1 /*
   2  * Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.lang;
  27 
  28 import sun.misc.FloatingDecimal;
  29 import java.util.Arrays;
  30 
  31 /**
  32  * A mutable sequence of characters.
  33  * <p>
  34  * Implements a modifiable string. At any point in time it contains some
  35  * particular sequence of characters, but the length and content of the
  36  * sequence can be changed through certain method calls.
  37  *
  38  * <p>Unless otherwise noted, passing a {@code null} argument to a constructor
  39  * or method in this class will cause a {@link NullPointerException} to be
  40  * thrown.
  41  *
  42  * @author      Michael McCloskey
  43  * @author      Martin Buchholz
  44  * @author      Ulf Zibis
  45  * @since       1.5
  46  */
  47 abstract class AbstractStringBuilder implements Appendable, CharSequence {
  48     /**
  49      * The value is used for character storage.
  50      */
  51     char[] value;
  52 
  53     /**
  54      * The count is the number of characters used.
  55      */
  56     int count;
  57 
  58     /**
  59      * This no-arg constructor is necessary for serialization of subclasses.
  60      */
  61     AbstractStringBuilder() {
  62     }
  63 
  64     /**
  65      * Creates an AbstractStringBuilder of the specified capacity.
  66      */
  67     AbstractStringBuilder(int capacity) {
  68         value = new char[capacity];
  69     }
  70 
  71     /**
  72      * Returns the length (character count).
  73      *
  74      * @return  the length of the sequence of characters currently
  75      *          represented by this object
  76      */
  77     @Override
  78     public int length() {
  79         return count;
  80     }
  81 
  82     /**
  83      * Returns the current capacity. The capacity is the amount of storage
  84      * available for newly inserted characters, beyond which an allocation
  85      * will occur.
  86      *
  87      * @return  the current capacity
  88      */
  89     public int capacity() {
  90         return value.length;
  91     }
  92 
  93     /**
  94      * Ensures that the capacity is at least equal to the specified minimum.
  95      * If the current capacity is less than the argument, then a new internal
  96      * array is allocated with greater capacity. The new capacity is the
  97      * larger of:
  98      * <ul>
  99      * <li>The {@code minimumCapacity} argument.
 100      * <li>Twice the old capacity, plus {@code 2}.
 101      * </ul>
 102      * If the {@code minimumCapacity} argument is nonpositive, this
 103      * method takes no action and simply returns.
 104      * Note that subsequent operations on this object can reduce the
 105      * actual capacity below that requested here.
 106      *
 107      * @param   minimumCapacity   the minimum desired capacity.
 108      */
 109     public void ensureCapacity(int minimumCapacity) {
 110         if (minimumCapacity > 0)
 111             ensureCapacityInternal(minimumCapacity);
 112     }
 113 
 114     /**
 115      * For positive values of {@code minimumCapacity}, this method
 116      * behaves like {@code ensureCapacity}, however it is never
 117      * synchronized.
 118      * If {@code minimumCapacity} is non positive due to numeric
 119      * overflow, this method throws {@code OutOfMemoryError}.
 120      */
 121     private void ensureCapacityInternal(int minimumCapacity) {
 122         // overflow-conscious code
 123         if (minimumCapacity - value.length > 0) {
 124             value = Arrays.copyOf(value,
 125                     newCapacity(minimumCapacity));
 126         }
 127     }
 128 
 129     /**
 130      * The maximum size of array to allocate (unless necessary).
 131      * Some VMs reserve some header words in an array.
 132      * Attempts to allocate larger arrays may result in
 133      * OutOfMemoryError: Requested array size exceeds VM limit
 134      */
 135     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
 136 
 137     /**
 138      * Returns a capacity at least as large as the given minimum capacity.
 139      * Returns the current capacity increased by the same amount + 2 if
 140      * that suffices.
 141      * Will not return a capacity greater than {@code MAX_ARRAY_SIZE}
 142      * unless the given minimum capacity is greater than that.
 143      *
 144      * @param  minCapacity the desired minimum capacity
 145      * @throws OutOfMemoryError if minCapacity is less than zero or
 146      *         greater than Integer.MAX_VALUE
 147      */
 148     private int newCapacity(int minCapacity) {
 149         // overflow-conscious code
 150         int newCapacity = (value.length << 1) + 2;
 151         if (newCapacity - minCapacity < 0) {
 152             newCapacity = minCapacity;
 153         }
 154         return (newCapacity <= 0 || MAX_ARRAY_SIZE - newCapacity < 0)
 155             ? hugeCapacity(minCapacity)
 156             : newCapacity;
 157     }
 158 
 159     private int hugeCapacity(int minCapacity) {
 160         if (Integer.MAX_VALUE - minCapacity < 0) { // overflow
 161             throw new OutOfMemoryError();
 162         }
 163         return (minCapacity > MAX_ARRAY_SIZE)
 164             ? minCapacity : MAX_ARRAY_SIZE;
 165     }
 166 
 167     /**
 168      * Attempts to reduce storage used for the character sequence.
 169      * If the buffer is larger than necessary to hold its current sequence of
 170      * characters, then it may be resized to become more space efficient.
 171      * Calling this method may, but is not required to, affect the value
 172      * returned by a subsequent call to the {@link #capacity()} method.
 173      */
 174     public void trimToSize() {
 175         if (count < value.length) {
 176             value = Arrays.copyOf(value, count);
 177         }
 178     }
 179 
 180     /**
 181      * Sets the length of the character sequence.
 182      * The sequence is changed to a new character sequence
 183      * whose length is specified by the argument. For every nonnegative
 184      * index <i>k</i> less than {@code newLength}, the character at
 185      * index <i>k</i> in the new character sequence is the same as the
 186      * character at index <i>k</i> in the old sequence if <i>k</i> is less
 187      * than the length of the old character sequence; otherwise, it is the
 188      * null character {@code '\u005Cu0000'}.
 189      *
 190      * In other words, if the {@code newLength} argument is less than
 191      * the current length, the length is changed to the specified length.
 192      * <p>
 193      * If the {@code newLength} argument is greater than or equal
 194      * to the current length, sufficient null characters
 195      * ({@code '\u005Cu0000'}) are appended so that
 196      * length becomes the {@code newLength} argument.
