABC"
     * </pre>
     *
     * <p><strong>Note:</strong> As described in the documentation for {@link String#toUpperCase()},
     * the result of this method is affected by the current locale.
     * For platform-independent case transformations, the method {@link #lowerCase(String, Locale)}
     * should be used with a specific locale (e.g. {@link Locale#ENGLISH}).</p>
     *
     * @param str  the String to upper case, may be null
     * @return the upper cased String, {@code null} if null String input
     */
    public static String upperCase(final String str) {
        if (str == null) {
            return null;
        }
        return str.toUpperCase();
    }

    
Converts a String to upper case as per String.toUpperCase(Locale).
A null input String returns null.
StringUtils.upperCase(null, Locale.ENGLISH)  = null
StringUtils.upperCase("", Locale.ENGLISH)    = ""
StringUtils.upperCase("aBc", Locale.ENGLISH) = "ABC"

Params:
str –  the String to upper case, may be null
locale –  the locale that defines the case transformation rules, must not be null
Returns:
the upper cased String, null if null String input
Since:
2.5/**
     * <p>Converts a String to upper case as per {@link String#toUpperCase(Locale)}.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.upperCase(null, Locale.ENGLISH)  = null
     * StringUtils.upperCase("", Locale.ENGLISH)    = ""
     * StringUtils.upperCase("aBc", Locale.ENGLISH) = "ABC"
     * </pre>
     *
     * @param str  the String to upper case, may be null
     * @param locale  the locale that defines the case transformation rules, must not be null
     * @return the upper cased String, {@code null} if null String input
     * @since 2.5
     */
    public static String upperCase(final String str, final Locale locale) {
        if (str == null) {
            return null;
        }
        return str.toUpperCase(locale);
    }

    
Returns the string representation of the char array or null. 
Params:
value – the character array.
See Also:
String.valueOf(char[])
Returns:
a String or null
Since:
3.9/**
     * Returns the string representation of the {@code char} array or null.
     *
     * @param value the character array.
     * @return a String or null
     * @see String#valueOf(char[])
     * @since 3.9
     */
    public static String valueOf(final char[] value) {
        return value == null ? null : String.valueOf(value);
    }

    

Wraps a string with a char.

StringUtils.wrap(null, *)        = null
StringUtils.wrap("", *)          = ""
StringUtils.wrap("ab", '\0')     = "ab"
StringUtils.wrap("ab", 'x')      = "xabx"
StringUtils.wrap("ab", '\'')     = "'ab'"
StringUtils.wrap("\"ab\"", '\"') = "\"\"ab\"\""

Params:
str –  the string to be wrapped, may be null
wrapWith –  the char that will wrap str
Returns:
the wrapped string, or null if str==null
Since:
3.4/**
     * <p>
     * Wraps a string with a char.
     * </p>
     *
     * <pre>
     * StringUtils.wrap(null, *)        = null
     * StringUtils.wrap("", *)          = ""
     * StringUtils.wrap("ab", '\0')     = "ab"
     * StringUtils.wrap("ab", 'x')      = "xabx"
     * StringUtils.wrap("ab", '\'')     = "'ab'"
     * StringUtils.wrap("\"ab\"", '\"') = "\"\"ab\"\""
     * </pre>
     *
     * @param str
     *            the string to be wrapped, may be {@code null}
     * @param wrapWith
     *            the char that will wrap {@code str}
     * @return the wrapped string, or {@code null} if {@code str==null}
     * @since 3.4
     */
    public static String wrap(final String str, final char wrapWith) {

        if (isEmpty(str) || wrapWith == CharUtils.NUL) {
            return str;
        }

        return wrapWith + str + wrapWith;
    }

    

Wraps a String with another String.

