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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package java.lang;

import sun.misc.FloatingDecimal;
import java.util.Arrays;

A mutable sequence of characters.

Implements a modifiable string. At any point in time it contains some
particular sequence of characters, but the length and content of the
sequence can be changed through certain method calls.
Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown. 
Author:
     Michael McCloskey,      Martin Buchholz,      Ulf Zibis
Since:
      1.5/**
 * A mutable sequence of characters.
 * <p>
 * Implements a modifiable string. At any point in time it contains some
 * particular sequence of characters, but the length and content of the
 * sequence can be changed through certain method calls.
 *
 * <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.
 *
 * @author      Michael McCloskey
 * @author      Martin Buchholz
 * @author      Ulf Zibis
 * @since       1.5
 */
abstract class AbstractStringBuilder implements Appendable, CharSequence {
    
The value is used for character storage.
/**
     * The value is used for character storage.
     */
    char[] value;

    
The count is the number of characters used.
/**
     * The count is the number of characters used.
     */
    int count;

    
This no-arg constructor is necessary for serialization of subclasses.
/**
     * This no-arg constructor is necessary for serialization of subclasses.
     */
    AbstractStringBuilder() {
    }

    
Creates an AbstractStringBuilder of the specified capacity.
/**
     * Creates an AbstractStringBuilder of the specified capacity.
     */
    AbstractStringBuilder(int capacity) {
        value = new char[capacity];
    }

    
Returns the length (character count).
Returns:
 the length of the sequence of characters currently
         represented by this object/**
     * Returns the length (character count).
     *
     * @return  the length of the sequence of characters currently
     *          represented by this object
     */
    @Override
    public int length() {
        return count;
    }

    
Returns the current capacity. The capacity is the amount of storage
available for newly inserted characters, beyond which an allocation
will occur.
Returns:
 the current capacity/**
     * Returns the current capacity. The capacity is the amount of storage
     * available for newly inserted characters, beyond which an allocation
     * will occur.
     *
     * @return  the current capacity
     */
    public int capacity() {
        return value.length;
    }

    
Ensures that the capacity is at least equal to the specified minimum.
If the current capacity is less than the argument, then a new internal
array is allocated with greater capacity. The new capacity is the
larger of:

The minimumCapacity argument. 
Twice the old capacity, plus 2. 
 If the minimumCapacity argument is nonpositive, this method takes no action and simply returns. Note that subsequent operations on this object can reduce the actual capacity below that requested here. 
Params:
minimumCapacity –   the minimum desired capacity./**
     * Ensures that the capacity is at least equal to the specified minimum.
     * If the current capacity is less than the argument, then a new internal
     * array is allocated with greater capacity. The new capacity is the
     * larger of:
     * <ul>
     * <li>The {@code minimumCapacity} argument.
     * <li>Twice the old capacity, plus {@code 2}.
     * </ul>
     * If the {@code minimumCapacity} argument is nonpositive, this
     * method takes no action and simply returns.
     * Note that subsequent operations on this object can reduce the
     * actual capacity below that requested here.
     *
     * @param   minimumCapacity   the minimum desired capacity.
     */
    public void ensureCapacity(int minimumCapacity) {
        if (minimumCapacity > 0)
            ensureCapacityInternal(minimumCapacity);
    }

    
For positive values of minimumCapacity, this method behaves like ensureCapacity, however it is never synchronized. If minimumCapacity is non positive due to numeric overflow, this method throws OutOfMemoryError. /**
     * For positive values of {@code minimumCapacity}, this method
     * behaves like {@code ensureCapacity}, however it is never
     * synchronized.
     * If {@code minimumCapacity} is non positive due to numeric
     * overflow, this method throws {@code OutOfMemoryError}.
     */
    private void ensureCapacityInternal(int minimumCapacity) {
        // overflow-conscious code
        if (minimumCapacity - value.length > 0) {
            value = Arrays.copyOf(value,
                    newCapacity(minimumCapacity));
        }
    }

    
The maximum size of array to allocate (unless necessary).
Some VMs reserve some header words in an array.
Attempts to allocate larger arrays may result in
OutOfMemoryError: Requested array size exceeds VM limit
/**
     * The maximum size of array to allocate (unless necessary).
     * Some VMs reserve some header words in an array.
     * Attempts to allocate larger arrays may result in
     * OutOfMemoryError: Requested array size exceeds VM limit
     */
    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

    
Returns a capacity at least as large as the given minimum capacity. Returns the current capacity increased by the same amount + 2 if that suffices. Will not return a capacity greater than MAX_ARRAY_SIZE unless the given minimum capacity is greater than that. 
Params:
minCapacity – the desired minimum capacity
Throws:
OutOfMemoryError – if minCapacity is less than zero or
        greater than Integer.MAX_VALUE/**
     * Returns a capacity at least as large as the given minimum capacity.
     * Returns the current capacity increased by the same amount + 2 if
     * that suffices.
     * Will not return a capacity greater than {@code MAX_ARRAY_SIZE}
     * unless the given minimum capacity is greater than that.
     *
     * @param  minCapacity the desired minimum capacity
     * @throws OutOfMemoryError if minCapacity is less than zero or
     *         greater than Integer.MAX_VALUE
     */
    private int newCapacity(int minCapacity) {
        // overflow-conscious code
        int newCapacity = (value.length << 1) + 2;
        if (newCapacity - minCapacity < 0) {
            newCapacity = minCapacity;
        }
        return (newCapacity <= 0 || MAX_ARRAY_SIZE - newCapacity < 0)
            ? hugeCapacity(minCapacity)
            : newCapacity;
    }

    private int hugeCapacity(int minCapacity) {
        if (Integer.MAX_VALUE - minCapacity < 0) { // overflow
            throw new OutOfMemoryError();
        }
        return (minCapacity > MAX_ARRAY_SIZE)
            ? minCapacity : MAX_ARRAY_SIZE;
    }

    
Attempts to reduce storage used for the character sequence. If the buffer is larger than necessary to hold its current sequence of characters, then it may be resized to become more space efficient. Calling this method may, but is not required to, affect the value returned by a subsequent call to the capacity() method. /**
     * Attempts to reduce storage used for the character sequence.
     * If the buffer is larger than necessary to hold its current sequence of
     * characters, then it may be resized to become more space efficient.
     * Calling this method may, but is not required to, affect the value
     * returned by a subsequent call to the {@link #capacity()} method.
     */
    public void trimToSize() {
        if (count < value.length) {
            value = Arrays.copyOf(value, count);
        }
    }

