/*
- * Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 
 package java.lang;
 
 import java.io.ObjectStreamField;
 import java.io.UnsupportedEncodingException;
 import java.lang.annotation.Native;
 import java.lang.invoke.MethodHandles;
 import java.lang.constant.Constable;
 import java.lang.constant.ConstantDesc;
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.charset.*;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Formatter;
 import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Spliterator;
-import java.util.StringJoiner;
 import java.util.function.Function;
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
+
+import jdk.internal.util.Preconditions;
+import jdk.internal.vm.annotation.ForceInline;
 import jdk.internal.vm.annotation.IntrinsicCandidate;
 import jdk.internal.vm.annotation.Stable;
 import sun.nio.cs.ArrayDecoder;
 import sun.nio.cs.ArrayEncoder;
 
 import sun.nio.cs.ISO_8859_1;
 import sun.nio.cs.US_ASCII;
 import sun.nio.cs.UTF_8;
 
 /**
  * The {@code String} class represents character strings. All
  * string literals in Java programs, such as {@code "abc"}, are
  * implemented as instances of this class.
  * <p>
  * Strings are constant; their values cannot be changed after they
  * are created. String buffers support mutable strings.
  * Because String objects are immutable they can be shared. For example:
  * <blockquote><pre>
  *     String str = "abc";
  * </pre></blockquote><p>
  * is equivalent to:
  * <blockquote><pre>
  *     char data[] = {'a', 'b', 'c'};
  *     String str = new String(data);
  * </pre></blockquote><p>
  * Here are some more examples of how strings can be used:
  * <blockquote><pre>
  *     System.out.println("abc");
  *     String cde = "cde";
  *     System.out.println("abc" + cde);
  *     String c = "abc".substring(2, 3);
  *     String d = cde.substring(1, 2);
  * </pre></blockquote>
  * <p>
  * The class {@code String} includes methods for examining
  * individual characters of the sequence, for comparing strings, for
  * searching strings, for extracting substrings, and for creating a
  * copy of a string with all characters translated to uppercase or to
  * lowercase. Case mapping is based on the Unicode Standard version
  * specified by the {@link java.lang.Character Character} class.
  * <p>
  * The Java language provides special support for the string
  * concatenation operator (&nbsp;+&nbsp;), and for conversion of
  * other objects to strings. For additional information on string
  * concatenation and conversion, see <i>The Java Language Specification</i>.
  *
  * <p> Unless otherwise noted, passing a {@code null} argument to a constructor
  * or method in this class will cause a {@link NullPointerException} to be
  * thrown.
  *
  * <p>A {@code String} represents a string in the UTF-16 format
  * in which <em>supplementary characters</em> are represented by <em>surrogate
  * pairs</em> (see the section <a href="Character.html#unicode">Unicode
  * Character Representations</a> in the {@code Character} class for
  * more information).
  * Index values refer to {@code char} code units, so a supplementary
  * character uses two positions in a {@code String}.
  * <p>The {@code String} class provides methods for dealing with
  * Unicode code points (i.e., characters), in addition to those for
  * dealing with Unicode code units (i.e., {@code char} values).
  *
  * <p>Unless otherwise noted, methods for comparing Strings do not take locale
  * into account.  The {@link java.text.Collator} class provides methods for
  * finer-grain, locale-sensitive String comparison.
  *
  * @implNote The implementation of the string concatenation operator is left to
  * the discretion of a Java compiler, as long as the compiler ultimately conforms
  * to <i>The Java Language Specification</i>. For example, the {@code javac} compiler
  * may implement the operator with {@code StringBuffer}, {@code StringBuilder},
  * or {@code java.lang.invoke.StringConcatFactory} depending on the JDK version. The
  * implementation of string conversion is typically through the method {@code toString},
  * defined by {@code Object} and inherited by all classes in Java.
  *
  * @author  Lee Boynton
  * @author  Arthur van Hoff
  * @author  Martin Buchholz
  * @author  Ulf Zibis
  * @see     java.lang.Object#toString()
  * @see     java.lang.StringBuffer
  * @see     java.lang.StringBuilder
  * @see     java.nio.charset.Charset
  * @since   1.0
  * @jls     15.18.1 String Concatenation Operator +
  */
 
 public final class String
     implements java.io.Serializable, Comparable<String>, CharSequence,
                Constable, ConstantDesc {
 
     /**
      * The value is used for character storage.
      *
      * @implNote This field is trusted by the VM, and is a subject to
      * constant folding if String instance is constant. Overwriting this
      * field after construction will cause problems.
      *
      * Additionally, it is marked with {@link Stable} to trust the contents
      * of the array. No other facility in JDK provides this functionality (yet).
      * {@link Stable} is safe here, because value is never null.
      */
     @Stable
     private final byte[] value;
 
     /**
      * The identifier of the encoding used to encode the bytes in
      * {@code value}. The supported values in this implementation are
      *
      * LATIN1
      * UTF16
      *
      * @implNote This field is trusted by the VM, and is a subject to
      * constant folding if String instance is constant. Overwriting this
      * field after construction will cause problems.
      */
     private final byte coder;
 
     /** Cache the hash code for the string */
     private int hash; // Default to 0
 
     /**
      * Cache if the hash has been calculated as actually being zero, enabling
      * us to avoid recalculating this.
      */
     private boolean hashIsZero; // Default to false;
 
     /** use serialVersionUID from JDK 1.0.2 for interoperability */
     @java.io.Serial
     private static final long serialVersionUID = -6849794470754667710L;
 
     /**
      * If String compaction is disabled, the bytes in {@code value} are
      * always encoded in UTF16.
      *
      * For methods with several possible implementation paths, when String
      * compaction is disabled, only one code path is taken.
      *
      * The instance field value is generally opaque to optimizing JIT
      * compilers. Therefore, in performance-sensitive place, an explicit
      * check of the static boolean {@code COMPACT_STRINGS} is done first
      * before checking the {@code coder} field since the static boolean
      * {@code COMPACT_STRINGS} would be constant folded away by an
      * optimizing JIT compiler. The idioms for these cases are as follows.
      *
      * For code such as:
      *
      *    if (coder == LATIN1) { ... }
      *
      * can be written more optimally as
      *
      *    if (coder() == LATIN1) { ... }
      *
      * or:
      *
      *    if (COMPACT_STRINGS && coder == LATIN1) { ... }
      *
      * An optimizing JIT compiler can fold the above conditional as:
      *
      *    COMPACT_STRINGS == true  => if (coder == LATIN1) { ... }
      *    COMPACT_STRINGS == false => if (false)           { ... }
      *
      * @implNote
      * The actual value for this field is injected by JVM. The static
      * initialization block is used to set the value here to communicate
      * that this static final field is not statically foldable, and to
      * avoid any possible circular dependency during vm initialization.
      */
     static final boolean COMPACT_STRINGS;
 
     static {
         COMPACT_STRINGS = true;
     }
 
     /**
      * Class String is special cased within the Serialization Stream Protocol.
      *
      * A String instance is written into an ObjectOutputStream according to
      * <a href="{@docRoot}/../specs/serialization/protocol.html#stream-elements">
      * Object Serialization Specification, Section 6.2, "Stream Elements"</a>
      */
     @java.io.Serial
     private static final ObjectStreamField[] serialPersistentFields =
         new ObjectStreamField[0];
 
     /**
      * Initializes a newly created {@code String} object so that it represents
      * an empty character sequence.  Note that use of this constructor is
      * unnecessary since Strings are immutable.
      */
     public String() {
         this.value = "".value;
         this.coder = "".coder;
     }
 
     /**
      * Initializes a newly created {@code String} object so that it represents
      * the same sequence of characters as the argument; in other words, the
      * newly created string is a copy of the argument string. Unless an
      * explicit copy of {@code original} is needed, use of this constructor is
      * unnecessary since Strings are immutable.
      *
      * @param  original
      *         A {@code String}
      */
     @IntrinsicCandidate
     public String(String original) {
         this.value = original.value;
         this.coder = original.coder;
         this.hash = original.hash;
+        this.hashIsZero = original.hashIsZero;
     }
 
     /**
      * Allocates a new {@code String} so that it represents the sequence of
      * characters currently contained in the character array argument. The
      * contents of the character array are copied; subsequent modification of
      * the character array does not affect the newly created string.
      *
      * @param  value
      *         The initial value of the string
      */
-    public String(char value[]) {
+    public String(char[] value) {
         this(value, 0, value.length, null);
     }
 
     /**
      * Allocates a new {@code String} that contains characters from a subarray
      * of the character array argument. The {@code offset} argument is the
      * index of the first character of the subarray and the {@code count}
      * argument specifies the length of the subarray. The contents of the
      * subarray are copied; subsequent modification of the character array does
      * not affect the newly created string.
      *
      * @param  value
      *         Array that is the source of characters
      *
      * @param  offset
      *         The initial offset
      *
      * @param  count
      *         The length
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code count} is negative, or
      *          {@code offset} is greater than {@code value.length - count}
      */
-    public String(char value[], int offset, int count) {
+    public String(char[] value, int offset, int count) {
         this(value, offset, count, rangeCheck(value, offset, count));
     }
 
     private static Void rangeCheck(char[] value, int offset, int count) {
         checkBoundsOffCount(offset, count, value.length);
         return null;
     }
 
     /**
      * Allocates a new {@code String} that contains characters from a subarray
      * of the <a href="Character.html#unicode">Unicode code point</a> array
      * argument.  The {@code offset} argument is the index of the first code
      * point of the subarray and the {@code count} argument specifies the
      * length of the subarray.  The contents of the subarray are converted to
      * {@code char}s; subsequent modification of the {@code int} array does not
      * affect the newly created string.
      *
      * @param  codePoints
      *         Array that is the source of Unicode code points
      *
      * @param  offset
      *         The initial offset
      *
      * @param  count
      *         The length
      *
      * @throws  IllegalArgumentException
      *          If any invalid Unicode code point is found in {@code
      *          codePoints}
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code count} is negative, or
      *          {@code offset} is greater than {@code codePoints.length - count}
      *
      * @since  1.5
      */
     public String(int[] codePoints, int offset, int count) {
         checkBoundsOffCount(offset, count, codePoints.length);
         if (count == 0) {
             this.value = "".value;
             this.coder = "".coder;
             return;
         }
         if (COMPACT_STRINGS) {
             byte[] val = StringLatin1.toBytes(codePoints, offset, count);
             if (val != null) {
                 this.coder = LATIN1;
                 this.value = val;
                 return;
             }
         }
         this.coder = UTF16;
         this.value = StringUTF16.toBytes(codePoints, offset, count);
     }
 
     /**
      * Allocates a new {@code String} constructed from a subarray of an array
      * of 8-bit integer values.
      *
      * <p> The {@code offset} argument is the index of the first byte of the
      * subarray, and the {@code count} argument specifies the length of the
      * subarray.
      *
      * <p> Each {@code byte} in the subarray is converted to a {@code char} as
      * specified in the {@link #String(byte[],int) String(byte[],int)} constructor.
      *
      * @deprecated This method does not properly convert bytes into characters.
      * As of JDK&nbsp;1.1, the preferred way to do this is via the
-     * {@code String} constructors that take a {@link
-     * java.nio.charset.Charset}, charset name, or that use the platform's
-     * default charset.
+     * {@code String} constructors that take a {@link Charset}, charset name,
+     * or that use the {@link Charset#defaultCharset() default charset}.
      *
      * @param  ascii
      *         The bytes to be converted to characters
      *
      * @param  hibyte
      *         The top 8 bits of each 16-bit Unicode code unit
      *
      * @param  offset
      *         The initial offset
      * @param  count
      *         The length
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code count} is negative, or
      *          {@code offset} is greater than {@code ascii.length - count}
      *
      * @see  #String(byte[], int)
      * @see  #String(byte[], int, int, java.lang.String)
      * @see  #String(byte[], int, int, java.nio.charset.Charset)
      * @see  #String(byte[], int, int)
      * @see  #String(byte[], java.lang.String)
      * @see  #String(byte[], java.nio.charset.Charset)
      * @see  #String(byte[])
      */
     @Deprecated(since="1.1")
-    public String(byte ascii[], int hibyte, int offset, int count) {
+    public String(byte[] ascii, int hibyte, int offset, int count) {
         checkBoundsOffCount(offset, count, ascii.length);
         if (count == 0) {
             this.value = "".value;
             this.coder = "".coder;
             return;
         }
         if (COMPACT_STRINGS && (byte)hibyte == 0) {
             this.value = Arrays.copyOfRange(ascii, offset, offset + count);
             this.coder = LATIN1;
         } else {
             hibyte <<= 8;
             byte[] val = StringUTF16.newBytesFor(count);
             for (int i = 0; i < count; i++) {
                 StringUTF16.putChar(val, i, hibyte | (ascii[offset++] & 0xff));
             }
             this.value = val;
             this.coder = UTF16;
         }
     }
 
     /**
      * Allocates a new {@code String} containing characters constructed from
      * an array of 8-bit integer values. Each character <i>c</i> in the
      * resulting string is constructed from the corresponding component
      * <i>b</i> in the byte array such that:
      *
      * <blockquote><pre>
      *     <b><i>c</i></b> == (char)(((hibyte &amp; 0xff) &lt;&lt; 8)
      *                         | (<b><i>b</i></b> &amp; 0xff))
      * </pre></blockquote>
      *
      * @deprecated  This method does not properly convert bytes into
      * characters.  As of JDK&nbsp;1.1, the preferred way to do this is via the
-     * {@code String} constructors that take a {@link
-     * java.nio.charset.Charset}, charset name, or that use the platform's
-     * default charset.
+     * {@code String} constructors that take a {@link Charset}, charset name,
+     * or that use the {@link Charset#defaultCharset() default charset}.
      *
      * @param  ascii
      *         The bytes to be converted to characters
      *
      * @param  hibyte
      *         The top 8 bits of each 16-bit Unicode code unit
      *
      * @see  #String(byte[], int, int, java.lang.String)
      * @see  #String(byte[], int, int, java.nio.charset.Charset)
      * @see  #String(byte[], int, int)
      * @see  #String(byte[], java.lang.String)
      * @see  #String(byte[], java.nio.charset.Charset)
      * @see  #String(byte[])
      */
     @Deprecated(since="1.1")
-    public String(byte ascii[], int hibyte) {
+    public String(byte[] ascii, int hibyte) {
         this(ascii, hibyte, 0, ascii.length);
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified subarray of
      * bytes using the specified charset.  The length of the new {@code String}
      * is a function of the charset, and hence may not be equal to the length
      * of the subarray.
      *
      * <p> The behavior of this constructor when the given bytes are not valid
      * in the given charset is unspecified.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @param  offset
      *         The index of the first byte to decode
      *
      * @param  length
      *         The number of bytes to decode
      *
      * @param  charsetName
      *         The name of a supported {@linkplain java.nio.charset.Charset
      *         charset}
      *
      * @throws  UnsupportedEncodingException
      *          If the named charset is not supported
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code length} is negative, or
      *          {@code offset} is greater than {@code bytes.length - length}
      *
      * @since  1.1
      */
     public String(byte[] bytes, int offset, int length, String charsetName)
             throws UnsupportedEncodingException {
         this(bytes, offset, length, lookupCharset(charsetName));
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified subarray of
      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
      * The length of the new {@code String} is a function of the charset, and
      * hence may not be equal to the length of the subarray.
      *
      * <p> This method always replaces malformed-input and unmappable-character
      * sequences with this charset's default replacement string.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @param  offset
      *         The index of the first byte to decode
      *
      * @param  length
      *         The number of bytes to decode
      *
      * @param  charset
      *         The {@linkplain java.nio.charset.Charset charset} to be used to
      *         decode the {@code bytes}
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code length} is negative, or
      *          {@code offset} is greater than {@code bytes.length - length}
      *
      * @since  1.6
      */
+    @SuppressWarnings("removal")
     public String(byte[] bytes, int offset, int length, Charset charset) {
         Objects.requireNonNull(charset);
         checkBoundsOffCount(offset, length, bytes.length);
         if (length == 0) {
             this.value = "".value;
             this.coder = "".coder;
         } else if (charset == UTF_8.INSTANCE) {
             if (COMPACT_STRINGS && !StringCoding.hasNegatives(bytes, offset, length)) {
                 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
                 this.coder = LATIN1;
             } else {
                 int sl = offset + length;
                 int dp = 0;
                 byte[] dst = null;
                 if (COMPACT_STRINGS) {
                     dst = new byte[length];
                     while (offset < sl) {
                         int b1 = bytes[offset];
                         if (b1 >= 0) {
                             dst[dp++] = (byte)b1;
                             offset++;
                             continue;
                         }
                         if ((b1 == (byte)0xc2 || b1 == (byte)0xc3) &&
                                 offset + 1 < sl) {
                             int b2 = bytes[offset + 1];
                             if (!isNotContinuation(b2)) {
                                 dst[dp++] = (byte)decode2(b1, b2);
                                 offset += 2;
                                 continue;
                             }
                         }
                         // anything not a latin1, including the repl
                         // we have to go with the utf16
                         break;
                     }
                     if (offset == sl) {
                         if (dp != dst.length) {
                             dst = Arrays.copyOf(dst, dp);
                         }
                         this.value = dst;
                         this.coder = LATIN1;
                         return;
                     }
                 }
                 if (dp == 0 || dst == null) {
                     dst = new byte[length << 1];
                 } else {
                     byte[] buf = new byte[length << 1];
                     StringLatin1.inflate(dst, 0, buf, 0, dp);
                     dst = buf;
                 }
                 dp = decodeUTF8_UTF16(bytes, offset, sl, dst, dp, true);
                 if (dp != length) {
                     dst = Arrays.copyOf(dst, dp << 1);
                 }
                 this.value = dst;
                 this.coder = UTF16;
             }
         } else if (charset == ISO_8859_1.INSTANCE) {
             if (COMPACT_STRINGS) {
                 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
                 this.coder = LATIN1;
             } else {
                 this.value = StringLatin1.inflate(bytes, offset, length);
                 this.coder = UTF16;
             }
         } else if (charset == US_ASCII.INSTANCE) {
             if (COMPACT_STRINGS && !StringCoding.hasNegatives(bytes, offset, length)) {
                 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
                 this.coder = LATIN1;
             } else {
                 byte[] dst = new byte[length << 1];
                 int dp = 0;
                 while (dp < length) {
                     int b = bytes[offset++];
                     StringUTF16.putChar(dst, dp++, (b >= 0) ? (char) b : REPL);
                 }
                 this.value = dst;
                 this.coder = UTF16;
             }
         } else {
             // (1)We never cache the "external" cs, the only benefit of creating
             // an additional StringDe/Encoder object to wrap it is to share the
             // de/encode() method. These SD/E objects are short-lived, the young-gen
             // gc should be able to take care of them well. But the best approach
             // is still not to generate them if not really necessary.
             // (2)The defensive copy of the input byte/char[] has a big performance
             // impact, as well as the outgoing result byte/char[]. Need to do the
             // optimization check of (sm==null && classLoader0==null) for both.
             CharsetDecoder cd = charset.newDecoder();
             // ArrayDecoder fastpaths
             if (cd instanceof ArrayDecoder ad) {
                 // ascii
                 if (ad.isASCIICompatible() && !StringCoding.hasNegatives(bytes, offset, length)) {
                     if (COMPACT_STRINGS) {
                         this.value = Arrays.copyOfRange(bytes, offset, offset + length);
                         this.coder = LATIN1;
                         return;
                     }
                     this.value = StringLatin1.inflate(bytes, offset, length);
                     this.coder = UTF16;
                     return;
                 }
 