 197      * <p>
 198      * The {@code newLength} argument must be greater than or equal
 199      * to {@code 0}.
 200      *
 201      * @param      newLength   the new length
 202      * @throws     IndexOutOfBoundsException  if the
 203      *               {@code newLength} argument is negative.
 204      */
 205     public void setLength(int newLength) {
 206         if (newLength < 0)
 207             throw new StringIndexOutOfBoundsException(newLength);
 208         ensureCapacityInternal(newLength);
 209 
 210         if (count < newLength) {
 211             Arrays.fill(value, count, newLength, '\0');
 212         }
 213 
 214         count = newLength;
 215     }
 216 
 217     /**
 218      * Returns the {@code char} value in this sequence at the specified index.
 219      * The first {@code char} value is at index {@code 0}, the next at index
 220      * {@code 1}, and so on, as in array indexing.
 221      * <p>
 222      * The index argument must be greater than or equal to
 223      * {@code 0}, and less than the length of this sequence.
 224      *
 225      * <p>If the {@code char} value specified by the index is a
 226      * <a href="Character.html#unicode">surrogate</a>, the surrogate
 227      * value is returned.
 228      *
 229      * @param      index   the index of the desired {@code char} value.
 230      * @return     the {@code char} value at the specified index.
 231      * @throws     IndexOutOfBoundsException  if {@code index} is
 232      *             negative or greater than or equal to {@code length()}.
 233      */
 234     @Override
 235     public char charAt(int index) {
 236         if ((index < 0) || (index >= count))
 237             throw new StringIndexOutOfBoundsException(index);
 238         return value[index];
 239     }
 240 
 241     /**
 242      * Returns the character (Unicode code point) at the specified
 243      * index. The index refers to {@code char} values
 244      * (Unicode code units) and ranges from {@code 0} to
 245      * {@link #length()}{@code  - 1}.
 246      *
 247      * <p> If the {@code char} value specified at the given index
 248      * is in the high-surrogate range, the following index is less
 249      * than the length of this sequence, and the
 250      * {@code char} value at the following index is in the
 251      * low-surrogate range, then the supplementary code point
 252      * corresponding to this surrogate pair is returned. Otherwise,
 253      * the {@code char} value at the given index is returned.
 254      *
 255      * @param      index the index to the {@code char} values
 256      * @return     the code point value of the character at the
 257      *             {@code index}
 258      * @exception  IndexOutOfBoundsException  if the {@code index}
 259      *             argument is negative or not less than the length of this
 260      *             sequence.
 261      */
 262     public int codePointAt(int index) {
 263         if ((index < 0) || (index >= count)) {
 264             throw new StringIndexOutOfBoundsException(index);
 265         }
 266         return Character.codePointAtImpl(value, index, count);
 267     }
 268 
 269     /**
 270      * Returns the character (Unicode code point) before the specified
 271      * index. The index refers to {@code char} values
 272      * (Unicode code units) and ranges from {@code 1} to {@link
 273      * #length()}.
 274      *
 275      * <p> If the {@code char} value at {@code (index - 1)}
 276      * is in the low-surrogate range, {@code (index - 2)} is not
 277      * negative, and the {@code char} value at {@code (index -
 278      * 2)} is in the high-surrogate range, then the
 279      * supplementary code point value of the surrogate pair is
 280      * returned. If the {@code char} value at {@code index -
 281      * 1} is an unpaired low-surrogate or a high-surrogate, the
 282      * surrogate value is returned.
 283      *
 284      * @param     index the index following the code point that should be returned
 285      * @return    the Unicode code point value before the given index.
 286      * @exception IndexOutOfBoundsException if the {@code index}
 287      *            argument is less than 1 or greater than the length
 288      *            of this sequence.
 289      */
 290     public int codePointBefore(int index) {
 291         int i = index - 1;
 292         if ((i < 0) || (i >= count)) {
 293             throw new StringIndexOutOfBoundsException(index);
 294         }
 295         return Character.codePointBeforeImpl(value, index, 0);
 296     }
 297 
 298     /**
 299      * Returns the number of Unicode code points in the specified text
 300      * range of this sequence. The text range begins at the specified
 301      * {@code beginIndex} and extends to the {@code char} at
 302      * index {@code endIndex - 1}. Thus the length (in
 303      * {@code char}s) of the text range is
 304      * {@code endIndex-beginIndex}. Unpaired surrogates within
 305      * this sequence count as one code point each.
 306      *
 307      * @param beginIndex the index to the first {@code char} of
 308      * the text range.
 309      * @param endIndex the index after the last {@code char} of
 310      * the text range.
 311      * @return the number of Unicode code points in the specified text
 312      * range
 313      * @exception IndexOutOfBoundsException if the
 314      * {@code beginIndex} is negative, or {@code endIndex}
 315      * is larger than the length of this sequence, or
 316      * {@code beginIndex} is larger than {@code endIndex}.
 317      */
 318     public int codePointCount(int beginIndex, int endIndex) {
 319         if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
 320             throw new IndexOutOfBoundsException();
 321         }
 322         return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex);
 323     }
 324 
 325     /**
 326      * Returns the index within this sequence that is offset from the
 327      * given {@code index} by {@code codePointOffset} code
 328      * points. Unpaired surrogates within the text range given by
 329      * {@code index} and {@code codePointOffset} count as
 330      * one code point each.
 331      *
 332      * @param index the index to be offset
 333      * @param codePointOffset the offset in code points
 334      * @return the index within this sequence
 335      * @exception IndexOutOfBoundsException if {@code index}
 336      *   is negative or larger then the length of this sequence,
 337      *   or if {@code codePointOffset} is positive and the subsequence
 338      *   starting with {@code index} has fewer than
 339      *   {@code codePointOffset} code points,
 340      *   or if {@code codePointOffset} is negative and the subsequence
 341      *   before {@code index} has fewer than the absolute value of
 342      *   {@code codePointOffset} code points.