    
Sets the length of the character sequence.
The sequence is changed to a new character sequence
whose length is specified by the argument. For every nonnegative
index k less than newLength, the character at index k in the new character sequence is the same as the
character at index k in the old sequence if k is less than the length of the old character sequence; otherwise, it is the null character '\u005Cu0000'. In other words, if the newLength argument is less than the current length, the length is changed to the specified length. 
 If the newLength argument is greater than or equal to the current length, sufficient null characters ('\u005Cu0000') are appended so that length becomes the newLength argument. 
 The newLength argument must be greater than or equal to 0. 
Params:
newLength –   the new length
Throws:
IndexOutOfBoundsException –  if the newLength argument is negative./**
     * Sets the length of the character sequence.
     * The sequence is changed to a new character sequence
     * whose length is specified by the argument. For every nonnegative
     * index <i>k</i> less than {@code newLength}, the character at
     * index <i>k</i> in the new character sequence is the same as the
     * character at index <i>k</i> in the old sequence if <i>k</i> is less
     * than the length of the old character sequence; otherwise, it is the
     * null character {@code '\u005Cu0000'}.
     *
     * In other words, if the {@code newLength} argument is less than
     * the current length, the length is changed to the specified length.
     * <p>
     * If the {@code newLength} argument is greater than or equal
     * to the current length, sufficient null characters
     * ({@code '\u005Cu0000'}) are appended so that
     * length becomes the {@code newLength} argument.
     * <p>
     * The {@code newLength} argument must be greater than or equal
     * to {@code 0}.
     *
     * @param      newLength   the new length
     * @throws     IndexOutOfBoundsException  if the
     *               {@code newLength} argument is negative.
     */
    public void setLength(int newLength) {
        if (newLength < 0)
            throw new StringIndexOutOfBoundsException(newLength);
        ensureCapacityInternal(newLength);

        if (count < newLength) {
            Arrays.fill(value, count, newLength, '\0');
        }

        count = newLength;
    }

    
Returns the char value in this sequence at the specified index. The first char value is at index 0, the next at index 1, and so on, as in array indexing. 
 The index argument must be greater than or equal to 0, and less than the length of this sequence. 
If the char value specified by the index is a surrogate, the surrogate
value is returned.
Params:
index –  the index of the desired char value.
Throws:
IndexOutOfBoundsException –  if index is negative or greater than or equal to length().
Returns:
 the char value at the specified index./**
     * Returns the {@code char} value in this sequence at the specified index.
     * The first {@code char} value is at index {@code 0}, the next at index
     * {@code 1}, and so on, as in array indexing.
     * <p>
     * The index argument must be greater than or equal to
     * {@code 0}, and less than the length of this sequence.
     *
     * <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 desired {@code char} value.
     * @return     the {@code char} value at the specified index.
     * @throws     IndexOutOfBoundsException  if {@code index} is
     *             negative or greater than or equal to {@code length()}.
     */
    @Override
    public char charAt(int index) {
        if ((index < 0) || (index >= count))
            throw new StringIndexOutOfBoundsException(index);
        return value[index];
    }

    
Returns the character (Unicode code point) at the specified index. The index refers to char values (Unicode code units) and ranges from 0 to length() - 1. 
 If the char value specified at the given index is in the high-surrogate range, the following index is less than the length of this sequence, and the 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 char value at the given index is returned. 
Params:
index – the index to the char values
Throws:
IndexOutOfBoundsException –  if the index argument is negative or not less than the length of this sequence.
Returns:
 the code point value of the character at the 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 sequence, 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}
     * @exception  IndexOutOfBoundsException  if the {@code index}
     *             argument is negative or not less than the length of this
     *             sequence.
     */
    public int codePointAt(int index) {
        if ((index < 0) || (index >= count)) {
            throw new StringIndexOutOfBoundsException(index);
        }
        return Character.codePointAtImpl(value, index, count);
    }

    
Returns the character (Unicode code point) before the specified index. The index refers to char values (Unicode code units) and ranges from 1 to length(). 
 If the char value at (index - 1) is in the low-surrogate range, (index - 2) is not negative, and the char value at (index -
2) is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If the char value at index -
1 is an unpaired low-surrogate or a high-surrogate, the surrogate value is returned. 
Params:
index – the index following the code point that should be returned
Throws:
IndexOutOfBoundsException – if the index argument is less than 1 or greater than the length of this sequence.
Returns:
   the Unicode code point value before the given index./**
     * 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
     * #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.
     * @exception IndexOutOfBoundsException if the {@code index}
     *            argument is less than 1 or greater than the length
     *            of this sequence.
     */
    public int codePointBefore(int index) {
        int i = index - 1;
        if ((i < 0) || (i >= count)) {
            throw new StringIndexOutOfBoundsException(index);
        }
        return Character.codePointBeforeImpl(value, index, 0);
    }

    
Returns the number of Unicode code points in the specified text range of this sequence. The text range begins at the specified beginIndex and extends to the char at index endIndex - 1. Thus the length (in chars) of the text range is endIndex-beginIndex. Unpaired surrogates within this sequence count as one code point each. 
Params:
beginIndex – the index to the first char of the text range.
endIndex – the index after the last char of the text range.
Throws:
IndexOutOfBoundsException – if the beginIndex is negative, or endIndex is larger than the length of this sequence, or beginIndex is larger than endIndex.
Returns:
the number of Unicode code points in the specified text
range/**
     * Returns the number of Unicode code points in the specified text
     * range of this sequence. 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
     * this sequence 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
     * @exception IndexOutOfBoundsException if the
     * {@code beginIndex} is negative, or {@code endIndex}
     * is larger than the length of this sequence, or
     * {@code beginIndex} is larger than {@code endIndex}.
     */
    public int codePointCount(int beginIndex, int endIndex) {
        if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
            throw new IndexOutOfBoundsException();
        }
        return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex);
    }

    
Returns the index within this sequence that is offset from the given index by codePointOffset code points. Unpaired surrogates within the text range given by index and codePointOffset count as one code point each. 
Params:
index – the index to be offset
codePointOffset – the offset in code points
Throws:
IndexOutOfBoundsException – if index is negative or larger then the length of this sequence, or if codePointOffset is positive and the subsequence starting with index has fewer than codePointOffset code points, or if codePointOffset is negative and the subsequence before index has fewer than the absolute value of codePointOffset code points.
Returns:
the index within this sequence/**
     * Returns the index within this sequence 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 sequence
     * @exception IndexOutOfBoundsException if {@code index}
     *   is negative or larger then the length of this sequence,
     *   or if {@code codePointOffset} is positive and the subsequence
     *   starting with {@code index} has fewer than
     *   {@code codePointOffset} code points,
     *   or if {@code codePointOffset} is negative and the subsequence
     *   before {@code index} has fewer than the absolute value of
     *   {@code codePointOffset} code points.
     */
    public int offsetByCodePoints(int index, int codePointOffset) {
        if (index < 0 || index > count) {
            throw new IndexOutOfBoundsException();
        }
        return Character.offsetByCodePointsImpl(value, 0, count,
                                                index, codePointOffset);
    }