                 // fastpath for always Latin1 decodable single byte
                 if (COMPACT_STRINGS && ad.isLatin1Decodable()) {
                     byte[] dst = new byte[length];
                     ad.decodeToLatin1(bytes, offset, length, dst);
                     this.value = dst;
                     this.coder = LATIN1;
                     return;
                 }
 
                 int en = scale(length, cd.maxCharsPerByte());
                 cd.onMalformedInput(CodingErrorAction.REPLACE)
                         .onUnmappableCharacter(CodingErrorAction.REPLACE);
                 char[] ca = new char[en];
                 int clen = ad.decode(bytes, offset, length, ca);
                 if (COMPACT_STRINGS) {
                     byte[] bs = StringUTF16.compress(ca, 0, clen);
                     if (bs != null) {
                         value = bs;
                         coder = LATIN1;
                         return;
                     }
                 }
                 coder = UTF16;
                 value = StringUTF16.toBytes(ca, 0, clen);
                 return;
             }
 
             // decode using CharsetDecoder
             int en = scale(length, cd.maxCharsPerByte());
             cd.onMalformedInput(CodingErrorAction.REPLACE)
                     .onUnmappableCharacter(CodingErrorAction.REPLACE);
             char[] ca = new char[en];
             if (charset.getClass().getClassLoader0() != null &&
                     System.getSecurityManager() != null) {
                 bytes = Arrays.copyOfRange(bytes, offset, offset + length);
                 offset = 0;
             }
 
             int caLen = decodeWithDecoder(cd, ca, bytes, offset, length);
             if (COMPACT_STRINGS) {
                 byte[] bs = StringUTF16.compress(ca, 0, caLen);
                 if (bs != null) {
                     value = bs;
                     coder = LATIN1;
                     return;
                 }
             }
             coder = UTF16;
             value = StringUTF16.toBytes(ca, 0, caLen);
         }
     }
 
     /*
      * Throws iae, instead of replacing, if malformed or unmappable.
      */
     static String newStringUTF8NoRepl(byte[] bytes, int offset, int length) {
         checkBoundsOffCount(offset, length, bytes.length);
         if (length == 0) {
             return "";
         }
         if (COMPACT_STRINGS && !StringCoding.hasNegatives(bytes, offset, length)) {
             return new String(Arrays.copyOfRange(bytes, offset, offset + length), LATIN1);
         } else {
             int sl = offset + length;
             int dp = 0;
             byte[] dst = null;
             if (COMPACT_STRINGS) {
                 dst = new byte[length];
                 while (offset < sl) {
                     int b1 = bytes[offset];
                     if (b1 >= 0) {
                         dst[dp++] = (byte) b1;
                         offset++;
                         continue;
                     }
                     if ((b1 == (byte) 0xc2 || b1 == (byte) 0xc3) &&
                             offset + 1 < sl) {
                         int b2 = bytes[offset + 1];
                         if (!isNotContinuation(b2)) {
                             dst[dp++] = (byte) decode2(b1, b2);
                             offset += 2;
                             continue;
                         }
                     }
                     // anything not a latin1, including the REPL
                     // we have to go with the utf16
                     break;
                 }
                 if (offset == sl) {
                     if (dp != dst.length) {
                         dst = Arrays.copyOf(dst, dp);
                     }
                     return new String(dst, LATIN1);
                 }
             }
             if (dp == 0 || dst == null) {
                 dst = new byte[length << 1];
             } else {
                 byte[] buf = new byte[length << 1];
                 StringLatin1.inflate(dst, 0, buf, 0, dp);
                 dst = buf;
             }
             dp = decodeUTF8_UTF16(bytes, offset, sl, dst, dp, false);
             if (dp != length) {
                 dst = Arrays.copyOf(dst, dp << 1);
             }
             return new String(dst, UTF16);
         }
     }
 
     static String newStringNoRepl(byte[] src, Charset cs) throws CharacterCodingException {
         try {
             return newStringNoRepl1(src, cs);
         } catch (IllegalArgumentException e) {
             //newStringNoRepl1 throws IAE with MalformedInputException or CCE as the cause
             Throwable cause = e.getCause();
             if (cause instanceof MalformedInputException mie) {
                 throw mie;
             }
             throw (CharacterCodingException)cause;
         }
     }
 
+    @SuppressWarnings("removal")
     private static String newStringNoRepl1(byte[] src, Charset cs) {
         int len = src.length;
         if (len == 0) {
             return "";
         }
         if (cs == UTF_8.INSTANCE) {
             return newStringUTF8NoRepl(src, 0, src.length);
         }
         if (cs == ISO_8859_1.INSTANCE) {
             if (COMPACT_STRINGS)
                 return new String(src, LATIN1);
             return new String(StringLatin1.inflate(src, 0, src.length), UTF16);
         }
         if (cs == US_ASCII.INSTANCE) {
             if (!StringCoding.hasNegatives(src, 0, src.length)) {
                 if (COMPACT_STRINGS)
                     return new String(src, LATIN1);
                 return new String(StringLatin1.inflate(src, 0, src.length), UTF16);
             } else {
                 throwMalformed(src);
             }
         }
 
         CharsetDecoder cd = cs.newDecoder();
         // ascii fastpath
         if (cd instanceof ArrayDecoder ad &&
                 ad.isASCIICompatible() &&
                 !StringCoding.hasNegatives(src, 0, src.length)) {
             return new String(src, 0, src.length, ISO_8859_1.INSTANCE);
         }
         int en = scale(len, cd.maxCharsPerByte());
         char[] ca = new char[en];
         if (cs.getClass().getClassLoader0() != null &&
                 System.getSecurityManager() != null) {
             src = Arrays.copyOf(src, len);
         }
         int caLen = decodeWithDecoder(cd, ca, src, 0, src.length);
         if (COMPACT_STRINGS) {
             byte[] bs = StringUTF16.compress(ca, 0, caLen);
             if (bs != null) {
                 return new String(bs, LATIN1);
             }
         }
         return new String(StringUTF16.toBytes(ca, 0, caLen), UTF16);
     }
 
     private static final char REPL = '\ufffd';
 
     // Trim the given byte array to the given length
+    @SuppressWarnings("removal")
     private static byte[] safeTrim(byte[] ba, int len, boolean isTrusted) {
         if (len == ba.length && (isTrusted || System.getSecurityManager() == null)) {
             return ba;
         } else {
             return Arrays.copyOf(ba, len);
         }
     }
 
     private static int scale(int len, float expansionFactor) {
         // We need to perform double, not float, arithmetic; otherwise
         // we lose low order bits when len is larger than 2**24.
         return (int)(len * (double)expansionFactor);
     }
 
     private static Charset lookupCharset(String csn) throws UnsupportedEncodingException {
         Objects.requireNonNull(csn);
         try {
             return Charset.forName(csn);
         } catch (UnsupportedCharsetException | IllegalCharsetNameException x) {
             throw new UnsupportedEncodingException(csn);
         }
     }
 
     private static byte[] encode(Charset cs, byte coder, byte[] val) {
         if (cs == UTF_8.INSTANCE) {
             return encodeUTF8(coder, val, true);
         }
         if (cs == ISO_8859_1.INSTANCE) {
             return encode8859_1(coder, val);
         }
         if (cs == US_ASCII.INSTANCE) {
             return encodeASCII(coder, val);
         }
         return encodeWithEncoder(cs, coder, val, true);
     }
 
     private static byte[] encodeWithEncoder(Charset cs, byte coder, byte[] val, boolean doReplace) {
         CharsetEncoder ce = cs.newEncoder();
         int len = val.length >> coder;  // assume LATIN1=0/UTF16=1;
         int en = scale(len, ce.maxBytesPerChar());
         if (ce instanceof ArrayEncoder ae) {
             // fastpath for ascii compatible
             if (coder == LATIN1 &&
                     ae.isASCIICompatible() &&
                     !StringCoding.hasNegatives(val, 0, val.length)) {
                 return Arrays.copyOf(val, val.length);
             }
             byte[] ba = new byte[en];
             if (len == 0) {
                 return ba;
             }
             if (doReplace) {
                 ce.onMalformedInput(CodingErrorAction.REPLACE)
                         .onUnmappableCharacter(CodingErrorAction.REPLACE);
             }
 
             int blen = (coder == LATIN1) ? ae.encodeFromLatin1(val, 0, len, ba)
                     : ae.encodeFromUTF16(val, 0, len, ba);
             if (blen != -1) {
                 return safeTrim(ba, blen, true);
             }
         }
 
         byte[] ba = new byte[en];
         if (len == 0) {
             return ba;
         }
         if (doReplace) {
             ce.onMalformedInput(CodingErrorAction.REPLACE)
                     .onUnmappableCharacter(CodingErrorAction.REPLACE);
         }
         char[] ca = (coder == LATIN1 ) ? StringLatin1.toChars(val)
                 : StringUTF16.toChars(val);
         ByteBuffer bb = ByteBuffer.wrap(ba);
         CharBuffer cb = CharBuffer.wrap(ca, 0, len);
         try {
             CoderResult cr = ce.encode(cb, bb, true);
             if (!cr.isUnderflow())
                 cr.throwException();
             cr = ce.flush(bb);
             if (!cr.isUnderflow())
                 cr.throwException();
         } catch (CharacterCodingException x) {
             if (!doReplace) {
                 throw new IllegalArgumentException(x);
             } else {
                 throw new Error(x);
             }
         }
         return safeTrim(ba, bb.position(), cs.getClass().getClassLoader0() == null);
     }
 
     /*
      * Throws iae, instead of replacing, if unmappable.
      */
     static byte[] getBytesUTF8NoRepl(String s) {
         return encodeUTF8(s.coder(), s.value(), false);
     }
 
     private static boolean isASCII(byte[] src) {
         return !StringCoding.hasNegatives(src, 0, src.length);
     }
 
     /*
      * Throws CCE, instead of replacing, if unmappable.
      */
     static byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException {
         try {
             return getBytesNoRepl1(s, cs);
         } catch (IllegalArgumentException e) {
             //getBytesNoRepl1 throws IAE with UnmappableCharacterException or CCE as the cause
             Throwable cause = e.getCause();
             if (cause instanceof UnmappableCharacterException) {
                 throw (UnmappableCharacterException)cause;
             }
             throw (CharacterCodingException)cause;
         }
     }
 
     private static byte[] getBytesNoRepl1(String s, Charset cs) {
         byte[] val = s.value();
         byte coder = s.coder();
         if (cs == UTF_8.INSTANCE) {
             if (coder == LATIN1 && isASCII(val)) {
                 return val;
             }
             return encodeUTF8(coder, val, false);
         }
         if (cs == ISO_8859_1.INSTANCE) {
             if (coder == LATIN1) {
                 return val;
             }
             return encode8859_1(coder, val, false);
         }
         if (cs == US_ASCII.INSTANCE) {
             if (coder == LATIN1) {
                 if (isASCII(val)) {
                     return val;
                 } else {
                     throwUnmappable(val);
                 }
             }
         }
         return encodeWithEncoder(cs, coder, val, false);
     }
 
     private static byte[] encodeASCII(byte coder, byte[] val) {
         if (coder == LATIN1) {
             byte[] dst = Arrays.copyOf(val, val.length);
             for (int i = 0; i < dst.length; i++) {
                 if (dst[i] < 0) {
                     dst[i] = '?';
                 }
             }
             return dst;
         }
         int len = val.length >> 1;
         byte[] dst = new byte[len];
         int dp = 0;
         for (int i = 0; i < len; i++) {
             char c = StringUTF16.getChar(val, i);
             if (c < 0x80) {
                 dst[dp++] = (byte)c;
                 continue;
             }
             if (Character.isHighSurrogate(c) && i + 1 < len &&
                     Character.isLowSurrogate(StringUTF16.getChar(val, i + 1))) {
                 i++;
             }
             dst[dp++] = '?';
         }
         if (len == dp) {
             return dst;
         }
         return Arrays.copyOf(dst, dp);
     }
 
     private static byte[] encode8859_1(byte coder, byte[] val) {
         return encode8859_1(coder, val, true);
     }
 
     private static byte[] encode8859_1(byte coder, byte[] val, boolean doReplace) {
         if (coder == LATIN1) {
             return Arrays.copyOf(val, val.length);
         }
         int len = val.length >> 1;
         byte[] dst = new byte[len];
         int dp = 0;
         int sp = 0;
         int sl = len;
         while (sp < sl) {
             int ret = StringCoding.implEncodeISOArray(val, sp, dst, dp, len);
             sp = sp + ret;
             dp = dp + ret;
             if (ret != len) {
                 if (!doReplace) {
                     throwUnmappable(sp);
                 }
                 char c = StringUTF16.getChar(val, sp++);
                 if (Character.isHighSurrogate(c) && sp < sl &&
                         Character.isLowSurrogate(StringUTF16.getChar(val, sp))) {
                     sp++;
                 }
                 dst[dp++] = '?';
                 len = sl - sp;
             }
         }
         if (dp == dst.length) {
             return dst;
         }
         return Arrays.copyOf(dst, dp);
     }
 
     //////////////////////////////// utf8 ////////////////////////////////////
 
     /**
      * Decodes ASCII from the source byte array into the destination
      * char array. Used via JavaLangAccess from UTF_8 and other charset
      * decoders.
      *
      * @return the number of bytes successfully decoded, at most len
      */
     /* package-private */
     static int decodeASCII(byte[] sa, int sp, char[] da, int dp, int len) {
         if (!StringCoding.hasNegatives(sa, sp, len)) {
             StringLatin1.inflate(sa, sp, da, dp, len);
             return len;
         } else {
             int start = sp;
             int end = sp + len;
             while (sp < end && sa[sp] >= 0) {
                 da[dp++] = (char) sa[sp++];
             }
             return sp - start;
         }
     }
 
     private static boolean isNotContinuation(int b) {
         return (b & 0xc0) != 0x80;
     }
 
     private static boolean isMalformed3(int b1, int b2, int b3) {
         return (b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
                 (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80;
     }
 
     private static boolean isMalformed3_2(int b1, int b2) {
         return (b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
                 (b2 & 0xc0) != 0x80;
     }
 
     private static boolean isMalformed4(int b2, int b3, int b4) {
         return (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80 ||
                 (b4 & 0xc0) != 0x80;
     }
 
     private static boolean isMalformed4_2(int b1, int b2) {
         return (b1 == 0xf0 && (b2 < 0x90 || b2 > 0xbf)) ||
                 (b1 == 0xf4 && (b2 & 0xf0) != 0x80) ||
                 (b2 & 0xc0) != 0x80;
     }
 
     private static boolean isMalformed4_3(int b3) {
         return (b3 & 0xc0) != 0x80;
     }
 
     private static char decode2(int b1, int b2) {
         return (char)(((b1 << 6) ^ b2) ^
                 (((byte) 0xC0 << 6) ^
                         ((byte) 0x80 << 0)));
     }
 
     private static char decode3(int b1, int b2, int b3) {
         return (char)((b1 << 12) ^
                 (b2 <<  6) ^
                 (b3 ^
                         (((byte) 0xE0 << 12) ^
                                 ((byte) 0x80 <<  6) ^
                                 ((byte) 0x80 <<  0))));
     }
 
     private static int decode4(int b1, int b2, int b3, int b4) {
         return ((b1 << 18) ^
                 (b2 << 12) ^
                 (b3 <<  6) ^
                 (b4 ^
                         (((byte) 0xF0 << 18) ^
                                 ((byte) 0x80 << 12) ^
                                 ((byte) 0x80 <<  6) ^
                                 ((byte) 0x80 <<  0))));
     }
 
     private static int decodeUTF8_UTF16(byte[] src, int sp, int sl, byte[] dst, int dp, boolean doReplace) {
         while (sp < sl) {
             int b1 = src[sp++];
             if (b1 >= 0) {
                 StringUTF16.putChar(dst, dp++, (char) b1);
             } else if ((b1 >> 5) == -2 && (b1 & 0x1e) != 0) {
                 if (sp < sl) {
                     int b2 = src[sp++];
                     if (isNotContinuation(b2)) {
                         if (!doReplace) {
                             throwMalformed(sp - 1, 1);
                         }
                         StringUTF16.putChar(dst, dp++, REPL);
                         sp--;
                     } else {
                         StringUTF16.putChar(dst, dp++, decode2(b1, b2));
                     }
                     continue;
                 }
                 if (!doReplace) {
                     throwMalformed(sp, 1);  // underflow()
                 }
                 StringUTF16.putChar(dst, dp++, REPL);
                 break;
             } else if ((b1 >> 4) == -2) {
                 if (sp + 1 < sl) {
                     int b2 = src[sp++];
                     int b3 = src[sp++];
                     if (isMalformed3(b1, b2, b3)) {
                         if (!doReplace) {
                             throwMalformed(sp - 3, 3);
                         }
                         StringUTF16.putChar(dst, dp++, REPL);
                         sp -= 3;
                         sp += malformed3(src, sp);
                     } else {
                         char c = decode3(b1, b2, b3);
                         if (Character.isSurrogate(c)) {
                             if (!doReplace) {
                                 throwMalformed(sp - 3, 3);
                             }
                             StringUTF16.putChar(dst, dp++, REPL);
                         } else {
                             StringUTF16.putChar(dst, dp++, c);
                         }
                     }
                     continue;
                 }
                 if (sp < sl && isMalformed3_2(b1, src[sp])) {
                     if (!doReplace) {
                         throwMalformed(sp - 1, 2);
                     }
                     StringUTF16.putChar(dst, dp++, REPL);
                     continue;
                 }
                 if (!doReplace) {
                     throwMalformed(sp, 1);
                 }
                 StringUTF16.putChar(dst, dp++, REPL);
                 break;
             } else if ((b1 >> 3) == -2) {
                 if (sp + 2 < sl) {
                     int b2 = src[sp++];
                     int b3 = src[sp++];
                     int b4 = src[sp++];
                     int uc = decode4(b1, b2, b3, b4);
                     if (isMalformed4(b2, b3, b4) ||
                             !Character.isSupplementaryCodePoint(uc)) { // shortest form check
                         if (!doReplace) {
                             throwMalformed(sp - 4, 4);
                         }
                         StringUTF16.putChar(dst, dp++, REPL);
                         sp -= 4;
                         sp += malformed4(src, sp);
                     } else {
                         StringUTF16.putChar(dst, dp++, Character.highSurrogate(uc));
                         StringUTF16.putChar(dst, dp++, Character.lowSurrogate(uc));
                     }
                     continue;
                 }
                 b1 &= 0xff;
                 if (b1 > 0xf4 || sp < sl && isMalformed4_2(b1, src[sp] & 0xff)) {
                     if (!doReplace) {
                         throwMalformed(sp - 1, 1);  // or 2
                     }
                     StringUTF16.putChar(dst, dp++, REPL);
                     continue;
                 }
                 if (!doReplace) {
                     throwMalformed(sp - 1, 1);
                 }
                 sp++;
                 StringUTF16.putChar(dst, dp++, REPL);
                 if (sp < sl && isMalformed4_3(src[sp])) {
                     continue;
                 }
                 break;
             } else {
                 if (!doReplace) {
                     throwMalformed(sp - 1, 1);
                 }
                 StringUTF16.putChar(dst, dp++, REPL);
             }
         }
         return dp;
     }
 