 343      */
 344     public int offsetByCodePoints(int index, int codePointOffset) {
 345         if (index < 0 || index > count) {
 346             throw new IndexOutOfBoundsException();
 347         }
 348         return Character.offsetByCodePointsImpl(value, 0, count,
 349                                                 index, codePointOffset);
 350     }
 351 
 352     /**
 353      * Characters are copied from this sequence into the
 354      * destination character array {@code dst}. The first character to
 355      * be copied is at index {@code srcBegin}; the last character to
 356      * be copied is at index {@code srcEnd-1}. The total number of
 357      * characters to be copied is {@code srcEnd-srcBegin}. The
 358      * characters are copied into the subarray of {@code dst} starting
 359      * at index {@code dstBegin} and ending at index:
 360      * <pre>{@code
 361      * dstbegin + (srcEnd-srcBegin) - 1
 362      * }</pre>
 363      *
 364      * @param      srcBegin   start copying at this offset.
 365      * @param      srcEnd     stop copying at this offset.
 366      * @param      dst        the array to copy the data into.
 367      * @param      dstBegin   offset into {@code dst}.
 368      * @throws     IndexOutOfBoundsException  if any of the following is true:
 369      *             <ul>
 370      *             <li>{@code srcBegin} is negative
 371      *             <li>{@code dstBegin} is negative
 372      *             <li>the {@code srcBegin} argument is greater than
 373      *             the {@code srcEnd} argument.
 374      *             <li>{@code srcEnd} is greater than
 375      *             {@code this.length()}.
 376      *             <li>{@code dstBegin+srcEnd-srcBegin} is greater than
 377      *             {@code dst.length}
 378      *             </ul>
 379      */
 380     public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
 381     {
 382         if (srcBegin < 0)
 383             throw new StringIndexOutOfBoundsException(srcBegin);
 384         if ((srcEnd < 0) || (srcEnd > count))
 385             throw new StringIndexOutOfBoundsException(srcEnd);
 386         if (srcBegin > srcEnd)
 387             throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");
 388         System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
 389     }
 390 
 391     /**
 392      * The character at the specified index is set to {@code ch}. This
 393      * sequence is altered to represent a new character sequence that is
 394      * identical to the old character sequence, except that it contains the
 395      * character {@code ch} at position {@code index}.
 396      * <p>
 397      * The index argument must be greater than or equal to
 398      * {@code 0}, and less than the length of this sequence.
 399      *
 400      * @param      index   the index of the character to modify.
 401      * @param      ch      the new character.
 402      * @throws     IndexOutOfBoundsException  if {@code index} is
 403      *             negative or greater than or equal to {@code length()}.
 404      */
 405     public void setCharAt(int index, char ch) {
 406         if ((index < 0) || (index >= count))
 407             throw new StringIndexOutOfBoundsException(index);
 408         value[index] = ch;
 409     }
 410 
 411     /**
 412      * Appends the string representation of the {@code Object} argument.
 413      * <p>
 414      * The overall effect is exactly as if the argument were converted
 415      * to a string by the method {@link String#valueOf(Object)},
 416      * and the characters of that string were then
 417      * {@link #append(String) appended} to this character sequence.
 418      *
 419      * @param   obj   an {@code Object}.
 420      * @return  a reference to this object.
 421      */
 422     public AbstractStringBuilder append(Object obj) {
 423         return append(String.valueOf(obj));
 424     }
 425 
 426     /**
 427      * Appends the specified string to this character sequence.
 428      * <p>
 429      * The characters of the {@code String} argument are appended, in
 430      * order, increasing the length of this sequence by the length of the
 431      * argument. If {@code str} is {@code null}, then the four
 432      * characters {@code "null"} are appended.
 433      * <p>
 434      * Let <i>n</i> be the length of this character sequence just prior to
 435      * execution of the {@code append} method. Then the character at
 436      * index <i>k</i> in the new character sequence is equal to the character
 437      * at index <i>k</i> in the old character sequence, if <i>k</i> is less
 438      * than <i>n</i>; otherwise, it is equal to the character at index
 439      * <i>k-n</i> in the argument {@code str}.
 440      *
 441      * @param   str   a string.
 442      * @return  a reference to this object.
 443      */
 444     public AbstractStringBuilder append(String str) {
 445         if (str == null)
 446             return appendNull();
 447         int len = str.length();
 448         ensureCapacityInternal(count + len);
 449         str.getChars(0, len, value, count);
 450         count += len;
 451         return this;
 452     }
 453 
 454     // Documentation in subclasses because of synchro difference
 455     public AbstractStringBuilder append(StringBuffer sb) {
 456         if (sb == null)
 457             return appendNull();
 458         int len = sb.length();
 459         ensureCapacityInternal(count + len);
 460         sb.getChars(0, len, value, count);
 461         count += len;
 462         return this;
 463     }
 464 
 465     /**
 466      * @since 1.8
 467      */
 468     AbstractStringBuilder append(AbstractStringBuilder asb) {
 469         if (asb == null)
 470             return appendNull();
 471         int len = asb.length();
 472         ensureCapacityInternal(count + len);
 473         asb.getChars(0, len, value, count);
 474         count += len;
 475         return this;
 476     }
 477 
 478     // Documentation in subclasses because of synchro difference
 479     @Override
 480     public AbstractStringBuilder append(CharSequence s) {
 481         if (s == null)
 482             return appendNull();
 483         if (s instanceof String)
 484             return this.append((String)s);
 485         if (s instanceof AbstractStringBuilder)
 486             return this.append((AbstractStringBuilder)s);
 487 
 488         return this.append(s, 0, s.length());
 489     }
 490 
 491     private AbstractStringBuilder appendNull() {
 492         int c = count;
 493         ensureCapacityInternal(c + 4);
 494         final char[] value = this.value;
 495         value[c++] = 'n';
 496         value[c++] = 'u';
 497         value[c++] = 'l';
 498         value[c++] = 'l';
 499         count = c;
 500         return this;
 501     }
 502 
 503     /**
 504      * Appends a subsequence of the specified {@code CharSequence} to this
 505      * sequence.
 506      * <p>
 507      * Characters of the argument {@code s}, starting at
 508      * index {@code start}, are appended, in order, to the contents of
 509      * this sequence up to the (exclusive) index {@code end}. The length
 510      * of this sequence is increased by the value of {@code end - start}.
 511      * <p>
 512      * Let <i>n</i> be the length of this character sequence just prior to
 513      * execution of the {@code append} method. Then the character at
 514      * index <i>k</i> in this character sequence becomes equal to the
 515      * character at index <i>k</i> in this sequence, if <i>k</i> is less than
 516      * <i>n</i>; otherwise, it is equal to the character at index
 517      * <i>k+start-n</i> in the argument {@code s}.