    
Characters are copied from this sequence into the destination character array dst. The first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1. The total number of characters to be copied is srcEnd-srcBegin. The characters are copied into the subarray of dst starting at index dstBegin and ending at index: 

dstbegin + (srcEnd-srcBegin) - 1

Params:
srcBegin –   start copying at this offset.
srcEnd –     stop copying at this offset.
dst –        the array to copy the data into.
dstBegin –  offset into dst.
Throws:
IndexOutOfBoundsException –  if any of the following is true:
            

            
srcBegin is negative 
dstBegin is negative 
the srcBegin argument is greater than the srcEnd argument. 
srcEnd is greater than this.length(). 
dstBegin+srcEnd-srcBegin is greater than dst.length /**
     * Characters are copied from this sequence into the
     * destination character array {@code dst}. 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 are copied into the subarray of {@code dst} starting
     * at index {@code dstBegin} and ending at index:
     * <pre>{@code
     * dstbegin + (srcEnd-srcBegin) - 1
     * }</pre>
     *
     * @param      srcBegin   start copying at this offset.
     * @param      srcEnd     stop copying at this offset.
     * @param      dst        the array to copy the data into.
     * @param      dstBegin   offset into {@code dst}.
     * @throws     IndexOutOfBoundsException  if any of the following is true:
     *             <ul>
     *             <li>{@code srcBegin} is negative
     *             <li>{@code dstBegin} is negative
     *             <li>the {@code srcBegin} argument is greater than
     *             the {@code srcEnd} argument.
     *             <li>{@code srcEnd} is greater than
     *             {@code this.length()}.
     *             <li>{@code dstBegin+srcEnd-srcBegin} is greater than
     *             {@code dst.length}
     *             </ul>
     */
    public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
    {
        if (srcBegin < 0)
            throw new StringIndexOutOfBoundsException(srcBegin);
        if ((srcEnd < 0) || (srcEnd > count))
            throw new StringIndexOutOfBoundsException(srcEnd);
        if (srcBegin > srcEnd)
            throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");
        System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
    }

    
The character at the specified index is set to ch. This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the character ch at position index. 
 The index argument must be greater than or equal to 0, and less than the length of this sequence. 
Params:
index –   the index of the character to modify.
ch –      the new character.
Throws:
IndexOutOfBoundsException –  if index is negative or greater than or equal to length()./**
     * The character at the specified index is set to {@code ch}. This
     * sequence is altered to represent a new character sequence that is
     * identical to the old character sequence, except that it contains the
     * character {@code ch} at position {@code index}.
     * <p>
     * The index argument must be greater than or equal to
     * {@code 0}, and less than the length of this sequence.
     *
     * @param      index   the index of the character to modify.
     * @param      ch      the new character.
     * @throws     IndexOutOfBoundsException  if {@code index} is
     *             negative or greater than or equal to {@code length()}.
     */
    public void setCharAt(int index, char ch) {
        if ((index < 0) || (index >= count))
            throw new StringIndexOutOfBoundsException(index);
        value[index] = ch;
    }

    
Appends the string representation of the Object argument. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(Object), and the characters of that string were then appended to this character sequence. 
Params:
obj –  an Object.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code Object} argument.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(Object)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   obj   an {@code Object}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(Object obj) {
        return append(String.valueOf(obj));
    }

    
Appends the specified string to this character sequence.
 The characters of the String argument are appended, in order, increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are appended. 

Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in the new character sequence is equal to the character
at index k in the old character sequence, if k is less
than n; otherwise, it is equal to the character at index
k-n in the argument str. 
Params:
str –   a string.
Returns:
 a reference to this object./**
     * Appends the specified string to this character sequence.
     * <p>
     * The characters of the {@code String} argument are appended, in
     * order, increasing the length of this sequence by the length of the
     * argument. If {@code str} is {@code null}, then the four
     * characters {@code "null"} are appended.
     * <p>
     * Let <i>n</i> be the length of this character sequence just prior to
     * execution of the {@code append} method. Then the character at
     * index <i>k</i> in the new character sequence is equal to the character
     * at index <i>k</i> in the old character sequence, if <i>k</i> is less
     * than <i>n</i>; otherwise, it is equal to the character at index
     * <i>k-n</i> in the argument {@code str}.
     *
     * @param   str   a string.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(String str) {
        if (str == null)
            return appendNull();
        int len = str.length();
        ensureCapacityInternal(count + len);
        str.getChars(0, len, value, count);
        count += len;
        return this;
    }

    // Documentation in subclasses because of synchro difference
    public AbstractStringBuilder append(StringBuffer sb) {
        if (sb == null)
            return appendNull();
        int len = sb.length();
        ensureCapacityInternal(count + len);
        sb.getChars(0, len, value, count);
        count += len;
        return this;
    }

    
Since:
1.8/**
     * @since 1.8
     */
    AbstractStringBuilder append(AbstractStringBuilder asb) {
        if (asb == null)
            return appendNull();
        int len = asb.length();
        ensureCapacityInternal(count + len);
        asb.getChars(0, len, value, count);
        count += len;
        return this;
    }

    // Documentation in subclasses because of synchro difference
    @Override
    public AbstractStringBuilder append(CharSequence s) {
        if (s == null)
            return appendNull();
        if (s instanceof String)
            return this.append((String)s);
        if (s instanceof AbstractStringBuilder)
            return this.append((AbstractStringBuilder)s);

        return this.append(s, 0, s.length());
    }

    private AbstractStringBuilder appendNull() {
        int c = count;
        ensureCapacityInternal(c + 4);
        final char[] value = this.value;
        value[c++] = 'n';
        value[c++] = 'u';
        value[c++] = 'l';
        value[c++] = 'l';
        count = c;
        return this;
    }

    
Appends a subsequence of the specified CharSequence to this sequence. 
 Characters of the argument s, starting at index start, are appended, in order, to the contents of this sequence up to the (exclusive) index end. The length of this sequence is increased by the value of end - start. 

Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in this character sequence becomes equal to the
character at index k in this sequence, if k is less than
n; otherwise, it is equal to the character at index
k+start-n in the argument s. 
 If s is null, then this method appends characters as if the s parameter was a sequence containing the four characters "null". 
Params:
s – the sequence to append.
start –   the starting index of the subsequence to be appended.
end –     the end index of the subsequence to be appended.
Throws:
IndexOutOfBoundsException – if start is negative, or start is greater than end or end is greater than s.length()
Returns:
 a reference to this object./**
     * Appends a subsequence of the specified {@code CharSequence} to this
     * sequence.
     * <p>
     * Characters of the argument {@code s}, starting at
     * index {@code start}, are appended, in order, to the contents of
     * this sequence up to the (exclusive) index {@code end}. The length
     * of this sequence is increased by the value of {@code end - start}.
     * <p>
     * Let <i>n</i> be the length of this character sequence just prior to
     * execution of the {@code append} method. Then the character at
     * index <i>k</i> in this character sequence becomes equal to the
     * character at index <i>k</i> in this sequence, if <i>k</i> is less than
     * <i>n</i>; otherwise, it is equal to the character at index
     * <i>k+start-n</i> in the argument {@code s}.
     * <p>
     * If {@code s} is {@code null}, then this method appends
     * characters as if the s parameter was a sequence containing the four
     * characters {@code "null"}.
     *
     * @param   s the sequence to append.
     * @param   start   the starting index of the subsequence to be appended.
     * @param   end     the end index of the subsequence to be appended.
     * @return  a reference to this object.
     * @throws     IndexOutOfBoundsException if
     *             {@code start} is negative, or
     *             {@code start} is greater than {@code end} or
     *             {@code end} is greater than {@code s.length()}
     */
    @Override
    public AbstractStringBuilder append(CharSequence s, int start, int end) {
        if (s == null)
            s = "null";
        if ((start < 0) || (start > end) || (end > s.length()))
            throw new IndexOutOfBoundsException(
                "start " + start + ", end " + end + ", s.length() "
                + s.length());
        int len = end - start;
        ensureCapacityInternal(count + len);
        for (int i = start, j = count; i < end; i++, j++)
            value[j] = s.charAt(i);
        count += len;
        return this;
    }

    
Appends the string representation of the char array argument to this sequence. 

