/*
 * Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
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 *
 *
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 *
 *
 *
 *
 *
 *
 *
 */

package java.lang;

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

/**
 * 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.
 */
 char[] value;

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

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

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

 /**
 * 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.
 *
 * @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:
 * <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 {@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
 */
 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 {@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 {@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 <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円');
 }

 count = newLength;
 }

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

}