 518      * <p>
 519      * If {@code s} is {@code null}, then this method appends
 520      * characters as if the s parameter was a sequence containing the four
 521      * characters {@code "null"}.
 522      *
 523      * @param   s the sequence to append.
 524      * @param   start   the starting index of the subsequence to be appended.
 525      * @param   end     the end index of the subsequence to be appended.
 526      * @return  a reference to this object.
 527      * @throws     IndexOutOfBoundsException if
 528      *             {@code start} is negative, or
 529      *             {@code start} is greater than {@code end} or
 530      *             {@code end} is greater than {@code s.length()}
 531      */
 532     @Override
 533     public AbstractStringBuilder append(CharSequence s, int start, int end) {
 534         if (s == null)
 535             s = "null";
 536         if ((start < 0) || (start > end) || (end > s.length()))
 537             throw new IndexOutOfBoundsException(
 538                 "start " + start + ", end " + end + ", s.length() "
 539                 + s.length());
 540         int len = end - start;
 541         ensureCapacityInternal(count + len);
 542         for (int i = start, j = count; i < end; i++, j++)
 543             value[j] = s.charAt(i);
 544         count += len;
 545         return this;
 546     }
 547 
 548     /**
 549      * Appends the string representation of the {@code char} array
 550      * argument to this sequence.
 551      * <p>
 552      * The characters of the array argument are appended, in order, to
 553      * the contents of this sequence. The length of this sequence
 554      * increases by the length of the argument.
 555      * <p>
 556      * The overall effect is exactly as if the argument were converted
 557      * to a string by the method {@link String#valueOf(char[])},
 558      * and the characters of that string were then
 559      * {@link #append(String) appended} to this character sequence.
 560      *
 561      * @param   str   the characters to be appended.
 562      * @return  a reference to this object.
 563      */
 564     public AbstractStringBuilder append(char[] str) {
 565         int len = str.length;
 566         ensureCapacityInternal(count + len);
 567         System.arraycopy(str, 0, value, count, len);
 568         count += len;
 569         return this;
 570     }
 571 
 572     /**
 573      * Appends the string representation of a subarray of the
 574      * {@code char} array argument to this sequence.
 575      * <p>
 576      * Characters of the {@code char} array {@code str}, starting at
 577      * index {@code offset}, are appended, in order, to the contents
 578      * of this sequence. The length of this sequence increases
 579      * by the value of {@code len}.
 580      * <p>
 581      * The overall effect is exactly as if the arguments were converted
 582      * to a string by the method {@link String#valueOf(char[],int,int)},
 583      * and the characters of that string were then
 584      * {@link #append(String) appended} to this character sequence.
 585      *
 586      * @param   str      the characters to be appended.
 587      * @param   offset   the index of the first {@code char} to append.
 588      * @param   len      the number of {@code char}s to append.
 589      * @return  a reference to this object.
 590      * @throws IndexOutOfBoundsException
 591      *         if {@code offset < 0} or {@code len < 0}
 592      *         or {@code offset+len > str.length}
 593      */
 594     public AbstractStringBuilder append(char str[], int offset, int len) {
 595         if (len > 0)                // let arraycopy report AIOOBE for len < 0
 596             ensureCapacityInternal(count + len);
 597         System.arraycopy(str, offset, value, count, len);
 598         count += len;
 599         return this;
 600     }
 601 
 602     /**
 603      * Appends the string representation of the {@code boolean}
 604      * argument to the sequence.
 605      * <p>
 606      * The overall effect is exactly as if the argument were converted
 607      * to a string by the method {@link String#valueOf(boolean)},
 608      * and the characters of that string were then
 609      * {@link #append(String) appended} to this character sequence.
 610      *
 611      * @param   b   a {@code boolean}.
 612      * @return  a reference to this object.
 613      */
 614     public AbstractStringBuilder append(boolean b) {
 615         if (b) {
 616             ensureCapacityInternal(count + 4);
 617             value[count++] = 't';
 618             value[count++] = 'r';
 619             value[count++] = 'u';
 620             value[count++] = 'e';
 621         } else {
 622             ensureCapacityInternal(count + 5);
 623             value[count++] = 'f';
 624             value[count++] = 'a';
 625             value[count++] = 'l';
 626             value[count++] = 's';
 627             value[count++] = 'e';
 628         }
 629         return this;
 630     }
 631 
 632     /**
 633      * Appends the string representation of the {@code char}
 634      * argument to this sequence.
 635      * <p>
 636      * The argument is appended to the contents of this sequence.
 637      * The length of this sequence increases by {@code 1}.
 638      * <p>
 639      * The overall effect is exactly as if the argument were converted
 640      * to a string by the method {@link String#valueOf(char)},
 641      * and the character in that string were then
 642      * {@link #append(String) appended} to this character sequence.
 643      *
 644      * @param   c   a {@code char}.
 645      * @return  a reference to this object.
 646      */
 647     @Override
 648     public AbstractStringBuilder append(char c) {
 649         ensureCapacityInternal(count + 1);
 650         value[count++] = c;
 651         return this;
 652     }
 653 
 654     /**
 655      * Appends the string representation of the {@code int}
 656      * argument to this sequence.
 657      * <p>
 658      * The overall effect is exactly as if the argument were converted
 659      * to a string by the method {@link String#valueOf(int)},
 660      * and the characters of that string were then
 661      * {@link #append(String) appended} to this character sequence.
 662      *
 663      * @param   i   an {@code int}.
 664      * @return  a reference to this object.
 665      */
 666     public AbstractStringBuilder append(int i) {
 667         if (i == Integer.MIN_VALUE) {
 668             append("-2147483648");
 669             return this;
 670         }
 671         int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1
 672                                      : Integer.stringSize(i);
 673         int spaceNeeded = count + appendedLength;
 674         ensureCapacityInternal(spaceNeeded);
 675         Integer.getChars(i, spaceNeeded, value);
 676         count = spaceNeeded;
 677         return this;
 678     }
 679 
 680     /**
 681      * Appends the string representation of the {@code long}
 682      * argument to this sequence.