The characters of the array argument are appended, in order, to
the contents of this sequence. The length of this sequence
increases by the length of the argument.
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char[]), and the characters of that string were then appended to this character sequence. 
Params:
str –   the characters to be appended.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code char} array
     * argument to this sequence.
     * <p>
     * The characters of the array argument are appended, in order, to
     * the contents of this sequence. The length of this sequence
     * increases by the length of the argument.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(char[])},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   str   the characters to be appended.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(char[] str) {
        int len = str.length;
        ensureCapacityInternal(count + len);
        System.arraycopy(str, 0, value, count, len);
        count += len;
        return this;
    }

    
Appends the string representation of a subarray of the char array argument to this sequence. 
 Characters of the char array str, starting at index offset, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value of len. 
 The overall effect is exactly as if the arguments were converted to a string by the method String.valueOf(char[], int, int), and the characters of that string were then appended to this character sequence. 
Params:
str –      the characters to be appended.
offset –  the index of the first char to append.
len –  the number of chars to append.
Throws:
IndexOutOfBoundsException –  if offset < 0 or len < 0 or offset+len > str.length
Returns:
 a reference to this object./**
     * Appends the string representation of a subarray of the
     * {@code char} array argument to this sequence.
     * <p>
     * Characters of the {@code char} array {@code str}, starting at
     * index {@code offset}, are appended, in order, to the contents
     * of this sequence. The length of this sequence increases
     * by the value of {@code len}.
     * <p>
     * The overall effect is exactly as if the arguments were converted
     * to a string by the method {@link String#valueOf(char[],int,int)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   str      the characters to be appended.
     * @param   offset   the index of the first {@code char} to append.
     * @param   len      the number of {@code char}s to append.
     * @return  a reference to this object.
     * @throws IndexOutOfBoundsException
     *         if {@code offset < 0} or {@code len < 0}
     *         or {@code offset+len > str.length}
     */
    public AbstractStringBuilder append(char str[], int offset, int len) {
        if (len > 0)                // let arraycopy report AIOOBE for len < 0
            ensureCapacityInternal(count + len);
        System.arraycopy(str, offset, value, count, len);
        count += len;
        return this;
    }

    
Appends the string representation of the boolean argument to the sequence. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(boolean), and the characters of that string were then appended to this character sequence. 
Params:
b –  a boolean.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code boolean}
     * argument to the sequence.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(boolean)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   b   a {@code boolean}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(boolean b) {
        if (b) {
            ensureCapacityInternal(count + 4);
            value[count++] = 't';
            value[count++] = 'r';
            value[count++] = 'u';
            value[count++] = 'e';
        } else {
            ensureCapacityInternal(count + 5);
            value[count++] = 'f';
            value[count++] = 'a';
            value[count++] = 'l';
            value[count++] = 's';
            value[count++] = 'e';
        }
        return this;
    }

    
Appends the string representation of the char argument to this sequence. 
 The argument is appended to the contents of this sequence. The length of this sequence increases by 1. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char), and the character in that string were then appended to this character sequence. 
Params:
c –  a char.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code char}
     * argument to this sequence.
     * <p>
     * The argument is appended to the contents of this sequence.
     * The length of this sequence increases by {@code 1}.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(char)},
     * and the character in that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   c   a {@code char}.
     * @return  a reference to this object.
     */
    @Override
    public AbstractStringBuilder append(char c) {
        ensureCapacityInternal(count + 1);
        value[count++] = c;
        return this;
    }

    
Appends the string representation of the int argument to this sequence. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(int), and the characters of that string were then appended to this character sequence. 
Params:
i –  an int.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code int}
     * argument to this sequence.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(int)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   i   an {@code int}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(int i) {
        if (i == Integer.MIN_VALUE) {
            append("-2147483648");
            return this;
        }
        int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1
                                     : Integer.stringSize(i);
        int spaceNeeded = count + appendedLength;
        ensureCapacityInternal(spaceNeeded);
        Integer.getChars(i, spaceNeeded, value);
        count = spaceNeeded;
        return this;
    }

    
Appends the string representation of the long argument to this sequence. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(long), and the characters of that string were then appended to this character sequence. 
Params:
l –  a long.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code long}
     * argument to this sequence.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(long)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   l   a {@code long}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(long l) {
        if (l == Long.MIN_VALUE) {
            append("-9223372036854775808");
            return this;
        }
        int appendedLength = (l < 0) ? Long.stringSize(-l) + 1
                                     : Long.stringSize(l);
        int spaceNeeded = count + appendedLength;
        ensureCapacityInternal(spaceNeeded);
        Long.getChars(l, spaceNeeded, value);
        count = spaceNeeded;
        return this;
    }

    
Appends the string representation of the float argument to this sequence. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(float), and the characters of that string were then appended to this character sequence. 
Params:
f –  a float.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code float}
     * argument to this sequence.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(float)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   f   a {@code float}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(float f) {
        FloatingDecimal.appendTo(f,this);
        return this;
    }

    
Appends the string representation of the double argument to this sequence. 
 The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(double), and the characters of that string were then appended to this character sequence. 
Params:
d –  a double.
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code double}
     * argument to this sequence.
     * <p>
     * The overall effect is exactly as if the argument were converted
     * to a string by the method {@link String#valueOf(double)},
     * and the characters of that string were then
     * {@link #append(String) appended} to this character sequence.
     *
     * @param   d   a {@code double}.
     * @return  a reference to this object.
     */
    public AbstractStringBuilder append(double d) {
        FloatingDecimal.appendTo(d,this);
        return this;
    }