     private static int decodeWithDecoder(CharsetDecoder cd, char[] dst, byte[] src, int offset, int length) {
         ByteBuffer bb = ByteBuffer.wrap(src, offset, length);
         CharBuffer cb = CharBuffer.wrap(dst, 0, dst.length);
         try {
             CoderResult cr = cd.decode(bb, cb, true);
             if (!cr.isUnderflow())
                 cr.throwException();
             cr = cd.flush(cb);
             if (!cr.isUnderflow())
                 cr.throwException();
         } catch (CharacterCodingException x) {
             // Substitution is always enabled,
             // so this shouldn't happen
             throw new Error(x);
         }
         return cb.position();
     }
 
     private static int malformed3(byte[] src, int sp) {
         int b1 = src[sp++];
         int b2 = src[sp];    // no need to lookup b3
         return ((b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
                 isNotContinuation(b2)) ? 1 : 2;
     }
 
     private static int malformed4(byte[] src, int sp) {
         // we don't care the speed here
         int b1 = src[sp++] & 0xff;
         int b2 = src[sp++] & 0xff;
         if (b1 > 0xf4 ||
                 (b1 == 0xf0 && (b2 < 0x90 || b2 > 0xbf)) ||
                 (b1 == 0xf4 && (b2 & 0xf0) != 0x80) ||
                 isNotContinuation(b2))
             return 1;
         if (isNotContinuation(src[sp]))
             return 2;
         return 3;
     }
 
     private static void throwMalformed(int off, int nb) {
         String msg = "malformed input off : " + off + ", length : " + nb;
         throw new IllegalArgumentException(msg, new MalformedInputException(nb));
     }
 
     private static void throwMalformed(byte[] val) {
         int dp = 0;
         while (dp < val.length && val[dp] >=0) { dp++; }
         throwMalformed(dp, 1);
     }
 
     private static void throwUnmappable(int off) {
         String msg = "malformed input off : " + off + ", length : 1";
         throw new IllegalArgumentException(msg, new UnmappableCharacterException(1));
     }
 
     private static void throwUnmappable(byte[] val) {
         int dp = 0;
         while (dp < val.length && val[dp] >=0) { dp++; }
         throwUnmappable(dp);
     }
 
     private static byte[] encodeUTF8(byte coder, byte[] val, boolean doReplace) {
         if (coder == UTF16)
             return encodeUTF8_UTF16(val, doReplace);
 
         if (!StringCoding.hasNegatives(val, 0, val.length))
             return Arrays.copyOf(val, val.length);
 
         int dp = 0;
         byte[] dst = new byte[val.length << 1];
         for (byte c : val) {
             if (c < 0) {
                 dst[dp++] = (byte) (0xc0 | ((c & 0xff) >> 6));
                 dst[dp++] = (byte) (0x80 | (c & 0x3f));
             } else {
                 dst[dp++] = c;
             }
         }
         if (dp == dst.length)
             return dst;
         return Arrays.copyOf(dst, dp);
     }
 
     private static byte[] encodeUTF8_UTF16(byte[] val, boolean doReplace) {
         int dp = 0;
         int sp = 0;
         int sl = val.length >> 1;
         byte[] dst = new byte[sl * 3];
-        char c;
-        while (sp < sl && (c = StringUTF16.getChar(val, sp)) < '\u0080') {
+        while (sp < sl) {
             // ascii fast loop;
+            char c = StringUTF16.getChar(val, sp);
+            if (c >= '\u0080') {
+                break;
+            }
             dst[dp++] = (byte)c;
             sp++;
         }
         while (sp < sl) {
-            c = StringUTF16.getChar(val, sp++);
+            char c = StringUTF16.getChar(val, sp++);
             if (c < 0x80) {
                 dst[dp++] = (byte)c;
             } else if (c < 0x800) {
                 dst[dp++] = (byte)(0xc0 | (c >> 6));
                 dst[dp++] = (byte)(0x80 | (c & 0x3f));
             } else if (Character.isSurrogate(c)) {
                 int uc = -1;
                 char c2;
                 if (Character.isHighSurrogate(c) && sp < sl &&
                         Character.isLowSurrogate(c2 = StringUTF16.getChar(val, sp))) {
                     uc = Character.toCodePoint(c, c2);
                 }
                 if (uc < 0) {
                     if (doReplace) {
                         dst[dp++] = '?';
                     } else {
                         throwUnmappable(sp - 1);
                     }
                 } else {
                     dst[dp++] = (byte)(0xf0 | ((uc >> 18)));
                     dst[dp++] = (byte)(0x80 | ((uc >> 12) & 0x3f));
                     dst[dp++] = (byte)(0x80 | ((uc >>  6) & 0x3f));
                     dst[dp++] = (byte)(0x80 | (uc & 0x3f));
                     sp++;  // 2 chars
                 }
             } else {
                 // 3 bytes, 16 bits
                 dst[dp++] = (byte)(0xe0 | ((c >> 12)));
                 dst[dp++] = (byte)(0x80 | ((c >>  6) & 0x3f));
                 dst[dp++] = (byte)(0x80 | (c & 0x3f));
             }
         }
         if (dp == dst.length) {
             return dst;
         }
         return Arrays.copyOf(dst, dp);
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified array of bytes
      * using the specified {@linkplain java.nio.charset.Charset charset}.  The
      * length of the new {@code String} is a function of the charset, and hence
      * may not be equal to the length of the byte array.
      *
      * <p> The behavior of this constructor when the given bytes are not valid
      * in the given charset is unspecified.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @param  charsetName
      *         The name of a supported {@linkplain java.nio.charset.Charset
      *         charset}
      *
      * @throws  UnsupportedEncodingException
      *          If the named charset is not supported
      *
      * @since  1.1
      */
-    public String(byte bytes[], String charsetName)
+    public String(byte[] bytes, String charsetName)
             throws UnsupportedEncodingException {
         this(bytes, 0, bytes.length, charsetName);
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified array of
      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
      * The length of the new {@code String} is a function of the charset, and
      * hence may not be equal to the length of the byte array.
      *
      * <p> This method always replaces malformed-input and unmappable-character
      * sequences with this charset's default replacement string.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @param  charset
      *         The {@linkplain java.nio.charset.Charset charset} to be used to
      *         decode the {@code bytes}
      *
      * @since  1.6
      */
-    public String(byte bytes[], Charset charset) {
+    public String(byte[] bytes, Charset charset) {
         this(bytes, 0, bytes.length, charset);
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified subarray of
-     * bytes using the platform's default charset.  The length of the new
-     * {@code String} is a function of the charset, and hence may not be equal
-     * to the length of the subarray.
+     * bytes using the {@link Charset#defaultCharset() default charset}.
+     * The length of the new {@code String} is a function of the charset,
+     * and hence may not be equal to the length of the subarray.
      *
      * <p> The behavior of this constructor when the given bytes are not valid
      * in the default charset is unspecified.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @param  offset
      *         The index of the first byte to decode
      *
      * @param  length
      *         The number of bytes to decode
      *
      * @throws  IndexOutOfBoundsException
      *          If {@code offset} is negative, {@code length} is negative, or
      *          {@code offset} is greater than {@code bytes.length - length}
      *
      * @since  1.1
      */
     public String(byte[] bytes, int offset, int length) {
         this(bytes, offset, length, Charset.defaultCharset());
     }
 
     /**
      * Constructs a new {@code String} by decoding the specified array of bytes
-     * using the platform's default charset.  The length of the new {@code
-     * String} is a function of the charset, and hence may not be equal to the
-     * length of the byte array.
+     * using the {@link Charset#defaultCharset() default charset}. The length
+     * of the new {@code String} is a function of the charset, and hence may not
+     * be equal to the length of the byte array.
      *
      * <p> The behavior of this constructor when the given bytes are not valid
      * in the default charset is unspecified.  The {@link
      * java.nio.charset.CharsetDecoder} class should be used when more control
      * over the decoding process is required.
      *
      * @param  bytes
      *         The bytes to be decoded into characters
      *
      * @since  1.1
      */
     public String(byte[] bytes) {
         this(bytes, 0, bytes.length);
     }
 
     /**
      * Allocates a new string that contains the sequence of characters
      * currently contained in the string buffer argument. The contents of the
      * string buffer are copied; subsequent modification of the string buffer
      * does not affect the newly created string.
      *
      * @param  buffer
      *         A {@code StringBuffer}
      */
     public String(StringBuffer buffer) {
         this(buffer.toString());
     }
 
     /**
      * Allocates a new string that contains the sequence of characters
      * currently contained in the string builder argument. The contents of the
      * string builder are copied; subsequent modification of the string builder
      * does not affect the newly created string.
      *
      * <p> This constructor is provided to ease migration to {@code
      * StringBuilder}. Obtaining a string from a string builder via the {@code
      * toString} method is likely to run faster and is generally preferred.
      *
      * @param   builder
      *          A {@code StringBuilder}
      *
      * @since  1.5
      */
     public String(StringBuilder builder) {
         this(builder, null);
     }
 
     /**
      * Returns the length of this string.
      * The length is equal to the number of <a href="Character.html#unicode">Unicode
      * code units</a> in the string.
      *
      * @return  the length of the sequence of characters represented by this
      *          object.
      */
     public int length() {
         return value.length >> coder();
     }
 
     /**
      * Returns {@code true} if, and only if, {@link #length()} is {@code 0}.
      *
      * @return {@code true} if {@link #length()} is {@code 0}, otherwise
      * {@code false}
      *
      * @since 1.6
      */
     @Override
     public boolean isEmpty() {
         return value.length == 0;
     }
 
     /**
      * Returns the {@code char} value at the
      * specified index. An index ranges from {@code 0} to
      * {@code length() - 1}. The first {@code char} value of the sequence
      * is at index {@code 0}, the next at index {@code 1},
      * and so on, as for array indexing.
      *
      * <p>If the {@code char} value specified by the index is a
      * <a href="Character.html#unicode">surrogate</a>, the surrogate
      * value is returned.
      *
      * @param      index   the index of the {@code char} value.
      * @return     the {@code char} value at the specified index of this string.
      *             The first {@code char} value is at index {@code 0}.
      * @throws     IndexOutOfBoundsException  if the {@code index}
      *             argument is negative or not less than the length of this
      *             string.
      */
     public char charAt(int index) {
         if (isLatin1()) {
             return StringLatin1.charAt(value, index);
         } else {
             return StringUTF16.charAt(value, index);
         }
     }
 
     /**
      * Returns the character (Unicode code point) at the specified
      * index. The index refers to {@code char} values
      * (Unicode code units) and ranges from {@code 0} to
      * {@link #length()}{@code  - 1}.
      *
      * <p> If the {@code char} value specified at the given index
      * is in the high-surrogate range, the following index is less
      * than the length of this {@code String}, and the
      * {@code char} value at the following index is in the
      * low-surrogate range, then the supplementary code point
      * corresponding to this surrogate pair is returned. Otherwise,
      * the {@code char} value at the given index is returned.
      *
      * @param      index the index to the {@code char} values
      * @return     the code point value of the character at the
      *             {@code index}
      * @throws     IndexOutOfBoundsException  if the {@code index}
      *             argument is negative or not less than the length of this
      *             string.
      * @since      1.5
      */
     public int codePointAt(int index) {
         if (isLatin1()) {
             checkIndex(index, value.length);
             return value[index] & 0xff;
         }
         int length = value.length >> 1;
         checkIndex(index, length);
         return StringUTF16.codePointAt(value, index, length);
     }
 
     /**
      * Returns the character (Unicode code point) before the specified
      * index. The index refers to {@code char} values
      * (Unicode code units) and ranges from {@code 1} to {@link
      * CharSequence#length() length}.
      *
      * <p> If the {@code char} value at {@code (index - 1)}
      * is in the low-surrogate range, {@code (index - 2)} is not
      * negative, and the {@code char} value at {@code (index -
      * 2)} is in the high-surrogate range, then the
      * supplementary code point value of the surrogate pair is
      * returned. If the {@code char} value at {@code index -
      * 1} is an unpaired low-surrogate or a high-surrogate, the
      * surrogate value is returned.
      *
      * @param     index the index following the code point that should be returned
      * @return    the Unicode code point value before the given index.
      * @throws    IndexOutOfBoundsException if the {@code index}
      *            argument is less than 1 or greater than the length
      *            of this string.
      * @since     1.5
      */
     public int codePointBefore(int index) {
         int i = index - 1;
-        if (i < 0 || i >= length()) {
-            throw new StringIndexOutOfBoundsException(index);
-        }
+        checkIndex(i, length());
         if (isLatin1()) {
             return (value[i] & 0xff);
         }
         return StringUTF16.codePointBefore(value, index);
     }
 
     /**
      * Returns the number of Unicode code points in the specified text
      * range of this {@code String}. The text range begins at the
      * specified {@code beginIndex} and extends to the
      * {@code char} at index {@code endIndex - 1}. Thus the
      * length (in {@code char}s) of the text range is
      * {@code endIndex-beginIndex}. Unpaired surrogates within
      * the text range count as one code point each.
      *
      * @param beginIndex the index to the first {@code char} of
      * the text range.
      * @param endIndex the index after the last {@code char} of
      * the text range.
      * @return the number of Unicode code points in the specified text
      * range
      * @throws    IndexOutOfBoundsException if the
      * {@code beginIndex} is negative, or {@code endIndex}
      * is larger than the length of this {@code String}, or
      * {@code beginIndex} is larger than {@code endIndex}.
      * @since  1.5
      */
     public int codePointCount(int beginIndex, int endIndex) {
-        if (beginIndex < 0 || beginIndex > endIndex ||
-            endIndex > length()) {
-            throw new IndexOutOfBoundsException();
-        }
+        Objects.checkFromToIndex(beginIndex, endIndex, length());
         if (isLatin1()) {
             return endIndex - beginIndex;
         }
         return StringUTF16.codePointCount(value, beginIndex, endIndex);
     }
 
     /**
      * Returns the index within this {@code String} that is
      * offset from the given {@code index} by
      * {@code codePointOffset} code points. Unpaired surrogates
      * within the text range given by {@code index} and
      * {@code codePointOffset} count as one code point each.
      *
      * @param index the index to be offset
      * @param codePointOffset the offset in code points
      * @return the index within this {@code String}
      * @throws    IndexOutOfBoundsException if {@code index}
      *   is negative or larger then the length of this
      *   {@code String}, or if {@code codePointOffset} is positive
      *   and the substring starting with {@code index} has fewer
      *   than {@code codePointOffset} code points,
      *   or if {@code codePointOffset} is negative and the substring
      *   before {@code index} has fewer than the absolute value
      *   of {@code codePointOffset} code points.
      * @since 1.5
      */
     public int offsetByCodePoints(int index, int codePointOffset) {
         if (index < 0 || index > length()) {
             throw new IndexOutOfBoundsException();
         }
         return Character.offsetByCodePoints(this, index, codePointOffset);
     }
 
     /**
      * Copies characters from this string into the destination character
      * array.
      * <p>
      * The first character to be copied is at index {@code srcBegin};
      * the last character to be copied is at index {@code srcEnd-1}
      * (thus the total number of characters to be copied is
      * {@code srcEnd-srcBegin}). The characters are copied into the
      * subarray of {@code dst} starting at index {@code dstBegin}
      * and ending at index:
      * <blockquote><pre>
      *     dstBegin + (srcEnd-srcBegin) - 1
      * </pre></blockquote>
      *
      * @param      srcBegin   index of the first character in the string
      *                        to copy.
      * @param      srcEnd     index after the last character in the string
      *                        to copy.
      * @param      dst        the destination array.
      * @param      dstBegin   the start offset in the destination array.
      * @throws    IndexOutOfBoundsException If any of the following
      *            is true:
      *            <ul><li>{@code srcBegin} is negative.
      *            <li>{@code srcBegin} is greater than {@code srcEnd}
      *            <li>{@code srcEnd} is greater than the length of this
      *                string
      *            <li>{@code dstBegin} is negative
      *            <li>{@code dstBegin+(srcEnd-srcBegin)} is larger than
      *                {@code dst.length}</ul>
      */
-    public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
+    public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) {
         checkBoundsBeginEnd(srcBegin, srcEnd, length());
         checkBoundsOffCount(dstBegin, srcEnd - srcBegin, dst.length);
         if (isLatin1()) {
             StringLatin1.getChars(value, srcBegin, srcEnd, dst, dstBegin);
         } else {
             StringUTF16.getChars(value, srcBegin, srcEnd, dst, dstBegin);
         }
     }
 
     /**
      * Copies characters from this string into the destination byte array. Each
      * byte receives the 8 low-order bits of the corresponding character. The
      * eight high-order bits of each character are not copied and do not
      * participate in the transfer in any way.
      *
      * <p> The first character to be copied is at index {@code srcBegin}; the
      * last character to be copied is at index {@code srcEnd-1}.  The total
      * number of characters to be copied is {@code srcEnd-srcBegin}. The
      * characters, converted to bytes, are copied into the subarray of {@code
      * dst} starting at index {@code dstBegin} and ending at index:
      *
      * <blockquote><pre>
      *     dstBegin + (srcEnd-srcBegin) - 1
      * </pre></blockquote>
      *
      * @deprecated  This method does not properly convert characters into
      * bytes.  As of JDK&nbsp;1.1, the preferred way to do this is via the
-     * {@link #getBytes()} method, which uses the platform's default charset.
+     * {@link #getBytes()} method, which uses the {@link Charset#defaultCharset()
+     * default charset}.
      *
      * @param  srcBegin
      *         Index of the first character in the string to copy
      *
      * @param  srcEnd
      *         Index after the last character in the string to copy
      *
      * @param  dst
      *         The destination array
      *
      * @param  dstBegin
      *         The start offset in the destination array
      *
      * @throws  IndexOutOfBoundsException
      *          If any of the following is true:
      *          <ul>
      *            <li> {@code srcBegin} is negative
      *            <li> {@code srcBegin} is greater than {@code srcEnd}
      *            <li> {@code srcEnd} is greater than the length of this String
      *            <li> {@code dstBegin} is negative
      *            <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
      *                 dst.length}
      *          </ul>
      */
     @Deprecated(since="1.1")
-    public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
+    public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) {
         checkBoundsBeginEnd(srcBegin, srcEnd, length());
         Objects.requireNonNull(dst);
         checkBoundsOffCount(dstBegin, srcEnd - srcBegin, dst.length);
         if (isLatin1()) {
             StringLatin1.getBytes(value, srcBegin, srcEnd, dst, dstBegin);
         } else {
             StringUTF16.getBytes(value, srcBegin, srcEnd, dst, dstBegin);
         }
     }
 
     /**
      * Encodes this {@code String} into a sequence of bytes using the named
      * charset, storing the result into a new byte array.
      *
      * <p> The behavior of this method when this string cannot be encoded in
      * the given charset is unspecified.  The {@link
      * java.nio.charset.CharsetEncoder} class should be used when more control
      * over the encoding process is required.
      *
      * @param  charsetName
      *         The name of a supported {@linkplain java.nio.charset.Charset
      *         charset}
      *
      * @return  The resultant byte array
      *
      * @throws  UnsupportedEncodingException
      *          If the named charset is not supported
      *
      * @since  1.1
      */
     public byte[] getBytes(String charsetName)
             throws UnsupportedEncodingException {
-        if (charsetName == null) throw new NullPointerException();
         return encode(lookupCharset(charsetName), coder(), value);
     }
 