 683      * <p>
 684      * The overall effect is exactly as if the argument were converted
 685      * to a string by the method {@link String#valueOf(long)},
 686      * and the characters of that string were then
 687      * {@link #append(String) appended} to this character sequence.
 688      *
 689      * @param   l   a {@code long}.
 690      * @return  a reference to this object.
 691      */
 692     public AbstractStringBuilder append(long l) {
 693         if (l == Long.MIN_VALUE) {
 694             append("-9223372036854775808");
 695             return this;
 696         }
 697         int appendedLength = (l < 0) ? Long.stringSize(-l) + 1
 698                                      : Long.stringSize(l);
 699         int spaceNeeded = count + appendedLength;
 700         ensureCapacityInternal(spaceNeeded);
 701         Long.getChars(l, spaceNeeded, value);
 702         count = spaceNeeded;
 703         return this;
 704     }
 705 
 706     /**
 707      * Appends the string representation of the {@code float}
 708      * argument to this sequence.
 709      * <p>
 710      * The overall effect is exactly as if the argument were converted
 711      * to a string by the method {@link String#valueOf(float)},
 712      * and the characters of that string were then
 713      * {@link #append(String) appended} to this character sequence.
 714      *
 715      * @param   f   a {@code float}.
 716      * @return  a reference to this object.
 717      */
 718     public AbstractStringBuilder append(float f) {
 719         FloatingDecimal.appendTo(f,this);
 720         return this;
 721     }
 722 
 723     /**
 724      * Appends the string representation of the {@code double}
 725      * argument to this sequence.
 726      * <p>
 727      * The overall effect is exactly as if the argument were converted
 728      * to a string by the method {@link String#valueOf(double)},
 729      * and the characters of that string were then
 730      * {@link #append(String) appended} to this character sequence.
 731      *
 732      * @param   d   a {@code double}.
 733      * @return  a reference to this object.
 734      */
 735     public AbstractStringBuilder append(double d) {
 736         FloatingDecimal.appendTo(d,this);
 737         return this;
 738     }
 739 
 740     /**
 741      * Removes the characters in a substring of this sequence.
 742      * The substring begins at the specified {@code start} and extends to
 743      * the character at index {@code end - 1} or to the end of the
 744      * sequence if no such character exists. If
 745      * {@code start} is equal to {@code end}, no changes are made.
 746      *
 747      * @param      start  The beginning index, inclusive.
 748      * @param      end    The ending index, exclusive.
 749      * @return     This object.
 750      * @throws     StringIndexOutOfBoundsException  if {@code start}
 751      *             is negative, greater than {@code length()}, or
 752      *             greater than {@code end}.
 753      */
 754     public AbstractStringBuilder delete(int start, int end) {
 755         if (start < 0)
 756             throw new StringIndexOutOfBoundsException(start);
 757         if (end > count)
 758             end = count;
 759         if (start > end)
 760             throw new StringIndexOutOfBoundsException();
 761         int len = end - start;
 762         if (len > 0) {
 763             System.arraycopy(value, start+len, value, start, count-end);
 764             count -= len;
 765         }
 766         return this;
 767     }
 768 
 769     /**
 770      * Appends the string representation of the {@code codePoint}
 771      * argument to this sequence.
 772      *
 773      * <p> The argument is appended to the contents of this sequence.
 774      * The length of this sequence increases by
 775      * {@link Character#charCount(int) Character.charCount(codePoint)}.
 776      *
 777      * <p> The overall effect is exactly as if the argument were
 778      * converted to a {@code char} array by the method
 779      * {@link Character#toChars(int)} and the character in that array
 780      * were then {@link #append(char[]) appended} to this character
 781      * sequence.
 782      *
 783      * @param   codePoint   a Unicode code point
 784      * @return  a reference to this object.
 785      * @exception IllegalArgumentException if the specified
 786      * {@code codePoint} isn't a valid Unicode code point
 787      */
 788     public AbstractStringBuilder appendCodePoint(int codePoint) {
 789         final int count = this.count;
 790 
 791         if (Character.isBmpCodePoint(codePoint)) {
 792             ensureCapacityInternal(count + 1);
 793             value[count] = (char) codePoint;
 794             this.count = count + 1;
 795         } else if (Character.isValidCodePoint(codePoint)) {
 796             ensureCapacityInternal(count + 2);
 797             Character.toSurrogates(codePoint, value, count);
 798             this.count = count + 2;
 799         } else {
 800             throw new IllegalArgumentException();
 801         }
 802         return this;
 803     }
 804 
 805     /**
 806      * Removes the {@code char} at the specified position in this
 807      * sequence. This sequence is shortened by one {@code char}.
 808      *
 809      * <p>Note: If the character at the given index is a supplementary
 810      * character, this method does not remove the entire character. If
 811      * correct handling of supplementary characters is required,
 812      * determine the number of {@code char}s to remove by calling
 813      * {@code Character.charCount(thisSequence.codePointAt(index))},
 814      * where {@code thisSequence} is this sequence.
 815      *
 816      * @param       index  Index of {@code char} to remove
 817      * @return      This object.
 818      * @throws      StringIndexOutOfBoundsException  if the {@code index}
 819      *              is negative or greater than or equal to
 820      *              {@code length()}.
 821      */
 822     public AbstractStringBuilder deleteCharAt(int index) {
 823         if ((index < 0) || (index >= count))
 824             throw new StringIndexOutOfBoundsException(index);
 825         System.arraycopy(value, index+1, value, index, count-index-1);
 826         count--;
 827         return this;
 828     }
 829 
 830     /**
 831      * Replaces the characters in a substring of this sequence
 832      * with characters in the specified {@code String}. The substring
 833      * begins at the specified {@code start} and extends to the character
 834      * at index {@code end - 1} or to the end of the
 835      * sequence if no such character exists. First the
 836      * characters in the substring are removed and then the specified
 837      * {@code String} is inserted at {@code start}. (This
 838      * sequence will be lengthened to accommodate the
 839      * specified String if necessary.)
 840      *
 841      * @param      start    The beginning index, inclusive.
 842      * @param      end      The ending index, exclusive.
 843      * @param      str   String that will replace previous contents.
 844      * @return     This object.