    
Removes the characters in a substring of this sequence. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. If start is equal to end, no changes are made. 
Params:
start –  The beginning index, inclusive.
end –    The ending index, exclusive.
Throws:
StringIndexOutOfBoundsException –  if start is negative, greater than length(), or greater than end.
Returns:
    This object./**
     * Removes the characters in a substring of this sequence.
     * The substring begins at the specified {@code start} and extends to
     * the character at index {@code end - 1} or to the end of the
     * sequence if no such character exists. If
     * {@code start} is equal to {@code end}, no changes are made.
     *
     * @param      start  The beginning index, inclusive.
     * @param      end    The ending index, exclusive.
     * @return     This object.
     * @throws     StringIndexOutOfBoundsException  if {@code start}
     *             is negative, greater than {@code length()}, or
     *             greater than {@code end}.
     */
    public AbstractStringBuilder delete(int start, int end) {
        if (start < 0)
            throw new StringIndexOutOfBoundsException(start);
        if (end > count)
            end = count;
        if (start > end)
            throw new StringIndexOutOfBoundsException();
        int len = end - start;
        if (len > 0) {
            System.arraycopy(value, start+len, value, start, count-end);
            count -= len;
        }
        return this;
    }

    
Appends the string representation of the codePoint argument to this sequence. 
 The argument is appended to the contents of this sequence. The length of this sequence increases by Character.charCount(codePoint). 
 The overall effect is exactly as if the argument were converted to a char array by the method Character.toChars(int) and the character in that array were then appended to this character sequence. 
Params:
codePoint –   a Unicode code point
Throws:
IllegalArgumentException – if the specified codePoint isn't a valid Unicode code point
Returns:
 a reference to this object./**
     * Appends the string representation of the {@code codePoint}
     * argument to this sequence.
     *
     * <p> The argument is appended to the contents of this sequence.
     * The length of this sequence increases by
     * {@link Character#charCount(int) Character.charCount(codePoint)}.
     *
     * <p> The overall effect is exactly as if the argument were
     * converted to a {@code char} array by the method
     * {@link Character#toChars(int)} and the character in that array
     * were then {@link #append(char[]) appended} to this character
     * sequence.
     *
     * @param   codePoint   a Unicode code point
     * @return  a reference to this object.
     * @exception IllegalArgumentException if the specified
     * {@code codePoint} isn't a valid Unicode code point
     */
    public AbstractStringBuilder appendCodePoint(int codePoint) {
        final int count = this.count;

        if (Character.isBmpCodePoint(codePoint)) {
            ensureCapacityInternal(count + 1);
            value[count] = (char) codePoint;
            this.count = count + 1;
        } else if (Character.isValidCodePoint(codePoint)) {
            ensureCapacityInternal(count + 2);
            Character.toSurrogates(codePoint, value, count);
            this.count = count + 2;
        } else {
            throw new IllegalArgumentException();
        }
        return this;
    }

    
Removes the char at the specified position in this sequence. This sequence is shortened by one char. 
Note: If the character at the given index is a supplementary character, this method does not remove the entire character. If correct handling of supplementary characters is required, determine the number of chars to remove by calling Character.charCount(thisSequence.codePointAt(index)), where thisSequence is this sequence. 
Params:
index –  Index of char to remove
Throws:
StringIndexOutOfBoundsException –  if the index is negative or greater than or equal to length().
Returns:
     This object./**
     * Removes the {@code char} at the specified position in this
     * sequence. This sequence is shortened by one {@code char}.
     *
     * <p>Note: If the character at the given index is a supplementary
     * character, this method does not remove the entire character. If
     * correct handling of supplementary characters is required,
     * determine the number of {@code char}s to remove by calling
     * {@code Character.charCount(thisSequence.codePointAt(index))},
     * where {@code thisSequence} is this sequence.
     *
     * @param       index  Index of {@code char} to remove
     * @return      This object.
     * @throws      StringIndexOutOfBoundsException  if the {@code index}
     *              is negative or greater than or equal to
     *              {@code length()}.
     */
    public AbstractStringBuilder deleteCharAt(int index) {
        if ((index < 0) || (index >= count))
            throw new StringIndexOutOfBoundsException(index);
        System.arraycopy(value, index+1, value, index, count-index-1);
        count--;
        return this;
    }

    
Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specified String is inserted at start. (This sequence will be lengthened to accommodate the specified String if necessary.) 
Params:
start –    The beginning index, inclusive.
end –      The ending index, exclusive.
str –   String that will replace previous contents.
Throws:
StringIndexOutOfBoundsException –  if start is negative, greater than length(), or greater than end.
Returns:
    This object./**
     * Replaces the characters in a substring of this sequence
     * with characters in the specified {@code String}. The substring
     * begins at the specified {@code start} and extends to the character
     * at index {@code end - 1} or to the end of the
     * sequence if no such character exists. First the
     * characters in the substring are removed and then the specified
     * {@code String} is inserted at {@code start}. (This
     * sequence will be lengthened to accommodate the
     * specified String if necessary.)
     *
     * @param      start    The beginning index, inclusive.
     * @param      end      The ending index, exclusive.
     * @param      str   String that will replace previous contents.
     * @return     This object.
     * @throws     StringIndexOutOfBoundsException  if {@code start}
     *             is negative, greater than {@code length()}, or
     *             greater than {@code end}.
     */
    public AbstractStringBuilder replace(int start, int end, String str) {
        if (start < 0)
            throw new StringIndexOutOfBoundsException(start);
        if (start > count)
            throw new StringIndexOutOfBoundsException("start > length()");
        if (start > end)
            throw new StringIndexOutOfBoundsException("start > end");

        if (end > count)
            end = count;
        int len = str.length();
        int newCount = count + len - (end - start);
        ensureCapacityInternal(newCount);

        System.arraycopy(value, end, value, start + len, count - end);
        str.getChars(value, start);
        count = newCount;
        return this;
    }

    
Returns a new String that contains a subsequence of characters currently contained in this character sequence. The substring begins at the specified index and extends to the end of this sequence. 
Params:
start –    The beginning index, inclusive.
Throws:
StringIndexOutOfBoundsException –  if start is less than zero, or greater than the length of this object.
Returns:
    The new string./**
     * Returns a new {@code String} that contains a subsequence of
     * characters currently contained in this character sequence. The
     * substring begins at the specified index and extends to the end of
     * this sequence.
     *
     * @param      start    The beginning index, inclusive.
     * @return     The new string.
     * @throws     StringIndexOutOfBoundsException  if {@code start} is
     *             less than zero, or greater than the length of this object.
     */
    public String substring(int start) {
        return substring(start, count);
    }

    
Returns a new character sequence that is a subsequence of this sequence.
 An invocation of this method of the form

sb.subSequence(begin,&nbsp;end)
behaves in exactly the same way as the invocation

sb.substring(begin,&nbsp;end)
 This method is provided so that this class can implement the CharSequence interface. 
Params:
start –   the start index, inclusive.
end –     the end index, exclusive.
Throws:
IndexOutOfBoundsException –  if start or end are negative, if end is greater than length(), or if start is greater than end
Returns:
    the specified subsequence.
@spec
JSR-51/**
     * Returns a new character sequence that is a subsequence of this sequence.
     *
     * <p> An invocation of this method of the form
     *
     * <pre>{@code
     * sb.subSequence(begin,&nbsp;end)}</pre>
     *
     * behaves in exactly the same way as the invocation
     *
     * <pre>{@code
     * sb.substring(begin,&nbsp;end)}</pre>
     *
     * This method is provided so that this class can
     * implement the {@link CharSequence} interface.
     *
     * @param      start   the start index, inclusive.
     * @param      end     the end index, exclusive.
     * @return     the specified subsequence.
     *
     * @throws  IndexOutOfBoundsException
     *          if {@code start} or {@code end} are negative,
     *          if {@code end} is greater than {@code length()},
     *          or if {@code start} is greater than {@code end}
     * @spec JSR-51
     */
    @Override
    public CharSequence subSequence(int start, int end) {
        return substring(start, end);
    }