     /**
      * Encodes this {@code String} into a sequence of bytes using the given
      * {@linkplain java.nio.charset.Charset charset}, storing the result into a
      * new byte array.
      *
      * <p> This method always replaces malformed-input and unmappable-character
      * sequences with this charset's default replacement byte array.  The
      * {@link java.nio.charset.CharsetEncoder} class should be used when more
      * control over the encoding process is required.
      *
      * @param  charset
      *         The {@linkplain java.nio.charset.Charset} to be used to encode
      *         the {@code String}
      *
      * @return  The resultant byte array
      *
      * @since  1.6
      */
     public byte[] getBytes(Charset charset) {
         if (charset == null) throw new NullPointerException();
         return encode(charset, coder(), value);
      }
 
     /**
      * Encodes this {@code String} into a sequence of bytes using the
-     * platform's default charset, storing the result into a new byte array.
+     * {@link Charset#defaultCharset() default charset}, storing the result
+     * into a new byte array.
      *
      * <p> The behavior of this method when this string cannot be encoded in
      * the default charset is unspecified.  The {@link
      * java.nio.charset.CharsetEncoder} class should be used when more control
      * over the encoding process is required.
      *
      * @return  The resultant byte array
      *
      * @since      1.1
      */
     public byte[] getBytes() {
         return encode(Charset.defaultCharset(), coder(), value);
     }
 
     /**
      * Compares this string to the specified object.  The result is {@code
      * true} if and only if the argument is not {@code null} and is a {@code
      * String} object that represents the same sequence of characters as this
      * object.
      *
      * <p>For finer-grained String comparison, refer to
      * {@link java.text.Collator}.
      *
      * @param  anObject
      *         The object to compare this {@code String} against
      *
      * @return  {@code true} if the given object represents a {@code String}
      *          equivalent to this string, {@code false} otherwise
      *
      * @see  #compareTo(String)
      * @see  #equalsIgnoreCase(String)
      */
     public boolean equals(Object anObject) {
         if (this == anObject) {
             return true;
         }
-        if (anObject instanceof String) {
-            String aString = (String)anObject;
-            if (!COMPACT_STRINGS || this.coder == aString.coder) {
-                return StringLatin1.equals(value, aString.value);
-            }
-        }
-        return false;
+        return (anObject instanceof String aString)
+                && (!COMPACT_STRINGS || this.coder == aString.coder)
+                && StringLatin1.equals(value, aString.value);
     }
 
     /**
      * Compares this string to the specified {@code StringBuffer}.  The result
      * is {@code true} if and only if this {@code String} represents the same
      * sequence of characters as the specified {@code StringBuffer}. This method
      * synchronizes on the {@code StringBuffer}.
      *
      * <p>For finer-grained String comparison, refer to
      * {@link java.text.Collator}.
      *
      * @param  sb
      *         The {@code StringBuffer} to compare this {@code String} against
      *
      * @return  {@code true} if this {@code String} represents the same
      *          sequence of characters as the specified {@code StringBuffer},
      *          {@code false} otherwise
      *
      * @since  1.4
      */
     public boolean contentEquals(StringBuffer sb) {
         return contentEquals((CharSequence)sb);
     }
 
     private boolean nonSyncContentEquals(AbstractStringBuilder sb) {
         int len = length();
         if (len != sb.length()) {
             return false;
         }
         byte v1[] = value;
         byte v2[] = sb.getValue();
         byte coder = coder();
         if (coder == sb.getCoder()) {
             int n = v1.length;
             for (int i = 0; i < n; i++) {
                 if (v1[i] != v2[i]) {
                     return false;
                 }
             }
         } else {
             if (coder != LATIN1) {  // utf16 str and latin1 abs can never be "equal"
                 return false;
             }
             return StringUTF16.contentEquals(v1, v2, len);
         }
         return true;
     }
 
     /**
      * Compares this string to the specified {@code CharSequence}.  The
      * result is {@code true} if and only if this {@code String} represents the
      * same sequence of char values as the specified sequence. Note that if the
      * {@code CharSequence} is a {@code StringBuffer} then the method
      * synchronizes on it.
      *
      * <p>For finer-grained String comparison, refer to
      * {@link java.text.Collator}.
      *
      * @param  cs
      *         The sequence to compare this {@code String} against
      *
      * @return  {@code true} if this {@code String} represents the same
      *          sequence of char values as the specified sequence, {@code
      *          false} otherwise
      *
      * @since  1.5
      */
     public boolean contentEquals(CharSequence cs) {
         // Argument is a StringBuffer, StringBuilder
         if (cs instanceof AbstractStringBuilder) {
             if (cs instanceof StringBuffer) {
                 synchronized(cs) {
                    return nonSyncContentEquals((AbstractStringBuilder)cs);
                 }
             } else {
                 return nonSyncContentEquals((AbstractStringBuilder)cs);
             }
         }
         // Argument is a String
         if (cs instanceof String) {
             return equals(cs);
         }
         // Argument is a generic CharSequence
         int n = cs.length();
         if (n != length()) {
             return false;
         }
         byte[] val = this.value;
         if (isLatin1()) {
             for (int i = 0; i < n; i++) {
                 if ((val[i] & 0xff) != cs.charAt(i)) {
                     return false;
                 }
             }
         } else {
             if (!StringUTF16.contentEquals(val, cs, n)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Compares this {@code String} to another {@code String}, ignoring case
      * considerations.  Two strings are considered equal ignoring case if they
      * are of the same length and corresponding Unicode code points in the two
      * strings are equal ignoring case.
      *
      * <p> Two Unicode code points are considered the same
      * ignoring case if at least one of the following is true:
      * <ul>
      *   <li> The two Unicode code points are the same (as compared by the
      *        {@code ==} operator)
      *   <li> Calling {@code Character.toLowerCase(Character.toUpperCase(int))}
      *        on each Unicode code point produces the same result
      * </ul>
      *
      * <p>Note that this method does <em>not</em> take locale into account, and
      * will result in unsatisfactory results for certain locales.  The
      * {@link java.text.Collator} class provides locale-sensitive comparison.
      *
      * @param  anotherString
      *         The {@code String} to compare this {@code String} against
      *
      * @return  {@code true} if the argument is not {@code null} and it
      *          represents an equivalent {@code String} ignoring case; {@code
      *          false} otherwise
      *
      * @see  #equals(Object)
      * @see  #codePoints()
      */
     public boolean equalsIgnoreCase(String anotherString) {
         return (this == anotherString) ? true
                 : (anotherString != null)
                 && (anotherString.length() == length())
                 && regionMatches(true, 0, anotherString, 0, length());
     }
 
     /**
      * Compares two strings lexicographically.
      * The comparison is based on the Unicode value of each character in
      * the strings. The character sequence represented by this
      * {@code String} object is compared lexicographically to the
      * character sequence represented by the argument string. The result is
      * a negative integer if this {@code String} object
      * lexicographically precedes the argument string. The result is a
      * positive integer if this {@code String} object lexicographically
      * follows the argument string. The result is zero if the strings
      * are equal; {@code compareTo} returns {@code 0} exactly when
      * the {@link #equals(Object)} method would return {@code true}.
      * <p>
      * This is the definition of lexicographic ordering. If two strings are
      * different, then either they have different characters at some index
      * that is a valid index for both strings, or their lengths are different,
      * or both. If they have different characters at one or more index
      * positions, let <i>k</i> be the smallest such index; then the string
      * whose character at position <i>k</i> has the smaller value, as
      * determined by using the {@code <} operator, lexicographically precedes the
      * other string. In this case, {@code compareTo} returns the
      * difference of the two character values at position {@code k} in
      * the two string -- that is, the value:
      * <blockquote><pre>
      * this.charAt(k)-anotherString.charAt(k)
      * </pre></blockquote>
      * If there is no index position at which they differ, then the shorter
      * string lexicographically precedes the longer string. In this case,
      * {@code compareTo} returns the difference of the lengths of the
      * strings -- that is, the value:
      * <blockquote><pre>
      * this.length()-anotherString.length()
      * </pre></blockquote>
      *
      * <p>For finer-grained String comparison, refer to
      * {@link java.text.Collator}.
      *
      * @param   anotherString   the {@code String} to be compared.
      * @return  the value {@code 0} if the argument string is equal to
      *          this string; a value less than {@code 0} if this string
      *          is lexicographically less than the string argument; and a
      *          value greater than {@code 0} if this string is
      *          lexicographically greater than the string argument.
      */
     public int compareTo(String anotherString) {
         byte v1[] = value;
         byte v2[] = anotherString.value;
         byte coder = coder();
         if (coder == anotherString.coder()) {
             return coder == LATIN1 ? StringLatin1.compareTo(v1, v2)
                                    : StringUTF16.compareTo(v1, v2);
         }
         return coder == LATIN1 ? StringLatin1.compareToUTF16(v1, v2)
                                : StringUTF16.compareToLatin1(v1, v2);
      }
 
     /**
      * A Comparator that orders {@code String} objects as by
      * {@link #compareToIgnoreCase(String) compareToIgnoreCase}.
      * This comparator is serializable.
      * <p>
      * Note that this Comparator does <em>not</em> take locale into account,
      * and will result in an unsatisfactory ordering for certain locales.
      * The {@link java.text.Collator} class provides locale-sensitive comparison.
      *
      * @see     java.text.Collator
      * @since   1.2
      */
     public static final Comparator<String> CASE_INSENSITIVE_ORDER
                                          = new CaseInsensitiveComparator();
 
     /**
      * CaseInsensitiveComparator for Strings.
      */
     private static class CaseInsensitiveComparator
             implements Comparator<String>, java.io.Serializable {
         // use serialVersionUID from JDK 1.2.2 for interoperability
         @java.io.Serial
         private static final long serialVersionUID = 8575799808933029326L;
 
         public int compare(String s1, String s2) {
             byte v1[] = s1.value;
             byte v2[] = s2.value;
             byte coder = s1.coder();
             if (coder == s2.coder()) {
                 return coder == LATIN1 ? StringLatin1.compareToCI(v1, v2)
                                        : StringUTF16.compareToCI(v1, v2);
             }
             return coder == LATIN1 ? StringLatin1.compareToCI_UTF16(v1, v2)
                                    : StringUTF16.compareToCI_Latin1(v1, v2);
         }
 
         /** Replaces the de-serialized object. */
         @java.io.Serial
         private Object readResolve() { return CASE_INSENSITIVE_ORDER; }
     }
 
     /**
      * Compares two strings lexicographically, ignoring case
      * differences. This method returns an integer whose sign is that of
      * calling {@code compareTo} with case folded versions of the strings
      * where case differences have been eliminated by calling
      * {@code Character.toLowerCase(Character.toUpperCase(int))} on
      * each Unicode code point.
      * <p>
      * Note that this method does <em>not</em> take locale into account,
      * and will result in an unsatisfactory ordering for certain locales.
      * The {@link java.text.Collator} class provides locale-sensitive comparison.
      *
      * @param   str   the {@code String} to be compared.
      * @return  a negative integer, zero, or a positive integer as the
      *          specified String is greater than, equal to, or less
      *          than this String, ignoring case considerations.
      * @see     java.text.Collator
      * @see     #codePoints()
      * @since   1.2
      */
     public int compareToIgnoreCase(String str) {
         return CASE_INSENSITIVE_ORDER.compare(this, str);
     }
 
     /**
      * Tests if two string regions are equal.
      * <p>
      * A substring of this {@code String} object is compared to a substring
      * of the argument other. The result is true if these substrings
      * represent identical character sequences. The substring of this
      * {@code String} object to be compared begins at index {@code toffset}
      * and has length {@code len}. The substring of other to be compared
      * begins at index {@code ooffset} and has length {@code len}. The
      * result is {@code false} if and only if at least one of the following
      * is true:
      * <ul><li>{@code toffset} is negative.
      * <li>{@code ooffset} is negative.
      * <li>{@code toffset+len} is greater than the length of this
      * {@code String} object.
      * <li>{@code ooffset+len} is greater than the length of the other
      * argument.
      * <li>There is some nonnegative integer <i>k</i> less than {@code len}
      * such that:
      * {@code this.charAt(toffset + }<i>k</i>{@code ) != other.charAt(ooffset + }
      * <i>k</i>{@code )}
      * </ul>
      *
      * <p>Note that this method does <em>not</em> take locale into account.  The
      * {@link java.text.Collator} class provides locale-sensitive comparison.
      *
      * @param   toffset   the starting offset of the subregion in this string.
      * @param   other     the string argument.
      * @param   ooffset   the starting offset of the subregion in the string
      *                    argument.
      * @param   len       the number of characters to compare.
      * @return  {@code true} if the specified subregion of this string
      *          exactly matches the specified subregion of the string argument;
      *          {@code false} otherwise.
      */
     public boolean regionMatches(int toffset, String other, int ooffset, int len) {
         byte tv[] = value;
         byte ov[] = other.value;
         // Note: toffset, ooffset, or len might be near -1>>>1.
         if ((ooffset < 0) || (toffset < 0) ||
              (toffset > (long)length() - len) ||
              (ooffset > (long)other.length() - len)) {
             return false;
         }
         byte coder = coder();
         if (coder == other.coder()) {
             if (!isLatin1() && (len > 0)) {
                 toffset = toffset << 1;
                 ooffset = ooffset << 1;
                 len = len << 1;
             }
             while (len-- > 0) {
                 if (tv[toffset++] != ov[ooffset++]) {
                     return false;
                 }
             }
         } else {
             if (coder == LATIN1) {
                 while (len-- > 0) {
                     if (StringLatin1.getChar(tv, toffset++) !=
                         StringUTF16.getChar(ov, ooffset++)) {
                         return false;
                     }
                 }
             } else {
                 while (len-- > 0) {
                     if (StringUTF16.getChar(tv, toffset++) !=
                         StringLatin1.getChar(ov, ooffset++)) {
                         return false;
                     }
                 }
             }
         }
         return true;
     }
 
     /**
      * Tests if two string regions are equal.
      * <p>
      * A substring of this {@code String} object is compared to a substring
      * of the argument {@code other}. The result is {@code true} if these
      * substrings represent Unicode code point sequences that are the same,
      * ignoring case if and only if {@code ignoreCase} is true.
      * The sequences {@code tsequence} and {@code osequence} are compared,
      * where {@code tsequence} is the sequence produced as if by calling
-     * {@code this.substring(toffset, len).codePoints()} and {@code osequence}
-     * is the sequence produced as if by calling
-     * {@code other.substring(ooffset, len).codePoints()}.
+     * {@code this.substring(toffset, toffset + len).codePoints()} and
+     * {@code osequence} is the sequence produced as if by calling
+     * {@code other.substring(ooffset, ooffset + len).codePoints()}.
      * The result is {@code true} if and only if all of the following
      * are true:
      * <ul><li>{@code toffset} is non-negative.
      * <li>{@code ooffset} is non-negative.
      * <li>{@code toffset+len} is less than or equal to the length of this
      * {@code String} object.
      * <li>{@code ooffset+len} is less than or equal to the length of the other
      * argument.
      * <li>if {@code ignoreCase} is {@code false}, all pairs of corresponding Unicode
      * code points are equal integer values; or if {@code ignoreCase} is {@code true},
      * {@link Character#toLowerCase(int) Character.toLowerCase(}
      * {@link Character#toUpperCase(int)}{@code )} on all pairs of Unicode code points
      * results in equal integer values.
      * </ul>
      *
      * <p>Note that this method does <em>not</em> take locale into account,
      * and will result in unsatisfactory results for certain locales when
      * {@code ignoreCase} is {@code true}.  The {@link java.text.Collator} class
      * provides locale-sensitive comparison.
      *
      * @param   ignoreCase   if {@code true}, ignore case when comparing
      *                       characters.
      * @param   toffset      the starting offset of the subregion in this
      *                       string.
      * @param   other        the string argument.
      * @param   ooffset      the starting offset of the subregion in the string
      *                       argument.
      * @param   len          the number of characters (Unicode code units -
      *                       16bit {@code char} value) to compare.
      * @return  {@code true} if the specified subregion of this string
      *          matches the specified subregion of the string argument;
      *          {@code false} otherwise. Whether the matching is exact
      *          or case insensitive depends on the {@code ignoreCase}
      *          argument.
      * @see     #codePoints()
      */
     public boolean regionMatches(boolean ignoreCase, int toffset,
             String other, int ooffset, int len) {
         if (!ignoreCase) {
             return regionMatches(toffset, other, ooffset, len);
         }
         // Note: toffset, ooffset, or len might be near -1>>>1.
         if ((ooffset < 0) || (toffset < 0)
                 || (toffset > (long)length() - len)
                 || (ooffset > (long)other.length() - len)) {
             return false;
         }
         byte tv[] = value;
         byte ov[] = other.value;
         byte coder = coder();
         if (coder == other.coder()) {
             return coder == LATIN1
               ? StringLatin1.regionMatchesCI(tv, toffset, ov, ooffset, len)
               : StringUTF16.regionMatchesCI(tv, toffset, ov, ooffset, len);
         }
         return coder == LATIN1
               ? StringLatin1.regionMatchesCI_UTF16(tv, toffset, ov, ooffset, len)
               : StringUTF16.regionMatchesCI_Latin1(tv, toffset, ov, ooffset, len);
     }
 
     /**
      * Tests if the substring of this string beginning at the
      * specified index starts with the specified prefix.
      *
      * @param   prefix    the prefix.
      * @param   toffset   where to begin looking in this string.
      * @return  {@code true} if the character sequence represented by the
      *          argument is a prefix of the substring of this object starting
      *          at index {@code toffset}; {@code false} otherwise.
      *          The result is {@code false} if {@code toffset} is
      *          negative or greater than the length of this
      *          {@code String} object; otherwise the result is the same
      *          as the result of the expression
      *          <pre>
      *          this.substring(toffset).startsWith(prefix)
      *          </pre>
      */
     public boolean startsWith(String prefix, int toffset) {
         // Note: toffset might be near -1>>>1.
         if (toffset < 0 || toffset > length() - prefix.length()) {
             return false;
         }
         byte ta[] = value;
         byte pa[] = prefix.value;
         int po = 0;
         int pc = pa.length;
         byte coder = coder();
         if (coder == prefix.coder()) {
             int to = (coder == LATIN1) ? toffset : toffset << 1;
             while (po < pc) {
                 if (ta[to++] != pa[po++]) {
                     return false;
                 }
             }
         } else {
             if (coder == LATIN1) {  // && pcoder == UTF16
                 return false;
             }
             // coder == UTF16 && pcoder == LATIN1)
             while (po < pc) {
                 if (StringUTF16.getChar(ta, toffset++) != (pa[po++] & 0xff)) {
                     return false;
                }
             }
         }
         return true;
     }
 
     /**
      * Tests if this string starts with the specified prefix.
      *
      * @param   prefix   the prefix.
      * @return  {@code true} if the character sequence represented by the
      *          argument is a prefix of the character sequence represented by
      *          this string; {@code false} otherwise.
      *          Note also that {@code true} will be returned if the
      *          argument is an empty string or is equal to this
      *          {@code String} object as determined by the
      *          {@link #equals(Object)} method.
      * @since   1.0
      */
     public boolean startsWith(String prefix) {
         return startsWith(prefix, 0);
     }
 