 A null input String returns null. 
StringUtils.wrap(null, *)         = null
StringUtils.wrap("", *)           = ""
StringUtils.wrap("ab", null)      = "ab"
StringUtils.wrap("ab", "x")       = "xabx"
StringUtils.wrap("ab", "\"")      = "\"ab\""
StringUtils.wrap("\"ab\"", "\"")  = "\"\"ab\"\""
StringUtils.wrap("ab", "'")       = "'ab'"
StringUtils.wrap("'abcd'", "'")   = "''abcd''"
StringUtils.wrap("\"abcd\"", "'") = "'\"abcd\"'"
StringUtils.wrap("'abcd'", "\"")  = "\"'abcd'\""

Params:
str – 
           the String to be wrapper, may be null
wrapWith – 
           the String that will wrap str
Returns:
wrapped String, null if null String input
Since:
3.4/**
     * <p>
     * Wraps a String with another String.
     * </p>
     *
     * <p>
     * A {@code null} input String returns {@code null}.
     * </p>
     *
     * <pre>
     * StringUtils.wrap(null, *)         = null
     * StringUtils.wrap("", *)           = ""
     * StringUtils.wrap("ab", null)      = "ab"
     * StringUtils.wrap("ab", "x")       = "xabx"
     * StringUtils.wrap("ab", "\"")      = "\"ab\""
     * StringUtils.wrap("\"ab\"", "\"")  = "\"\"ab\"\""
     * StringUtils.wrap("ab", "'")       = "'ab'"
     * StringUtils.wrap("'abcd'", "'")   = "''abcd''"
     * StringUtils.wrap("\"abcd\"", "'") = "'\"abcd\"'"
     * StringUtils.wrap("'abcd'", "\"")  = "\"'abcd'\""
     * </pre>
     *
     * @param str
     *            the String to be wrapper, may be null
     * @param wrapWith
     *            the String that will wrap str
     * @return wrapped String, {@code null} if null String input
     * @since 3.4
     */
    public static String wrap(final String str, final String wrapWith) {

        if (isEmpty(str) || isEmpty(wrapWith)) {
            return str;
        }

        return wrapWith.concat(str).concat(wrapWith);
    }

    

Wraps a string with a char if that char is missing from the start or end of the given string.

A new String will not be created if str is already wrapped.
StringUtils.wrapIfMissing(null, *)        = null
StringUtils.wrapIfMissing("", *)          = ""
StringUtils.wrapIfMissing("ab", '\0')     = "ab"
StringUtils.wrapIfMissing("ab", 'x')      = "xabx"
StringUtils.wrapIfMissing("ab", '\'')     = "'ab'"
StringUtils.wrapIfMissing("\"ab\"", '\"') = "\"ab\""
StringUtils.wrapIfMissing("/", '/')  = "/"
StringUtils.wrapIfMissing("a/b/c", '/')  = "/a/b/c/"
StringUtils.wrapIfMissing("/a/b/c", '/')  = "/a/b/c/"
StringUtils.wrapIfMissing("a/b/c/", '/')  = "/a/b/c/"

Params:
str –  the string to be wrapped, may be null
wrapWith –  the char that will wrap str
Returns:
the wrapped string, or null if str==null
Since:
3.5/**
     * <p>
     * Wraps a string with a char if that char is missing from the start or end of the given string.
     * </p>
     *
     * <p>A new {@code String} will not be created if {@code str} is already wrapped.</p>
     *
     * <pre>
     * StringUtils.wrapIfMissing(null, *)        = null
     * StringUtils.wrapIfMissing("", *)          = ""
     * StringUtils.wrapIfMissing("ab", '\0')     = "ab"
     * StringUtils.wrapIfMissing("ab", 'x')      = "xabx"
     * StringUtils.wrapIfMissing("ab", '\'')     = "'ab'"
     * StringUtils.wrapIfMissing("\"ab\"", '\"') = "\"ab\""
     * StringUtils.wrapIfMissing("/", '/')  = "/"
     * StringUtils.wrapIfMissing("a/b/c", '/')  = "/a/b/c/"
     * StringUtils.wrapIfMissing("/a/b/c", '/')  = "/a/b/c/"
     * StringUtils.wrapIfMissing("a/b/c/", '/')  = "/a/b/c/"
     * </pre>
     *
     * @param str
     *            the string to be wrapped, may be {@code null}
     * @param wrapWith
     *            the char that will wrap {@code str}
     * @return the wrapped string, or {@code null} if {@code str==null}
     * @since 3.5
     */
    public static String wrapIfMissing(final String str, final char wrapWith) {
        if (isEmpty(str) || wrapWith == CharUtils.NUL) {
            return str;
        }
        final boolean wrapStart = str.charAt(0) != wrapWith;
        final boolean wrapEnd = str.charAt(str.length() - 1) != wrapWith;
        if (!wrapStart && !wrapEnd) {
            return str;
        }

        final StringBuilder builder = new StringBuilder(str.length() + 2);
        if (wrapStart) {
            builder.append(wrapWith);
        }
        builder.append(str);
        if (wrapEnd) {
            builder.append(wrapWith);
        }
        return builder.toString();
    }

    

Wraps a string with a string if that string is missing from the start or end of the given string.