 845      * @throws     StringIndexOutOfBoundsException  if {@code start}
 846      *             is negative, greater than {@code length()}, or
 847      *             greater than {@code end}.
 848      */
 849     public AbstractStringBuilder replace(int start, int end, String str) {
 850         if (start < 0)
 851             throw new StringIndexOutOfBoundsException(start);
 852         if (start > count)
 853             throw new StringIndexOutOfBoundsException("start > length()");
 854         if (start > end)
 855             throw new StringIndexOutOfBoundsException("start > end");
 856 
 857         if (end > count)
 858             end = count;
 859         int len = str.length();
 860         int newCount = count + len - (end - start);
 861         ensureCapacityInternal(newCount);
 862 
 863         System.arraycopy(value, end, value, start + len, count - end);
 864         str.getChars(value, start);
 865         count = newCount;
 866         return this;
 867     }
 868 
 869     /**
 870      * Returns a new {@code String} that contains a subsequence of
 871      * characters currently contained in this character sequence. The
 872      * substring begins at the specified index and extends to the end of
 873      * this sequence.
 874      *
 875      * @param      start    The beginning index, inclusive.
 876      * @return     The new string.
 877      * @throws     StringIndexOutOfBoundsException  if {@code start} is
 878      *             less than zero, or greater than the length of this object.
 879      */
 880     public String substring(int start) {
 881         return substring(start, count);
 882     }
 883 
 884     /**
 885      * Returns a new character sequence that is a subsequence of this sequence.
 886      *
 887      * <p> An invocation of this method of the form
 888      *
 889      * <pre>{@code
 890      * sb.subSequence(begin,&nbsp;end)}</pre>
 891      *
 892      * behaves in exactly the same way as the invocation
 893      *
 894      * <pre>{@code
 895      * sb.substring(begin,&nbsp;end)}</pre>
 896      *
 897      * This method is provided so that this class can
 898      * implement the {@link CharSequence} interface.
 899      *
 900      * @param      start   the start index, inclusive.
 901      * @param      end     the end index, exclusive.
 902      * @return     the specified subsequence.
 903      *
 904      * @throws  IndexOutOfBoundsException
 905      *          if {@code start} or {@code end} are negative,
 906      *          if {@code end} is greater than {@code length()},
 907      *          or if {@code start} is greater than {@code end}
 908      * @spec JSR-51
 909      */
 910     @Override
 911     public CharSequence subSequence(int start, int end) {
 912         return substring(start, end);
 913     }
 914 
 915     /**
 916      * Returns a new {@code String} that contains a subsequence of
 917      * characters currently contained in this sequence. The
 918      * substring begins at the specified {@code start} and
 919      * extends to the character at index {@code end - 1}.
 920      *
 921      * @param      start    The beginning index, inclusive.
 922      * @param      end      The ending index, exclusive.
 923      * @return     The new string.
 924      * @throws     StringIndexOutOfBoundsException  if {@code start}
 925      *             or {@code end} are negative or greater than
 926      *             {@code length()}, or {@code start} is
 927      *             greater than {@code end}.
 928      */
 929     public String substring(int start, int end) {
 930         if (start < 0)
 931             throw new StringIndexOutOfBoundsException(start);
 932         if (end > count)
 933             throw new StringIndexOutOfBoundsException(end);
 934         if (start > end)
 935             throw new StringIndexOutOfBoundsException(end - start);
 936         return new String(value, start, end - start);
 937     }
 938 
 939     /**
 940      * Inserts the string representation of a subarray of the {@code str}
 941      * array argument into this sequence. The subarray begins at the
 942      * specified {@code offset} and extends {@code len} {@code char}s.
 943      * The characters of the subarray are inserted into this sequence at
 944      * the position indicated by {@code index}. The length of this
 945      * sequence increases by {@code len} {@code char}s.
 946      *
 947      * @param      index    position at which to insert subarray.
 948      * @param      str       A {@code char} array.
 949      * @param      offset   the index of the first {@code char} in subarray to
 950      *             be inserted.
 951      * @param      len      the number of {@code char}s in the subarray to
 952      *             be inserted.
 953      * @return     This object
 954      * @throws     StringIndexOutOfBoundsException  if {@code index}
 955      *             is negative or greater than {@code length()}, or
 956      *             {@code offset} or {@code len} are negative, or
 957      *             {@code (offset+len)} is greater than
 958      *             {@code str.length}.
 959      */
 960     public AbstractStringBuilder insert(int index, char[] str, int offset,
 961                                         int len)
 962     {
 963         if ((index < 0) || (index > length()))
 964             throw new StringIndexOutOfBoundsException(index);
 965         if ((offset < 0) || (len < 0) || (offset > str.length - len))
 966             throw new StringIndexOutOfBoundsException(
 967                 "offset " + offset + ", len " + len + ", str.length "
 968                 + str.length);
 969         ensureCapacityInternal(count + len);
 970         System.arraycopy(value, index, value, index + len, count - index);
 971         System.arraycopy(str, offset, value, index, len);
 972         count += len;
 973         return this;
 974     }
 975 
 976     /**
 977      * Inserts the string representation of the {@code Object}
 978      * argument into this character sequence.
 979      * <p>
 980      * The overall effect is exactly as if the second argument were
 981      * converted to a string by the method {@link String#valueOf(Object)},
 982      * and the characters of that string were then
 983      * {@link #insert(int,String) inserted} into this character
 984      * sequence at the indicated offset.
 985      * <p>
 986      * The {@code offset} argument must be greater than or equal to
 987      * {@code 0}, and less than or equal to the {@linkplain #length() length}
 988      * of this sequence.
 989      *
 990      * @param      offset   the offset.
 991      * @param      obj      an {@code Object}.
 992      * @return     a reference to this object.
 993      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
 994      */
 995     public AbstractStringBuilder insert(int offset, Object obj) {
 996         return insert(offset, String.valueOf(obj));
 997     }
 998 
 999     /**
1000      * Inserts the string into this character sequence.
1001      * <p>
1002      * The characters of the {@code String} argument are inserted, in
1003      * order, into this sequence at the indicated offset, moving up any
1004      * characters originally above that position and increasing the length
1005      * of this sequence by the length of the argument. If
1006      * {@code str} is {@code null}, then the four characters
1007      * {@code "null"} are inserted into this sequence.