     /**
      * Tests if this string ends with the specified suffix.
      *
      * @param   suffix   the suffix.
      * @return  {@code true} if the character sequence represented by the
      *          argument is a suffix of the character sequence represented by
      *          this object; {@code false} otherwise. Note that the
      *          result will be {@code true} if the argument is the
      *          empty string or is equal to this {@code String} object
      *          as determined by the {@link #equals(Object)} method.
      */
     public boolean endsWith(String suffix) {
         return startsWith(suffix, length() - suffix.length());
     }
 
     /**
      * Returns a hash code for this string. The hash code for a
      * {@code String} object is computed as
      * <blockquote><pre>
      * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
      * </pre></blockquote>
      * using {@code int} arithmetic, where {@code s[i]} is the
      * <i>i</i>th character of the string, {@code n} is the length of
      * the string, and {@code ^} indicates exponentiation.
      * (The hash value of the empty string is zero.)
      *
      * @return  a hash code value for this object.
      */
     public int hashCode() {
         // The hash or hashIsZero fields are subject to a benign data race,
         // making it crucial to ensure that any observable result of the
         // calculation in this method stays correct under any possible read of
         // these fields. Necessary restrictions to allow this to be correct
         // without explicit memory fences or similar concurrency primitives is
         // that we can ever only write to one of these two fields for a given
         // String instance, and that the computation is idempotent and derived
         // from immutable state
         int h = hash;
         if (h == 0 && !hashIsZero) {
             h = isLatin1() ? StringLatin1.hashCode(value)
                            : StringUTF16.hashCode(value);
             if (h == 0) {
                 hashIsZero = true;
             } else {
                 hash = h;
             }
         }
         return h;
     }
 
     /**
      * Returns the index within this string of the first occurrence of
      * the specified character. If a character with value
      * {@code ch} occurs in the character sequence represented by
      * this {@code String} object, then the index (in Unicode
      * code units) of the first such occurrence is returned. For
      * values of {@code ch} 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>) == ch
      * </pre></blockquote>
      * is true. For other values of {@code ch}, it is the
      * smallest value <i>k</i> such that:
      * <blockquote><pre>
      * this.codePointAt(<i>k</i>) == ch
      * </pre></blockquote>
      * is true. In either case, if no such character occurs in this
      * string, then {@code -1} is returned.
      *
      * @param   ch   a character (Unicode code point).
      * @return  the index of the first occurrence of the character in the
      *          character sequence represented by this object, or
      *          {@code -1} if the character does not occur.
      */
     public int indexOf(int ch) {
         return indexOf(ch, 0);
     }
 
     /**
      * Returns the index within this string of the first occurrence of the
      * specified character, starting the search at the specified index.
      * <p>
      * If a character with value {@code ch} occurs in the
      * character sequence represented by this {@code String}
      * object at an index no smaller than {@code fromIndex}, then
      * the index of the first such occurrence is returned. For values
      * of {@code ch} 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>) == ch) {@code &&} (<i>k</i> &gt;= fromIndex)
      * </pre></blockquote>
      * is true. For other values of {@code ch}, it is the
      * smallest value <i>k</i> such that:
      * <blockquote><pre>
      * (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &gt;= fromIndex)
      * </pre></blockquote>
      * is true. In either case, if no such character occurs in this
      * string at or after position {@code fromIndex}, then
      * {@code -1} is returned.
      *
      * <p>
      * There is no restriction on the value of {@code fromIndex}. 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 -1} is returned.
      *
      * <p>All indices are specified in {@code char} values
      * (Unicode code units).
      *
      * @param   ch          a character (Unicode code point).
      * @param   fromIndex   the index to start the search from.
      * @return  the index of the first occurrence of the character in the
      *          character sequence represented by this object that is greater
      *          than or equal to {@code fromIndex}, or {@code -1}
      *          if the character does not occur.
      */
     public int indexOf(int ch, int fromIndex) {
         return isLatin1() ? StringLatin1.indexOf(value, ch, fromIndex)
                           : StringUTF16.indexOf(value, ch, fromIndex);
     }
 
     /**
      * Returns the index within this string of the last occurrence of
      * the specified character. For values of {@code ch} 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>) == ch
      * </pre></blockquote>
      * is true. For other values of {@code ch}, it is the
      * largest value <i>k</i> such that:
      * <blockquote><pre>
      * this.codePointAt(<i>k</i>) == ch
      * </pre></blockquote>
      * is true.  In either case, if no such character occurs in this
      * string, then {@code -1} is returned.  The
      * {@code String} is searched backwards starting at the last
      * character.
      *
      * @param   ch   a character (Unicode code point).
      * @return  the index of the last occurrence of the character in the
      *          character sequence represented by this object, or
      *          {@code -1} if the character does not occur.
      */
     public int lastIndexOf(int ch) {
         return lastIndexOf(ch, length() - 1);
     }
 
     /**
      * Returns the index within this string of the last occurrence of
      * the specified character, searching backward starting at the
      * specified index. For values of {@code ch} 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>) == ch) {@code &&} (<i>k</i> &lt;= fromIndex)
      * </pre></blockquote>
      * is true. For other values of {@code ch}, it is the
      * largest value <i>k</i> such that:
      * <blockquote><pre>
      * (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &lt;= fromIndex)
      * </pre></blockquote>
      * is true. In either case, if no such character occurs in this
      * string at or before position {@code fromIndex}, then
      * {@code -1} is returned.
      *
      * <p>All indices are specified in {@code char} values
      * (Unicode code units).
      *
      * @param   ch          a character (Unicode code point).
      * @param   fromIndex   the index to start the search from. There is no
      *          restriction on the value of {@code fromIndex}. If it is
      *          greater than or equal to the length of this string, it has
      *          the same effect as if it were equal to one less than the
      *          length of this string: this entire string may be searched.
      *          If it is negative, it has the same effect as if it were -1:
      *          -1 is returned.
      * @return  the index of the last occurrence of the character in the
      *          character sequence represented by this object that is less
      *          than or equal to {@code fromIndex}, or {@code -1}
      *          if the character does not occur before that point.
      */
     public int lastIndexOf(int ch, int fromIndex) {
         return isLatin1() ? StringLatin1.lastIndexOf(value, ch, fromIndex)
                           : StringUTF16.lastIndexOf(value, ch, fromIndex);
     }
 
     /**
      * Returns the index within this string of the first occurrence of the
      * specified substring.
      *
      * <p>The returned index is the smallest value {@code k} for which:
      * <pre>{@code
      * this.startsWith(str, k)
      * }</pre>
      * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str   the substring to search for.
      * @return  the index of the first occurrence of the specified substring,
      *          or {@code -1} if there is no such occurrence.
      */
     public int indexOf(String str) {
         byte coder = coder();
         if (coder == str.coder()) {
             return isLatin1() ? StringLatin1.indexOf(value, str.value)
                               : StringUTF16.indexOf(value, str.value);
         }
         if (coder == LATIN1) {  // str.coder == UTF16
             return -1;
         }
         return StringUTF16.indexOfLatin1(value, str.value);
     }
 
     /**
      * Returns the index within this string of the first occurrence of the
      * specified substring, starting at the specified index.
      *
      * <p>The returned index is the smallest value {@code k} for which:
      * <pre>{@code
      *     k >= Math.min(fromIndex, this.length()) &&
      *                   this.startsWith(str, k)
      * }</pre>
      * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str         the substring to search for.
      * @param   fromIndex   the index from which to start the search.
      * @return  the index of the first occurrence of the specified substring,
      *          starting at the specified index,
      *          or {@code -1} if there is no such occurrence.
      */
     public int indexOf(String str, int fromIndex) {
         return indexOf(value, coder(), length(), str, fromIndex);
     }
 
     /**
      * Code shared by String and AbstractStringBuilder to do searches. The
      * source is the character array being searched, and the target
      * is the string being searched for.
      *
      * @param   src       the characters being searched.
      * @param   srcCoder  the coder of the source string.
      * @param   srcCount  length of the source string.
      * @param   tgtStr    the characters being searched for.
      * @param   fromIndex the index to begin searching from.
      */
     static int indexOf(byte[] src, byte srcCoder, int srcCount,
                        String tgtStr, int fromIndex) {
         byte[] tgt    = tgtStr.value;
         byte tgtCoder = tgtStr.coder();
         int tgtCount  = tgtStr.length();
 
         if (fromIndex >= srcCount) {
             return (tgtCount == 0 ? srcCount : -1);
         }
         if (fromIndex < 0) {
             fromIndex = 0;
         }
         if (tgtCount == 0) {
             return fromIndex;
         }
         if (tgtCount > srcCount) {
             return -1;
         }
         if (srcCoder == tgtCoder) {
             return srcCoder == LATIN1
                 ? StringLatin1.indexOf(src, srcCount, tgt, tgtCount, fromIndex)
                 : StringUTF16.indexOf(src, srcCount, tgt, tgtCount, fromIndex);
         }
         if (srcCoder == LATIN1) {    //  && tgtCoder == UTF16
             return -1;
         }
         // srcCoder == UTF16 && tgtCoder == LATIN1) {
         return StringUTF16.indexOfLatin1(src, srcCount, tgt, tgtCount, fromIndex);
     }
 
     /**
      * Returns the index within this string of the last occurrence of the
      * specified substring.  The last occurrence of the empty string ""
      * is considered to occur at the index value {@code this.length()}.
      *
      * <p>The returned index is the largest value {@code k} for which:
      * <pre>{@code
      * this.startsWith(str, k)
      * }</pre>
      * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str   the substring to search for.
      * @return  the index of the last occurrence of the specified substring,
      *          or {@code -1} if there is no such occurrence.
      */
     public int lastIndexOf(String str) {
         return lastIndexOf(str, length());
     }
 
     /**
      * Returns the index within this string of the last occurrence of the
      * specified substring, searching backward starting at the specified index.
      *
      * <p>The returned index is the largest value {@code k} for which:
      * <pre>{@code
      *     k <= Math.min(fromIndex, this.length()) &&
      *                   this.startsWith(str, k)
      * }</pre>
      * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str         the substring to search for.
      * @param   fromIndex   the index to start the search from.
      * @return  the index of the last occurrence of the specified substring,
      *          searching backward from the specified index,
      *          or {@code -1} if there is no such occurrence.
      */
     public int lastIndexOf(String str, int fromIndex) {
         return lastIndexOf(value, coder(), length(), str, fromIndex);
     }
 
     /**
      * Code shared by String and AbstractStringBuilder to do searches. The
      * source is the character array being searched, and the target
      * is the string being searched for.
      *
      * @param   src         the characters being searched.
      * @param   srcCoder    coder handles the mapping between bytes/chars
      * @param   srcCount    count of the source string.
      * @param   tgtStr      the characters being searched for.
      * @param   fromIndex   the index to begin searching from.
      */
     static int lastIndexOf(byte[] src, byte srcCoder, int srcCount,
                            String tgtStr, int fromIndex) {
         byte[] tgt = tgtStr.value;
         byte tgtCoder = tgtStr.coder();
         int tgtCount = tgtStr.length();
         /*
          * Check arguments; return immediately where possible. For
          * consistency, don't check for null str.
          */
         int rightIndex = srcCount - tgtCount;
         if (fromIndex > rightIndex) {
             fromIndex = rightIndex;
         }
         if (fromIndex < 0) {
             return -1;
         }
         /* Empty string always matches. */
         if (tgtCount == 0) {
             return fromIndex;
         }
         if (srcCoder == tgtCoder) {
             return srcCoder == LATIN1
                 ? StringLatin1.lastIndexOf(src, srcCount, tgt, tgtCount, fromIndex)
                 : StringUTF16.lastIndexOf(src, srcCount, tgt, tgtCount, fromIndex);
         }
         if (srcCoder == LATIN1) {    // && tgtCoder == UTF16
             return -1;
         }
         // srcCoder == UTF16 && tgtCoder == LATIN1
         return StringUTF16.lastIndexOfLatin1(src, srcCount, tgt, tgtCount, fromIndex);
     }
 
     /**
      * Returns a string that is a substring of this string. The
      * substring begins with the character at the specified index and
      * extends to the end of this string. <p>
      * Examples:
      * <blockquote><pre>
      * "unhappy".substring(2) returns "happy"
      * "Harbison".substring(3) returns "bison"
      * "emptiness".substring(9) returns "" (an empty string)
      * </pre></blockquote>
      *
      * @param      beginIndex   the beginning index, inclusive.
      * @return     the specified substring.
      * @throws     IndexOutOfBoundsException  if
      *             {@code beginIndex} is negative or larger than the
      *             length of this {@code String} object.
      */
     public String substring(int beginIndex) {
         return substring(beginIndex, length());
     }
 
     /**
      * Returns a string that is a substring of this string. The
      * substring begins at the specified {@code beginIndex} and
      * extends to the character at index {@code endIndex - 1}.
      * Thus the length of the substring is {@code endIndex-beginIndex}.
      * <p>
      * Examples:
      * <blockquote><pre>
      * "hamburger".substring(4, 8) returns "urge"
      * "smiles".substring(1, 5) returns "mile"
      * </pre></blockquote>
      *
      * @param      beginIndex   the beginning index, inclusive.
      * @param      endIndex     the ending index, exclusive.
      * @return     the specified substring.
      * @throws     IndexOutOfBoundsException  if the
      *             {@code beginIndex} is negative, or
      *             {@code endIndex} is larger than the length of
      *             this {@code String} object, or
      *             {@code beginIndex} is larger than
      *             {@code endIndex}.
      */
     public String substring(int beginIndex, int endIndex) {
         int length = length();
         checkBoundsBeginEnd(beginIndex, endIndex, length);
         if (beginIndex == 0 && endIndex == length) {
             return this;
         }
         int subLen = endIndex - beginIndex;
         return isLatin1() ? StringLatin1.newString(value, beginIndex, subLen)
                           : StringUTF16.newString(value, beginIndex, subLen);
     }
 
     /**
      * Returns a character sequence that is a subsequence of this sequence.
      *
      * <p> An invocation of this method of the form
      *
      * <blockquote><pre>
      * str.subSequence(begin,&nbsp;end)</pre></blockquote>
      *
      * behaves in exactly the same way as the invocation
      *
      * <blockquote><pre>
      * str.substring(begin,&nbsp;end)</pre></blockquote>
      *
      * @apiNote
      * This method is defined so that the {@code String} class can implement
      * the {@link CharSequence} interface.
      *
      * @param   beginIndex   the begin index, inclusive.
      * @param   endIndex     the end index, exclusive.
      * @return  the specified subsequence.
      *
      * @throws  IndexOutOfBoundsException
      *          if {@code beginIndex} or {@code endIndex} is negative,
      *          if {@code endIndex} is greater than {@code length()},
      *          or if {@code beginIndex} is greater than {@code endIndex}
      *
      * @since 1.4
      */
     public CharSequence subSequence(int beginIndex, int endIndex) {
         return this.substring(beginIndex, endIndex);
     }
 
     /**
      * Concatenates the specified string to the end of this string.
      * <p>
      * If the length of the argument string is {@code 0}, then this
      * {@code String} object is returned. Otherwise, a
      * {@code String} object is returned that represents a character
      * sequence that is the concatenation of the character sequence
      * represented by this {@code String} object and the character
      * sequence represented by the argument string.<p>
      * Examples:
      * <blockquote><pre>
      * "cares".concat("s") returns "caress"
      * "to".concat("get").concat("her") returns "together"
      * </pre></blockquote>
      *
      * @param   str   the {@code String} that is concatenated to the end
      *                of this {@code String}.
      * @return  a string that represents the concatenation of this object's
      *          characters followed by the string argument's characters.
      */
     public String concat(String str) {
         if (str.isEmpty()) {
             return this;
         }
         return StringConcatHelper.simpleConcat(this, str);
     }
 
     /**
      * Returns a string resulting from replacing all occurrences of
      * {@code oldChar} in this string with {@code newChar}.
      * <p>
      * If the character {@code oldChar} does not occur in the
      * character sequence represented by this {@code String} object,
      * then a reference to this {@code String} object is returned.
      * Otherwise, a {@code String} object is returned that
      * represents a character sequence identical to the character sequence
      * represented by this {@code String} object, except that every
      * occurrence of {@code oldChar} is replaced by an occurrence
      * of {@code newChar}.
      * <p>
      * Examples:
      * <blockquote><pre>
      * "mesquite in your cellar".replace('e', 'o')
      *         returns "mosquito in your collar"
      * "the war of baronets".replace('r', 'y')
      *         returns "the way of bayonets"
      * "sparring with a purple porpoise".replace('p', 't')
      *         returns "starring with a turtle tortoise"
      * "JonL".replace('q', 'x') returns "JonL" (no change)
      * </pre></blockquote>
      *
      * @param   oldChar   the old character.
      * @param   newChar   the new character.
      * @return  a string derived from this string by replacing every
      *          occurrence of {@code oldChar} with {@code newChar}.
      */
     public String replace(char oldChar, char newChar) {
         if (oldChar != newChar) {
             String ret = isLatin1() ? StringLatin1.replace(value, oldChar, newChar)
                                     : StringUTF16.replace(value, oldChar, newChar);
             if (ret != null) {
                 return ret;
             }
         }
         return this;
     }
 
     /**
      * Tells whether or not this string matches the given <a
      * href="../util/regex/Pattern.html#sum">regular expression</a>.
      *
      * <p> An invocation of this method of the form
      * <i>str</i>{@code .matches(}<i>regex</i>{@code )} yields exactly the
      * same result as the expression
      *
      * <blockquote>
      * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#matches(String,CharSequence)
      * matches(<i>regex</i>, <i>str</i>)}
      * </blockquote>
      *
      * @param   regex
      *          the regular expression to which this string is to be matched
      *
      * @return  {@code true} if, and only if, this string matches the
      *          given regular expression
      *
      * @throws  PatternSyntaxException
      *          if the regular expression's syntax is invalid
      *
      * @see java.util.regex.Pattern
      *
      * @since 1.4
      */
     public boolean matches(String regex) {
         return Pattern.matches(regex, this);
     }
 
     /**
      * Returns true if and only if this string contains the specified
      * sequence of char values.
      *
      * @param s the sequence to search for
      * @return true if this string contains {@code s}, false otherwise
      * @since 1.5
      */
     public boolean contains(CharSequence s) {
         return indexOf(s.toString()) >= 0;
     }
 
     /**
      * Replaces the first substring of this string that matches the given <a
      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
      * given replacement.
      *
      * <p> An invocation of this method of the form
      * <i>str</i>{@code .replaceFirst(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
      * yields exactly the same result as the expression
      *
      * <blockquote>
      * <code>
      * {@link java.util.regex.Pattern}.{@link
      * java.util.regex.Pattern#compile(String) compile}(<i>regex</i>).{@link
      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
      * java.util.regex.Matcher#replaceFirst(String) replaceFirst}(<i>repl</i>)
      * </code>
      * </blockquote>
      *
      *<p>
      * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
      * replacement string may cause the results to be different than if it were
      * being treated as a literal replacement string; see
      * {@link java.util.regex.Matcher#replaceFirst}.
      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
      * meaning of these characters, if desired.
      *
      * @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 resulting {@code String}
      *
      * @throws  PatternSyntaxException
      *          if the regular expression's syntax is invalid
      *
      * @see java.util.regex.Pattern
      *
      * @since 1.4
      */
     public String replaceFirst(String regex, String replacement) {
         return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
     }
 