A new String will not be created if str is already wrapped.
StringUtils.wrapIfMissing(null, *)         = null
StringUtils.wrapIfMissing("", *)           = ""
StringUtils.wrapIfMissing("ab", null)      = "ab"
StringUtils.wrapIfMissing("ab", "x")       = "xabx"
StringUtils.wrapIfMissing("ab", "\"")      = "\"ab\""
StringUtils.wrapIfMissing("\"ab\"", "\"")  = "\"ab\""
StringUtils.wrapIfMissing("ab", "'")       = "'ab'"
StringUtils.wrapIfMissing("'abcd'", "'")   = "'abcd'"
StringUtils.wrapIfMissing("\"abcd\"", "'") = "'\"abcd\"'"
StringUtils.wrapIfMissing("'abcd'", "\"")  = "\"'abcd'\""
StringUtils.wrapIfMissing("/", "/")  = "/"
StringUtils.wrapIfMissing("a/b/c", "/")  = "/a/b/c/"
StringUtils.wrapIfMissing("/a/b/c", "/")  = "/a/b/c/"
StringUtils.wrapIfMissing("a/b/c/", "/")  = "/a/b/c/"

Params:
str –  the string to be wrapped, may be null
wrapWith –  the string that will wrap str
Returns:
the wrapped string, or null if str==null
Since:
3.5/**
     * <p>
     * Wraps a string with a string if that string is missing from the start or end of the given string.
     * </p>
     *
     * <p>A new {@code String} will not be created if {@code str} is already wrapped.</p>
     *
     * <pre>
     * StringUtils.wrapIfMissing(null, *)         = null
     * StringUtils.wrapIfMissing("", *)           = ""
     * StringUtils.wrapIfMissing("ab", null)      = "ab"
     * StringUtils.wrapIfMissing("ab", "x")       = "xabx"
     * StringUtils.wrapIfMissing("ab", "\"")      = "\"ab\""
     * StringUtils.wrapIfMissing("\"ab\"", "\"")  = "\"ab\""
     * StringUtils.wrapIfMissing("ab", "'")       = "'ab'"
     * StringUtils.wrapIfMissing("'abcd'", "'")   = "'abcd'"
     * StringUtils.wrapIfMissing("\"abcd\"", "'") = "'\"abcd\"'"
     * StringUtils.wrapIfMissing("'abcd'", "\"")  = "\"'abcd'\""
     * StringUtils.wrapIfMissing("/", "/")  = "/"
     * StringUtils.wrapIfMissing("a/b/c", "/")  = "/a/b/c/"
     * StringUtils.wrapIfMissing("/a/b/c", "/")  = "/a/b/c/"
     * StringUtils.wrapIfMissing("a/b/c/", "/")  = "/a/b/c/"
     * </pre>
     *
     * @param str
     *            the string to be wrapped, may be {@code null}
     * @param wrapWith
     *            the string that will wrap {@code str}
     * @return the wrapped string, or {@code null} if {@code str==null}
     * @since 3.5
     */
    public static String wrapIfMissing(final String str, final String wrapWith) {
        if (isEmpty(str) || isEmpty(wrapWith)) {
            return str;
        }

        final boolean wrapStart = !str.startsWith(wrapWith);
        final boolean wrapEnd = !str.endsWith(wrapWith);
        if (!wrapStart && !wrapEnd) {
            return str;
        }

        final StringBuilder builder = new StringBuilder(str.length() + wrapWith.length() + wrapWith.length());
        if (wrapStart) {
            builder.append(wrapWith);
        }
        builder.append(str);
        if (wrapEnd) {
            builder.append(wrapWith);
        }
        return builder.toString();
    }

    
StringUtils instances should NOT be constructed in standard programming. Instead, the class should be used as StringUtils.trim(" foo ");.
This constructor is public to permit tools that require a JavaBean
instance to operate.
/**
     * <p>{@code StringUtils} instances should NOT be constructed in
     * standard programming. Instead, the class should be used as
     * {@code StringUtils.trim(" foo ");}.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public StringUtils() {
        super();
    }

}