1008      * <p>
1009      * The character at index <i>k</i> in the new character sequence is
1010      * equal to:
1011      * <ul>
1012      * <li>the character at index <i>k</i> in the old character sequence, if
1013      * <i>k</i> is less than {@code offset}
1014      * <li>the character at index <i>k</i>{@code -offset} in the
1015      * argument {@code str}, if <i>k</i> is not less than
1016      * {@code offset} but is less than {@code offset+str.length()}
1017      * <li>the character at index <i>k</i>{@code -str.length()} in the
1018      * old character sequence, if <i>k</i> is not less than
1019      * {@code offset+str.length()}
1020      * </ul><p>
1021      * The {@code offset} argument must be greater than or equal to
1022      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1023      * of this sequence.
1024      *
1025      * @param      offset   the offset.
1026      * @param      str      a string.
1027      * @return     a reference to this object.
1028      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1029      */
1030     public AbstractStringBuilder insert(int offset, String str) {
1031         if ((offset < 0) || (offset > length()))
1032             throw new StringIndexOutOfBoundsException(offset);
1033         if (str == null)
1034             str = "null";
1035         int len = str.length();
1036         ensureCapacityInternal(count + len);
1037         System.arraycopy(value, offset, value, offset + len, count - offset);
1038         str.getChars(value, offset);
1039         count += len;
1040         return this;
1041     }
1042 
1043     /**
1044      * Inserts the string representation of the {@code char} array
1045      * argument into this sequence.
1046      * <p>
1047      * The characters of the array argument are inserted into the
1048      * contents of this sequence at the position indicated by
1049      * {@code offset}. The length of this sequence increases by
1050      * the length of the argument.
1051      * <p>
1052      * The overall effect is exactly as if the second argument were
1053      * converted to a string by the method {@link String#valueOf(char[])},
1054      * and the characters of that string were then
1055      * {@link #insert(int,String) inserted} into this character
1056      * sequence at the indicated offset.
1057      * <p>
1058      * The {@code offset} argument must be greater than or equal to
1059      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1060      * of this sequence.
1061      *
1062      * @param      offset   the offset.
1063      * @param      str      a character array.
1064      * @return     a reference to this object.
1065      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1066      */
1067     public AbstractStringBuilder insert(int offset, char[] str) {
1068         if ((offset < 0) || (offset > length()))
1069             throw new StringIndexOutOfBoundsException(offset);
1070         int len = str.length;
1071         ensureCapacityInternal(count + len);
1072         System.arraycopy(value, offset, value, offset + len, count - offset);
1073         System.arraycopy(str, 0, value, offset, len);
1074         count += len;
1075         return this;
1076     }
1077 
1078     /**
1079      * Inserts the specified {@code CharSequence} into this sequence.
1080      * <p>
1081      * The characters of the {@code CharSequence} argument are inserted,
1082      * in order, into this sequence at the indicated offset, moving up
1083      * any characters originally above that position and increasing the length
1084      * of this sequence by the length of the argument s.
1085      * <p>
1086      * The result of this method is exactly the same as if it were an
1087      * invocation of this object's
1088      * {@link #insert(int,CharSequence,int,int) insert}(dstOffset, s, 0, s.length())
1089      * method.
1090      *
1091      * <p>If {@code s} is {@code null}, then the four characters
1092      * {@code "null"} are inserted into this sequence.
1093      *
1094      * @param      dstOffset   the offset.
1095      * @param      s the sequence to be inserted
1096      * @return     a reference to this object.
1097      * @throws     IndexOutOfBoundsException  if the offset is invalid.
1098      */
1099     public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
1100         if (s == null)
1101             s = "null";
1102         if (s instanceof String)
1103             return this.insert(dstOffset, (String)s);
1104         return this.insert(dstOffset, s, 0, s.length());
1105     }
1106 
1107     /**
1108      * Inserts a subsequence of the specified {@code CharSequence} into
1109      * this sequence.
1110      * <p>
1111      * The subsequence of the argument {@code s} specified by
1112      * {@code start} and {@code end} are inserted,
1113      * in order, into this sequence at the specified destination offset, moving
1114      * up any characters originally above that position. The length of this
1115      * sequence is increased by {@code end - start}.
1116      * <p>
1117      * The character at index <i>k</i> in this sequence becomes equal to:
1118      * <ul>
1119      * <li>the character at index <i>k</i> in this sequence, if
1120      * <i>k</i> is less than {@code dstOffset}
1121      * <li>the character at index <i>k</i>{@code +start-dstOffset} in
1122      * the argument {@code s}, if <i>k</i> is greater than or equal to
1123      * {@code dstOffset} but is less than {@code dstOffset+end-start}
1124      * <li>the character at index <i>k</i>{@code -(end-start)} in this
1125      * sequence, if <i>k</i> is greater than or equal to
1126      * {@code dstOffset+end-start}
1127      * </ul><p>
1128      * The {@code dstOffset} argument must be greater than or equal to
1129      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1130      * of this sequence.
1131      * <p>The start argument must be nonnegative, and not greater than
1132      * {@code end}.
1133      * <p>The end argument must be greater than or equal to
1134      * {@code start}, and less than or equal to the length of s.
1135      *
1136      * <p>If {@code s} is {@code null}, then this method inserts
1137      * characters as if the s parameter was a sequence containing the four
1138      * characters {@code "null"}.
1139      *
1140      * @param      dstOffset   the offset in this sequence.
1141      * @param      s       the sequence to be inserted.
1142      * @param      start   the starting index of the subsequence to be inserted.
1143      * @param      end     the end index of the subsequence to be inserted.
1144      * @return     a reference to this object.