     /**
      * Replaces each substring of this string that matches the given <a
      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
      * given replacement.
      *
      * <p> An invocation of this method of the form
      * <i>str</i>{@code .replaceAll(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
      * yields exactly the same result as the expression
      *
      * <blockquote>
      * <code>
      * {@link java.util.regex.Pattern}.{@link
      * java.util.regex.Pattern#compile(String) compile}(<i>regex</i>).{@link
      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
      * java.util.regex.Matcher#replaceAll(String) replaceAll}(<i>repl</i>)
      * </code>
      * </blockquote>
      *
      *<p>
      * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
      * replacement string may cause the results to be different than if it were
      * being treated as a literal replacement string; see
      * {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
      * meaning of these characters, if desired.
      *
      * @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}
      *
      * @throws  PatternSyntaxException
      *          if the regular expression's syntax is invalid
      *
      * @see java.util.regex.Pattern
      *
      * @since 1.4
      */
     public String replaceAll(String regex, String replacement) {
         return Pattern.compile(regex).matcher(this).replaceAll(replacement);
     }
 
     /**
      * Replaces each substring of this string that matches the literal target
      * sequence with the specified literal replacement sequence. The
      * replacement proceeds from the beginning of the string to the end, for
      * example, replacing "aa" with "b" in the string "aaa" will result in
      * "ba" rather than "ab".
      *
      * @param  target The sequence of char values to be replaced
      * @param  replacement The replacement sequence of char values
      * @return  The resulting string
      * @since 1.5
      */
     public String replace(CharSequence target, CharSequence replacement) {
         String trgtStr = target.toString();
         String replStr = replacement.toString();
         int thisLen = length();
         int trgtLen = trgtStr.length();
         int replLen = replStr.length();
 
         if (trgtLen > 0) {
             if (trgtLen == 1 && replLen == 1) {
                 return replace(trgtStr.charAt(0), replStr.charAt(0));
             }
 
             boolean thisIsLatin1 = this.isLatin1();
             boolean trgtIsLatin1 = trgtStr.isLatin1();
             boolean replIsLatin1 = replStr.isLatin1();
             String ret = (thisIsLatin1 && trgtIsLatin1 && replIsLatin1)
                     ? StringLatin1.replace(value, thisLen,
                                            trgtStr.value, trgtLen,
                                            replStr.value, replLen)
                     : StringUTF16.replace(value, thisLen, thisIsLatin1,
                                           trgtStr.value, trgtLen, trgtIsLatin1,
                                           replStr.value, replLen, replIsLatin1);
             if (ret != null) {
                 return ret;
             }
             return this;
 
         } else { // trgtLen == 0
             int resultLen;
             try {
                 resultLen = Math.addExact(thisLen, Math.multiplyExact(
                         Math.addExact(thisLen, 1), replLen));
             } catch (ArithmeticException ignored) {
                 throw new OutOfMemoryError("Required length exceeds implementation limit");
             }
 
             StringBuilder sb = new StringBuilder(resultLen);
             sb.append(replStr);
             for (int i = 0; i < thisLen; ++i) {
                 sb.append(charAt(i)).append(replStr);
             }
             return sb.toString();
         }
     }
 
     /**
      * Splits this string around matches of the given
      * <a href="../util/regex/Pattern.html#sum">regular expression</a>.
      *
      * <p> The array returned by this method contains each substring of this
      * string that is terminated by another substring that matches the given
      * expression or is terminated by the end of the string.  The substrings in
      * the array are in the order in which they occur in this string.  If the
      * expression does not match any part of the input then the resulting array
      * has just one element, namely this string.
      *
      * <p> When there is a positive-width match at the beginning of this
      * string then an empty leading substring is included at the beginning
      * of the resulting array. A zero-width match at the beginning however
      * never produces such empty leading substring.
      *
      * <p> The {@code limit} parameter controls the number of times the
      * pattern is applied and therefore affects the length of the resulting
      * array.
      * <ul>
      *    <li><p>
      *    If the <i>limit</i> is positive then the pattern will be applied
      *    at most <i>limit</i>&nbsp;-&nbsp;1 times, the array's length will be
      *    no greater than <i>limit</i>, and the array's last entry will contain
      *    all input beyond the last matched delimiter.</p></li>
      *
      *    <li><p>
      *    If the <i>limit</i> is zero then the pattern will be applied as
      *    many times as possible, the array can have any length, and trailing
      *    empty strings will be discarded.</p></li>
      *
      *    <li><p>
      *    If the <i>limit</i> is negative then the pattern will be applied
      *    as many times as possible and the array can have any length.</p></li>
      * </ul>
      *
      * <p> The string {@code "boo:and:foo"}, for example, yields the
      * following results with these parameters:
      *
      * <blockquote><table class="plain">
      * <caption style="display:none">Split example showing regex, limit, and result</caption>
      * <thead>
      * <tr>
      *     <th scope="col">Regex</th>
      *     <th scope="col">Limit</th>
      *     <th scope="col">Result</th>
      * </tr>
      * </thead>
      * <tbody>
      * <tr><th scope="row" rowspan="3" style="font-weight:normal">:</th>
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">2</th>
      *     <td>{@code { "boo", "and:foo" }}</td></tr>
      * <tr><!-- : -->
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
      * <tr><!-- : -->
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
      * <tr><th scope="row" rowspan="3" style="font-weight:normal">o</th>
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
      * <tr><!-- o -->
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
      * <tr><!-- o -->
      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
      * </tbody>
      * </table></blockquote>
      *
      * <p> An invocation of this method of the form
      * <i>str.</i>{@code split(}<i>regex</i>{@code ,}&nbsp;<i>n</i>{@code )}
      * yields the same result as the expression
      *
      * <blockquote>
      * <code>
      * {@link java.util.regex.Pattern}.{@link
      * java.util.regex.Pattern#compile(String) compile}(<i>regex</i>).{@link
      * java.util.regex.Pattern#split(java.lang.CharSequence,int) split}(<i>str</i>,&nbsp;<i>n</i>)
      * </code>
      * </blockquote>
      *
      *
      * @param  regex
      *         the delimiting regular expression
      *
      * @param  limit
      *         the result threshold, as described above
      *
      * @return  the array of strings computed by splitting this string
      *          around matches of the given regular expression
      *
      * @throws  PatternSyntaxException
      *          if the regular expression's syntax is invalid
      *
      * @see java.util.regex.Pattern
      *
      * @since 1.4
      */
     public String[] split(String regex, int limit) {
         /* fastpath if the regex is a
          * (1) one-char String and this character is not one of the
          *     RegEx's meta characters ".$|()[{^?*+\\", or
          * (2) two-char String and the first char is the backslash and
          *     the second is not the ascii digit or ascii letter.
          */
         char ch = 0;
         if (((regex.length() == 1 &&
              ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||
              (regex.length() == 2 &&
               regex.charAt(0) == '\\' &&
               (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
               ((ch-'a')|('z'-ch)) < 0 &&
               ((ch-'A')|('Z'-ch)) < 0)) &&
             (ch < Character.MIN_HIGH_SURROGATE ||
              ch > Character.MAX_LOW_SURROGATE))
         {
             int off = 0;
             int next = 0;
             boolean limited = limit > 0;
             ArrayList<String> list = new ArrayList<>();
             while ((next = indexOf(ch, off)) != -1) {
                 if (!limited || list.size() < limit - 1) {
                     list.add(substring(off, next));
                     off = next + 1;
                 } else {    // last one
                     //assert (list.size() == limit - 1);
                     int last = length();
                     list.add(substring(off, last));
                     off = last;
                     break;
                 }
             }
             // If no match was found, return this
             if (off == 0)
                 return new String[]{this};
 
             // Add remaining segment
             if (!limited || list.size() < limit)
                 list.add(substring(off, length()));
 
             // Construct result
             int resultSize = list.size();
             if (limit == 0) {
                 while (resultSize > 0 && list.get(resultSize - 1).isEmpty()) {
                     resultSize--;
                 }
             }
             String[] result = new String[resultSize];
             return list.subList(0, resultSize).toArray(result);
         }
         return Pattern.compile(regex).split(this, limit);
     }
 
     /**
      * Splits this string around matches of the given <a
      * href="../util/regex/Pattern.html#sum">regular expression</a>.
      *
      * <p> This method works as if by invoking the two-argument {@link
      * #split(String, int) split} method with the given expression and a limit
      * argument of zero.  Trailing empty strings are therefore not included in
      * the resulting array.
      *
      * <p> The string {@code "boo:and:foo"}, for example, yields the following
      * results with these expressions:
      *
      * <blockquote><table class="plain">
      * <caption style="display:none">Split examples showing regex and result</caption>
      * <thead>
      * <tr>
      *  <th scope="col">Regex</th>
      *  <th scope="col">Result</th>
      * </tr>
      * </thead>
      * <tbody>
      * <tr><th scope="row" style="text-weight:normal">:</th>
      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
      * <tr><th scope="row" style="text-weight:normal">o</th>
      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
      * </tbody>
      * </table></blockquote>
      *
      *
      * @param  regex
      *         the delimiting regular expression
      *
      * @return  the array of strings computed by splitting this string
      *          around matches of the given regular expression
      *
      * @throws  PatternSyntaxException
      *          if the regular expression's syntax is invalid
      *
      * @see java.util.regex.Pattern
      *
      * @since 1.4
      */
     public String[] split(String regex) {
         return split(regex, 0);
     }
 
     /**
      * Returns a new String composed of copies of the
      * {@code CharSequence elements} joined together with a copy of
      * the specified {@code delimiter}.
      *
      * <blockquote>For example,
      * <pre>{@code
      *     String message = String.join("-", "Java", "is", "cool");
      *     // message returned is: "Java-is-cool"
      * }</pre></blockquote>
      *
      * Note that if an element is null, then {@code "null"} is added.
      *
      * @param  delimiter the delimiter that separates each element
      * @param  elements the elements to join together.
      *
      * @return a new {@code String} that is composed of the {@code elements}
      *         separated by the {@code delimiter}
      *
      * @throws NullPointerException If {@code delimiter} or {@code elements}
      *         is {@code null}
      *
      * @see java.util.StringJoiner
      * @since 1.8
      */
     public static String join(CharSequence delimiter, CharSequence... elements) {
-        Objects.requireNonNull(delimiter);
-        Objects.requireNonNull(elements);
-        // Number of elements not likely worth Arrays.stream overhead.
-        StringJoiner joiner = new StringJoiner(delimiter);
-        for (CharSequence cs: elements) {
-            joiner.add(cs);
+        var delim = delimiter.toString();
+        var elems = new String[elements.length];
+        for (int i = 0; i < elements.length; i++) {
+            elems[i] = String.valueOf(elements[i]);
         }
-        return joiner.toString();
+        return join("", "", delim, elems, elems.length);
+    }
+
+    /**
+     * Designated join routine.
+     *
+     * @param prefix the non-null prefix
+     * @param suffix the non-null suffix
+     * @param delimiter the non-null delimiter
+     * @param elements the non-null array of non-null elements
+     * @param size the number of elements in the array (<= elements.length)
+     * @return the joined string
+     */
+    @ForceInline
+    static String join(String prefix, String suffix, String delimiter, String[] elements, int size) {
+        int icoder = prefix.coder() | suffix.coder();
+        long len = (long) prefix.length() + suffix.length();
+        if (size > 1) { // when there are more than one element, size - 1 delimiters will be emitted
+            len += (long) (size - 1) * delimiter.length();
+            icoder |= delimiter.coder();
+        }
+        // assert len > 0L; // max: (long) Integer.MAX_VALUE << 32
+        // following loop wil add max: (long) Integer.MAX_VALUE * Integer.MAX_VALUE to len
+        // so len can overflow at most once
+        for (int i = 0; i < size; i++) {
+            var el = elements[i];
+            len += el.length();
+            icoder |= el.coder();
+        }
+        byte coder = (byte) icoder;
+        // long len overflow check, char -> byte length, int len overflow check
+        if (len < 0L || (len <<= coder) != (int) len) {
+            throw new OutOfMemoryError("Requested string length exceeds VM limit");
+        }
+        byte[] value = StringConcatHelper.newArray(len);
+
+        int off = 0;
+        prefix.getBytes(value, off, coder); off += prefix.length();
+        if (size > 0) {
+            var el = elements[0];
+            el.getBytes(value, off, coder); off += el.length();
+            for (int i = 1; i < size; i++) {
+                delimiter.getBytes(value, off, coder); off += delimiter.length();
+                el = elements[i];
+                el.getBytes(value, off, coder); off += el.length();
+            }
+        }
+        suffix.getBytes(value, off, coder);
+        // assert off + suffix.length() == value.length >> coder;
+
+        return new String(value, coder);
     }
 
     /**
      * Returns a new {@code String} composed of copies of the
      * {@code CharSequence elements} joined together with a copy of the
      * specified {@code delimiter}.
      *
      * <blockquote>For example,
      * <pre>{@code
      *     List<String> strings = List.of("Java", "is", "cool");
      *     String message = String.join(" ", strings);
      *     // message returned is: "Java is cool"
      *
      *     Set<String> strings =
      *         new LinkedHashSet<>(List.of("Java", "is", "very", "cool"));
      *     String message = String.join("-", strings);
      *     // message returned is: "Java-is-very-cool"
      * }</pre></blockquote>
      *
      * Note that if an individual element is {@code null}, then {@code "null"} is added.
      *
      * @param  delimiter a sequence of characters that is used to separate each
      *         of the {@code elements} in the resulting {@code String}
      * @param  elements an {@code Iterable} that will have its {@code elements}
      *         joined together.
      *
      * @return a new {@code String} that is composed from the {@code elements}
      *         argument
      *
      * @throws NullPointerException If {@code delimiter} or {@code elements}
      *         is {@code null}
      *
      * @see    #join(CharSequence,CharSequence...)
      * @see    java.util.StringJoiner
      * @since 1.8
      */
     public static String join(CharSequence delimiter,
             Iterable<? extends CharSequence> elements) {
         Objects.requireNonNull(delimiter);
         Objects.requireNonNull(elements);
-        StringJoiner joiner = new StringJoiner(delimiter);
+        var delim = delimiter.toString();
+        var elems = new String[8];
+        int size = 0;
         for (CharSequence cs: elements) {
-            joiner.add(cs);
+            if (size >= elems.length) {
+                elems = Arrays.copyOf(elems, elems.length << 1);
+            }
+            elems[size++] = String.valueOf(cs);
         }
-        return joiner.toString();
+        return join("", "", delim, elems, size);
     }
 
     /**
      * Converts all of the characters in this {@code String} to lower
      * case using the rules of the given {@code Locale}.  Case mapping is based
      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
-     * class. Since case mappings are not always 1:1 char mappings, the resulting
-     * {@code String} may be a different length than the original {@code String}.
+     * class. Since case mappings are not always 1:1 char mappings, the resulting {@code String}
+     * and this {@code String} may differ in length.
      * <p>
-     * Examples of lowercase  mappings are in the following table:
+     * Examples of lowercase mappings are in the following table:
      * <table class="plain">
      * <caption style="display:none">Lowercase mapping examples showing language code of locale, upper case, lower case, and description</caption>
      * <thead>
      * <tr>
      *   <th scope="col">Language Code of Locale</th>
      *   <th scope="col">Upper Case</th>
      *   <th scope="col">Lower Case</th>
      *   <th scope="col">Description</th>
      * </tr>
      * </thead>
      * <tbody>
      * <tr>
      *   <td>tr (Turkish)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">&#92;u0130</th>
      *   <td>&#92;u0069</td>
      *   <td>capital letter I with dot above -&gt; small letter i</td>
      * </tr>
      * <tr>
      *   <td>tr (Turkish)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">&#92;u0049</th>
      *   <td>&#92;u0131</td>
      *   <td>capital letter I -&gt; small letter dotless i </td>
      * </tr>
      * <tr>
      *   <td>(all)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">French Fries</th>
      *   <td>french fries</td>
      *   <td>lowercased all chars in String</td>
      * </tr>
      * <tr>
      *   <td>(all)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">
      *       &Iota;&Chi;&Theta;&Upsilon;&Sigma;</th>
      *   <td>&iota;&chi;&theta;&upsilon;&sigma;</td>
      *   <td>lowercased all chars in String</td>
      * </tr>
      * </tbody>
      * </table>
      *
      * @param locale use the case transformation rules for this locale
      * @return the {@code String}, converted to lowercase.
      * @see     java.lang.String#toLowerCase()
      * @see     java.lang.String#toUpperCase()
      * @see     java.lang.String#toUpperCase(Locale)
      * @since   1.1
      */
     public String toLowerCase(Locale locale) {
         return isLatin1() ? StringLatin1.toLowerCase(this, value, locale)
                           : StringUTF16.toLowerCase(this, value, locale);
     }
 
     /**
      * Converts all of the characters in this {@code String} to lower
-     * case using the rules of the default locale. This is equivalent to calling
+     * case using the rules of the default locale. This method is equivalent to
      * {@code toLowerCase(Locale.getDefault())}.
      * <p>
      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
      * results if used for strings that are intended to be interpreted locale
      * independently.
      * Examples are programming language identifiers, protocol keys, and HTML
      * tags.
      * For instance, {@code "TITLE".toLowerCase()} in a Turkish locale
      * returns {@code "t\u005Cu0131tle"}, where '\u005Cu0131' is the
      * LATIN SMALL LETTER DOTLESS I character.
      * To obtain correct results for locale insensitive strings, use
      * {@code toLowerCase(Locale.ROOT)}.
      *
      * @return  the {@code String}, converted to lowercase.
      * @see     java.lang.String#toLowerCase(Locale)
      */
     public String toLowerCase() {
         return toLowerCase(Locale.getDefault());
     }
 
     /**
      * Converts all of the characters in this {@code String} to upper
      * case using the rules of the given {@code Locale}. Case mapping is based
      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
-     * class. Since case mappings are not always 1:1 char mappings, the resulting
-     * {@code String} may be a different length than the original {@code String}.
+     * class. Since case mappings are not always 1:1 char mappings, the resulting {@code String}
+     * and this {@code String} may differ in length.
      * <p>
-     * Examples of locale-sensitive and 1:M case mappings are in the following table.
-     *
+     * Examples of locale-sensitive and 1:M case mappings are in the following table:
      * <table class="plain">
      * <caption style="display:none">Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.</caption>
      * <thead>
      * <tr>
      *   <th scope="col">Language Code of Locale</th>
      *   <th scope="col">Lower Case</th>
      *   <th scope="col">Upper Case</th>
      *   <th scope="col">Description</th>
      * </tr>
      * </thead>
      * <tbody>
      * <tr>
      *   <td>tr (Turkish)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">&#92;u0069</th>
      *   <td>&#92;u0130</td>
      *   <td>small letter i -&gt; capital letter I with dot above</td>
      * </tr>
      * <tr>
      *   <td>tr (Turkish)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">&#92;u0131</th>
      *   <td>&#92;u0049</td>
      *   <td>small letter dotless i -&gt; capital letter I</td>
      * </tr>
      * <tr>
      *   <td>(all)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">&#92;u00df</th>
      *   <td>&#92;u0053 &#92;u0053</td>
      *   <td>small letter sharp s -&gt; two letters: SS</td>
      * </tr>
      * <tr>
      *   <td>(all)</td>
      *   <th scope="row" style="font-weight:normal; text-align:left">Fahrvergn&uuml;gen</th>
      *   <td>FAHRVERGN&Uuml;GEN</td>
      *   <td></td>
      * </tr>
      * </tbody>
      * </table>
      * @param locale use the case transformation rules for this locale
      * @return the {@code String}, converted to uppercase.
      * @see     java.lang.String#toUpperCase()
      * @see     java.lang.String#toLowerCase()
      * @see     java.lang.String#toLowerCase(Locale)
      * @since   1.1
      */
     public String toUpperCase(Locale locale) {
         return isLatin1() ? StringLatin1.toUpperCase(this, value, locale)
                           : StringUTF16.toUpperCase(this, value, locale);
     }
 