    
Returns a new String that contains a subsequence of characters currently contained in this sequence. The substring begins at the specified start and extends to the character at index end - 1. 
Params:
start –    The beginning index, inclusive.
end –      The ending index, exclusive.
Throws:
StringIndexOutOfBoundsException –  if start or end are negative or greater than length(), or start is greater than end.
Returns:
    The new string./**
     * Returns a new {@code String} that contains a subsequence of
     * characters currently contained in this sequence. The
     * substring begins at the specified {@code start} and
     * extends to the character at index {@code end - 1}.
     *
     * @param      start    The beginning index, inclusive.
     * @param      end      The ending index, exclusive.
     * @return     The new string.
     * @throws     StringIndexOutOfBoundsException  if {@code start}
     *             or {@code end} are negative or greater than
     *             {@code length()}, or {@code start} is
     *             greater than {@code end}.
     */
    public String substring(int start, int end) {
        if (start < 0)
            throw new StringIndexOutOfBoundsException(start);
        if (end > count)
            throw new StringIndexOutOfBoundsException(end);
        if (start > end)
            throw new StringIndexOutOfBoundsException(end - start);
        return new String(value, start, end - start);
    }

    
Inserts the string representation of a subarray of the str array argument into this sequence. The subarray begins at the specified offset and extends len chars. The characters of the subarray are inserted into this sequence at the position indicated by index. The length of this sequence increases by len chars. 
Params:
index –    position at which to insert subarray.
str –  A char array.
offset –  the index of the first char in subarray to be inserted.
len –  the number of chars in the subarray to be inserted.
Throws:
StringIndexOutOfBoundsException –  if index is negative or greater than length(), or offset or len are negative, or (offset+len) is greater than str.length.
Returns:
    This object/**
     * Inserts the string representation of a subarray of the {@code str}
     * array argument into this sequence. The subarray begins at the
     * specified {@code offset} and extends {@code len} {@code char}s.
     * The characters of the subarray are inserted into this sequence at
     * the position indicated by {@code index}. The length of this
     * sequence increases by {@code len} {@code char}s.
     *
     * @param      index    position at which to insert subarray.
     * @param      str       A {@code char} array.
     * @param      offset   the index of the first {@code char} in subarray to
     *             be inserted.
     * @param      len      the number of {@code char}s in the subarray to
     *             be inserted.
     * @return     This object
     * @throws     StringIndexOutOfBoundsException  if {@code index}
     *             is negative or greater than {@code length()}, or
     *             {@code offset} or {@code len} are negative, or
     *             {@code (offset+len)} is greater than
     *             {@code str.length}.
     */
    public AbstractStringBuilder insert(int index, char[] str, int offset,
                                        int len)
    {
        if ((index < 0) || (index > length()))
            throw new StringIndexOutOfBoundsException(index);
        if ((offset < 0) || (len < 0) || (offset > str.length - len))
            throw new StringIndexOutOfBoundsException(
                "offset " + offset + ", len " + len + ", str.length "
                + str.length);
        ensureCapacityInternal(count + len);
        System.arraycopy(value, index, value, index + len, count - index);
        System.arraycopy(str, offset, value, index, len);
        count += len;
        return this;
    }

    
Inserts the string representation of the Object argument into this character sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(Object), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
obj –  an Object.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code Object}
     * argument into this character sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(Object)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      obj      an {@code Object}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, Object obj) {
        return insert(offset, String.valueOf(obj));
    }

    
Inserts the string into this character sequence.
 The characters of the String argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are inserted into this sequence. 

The character at index k in the new character sequence is
equal to:

the character at index k in the old character sequence, if
k is less than offset 
the character at index k-offset in the argument str, if k is not less than offset but is less than offset+str.length() 
the character at index k-str.length() in the old character sequence, if k is not less than offset+str.length() 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
str –      a string.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string into this character sequence.
     * <p>
     * The characters of the {@code String} argument are inserted, in
     * order, into this sequence at the indicated offset, moving up any
     * characters originally above that position and increasing the length
     * of this sequence by the length of the argument. If
     * {@code str} is {@code null}, then the four characters
     * {@code "null"} are inserted into this sequence.
     * <p>
     * The character at index <i>k</i> in the new character sequence is
     * equal to:
     * <ul>
     * <li>the character at index <i>k</i> in the old character sequence, if
     * <i>k</i> is less than {@code offset}
     * <li>the character at index <i>k</i>{@code -offset} in the
     * argument {@code str}, if <i>k</i> is not less than
     * {@code offset} but is less than {@code offset+str.length()}
     * <li>the character at index <i>k</i>{@code -str.length()} in the
     * old character sequence, if <i>k</i> is not less than
     * {@code offset+str.length()}
     * </ul><p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      str      a string.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, String str) {
        if ((offset < 0) || (offset > length()))
            throw new StringIndexOutOfBoundsException(offset);
        if (str == null)
            str = "null";
        int len = str.length();
        ensureCapacityInternal(count + len);
        System.arraycopy(value, offset, value, offset + len, count - offset);
        str.getChars(value, offset);
        count += len;
        return this;
    }

    
Inserts the string representation of the char array argument into this sequence. 
 The characters of the array argument are inserted into the contents of this sequence at the position indicated by offset. The length of this sequence increases by the length of the argument. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char[]), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
str –      a character array.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code char} array
     * argument into this sequence.
     * <p>
     * The characters of the array argument are inserted into the
     * contents of this sequence at the position indicated by
     * {@code offset}. The length of this sequence increases by
     * the length of the argument.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(char[])},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      str      a character array.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, char[] str) {
        if ((offset < 0) || (offset > length()))
            throw new StringIndexOutOfBoundsException(offset);
        int len = str.length;
        ensureCapacityInternal(count + len);
        System.arraycopy(value, offset, value, offset + len, count - offset);
        System.arraycopy(str, 0, value, offset, len);
        count += len;
        return this;
    }