     /**
      * Converts all of the characters in this {@code String} to upper
      * case using the rules of the default locale. This method is equivalent to
      * {@code toUpperCase(Locale.getDefault())}.
      * <p>
      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
      * results if used for strings that are intended to be interpreted locale
      * independently.
      * Examples are programming language identifiers, protocol keys, and HTML
      * tags.
      * For instance, {@code "title".toUpperCase()} in a Turkish locale
      * returns {@code "T\u005Cu0130TLE"}, where '\u005Cu0130' is the
      * LATIN CAPITAL LETTER I WITH DOT ABOVE character.
      * To obtain correct results for locale insensitive strings, use
      * {@code toUpperCase(Locale.ROOT)}.
      *
      * @return  the {@code String}, converted to uppercase.
      * @see     java.lang.String#toUpperCase(Locale)
      */
     public String toUpperCase() {
         return toUpperCase(Locale.getDefault());
     }
 
     /**
      * Returns a string whose value is this string, with all leading
      * and trailing space removed, where space is defined
      * as any character whose codepoint is less than or equal to
      * {@code 'U+0020'} (the space character).
      * <p>
      * If this {@code String} object represents an empty character
      * sequence, or the first and last characters of character sequence
      * represented by this {@code String} object both have codes
      * that are not space (as defined above), then a
      * reference to this {@code String} object is returned.
      * <p>
      * Otherwise, if all characters in this string are space (as
      * defined above), then a  {@code String} object representing an
      * empty string is returned.
      * <p>
      * Otherwise, let <i>k</i> be the index of the first character in the
      * string whose code is not a space (as defined above) and let
      * <i>m</i> be the index of the last character in the string whose code
      * is not a space (as defined above). A {@code String}
      * object is returned, representing the substring of this string that
      * begins with the character at index <i>k</i> and ends with the
      * character at index <i>m</i>-that is, the result of
      * {@code this.substring(k, m + 1)}.
      * <p>
      * This method may be used to trim space (as defined above) from
      * the beginning and end of a string.
      *
      * @return  a string whose value is this string, with all leading
      *          and trailing space removed, or this string if it
      *          has no leading or trailing space.
      */
     public String trim() {
         String ret = isLatin1() ? StringLatin1.trim(value)
                                 : StringUTF16.trim(value);
         return ret == null ? this : ret;
     }
 
     /**
      * Returns a string whose value is this string, with all leading
      * and trailing {@linkplain Character#isWhitespace(int) white space}
      * removed.
      * <p>
      * If this {@code String} object represents an empty string,
      * or if all code points in this string are
      * {@linkplain Character#isWhitespace(int) white space}, then an empty string
      * is returned.
      * <p>
      * Otherwise, returns a substring of this string beginning with the first
      * code point that is not a {@linkplain Character#isWhitespace(int) white space}
      * up to and including the last code point that is not a
      * {@linkplain Character#isWhitespace(int) white space}.
      * <p>
      * This method may be used to strip
      * {@linkplain Character#isWhitespace(int) white space} from
      * the beginning and end of a string.
      *
      * @return  a string whose value is this string, with all leading
      *          and trailing white space removed
      *
      * @see Character#isWhitespace(int)
      *
      * @since 11
      */
     public String strip() {
         String ret = isLatin1() ? StringLatin1.strip(value)
                                 : StringUTF16.strip(value);
         return ret == null ? this : ret;
     }
 
     /**
      * Returns a string whose value is this string, with all leading
      * {@linkplain Character#isWhitespace(int) white space} removed.
      * <p>
      * If this {@code String} object represents an empty string,
      * or if all code points in this string are
      * {@linkplain Character#isWhitespace(int) white space}, then an empty string
      * is returned.
      * <p>
      * Otherwise, returns a substring of this string beginning with the first
      * code point that is not a {@linkplain Character#isWhitespace(int) white space}
      * up to and including the last code point of this string.
      * <p>
      * This method may be used to trim
      * {@linkplain Character#isWhitespace(int) white space} from
      * the beginning of a string.
      *
      * @return  a string whose value is this string, with all leading white
      *          space removed
      *
      * @see Character#isWhitespace(int)
      *
      * @since 11
      */
     public String stripLeading() {
         String ret = isLatin1() ? StringLatin1.stripLeading(value)
                                 : StringUTF16.stripLeading(value);
         return ret == null ? this : ret;
     }
 
     /**
      * Returns a string whose value is this string, with all trailing
      * {@linkplain Character#isWhitespace(int) white space} removed.
      * <p>
      * If this {@code String} object represents an empty string,
      * or if all characters in this string are
      * {@linkplain Character#isWhitespace(int) white space}, then an empty string
      * is returned.
      * <p>
      * Otherwise, returns a substring of this string beginning with the first
      * code point of this string up to and including the last code point
      * that is not a {@linkplain Character#isWhitespace(int) white space}.
      * <p>
      * This method may be used to trim
      * {@linkplain Character#isWhitespace(int) white space} from
      * the end of a string.
      *
      * @return  a string whose value is this string, with all trailing white
      *          space removed
      *
      * @see Character#isWhitespace(int)
      *
      * @since 11
      */
     public String stripTrailing() {
         String ret = isLatin1() ? StringLatin1.stripTrailing(value)
                                 : StringUTF16.stripTrailing(value);
         return ret == null ? this : ret;
     }
 
     /**
      * Returns {@code true} if the string is empty or contains only
      * {@linkplain Character#isWhitespace(int) white space} codepoints,
      * otherwise {@code false}.
      *
      * @return {@code true} if the string is empty or contains only
      *         {@linkplain Character#isWhitespace(int) white space} codepoints,
      *         otherwise {@code false}
      *
      * @see Character#isWhitespace(int)
      *
      * @since 11
      */
     public boolean isBlank() {
         return indexOfNonWhitespace() == length();
     }
 
     /**
      * Returns a stream of lines extracted from this string,
      * separated by line terminators.
      * <p>
      * A <i>line terminator</i> is one of the following:
      * a line feed character {@code "\n"} (U+000A),
      * a carriage return character {@code "\r"} (U+000D),
      * or a carriage return followed immediately by a line feed
      * {@code "\r\n"} (U+000D U+000A).
      * <p>
      * A <i>line</i> is either a sequence of zero or more characters
      * followed by a line terminator, or it is a sequence of one or
      * more characters followed by the end of the string. A
      * line does not include the line terminator.
      * <p>
      * The stream returned by this method contains the lines from
      * this string in the order in which they occur.
      *
      * @apiNote This definition of <i>line</i> implies that an empty
      *          string has zero lines and that there is no empty line
      *          following a line terminator at the end of a string.
      *
      * @implNote This method provides better performance than
      *           split("\R") by supplying elements lazily and
      *           by faster search of new line terminators.
      *
      * @return  the stream of lines extracted from this string
      *
      * @since 11
      */
     public Stream<String> lines() {
         return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
     }
 
     /**
      * Adjusts the indentation of each line of this string based on the value of
      * {@code n}, and normalizes line termination characters.
      * <p>
      * This string is conceptually separated into lines using
      * {@link String#lines()}. Each line is then adjusted as described below
      * and then suffixed with a line feed {@code "\n"} (U+000A). The resulting
      * lines are then concatenated and returned.
      * <p>
      * If {@code n > 0} then {@code n} spaces (U+0020) are inserted at the
      * beginning of each line.
      * <p>
      * If {@code n < 0} then up to {@code n}
      * {@linkplain Character#isWhitespace(int) white space characters} are removed
      * from the beginning of each line. If a given line does not contain
      * sufficient white space then all leading
      * {@linkplain Character#isWhitespace(int) white space characters} are removed.
      * Each white space character is treated as a single character. In
      * particular, the tab character {@code "\t"} (U+0009) is considered a
      * single character; it is not expanded.
      * <p>
      * If {@code n == 0} then the line remains unchanged. However, line
      * terminators are still normalized.
      *
      * @param n  number of leading
      *           {@linkplain Character#isWhitespace(int) white space characters}
      *           to add or remove
      *
      * @return string with indentation adjusted and line endings normalized
      *
      * @see String#lines()
      * @see String#isBlank()
      * @see Character#isWhitespace(int)
      *
      * @since 12
      */
     public String indent(int n) {
         if (isEmpty()) {
             return "";
         }
         Stream<String> stream = lines();
         if (n > 0) {
             final String spaces = " ".repeat(n);
             stream = stream.map(s -> spaces + s);
         } else if (n == Integer.MIN_VALUE) {
             stream = stream.map(s -> s.stripLeading());
         } else if (n < 0) {
             stream = stream.map(s -> s.substring(Math.min(-n, s.indexOfNonWhitespace())));
         }
         return stream.collect(Collectors.joining("\n", "", "\n"));
     }
 
     private int indexOfNonWhitespace() {
         return isLatin1() ? StringLatin1.indexOfNonWhitespace(value)
                           : StringUTF16.indexOfNonWhitespace(value);
     }
 
     private int lastIndexOfNonWhitespace() {
         return isLatin1() ? StringLatin1.lastIndexOfNonWhitespace(value)
                           : StringUTF16.lastIndexOfNonWhitespace(value);
     }
 
     /**
      * Returns a string whose value is this string, with incidental
      * {@linkplain Character#isWhitespace(int) white space} removed from
      * the beginning and end of every line.
      * <p>
      * Incidental {@linkplain Character#isWhitespace(int) white space}
      * is often present in a text block to align the content with the opening
      * delimiter. For example, in the following code, dots represent incidental
      * {@linkplain Character#isWhitespace(int) white space}:
      * <blockquote><pre>
      * String html = """
      * ..............&lt;html&gt;
      * ..............    &lt;body&gt;
      * ..............        &lt;p&gt;Hello, world&lt;/p&gt;
      * ..............    &lt;/body&gt;
      * ..............&lt;/html&gt;
      * ..............""";
      * </pre></blockquote>
      * This method treats the incidental
      * {@linkplain Character#isWhitespace(int) white space} as indentation to be
      * stripped, producing a string that preserves the relative indentation of
      * the content. Using | to visualize the start of each line of the string:
      * <blockquote><pre>
      * |&lt;html&gt;
      * |    &lt;body&gt;
      * |        &lt;p&gt;Hello, world&lt;/p&gt;
      * |    &lt;/body&gt;
      * |&lt;/html&gt;
      * </pre></blockquote>
      * First, the individual lines of this string are extracted. A <i>line</i>
      * is a sequence of zero or more characters followed by either a line
      * terminator or the end of the string.
      * If the string has at least one line terminator, the last line consists
      * of the characters between the last terminator and the end of the string.
      * Otherwise, if the string has no terminators, the last line is the start
      * of the string to the end of the string, in other words, the entire
      * string.
      * A line does not include the line terminator.
      * <p>
      * Then, the <i>minimum indentation</i> (min) is determined as follows:
      * <ul>
      *   <li><p>For each non-blank line (as defined by {@link String#isBlank()}),
      *   the leading {@linkplain Character#isWhitespace(int) white space}
      *   characters are counted.</p>
      *   </li>
      *   <li><p>The leading {@linkplain Character#isWhitespace(int) white space}
      *   characters on the last line are also counted even if
      *   {@linkplain String#isBlank() blank}.</p>
      *   </li>
      * </ul>
      * <p>The <i>min</i> value is the smallest of these counts.
      * <p>
      * For each {@linkplain String#isBlank() non-blank} line, <i>min</i> leading
      * {@linkplain Character#isWhitespace(int) white space} characters are
      * removed, and any trailing {@linkplain Character#isWhitespace(int) white
      * space} characters are removed. {@linkplain String#isBlank() Blank} lines
      * are replaced with the empty string.
      *
      * <p>
      * Finally, the lines are joined into a new string, using the LF character
      * {@code "\n"} (U+000A) to separate lines.
      *
      * @apiNote
      * This method's primary purpose is to shift a block of lines as far as
      * possible to the left, while preserving relative indentation. Lines
      * that were indented the least will thus have no leading
      * {@linkplain Character#isWhitespace(int) white space}.
      * The result will have the same number of line terminators as this string.
      * If this string ends with a line terminator then the result will end
      * with a line terminator.
      *
      * @implSpec
      * This method treats all {@linkplain Character#isWhitespace(int) white space}
      * characters as having equal width. As long as the indentation on every
      * line is consistently composed of the same character sequences, then the
      * result will be as described above.
      *
      * @return string with incidental indentation removed and line
      *         terminators normalized
      *
      * @see String#lines()
      * @see String#isBlank()
      * @see String#indent(int)
      * @see Character#isWhitespace(int)
      *
      * @since 15
      *
      */
     public String stripIndent() {
         int length = length();
         if (length == 0) {
             return "";
         }
         char lastChar = charAt(length - 1);
         boolean optOut = lastChar == '\n' || lastChar == '\r';
-        List<String> lines = lines().collect(Collectors.toList());
+        List<String> lines = lines().toList();
         final int outdent = optOut ? 0 : outdent(lines);
         return lines.stream()
             .map(line -> {
                 int firstNonWhitespace = line.indexOfNonWhitespace();
                 int lastNonWhitespace = line.lastIndexOfNonWhitespace();
                 int incidentalWhitespace = Math.min(outdent, firstNonWhitespace);
                 return firstNonWhitespace > lastNonWhitespace
                     ? "" : line.substring(incidentalWhitespace, lastNonWhitespace);
             })
             .collect(Collectors.joining("\n", "", optOut ? "\n" : ""));
     }
 
     private static int outdent(List<String> lines) {
         // Note: outdent is guaranteed to be zero or positive number.
         // If there isn't a non-blank line then the last must be blank
         int outdent = Integer.MAX_VALUE;
         for (String line : lines) {
             int leadingWhitespace = line.indexOfNonWhitespace();
             if (leadingWhitespace != line.length()) {
                 outdent = Integer.min(outdent, leadingWhitespace);
             }
         }
         String lastLine = lines.get(lines.size() - 1);
         if (lastLine.isBlank()) {
             outdent = Integer.min(outdent, lastLine.length());
         }
         return outdent;
     }
 
     /**
      * Returns a string whose value is this string, with escape sequences
      * translated as if in a string literal.
      * <p>
      * Escape sequences are translated as follows;
      * <table class="striped">
      *   <caption style="display:none">Translation</caption>
      *   <thead>
      *   <tr>
      *     <th scope="col">Escape</th>
      *     <th scope="col">Name</th>
      *     <th scope="col">Translation</th>
      *   </tr>
      *   </thead>
      *   <tbody>
      *   <tr>
      *     <th scope="row">{@code \u005Cb}</th>
      *     <td>backspace</td>
      *     <td>{@code U+0008}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005Ct}</th>
      *     <td>horizontal tab</td>
      *     <td>{@code U+0009}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005Cn}</th>
      *     <td>line feed</td>
      *     <td>{@code U+000A}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005Cf}</th>
      *     <td>form feed</td>
      *     <td>{@code U+000C}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005Cr}</th>
      *     <td>carriage return</td>
      *     <td>{@code U+000D}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005Cs}</th>
      *     <td>space</td>
      *     <td>{@code U+0020}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005C"}</th>
      *     <td>double quote</td>
      *     <td>{@code U+0022}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005C'}</th>
      *     <td>single quote</td>
      *     <td>{@code U+0027}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005C\u005C}</th>
      *     <td>backslash</td>
      *     <td>{@code U+005C}</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005C0 - \u005C377}</th>
      *     <td>octal escape</td>
      *     <td>code point equivalents</td>
      *   </tr>
      *   <tr>
      *     <th scope="row">{@code \u005C<line-terminator>}</th>
      *     <td>continuation</td>
      *     <td>discard</td>
      *   </tr>
      *   </tbody>
      * </table>
      *
      * @implNote
      * This method does <em>not</em> translate Unicode escapes such as "{@code \u005cu2022}".
      * Unicode escapes are translated by the Java compiler when reading input characters and
      * are not part of the string literal specification.
      *
      * @throws IllegalArgumentException when an escape sequence is malformed.
      *
      * @return String with escape sequences translated.
      *
      * @jls 3.10.7 Escape Sequences
      *
      * @since 15
      */
     public String translateEscapes() {
         if (isEmpty()) {
             return "";
         }
         char[] chars = toCharArray();
         int length = chars.length;
         int from = 0;
         int to = 0;
         while (from < length) {
             char ch = chars[from++];
             if (ch == '\\') {
                 ch = from < length ? chars[from++] : '\0';
                 switch (ch) {
                 case 'b':
                     ch = '\b';
                     break;
                 case 'f':
                     ch = '\f';
                     break;
                 case 'n':
                     ch = '\n';
                     break;
                 case 'r':
                     ch = '\r';
                     break;
                 case 's':
                     ch = ' ';
                     break;
                 case 't':
                     ch = '\t';
                     break;
                 case '\'':
                 case '\"':
                 case '\\':
                     // as is
                     break;
                 case '0': case '1': case '2': case '3':
                 case '4': case '5': case '6': case '7':
                     int limit = Integer.min(from + (ch <= '3' ? 2 : 1), length);
                     int code = ch - '0';
                     while (from < limit) {
                         ch = chars[from];
                         if (ch < '0' || '7' < ch) {
                             break;
                         }
                         from++;
                         code = (code << 3) | (ch - '0');
                     }
                     ch = (char)code;
                     break;
                 case '\n':
                     continue;
                 case '\r':
                     if (from < length && chars[from] == '\n') {
                         from++;
                     }
                     continue;
                 default: {
                     String msg = String.format(
                         "Invalid escape sequence: \\%c \\\\u%04X",
                         ch, (int)ch);
                     throw new IllegalArgumentException(msg);
                 }
                 }
             }
 
             chars[to++] = ch;
         }
 
         return new String(chars, 0, to);
     }
 
     /**
      * This method allows the application of a function to {@code this}
      * string. The function should expect a single String argument
      * and produce an {@code R} result.
      * <p>
      * Any exception thrown by {@code f.apply()} will be propagated to the
      * caller.
      *
      * @param f    a function to apply
      *
      * @param <R>  the type of the result
      *
      * @return     the result of applying the function to this string
      *
      * @see java.util.function.Function
      *
      * @since 12
      */
     public <R> R transform(Function<? super String, ? extends R> f) {
         return f.apply(this);
     }
 
     /**
      * This object (which is already a string!) is itself returned.
      *
      * @return  the string itself.
      */
     public String toString() {
         return this;
     }
 