    
Inserts the specified CharSequence into this sequence. 
 The characters of the CharSequence argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument s. 
 The result of this method is exactly the same as if it were an invocation of this object's insert(dstOffset, s, 0, s.length()) method. 
If s is null, then the four characters "null" are inserted into this sequence. 
Params:
dstOffset –   the offset.
s – the sequence to be inserted
Throws:
IndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the specified {@code CharSequence} into this sequence.
     * <p>
     * The characters of the {@code CharSequence} argument are inserted,
     * in order, into this sequence at the indicated offset, moving up
     * any characters originally above that position and increasing the length
     * of this sequence by the length of the argument s.
     * <p>
     * The result of this method is exactly the same as if it were an
     * invocation of this object's
     * {@link #insert(int,CharSequence,int,int) insert}(dstOffset, s, 0, s.length())
     * method.
     *
     * <p>If {@code s} is {@code null}, then the four characters
     * {@code "null"} are inserted into this sequence.
     *
     * @param      dstOffset   the offset.
     * @param      s the sequence to be inserted
     * @return     a reference to this object.
     * @throws     IndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
        if (s == null)
            s = "null";
        if (s instanceof String)
            return this.insert(dstOffset, (String)s);
        return this.insert(dstOffset, s, 0, s.length());
    }

    
Inserts a subsequence of the specified CharSequence into this sequence. 
 The subsequence of the argument s specified by start and end are inserted, in order, into this sequence at the specified destination offset, moving up any characters originally above that position. The length of this sequence is increased by end - start. 

The character at index k in this sequence becomes equal to:

the character at index k in this sequence, if
k is less than dstOffset 
the character at index k+start-dstOffset in the argument s, if k is greater than or equal to dstOffset but is less than dstOffset+end-start 
the character at index k-(end-start) in this sequence, if k is greater than or equal to dstOffset+end-start 
 The dstOffset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
The start argument must be nonnegative, and not greater than end. 
The end argument must be greater than or equal to start, and less than or equal to the length of s. 
If s is null, then this method inserts characters as if the s parameter was a sequence containing the four characters "null". 
Params:
dstOffset –   the offset in this sequence.
s –       the sequence to be inserted.
start –   the starting index of the subsequence to be inserted.
end –     the end index of the subsequence to be inserted.
Throws:
IndexOutOfBoundsException –  if dstOffset is negative or greater than this.length(), or start or end are negative, or start is greater than end or end is greater than s.length()
Returns:
    a reference to this object./**
     * Inserts a subsequence of the specified {@code CharSequence} into
     * this sequence.
     * <p>
     * The subsequence of the argument {@code s} specified by
     * {@code start} and {@code end} are inserted,
     * in order, into this sequence at the specified destination offset, moving
     * up any characters originally above that position. The length of this
     * sequence is increased by {@code end - start}.
     * <p>
     * The character at index <i>k</i> in this sequence becomes equal to:
     * <ul>
     * <li>the character at index <i>k</i> in this sequence, if
     * <i>k</i> is less than {@code dstOffset}
     * <li>the character at index <i>k</i>{@code +start-dstOffset} in
     * the argument {@code s}, if <i>k</i> is greater than or equal to
     * {@code dstOffset} but is less than {@code dstOffset+end-start}
     * <li>the character at index <i>k</i>{@code -(end-start)} in this
     * sequence, if <i>k</i> is greater than or equal to
     * {@code dstOffset+end-start}
     * </ul><p>
     * The {@code dstOffset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     * <p>The start argument must be nonnegative, and not greater than
     * {@code end}.
     * <p>The end argument must be greater than or equal to
     * {@code start}, and less than or equal to the length of s.
     *
     * <p>If {@code s} is {@code null}, then this method inserts
     * characters as if the s parameter was a sequence containing the four
     * characters {@code "null"}.
     *
     * @param      dstOffset   the offset in this sequence.
     * @param      s       the sequence to be inserted.
     * @param      start   the starting index of the subsequence to be inserted.
     * @param      end     the end index of the subsequence to be inserted.
     * @return     a reference to this object.
     * @throws     IndexOutOfBoundsException  if {@code dstOffset}
     *             is negative or greater than {@code this.length()}, or
     *              {@code start} or {@code end} are negative, or
     *              {@code start} is greater than {@code end} or
     *              {@code end} is greater than {@code s.length()}
     */
     public AbstractStringBuilder insert(int dstOffset, CharSequence s,
                                         int start, int end) {
        if (s == null)
            s = "null";
        if ((dstOffset < 0) || (dstOffset > this.length()))
            throw new IndexOutOfBoundsException("dstOffset "+dstOffset);
        if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))
            throw new IndexOutOfBoundsException(
                "start " + start + ", end " + end + ", s.length() "
                + s.length());
        int len = end - start;
        ensureCapacityInternal(count + len);
        System.arraycopy(value, dstOffset, value, dstOffset + len,
                         count - dstOffset);
        for (int i=start; i<end; i++)
            value[dstOffset++] = s.charAt(i);
        count += len;
        return this;
    }

    
Inserts the string representation of the boolean argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(boolean), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
b –  a boolean.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code boolean}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(boolean)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      b        a {@code boolean}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, boolean b) {
        return insert(offset, String.valueOf(b));
    }

    
Inserts the string representation of the char argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char), and the character in that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
c –  a char.
Throws:
IndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code char}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(char)},
     * and the character in that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      c        a {@code char}.
     * @return     a reference to this object.
     * @throws     IndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, char c) {
        ensureCapacityInternal(count + 1);
        System.arraycopy(value, offset, value, offset + 1, count - offset);
        value[offset] = c;
        count += 1;
        return this;
    }

    
Inserts the string representation of the second int argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(int), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
i –  an int.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the second {@code int}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(int)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      i        an {@code int}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, int i) {
        return insert(offset, String.valueOf(i));
    }

    
Inserts the string representation of the long argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(long), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
l –  a long.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code long}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(long)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      l        a {@code long}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, long l) {
        return insert(offset, String.valueOf(l));
    }

    
Inserts the string representation of the float argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(float), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
f –  a float.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code float}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(float)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      f        a {@code float}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, float f) {
        return insert(offset, String.valueOf(f));
    }

    
Inserts the string representation of the double argument into this sequence. 
 The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(double), and the characters of that string were then inserted into this character sequence at the indicated offset. 
 The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence. 
Params:
offset –   the offset.
d –  a double.
Throws:
StringIndexOutOfBoundsException –  if the offset is invalid.
Returns:
    a reference to this object./**
     * Inserts the string representation of the {@code double}
     * argument into this sequence.
     * <p>
     * The overall effect is exactly as if the second argument were
     * converted to a string by the method {@link String#valueOf(double)},
     * and the characters of that string were then
     * {@link #insert(int,String) inserted} into this character
     * sequence at the indicated offset.
     * <p>
     * The {@code offset} argument must be greater than or equal to
     * {@code 0}, and less than or equal to the {@linkplain #length() length}
     * of this sequence.
     *
     * @param      offset   the offset.
     * @param      d        a {@code double}.
     * @return     a reference to this object.
     * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public AbstractStringBuilder insert(int offset, double d) {
        return insert(offset, String.valueOf(d));
    }

    
Returns the index within this string of the first occurrence of the
specified substring. The integer returned is the smallest value
k such that:

this.toString().startsWith(str, <i>k</i>)
 is true. 
Params:
str –   any string.
Returns:
 if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, -1 is returned./**
     * Returns the index within this string of the first occurrence of the
     * specified substring. The integer returned is the smallest value
     * <i>k</i> such that:
     * <pre>{@code
     * this.toString().startsWith(str, <i>k</i>)
     * }</pre>
     * is {@code true}.
     *
     * @param   str   any string.
     * @return  if the string argument occurs as a substring within this
     *          object, then the index of the first character of the first
     *          such substring is returned; if it does not occur as a
     *          substring, {@code -1} is returned.
     */
    public int indexOf(String str) {
        return indexOf(str, 0);
    }

    
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. The integer returned is the smallest value k for which: 

    k >= Math.min(fromIndex, this.length()) &&
                  this.toString().startsWith(str, k)

If no such value of k exists, then -1 is returned.
Params:
str –         the substring for which to search.
fromIndex –   the index from which to start the search.
Returns:
 the index within this string of the first occurrence of the
         specified substring, starting at the specified index./**
     * Returns the index within this string of the first occurrence of the
     * specified substring, starting at the specified index.  The integer
     * returned is the smallest value {@code k} for which:
     * <pre>{@code
     *     k >= Math.min(fromIndex, this.length()) &&
     *                   this.toString().startsWith(str, k)
     * }</pre>
     * If no such value of <i>k</i> exists, then -1 is returned.
     *
     * @param   str         the substring for which to search.
     * @param   fromIndex   the index from which to start the search.
     * @return  the index within this string of the first occurrence of the
     *          specified substring, starting at the specified index.
     */
    public int indexOf(String str, int fromIndex) {
        return String.indexOf(value, 0, count, str, fromIndex);
    }

    
Returns the index within this string of the rightmost occurrence of the specified substring. The rightmost empty string "" is considered to occur at the index value this.length(). The returned index is the largest value k such that

this.toString().startsWith(str, k)

is true.
Params:
str –   the substring to search for.
Returns:
 if the string argument occurs one or more times as a substring within this object, then the index of the first character of the last such substring is returned. If it does not occur as a substring, -1 is returned./**
     * Returns the index within this string of the rightmost occurrence
     * of the specified substring.  The rightmost empty string "" is
     * considered to occur at the index value {@code this.length()}.
     * The returned index is the largest value <i>k</i> such that
     * <pre>{@code
     * this.toString().startsWith(str, k)
     * }</pre>
     * is true.
     *
     * @param   str   the substring to search for.
     * @return  if the string argument occurs one or more times as a substring
     *          within this object, then the index of the first character of
     *          the last such substring is returned. If it does not occur as
     *          a substring, {@code -1} is returned.
     */
    public int lastIndexOf(String str) {
        return lastIndexOf(str, count);
    }

    
Returns the index within this string of the last occurrence of the
specified substring. The integer returned is the largest value k
such that:

    k <= Math.min(fromIndex, this.length()) &&
                  this.toString().startsWith(str, k)

If no such value of k exists, then -1 is returned.
Params:
str –         the substring to search for.
fromIndex –   the index to start the search from.
Returns:
 the index within this sequence of the last occurrence of the
         specified substring./**
     * Returns the index within this string of the last occurrence of the
     * specified substring. The integer returned is the largest value <i>k</i>
     * such that:
     * <pre>{@code
     *     k <= Math.min(fromIndex, this.length()) &&
     *                   this.toString().startsWith(str, k)
     * }</pre>
     * If no such value of <i>k</i> exists, then -1 is returned.
     *
     * @param   str         the substring to search for.
     * @param   fromIndex   the index to start the search from.
     * @return  the index within this sequence of the last occurrence of the
     *          specified substring.
     */
    public int lastIndexOf(String str, int fromIndex) {
        return String.lastIndexOf(value, 0, count, str, fromIndex);
    }

    
Causes this character sequence to be replaced by the reverse of
the sequence. If there are any surrogate pairs included in the
sequence, these are treated as single characters for the
reverse operation. Thus, the order of the high-low surrogates
is never reversed.
Let n be the character length of this character sequence (not the length in char values) just prior to execution of the reverse method. Then the character at index k in the new character sequence is
equal to the character at index n-k-1 in the old
character sequence.
Note that the reverse operation may result in producing
surrogate pairs that were unpaired low-surrogates and
high-surrogates before the operation. For example, reversing
"\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
a valid surrogate pair.
Returns:
 a reference to this object./**
     * Causes this character sequence to be replaced by the reverse of
     * the sequence. If there are any surrogate pairs included in the
     * sequence, these are treated as single characters for the
     * reverse operation. Thus, the order of the high-low surrogates
     * is never reversed.
     *
     * Let <i>n</i> be the character length of this character sequence
     * (not the length in {@code char} values) just prior to
     * execution of the {@code reverse} method. Then the
     * character at index <i>k</i> in the new character sequence is
     * equal to the character at index <i>n-k-1</i> in the old
     * character sequence.
     *
     * <p>Note that the reverse operation may result in producing
     * surrogate pairs that were unpaired low-surrogates and
     * high-surrogates before the operation. For example, reversing
     * "\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
     * a valid surrogate pair.
     *
     * @return  a reference to this object.
     */
    public AbstractStringBuilder reverse() {
        boolean hasSurrogates = false;
        int n = count - 1;
        for (int j = (n-1) >> 1; j >= 0; j--) {
            int k = n - j;
            char cj = value[j];
            char ck = value[k];
            value[j] = ck;
            value[k] = cj;
            if (Character.isSurrogate(cj) ||
                Character.isSurrogate(ck)) {
                hasSurrogates = true;
            }
        }
        if (hasSurrogates) {
            reverseAllValidSurrogatePairs();
        }
        return this;
    }

    
Outlined helper method for reverse() /** Outlined helper method for reverse() */
    private void reverseAllValidSurrogatePairs() {
        for (int i = 0; i < count - 1; i++) {
            char c2 = value[i];
            if (Character.isLowSurrogate(c2)) {
                char c1 = value[i + 1];
                if (Character.isHighSurrogate(c1)) {
                    value[i++] = c1;
                    value[i] = c2;
                }
            }
        }
    }

    
Returns a string representing the data in this sequence. A new String object is allocated and initialized to contain the character sequence currently represented by this object. This String is then returned. Subsequent changes to this sequence do not affect the contents of the String. 
Returns:
 a string representation of this sequence of characters./**
     * Returns a string representing the data in this sequence.
     * A new {@code String} object is allocated and initialized to
     * contain the character sequence currently represented by this
     * object. This {@code String} is then returned. Subsequent
     * changes to this sequence do not affect the contents of the
     * {@code String}.
     *
     * @return  a string representation of this sequence of characters.
     */
    @Override
    public abstract String toString();

    
Needed by String for the contentEquals method. /**
     * Needed by {@code String} for the contentEquals method.
     */
    final char[] getValue() {
        return value;
    }

}