     /**
      * Returns a stream of {@code int} zero-extending the {@code char} values
      * from this sequence.  Any char which maps to a <a
      * href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate code
      * point</a> is passed through uninterpreted.
      *
      * @return an IntStream of char values from this sequence
      * @since 9
      */
     @Override
     public IntStream chars() {
         return StreamSupport.intStream(
             isLatin1() ? new StringLatin1.CharsSpliterator(value, Spliterator.IMMUTABLE)
                        : new StringUTF16.CharsSpliterator(value, Spliterator.IMMUTABLE),
             false);
     }
 
 
     /**
      * Returns a stream of code point values from this sequence.  Any surrogate
      * pairs encountered in the sequence are combined as if by {@linkplain
      * Character#toCodePoint Character.toCodePoint} and the result is passed
      * to the stream. Any other code units, including ordinary BMP characters,
      * unpaired surrogates, and undefined code units, are zero-extended to
      * {@code int} values which are then passed to the stream.
      *
      * @return an IntStream of Unicode code points from this sequence
      * @since 9
      */
     @Override
     public IntStream codePoints() {
         return StreamSupport.intStream(
             isLatin1() ? new StringLatin1.CharsSpliterator(value, Spliterator.IMMUTABLE)
                        : new StringUTF16.CodePointsSpliterator(value, Spliterator.IMMUTABLE),
             false);
     }
 
     /**
      * Converts this string to a new character array.
      *
      * @return  a newly allocated character array whose length is the length
      *          of this string and whose contents are initialized to contain
      *          the character sequence represented by this string.
      */
     public char[] toCharArray() {
         return isLatin1() ? StringLatin1.toChars(value)
                           : StringUTF16.toChars(value);
     }
 
     /**
      * Returns a formatted string using the specified format string and
      * arguments.
      *
      * <p> The locale always used is the one returned by {@link
      * java.util.Locale#getDefault(java.util.Locale.Category)
      * Locale.getDefault(Locale.Category)} with
      * {@link java.util.Locale.Category#FORMAT FORMAT} category specified.
      *
      * @param  format
      *         A <a href="../util/Formatter.html#syntax">format string</a>
      *
      * @param  args
      *         Arguments referenced by the format specifiers in the format
      *         string.  If there are more arguments than format specifiers, the
      *         extra arguments are ignored.  The number of arguments is
      *         variable and may be zero.  The maximum number of arguments is
      *         limited by the maximum dimension of a Java array as defined by
      *         <cite>The Java Virtual Machine Specification</cite>.
      *         The behaviour on a
      *         {@code null} argument depends on the <a
      *         href="../util/Formatter.html#syntax">conversion</a>.
      *
      * @throws  java.util.IllegalFormatException
      *          If a format string contains an illegal syntax, a format
      *          specifier that is incompatible with the given arguments,
      *          insufficient arguments given the format string, or other
      *          illegal conditions.  For specification of all possible
      *          formatting errors, see the <a
      *          href="../util/Formatter.html#detail">Details</a> section of the
      *          formatter class specification.
      *
      * @return  A formatted string
      *
      * @see  java.util.Formatter
      * @since  1.5
      */
     public static String format(String format, Object... args) {
         return new Formatter().format(format, args).toString();
     }
 
     /**
      * Returns a formatted string using the specified locale, format string,
      * and arguments.
      *
      * @param  l
      *         The {@linkplain java.util.Locale locale} to apply during
      *         formatting.  If {@code l} is {@code null} then no localization
      *         is applied.
      *
      * @param  format
      *         A <a href="../util/Formatter.html#syntax">format string</a>
      *
      * @param  args
      *         Arguments referenced by the format specifiers in the format
      *         string.  If there are more arguments than format specifiers, the
      *         extra arguments are ignored.  The number of arguments is
      *         variable and may be zero.  The maximum number of arguments is
      *         limited by the maximum dimension of a Java array as defined by
      *         <cite>The Java Virtual Machine Specification</cite>.
      *         The behaviour on a
      *         {@code null} argument depends on the
      *         <a href="../util/Formatter.html#syntax">conversion</a>.
      *
      * @throws  java.util.IllegalFormatException
      *          If a format string contains an illegal syntax, a format
      *          specifier that is incompatible with the given arguments,
      *          insufficient arguments given the format string, or other
      *          illegal conditions.  For specification of all possible
      *          formatting errors, see the <a
      *          href="../util/Formatter.html#detail">Details</a> section of the
      *          formatter class specification
      *
      * @return  A formatted string
      *
      * @see  java.util.Formatter
      * @since  1.5
      */
     public static String format(Locale l, String format, Object... args) {
         return new Formatter(l).format(format, args).toString();
     }
 
     /**
      * Formats using this string as the format string, and the supplied
      * arguments.
      *
      * @implSpec This method is equivalent to {@code String.format(this, args)}.
      *
      * @param  args
      *         Arguments referenced by the format specifiers in this string.
      *
      * @return  A formatted string
      *
      * @see  java.lang.String#format(String,Object...)
      * @see  java.util.Formatter
      *
      * @since 15
      *
      */
     public String formatted(Object... args) {
         return new Formatter().format(this, args).toString();
     }
 
     /**
      * Returns the string representation of the {@code Object} argument.
      *
      * @param   obj   an {@code Object}.
      * @return  if the argument is {@code null}, then a string equal to
      *          {@code "null"}; otherwise, the value of
      *          {@code obj.toString()} is returned.
      * @see     java.lang.Object#toString()
      */
     public static String valueOf(Object obj) {
         return (obj == null) ? "null" : obj.toString();
     }
 
     /**
      * Returns the string representation of the {@code char} array
      * argument. The contents of the character array are copied; subsequent
      * modification of the character array does not affect the returned
      * string.
      *
      * @param   data     the character array.
      * @return  a {@code String} that contains the characters of the
      *          character array.
      */
-    public static String valueOf(char data[]) {
+    public static String valueOf(char[] data) {
         return new String(data);
     }
 
     /**
      * Returns the string representation of a specific subarray of the
      * {@code char} array argument.
      * <p>
      * The {@code offset} argument is the index of the first
      * character of the subarray. The {@code count} argument
      * specifies the length of the subarray. The contents of the subarray
      * are copied; subsequent modification of the character array does not
      * affect the returned string.
      *
      * @param   data     the character array.
      * @param   offset   initial offset of the subarray.
      * @param   count    length of the subarray.
      * @return  a {@code String} that contains the characters of the
      *          specified subarray of the character array.
      * @throws    IndexOutOfBoundsException if {@code offset} is
      *          negative, or {@code count} is negative, or
      *          {@code offset+count} is larger than
      *          {@code data.length}.
      */
-    public static String valueOf(char data[], int offset, int count) {
+    public static String valueOf(char[] data, int offset, int count) {
         return new String(data, offset, count);
     }
 
     /**
      * Equivalent to {@link #valueOf(char[], int, int)}.
      *
      * @param   data     the character array.
      * @param   offset   initial offset of the subarray.
      * @param   count    length of the subarray.
      * @return  a {@code String} that contains the characters of the
      *          specified subarray of the character array.
      * @throws    IndexOutOfBoundsException if {@code offset} is
      *          negative, or {@code count} is negative, or
      *          {@code offset+count} is larger than
      *          {@code data.length}.
      */
-    public static String copyValueOf(char data[], int offset, int count) {
+    public static String copyValueOf(char[] data, int offset, int count) {
         return new String(data, offset, count);
     }
 
     /**
      * Equivalent to {@link #valueOf(char[])}.
      *
      * @param   data   the character array.
      * @return  a {@code String} that contains the characters of the
      *          character array.
      */
-    public static String copyValueOf(char data[]) {
+    public static String copyValueOf(char[] data) {
         return new String(data);
     }
 
     /**
      * Returns the string representation of the {@code boolean} argument.
      *
      * @param   b   a {@code boolean}.
      * @return  if the argument is {@code true}, a string equal to
      *          {@code "true"} is returned; otherwise, a string equal to
      *          {@code "false"} is returned.
      */
     public static String valueOf(boolean b) {
         return b ? "true" : "false";
     }
 
     /**
      * Returns the string representation of the {@code char}
      * argument.
      *
      * @param   c   a {@code char}.
      * @return  a string of length {@code 1} containing
      *          as its single character the argument {@code c}.
      */
     public static String valueOf(char c) {
         if (COMPACT_STRINGS && StringLatin1.canEncode(c)) {
             return new String(StringLatin1.toBytes(c), LATIN1);
         }
         return new String(StringUTF16.toBytes(c), UTF16);
     }
 
     /**
      * Returns the string representation of the {@code int} argument.
      * <p>
      * The representation is exactly the one returned by the
      * {@code Integer.toString} method of one argument.
      *
      * @param   i   an {@code int}.
      * @return  a string representation of the {@code int} argument.
      * @see     java.lang.Integer#toString(int, int)
      */
     public static String valueOf(int i) {
         return Integer.toString(i);
     }
 
     /**
      * Returns the string representation of the {@code long} argument.
      * <p>
      * The representation is exactly the one returned by the
      * {@code Long.toString} method of one argument.
      *
      * @param   l   a {@code long}.
      * @return  a string representation of the {@code long} argument.
      * @see     java.lang.Long#toString(long)
      */
     public static String valueOf(long l) {
         return Long.toString(l);
     }
 
     /**
      * Returns the string representation of the {@code float} argument.
      * <p>
      * The representation is exactly the one returned by the
      * {@code Float.toString} method of one argument.
      *
      * @param   f   a {@code float}.
      * @return  a string representation of the {@code float} argument.
      * @see     java.lang.Float#toString(float)
      */
     public static String valueOf(float f) {
         return Float.toString(f);
     }
 
     /**
      * Returns the string representation of the {@code double} argument.
      * <p>
      * The representation is exactly the one returned by the
      * {@code Double.toString} method of one argument.
      *
      * @param   d   a {@code double}.
      * @return  a  string representation of the {@code double} argument.
      * @see     java.lang.Double#toString(double)
      */
     public static String valueOf(double d) {
         return Double.toString(d);
     }
 
     /**
      * Returns a canonical representation for the string object.
      * <p>
      * A pool of strings, initially empty, is maintained privately by the
      * class {@code String}.
      * <p>
      * When the intern method is invoked, if the pool already contains a
      * string equal to this {@code String} object as determined by
      * the {@link #equals(Object)} method, then the string from the pool is
      * returned. Otherwise, this {@code String} object is added to the
      * pool and a reference to this {@code String} object is returned.
      * <p>
      * It follows that for any two strings {@code s} and {@code t},
      * {@code s.intern() == t.intern()} is {@code true}
      * if and only if {@code s.equals(t)} is {@code true}.
      * <p>
      * All literal strings and string-valued constant expressions are
      * interned. String literals are defined in section {@jls 3.10.5} of the
      * <cite>The Java Language Specification</cite>.
      *
      * @return  a string that has the same contents as this string, but is
      *          guaranteed to be from a pool of unique strings.
      */
     public native String intern();
 
     /**
      * Returns a string whose value is the concatenation of this
      * string repeated {@code count} times.
      * <p>
      * If this string is empty or count is zero then the empty
      * string is returned.
      *
      * @param   count number of times to repeat
      *
      * @return  A string composed of this string repeated
      *          {@code count} times or the empty string if this
      *          string is empty or count is zero
      *
      * @throws  IllegalArgumentException if the {@code count} is
      *          negative.
      *
      * @since 11
      */
     public String repeat(int count) {
         if (count < 0) {
             throw new IllegalArgumentException("count is negative: " + count);
         }
         if (count == 1) {
             return this;
         }
         final int len = value.length;
         if (len == 0 || count == 0) {
             return "";
         }
         if (Integer.MAX_VALUE / count < len) {
             throw new OutOfMemoryError("Required length exceeds implementation limit");
         }
         if (len == 1) {
             final byte[] single = new byte[count];
             Arrays.fill(single, value[0]);
             return new String(single, coder);
         }
         final int limit = len * count;
         final byte[] multiple = new byte[limit];
         System.arraycopy(value, 0, multiple, 0, len);
         int copied = len;
         for (; copied < limit - copied; copied <<= 1) {
             System.arraycopy(multiple, 0, multiple, copied, copied);
         }
         System.arraycopy(multiple, 0, multiple, copied, limit - copied);
         return new String(multiple, coder);
     }
 
     ////////////////////////////////////////////////////////////////
 
     /**
      * Copy character bytes from this string into dst starting at dstBegin.
      * This method doesn't perform any range checking.
      *
      * Invoker guarantees: dst is in UTF16 (inflate itself for asb), if two
      * coders are different, and dst is big enough (range check)
      *
      * @param dstBegin  the char index, not offset of byte[]
      * @param coder     the coder of dst[]
      */
     void getBytes(byte[] dst, int dstBegin, byte coder) {
         if (coder() == coder) {
             System.arraycopy(value, 0, dst, dstBegin << coder, value.length);
         } else {    // this.coder == LATIN && coder == UTF16
             StringLatin1.inflate(value, 0, dst, dstBegin, value.length);
         }
     }
 
     /**
      * Copy character bytes from this string into dst starting at dstBegin.
      * This method doesn't perform any range checking.
      *
      * Invoker guarantees: dst is in UTF16 (inflate itself for asb), if two
      * coders are different, and dst is big enough (range check)
      *
      * @param srcPos    the char index, not offset of byte[]
      * @param dstBegin  the char index to start from
      * @param coder     the coder of dst[]
      * @param length    the amount of copied chars
      */
     void getBytes(byte[] dst, int srcPos, int dstBegin, byte coder, int length) {
         if (coder() == coder) {
             System.arraycopy(value, srcPos << coder, dst, dstBegin << coder, length << coder);
         } else {    // this.coder == LATIN && coder == UTF16
             StringLatin1.inflate(value, srcPos, dst, dstBegin, length);
         }
     }
 
     /*
      * Package private constructor. Trailing Void argument is there for
      * disambiguating it against other (public) constructors.
      *
      * Stores the char[] value into a byte[] that each byte represents
      * the8 low-order bits of the corresponding character, if the char[]
      * contains only latin1 character. Or a byte[] that stores all
      * characters in their byte sequences defined by the {@code StringUTF16}.
      */
     String(char[] value, int off, int len, Void sig) {
         if (len == 0) {
             this.value = "".value;
             this.coder = "".coder;
             return;
         }
         if (COMPACT_STRINGS) {
             byte[] val = StringUTF16.compress(value, off, len);
             if (val != null) {
                 this.value = val;
                 this.coder = LATIN1;
                 return;
             }
         }
         this.coder = UTF16;
         this.value = StringUTF16.toBytes(value, off, len);
     }
 
     /*
      * Package private constructor. Trailing Void argument is there for
      * disambiguating it against other (public) constructors.
      */
     String(AbstractStringBuilder asb, Void sig) {
         byte[] val = asb.getValue();
         int length = asb.length();
         if (asb.isLatin1()) {
             this.coder = LATIN1;
             this.value = Arrays.copyOfRange(val, 0, length);
         } else {
             if (COMPACT_STRINGS) {
                 byte[] buf = StringUTF16.compress(val, 0, length);
                 if (buf != null) {
                     this.coder = LATIN1;
                     this.value = buf;
                     return;
                 }
             }
             this.coder = UTF16;
             this.value = Arrays.copyOfRange(val, 0, length << 1);
         }
     }
 
    /*
     * Package private constructor which shares value array for speed.
     */
     String(byte[] value, byte coder) {
         this.value = value;
         this.coder = coder;
     }
 
     byte coder() {
         return COMPACT_STRINGS ? coder : UTF16;
     }
 
     byte[] value() {
         return value;
     }
 
     boolean isLatin1() {
         return COMPACT_STRINGS && coder == LATIN1;
     }
 
     @Native static final byte LATIN1 = 0;
     @Native static final byte UTF16  = 1;
 
     /*
      * StringIndexOutOfBoundsException  if {@code index} is
      * negative or greater than or equal to {@code length}.
      */
     static void checkIndex(int index, int length) {
-        if (index < 0 || index >= length) {
-            throw new StringIndexOutOfBoundsException("index " + index +
-                                                      ", length " + length);
-        }
+        Preconditions.checkIndex(index, length, Preconditions.SIOOBE_FORMATTER);
     }
 
     /*
      * StringIndexOutOfBoundsException  if {@code offset}
      * is negative or greater than {@code length}.
      */
     static void checkOffset(int offset, int length) {
-        if (offset < 0 || offset > length) {
-            throw new StringIndexOutOfBoundsException("offset " + offset +
-                                                      ", length " + length);
-        }
+        Preconditions.checkFromToIndex(offset, length, length, Preconditions.SIOOBE_FORMATTER);
     }
 
     /*
      * Check {@code offset}, {@code count} against {@code 0} and {@code length}
      * bounds.
      *
      * @throws  StringIndexOutOfBoundsException
      *          If {@code offset} is negative, {@code count} is negative,
      *          or {@code offset} is greater than {@code length - count}
      */
     static void checkBoundsOffCount(int offset, int count, int length) {
-        if (offset < 0 || count < 0 || offset > length - count) {
-            throw new StringIndexOutOfBoundsException(
-                "offset " + offset + ", count " + count + ", length " + length);
-        }
+        Preconditions.checkFromIndexSize(offset, count, length, Preconditions.SIOOBE_FORMATTER);
     }
 
     /*
      * Check {@code begin}, {@code end} against {@code 0} and {@code length}
      * bounds.
      *
      * @throws  StringIndexOutOfBoundsException
      *          If {@code begin} is negative, {@code begin} is greater than
      *          {@code end}, or {@code end} is greater than {@code length}.
      */
     static void checkBoundsBeginEnd(int begin, int end, int length) {
-        if (begin < 0 || begin > end || end > length) {
-            throw new StringIndexOutOfBoundsException(
-                "begin " + begin + ", end " + end + ", length " + length);
-        }
+        Preconditions.checkFromToIndex(begin, end, length, Preconditions.SIOOBE_FORMATTER);
     }
 
     /**
      * Returns the string representation of the {@code codePoint}
      * argument.
      *
      * @param   codePoint a {@code codePoint}.
      * @return  a string of length {@code 1} or {@code 2} containing
      *          as its single character the argument {@code codePoint}.
      * @throws IllegalArgumentException if the specified
      *          {@code codePoint} is not a {@linkplain Character#isValidCodePoint
      *          valid Unicode code point}.
      */
     static String valueOfCodePoint(int codePoint) {
         if (COMPACT_STRINGS && StringLatin1.canEncode(codePoint)) {
             return new String(StringLatin1.toBytes((char)codePoint), LATIN1);
         } else if (Character.isBmpCodePoint(codePoint)) {
             return new String(StringUTF16.toBytes((char)codePoint), UTF16);
         } else if (Character.isSupplementaryCodePoint(codePoint)) {
             return new String(StringUTF16.toBytesSupplementary(codePoint), UTF16);
         }
 
         throw new IllegalArgumentException(
             format("Not a valid Unicode code point: 0x%X", codePoint));
     }
 
     /**
      * Returns an {@link Optional} containing the nominal descriptor for this
      * instance, which is the instance itself.
      *
      * @return an {@link Optional} describing the {@linkplain String} instance
      * @since 12
      */
     @Override
     public Optional<String> describeConstable() {
         return Optional.of(this);
     }
 
     /**
      * Resolves this instance as a {@link ConstantDesc}, the result of which is
      * the instance itself.
      *
      * @param lookup ignored
      * @return the {@linkplain String} instance
      * @since 12
      */
     @Override
     public String resolveConstantDesc(MethodHandles.Lookup lookup) {
         return this;
     }
 
 }