1145      * @throws     IndexOutOfBoundsException  if {@code dstOffset}
1146      *             is negative or greater than {@code this.length()}, or
1147      *              {@code start} or {@code end} are negative, or
1148      *              {@code start} is greater than {@code end} or
1149      *              {@code end} is greater than {@code s.length()}
1150      */
1151      public AbstractStringBuilder insert(int dstOffset, CharSequence s,
1152                                          int start, int end) {
1153         if (s == null)
1154             s = "null";
1155         if ((dstOffset < 0) || (dstOffset > this.length()))
1156             throw new IndexOutOfBoundsException("dstOffset "+dstOffset);
1157         if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))
1158             throw new IndexOutOfBoundsException(
1159                 "start " + start + ", end " + end + ", s.length() "
1160                 + s.length());
1161         int len = end - start;
1162         ensureCapacityInternal(count + len);
1163         System.arraycopy(value, dstOffset, value, dstOffset + len,
1164                          count - dstOffset);
1165         for (int i=start; i<end; i++)
1166             value[dstOffset++] = s.charAt(i);
1167         count += len;
1168         return this;
1169     }
1170 
1171     /**
1172      * Inserts the string representation of the {@code boolean}
1173      * argument into this sequence.
1174      * <p>
1175      * The overall effect is exactly as if the second argument were
1176      * converted to a string by the method {@link String#valueOf(boolean)},
1177      * and the characters of that string were then
1178      * {@link #insert(int,String) inserted} into this character
1179      * sequence at the indicated offset.
1180      * <p>
1181      * The {@code offset} argument must be greater than or equal to
1182      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1183      * of this sequence.
1184      *
1185      * @param      offset   the offset.
1186      * @param      b        a {@code boolean}.
1187      * @return     a reference to this object.
1188      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1189      */
1190     public AbstractStringBuilder insert(int offset, boolean b) {
1191         return insert(offset, String.valueOf(b));
1192     }
1193 
1194     /**
1195      * Inserts the string representation of the {@code char}
1196      * argument into this sequence.
1197      * <p>
1198      * The overall effect is exactly as if the second argument were
1199      * converted to a string by the method {@link String#valueOf(char)},
1200      * and the character in that string were then
1201      * {@link #insert(int,String) inserted} into this character
1202      * sequence at the indicated offset.
1203      * <p>
1204      * The {@code offset} argument must be greater than or equal to
1205      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1206      * of this sequence.
1207      *
1208      * @param      offset   the offset.
1209      * @param      c        a {@code char}.
1210      * @return     a reference to this object.
1211      * @throws     IndexOutOfBoundsException  if the offset is invalid.
1212      */
1213     public AbstractStringBuilder insert(int offset, char c) {
1214         ensureCapacityInternal(count + 1);
1215         System.arraycopy(value, offset, value, offset + 1, count - offset);
1216         value[offset] = c;
1217         count += 1;
1218         return this;
1219     }
1220 
1221     /**
1222      * Inserts the string representation of the second {@code int}
1223      * argument into this sequence.
1224      * <p>
1225      * The overall effect is exactly as if the second argument were
1226      * converted to a string by the method {@link String#valueOf(int)},
1227      * and the characters of that string were then
1228      * {@link #insert(int,String) inserted} into this character
1229      * sequence at the indicated offset.
1230      * <p>
1231      * The {@code offset} argument must be greater than or equal to
1232      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1233      * of this sequence.
1234      *
1235      * @param      offset   the offset.
1236      * @param      i        an {@code int}.
1237      * @return     a reference to this object.
1238      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1239      */
1240     public AbstractStringBuilder insert(int offset, int i) {
1241         return insert(offset, String.valueOf(i));
1242     }
1243 
1244     /**
1245      * Inserts the string representation of the {@code long}
1246      * argument into this sequence.
1247      * <p>
1248      * The overall effect is exactly as if the second argument were
1249      * converted to a string by the method {@link String#valueOf(long)},
1250      * and the characters of that string were then
1251      * {@link #insert(int,String) inserted} into this character
1252      * sequence at the indicated offset.
1253      * <p>
1254      * The {@code offset} argument must be greater than or equal to
1255      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1256      * of this sequence.
1257      *
1258      * @param      offset   the offset.
1259      * @param      l        a {@code long}.
1260      * @return     a reference to this object.
1261      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1262      */
1263     public AbstractStringBuilder insert(int offset, long l) {
1264         return insert(offset, String.valueOf(l));
1265     }
1266 
1267     /**
1268      * Inserts the string representation of the {@code float}
1269      * argument into this sequence.
1270      * <p>
1271      * The overall effect is exactly as if the second argument were
1272      * converted to a string by the method {@link String#valueOf(float)},
1273      * and the characters of that string were then
1274      * {@link #insert(int,String) inserted} into this character
1275      * sequence at the indicated offset.
1276      * <p>
1277      * The {@code offset} argument must be greater than or equal to
1278      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1279      * of this sequence.
1280      *
1281      * @param      offset   the offset.
1282      * @param      f        a {@code float}.
1283      * @return     a reference to this object.
1284      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1285      */
1286     public AbstractStringBuilder insert(int offset, float f) {
1287         return insert(offset, String.valueOf(f));
1288     }
1289 
1290     /**
1291      * Inserts the string representation of the {@code double}
1292      * argument into this sequence.
1293      * <p>
1294      * The overall effect is exactly as if the second argument were
1295      * converted to a string by the method {@link String#valueOf(double)},
1296      * and the characters of that string were then
1297      * {@link #insert(int,String) inserted} into this character
1298      * sequence at the indicated offset.
1299      * <p>
1300      * The {@code offset} argument must be greater than or equal to
1301      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1302      * of this sequence.
1303      *
1304      * @param      offset   the offset.
1305      * @param      d        a {@code double}.
1306      * @return     a reference to this object.
1307      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1308      */
1309     public AbstractStringBuilder insert(int offset, double d) {
1310         return insert(offset, String.valueOf(d));
1311     }
1312 
1313     /**
1314      * Returns the index within this string of the first occurrence of the
1315      * specified substring. The integer returned is the smallest value
1316      * <i>k</i> such that:
1317      * <pre>{@code
1318      * this.toString().startsWith(str, <i>k</i>)
1319      * }</pre>
1320      * is {@code true}.
1321      *
1322      * @param   str   any string.
1323      * @return  if the string argument occurs as a substring within this
1324      *          object, then the index of the first character of the first
1325      *          such substring is returned; if it does not occur as a
1326      *          substring, {@code -1} is returned.
1327      */
1328     public int indexOf(String str) {
1329         return indexOf(str, 0);
1330     }
1331 
1332     /**
1333      * Returns the index within this string of the first occurrence of the
1334      * specified substring, starting at the specified index.  The integer
1335      * returned is the smallest value {@code k} for which:
1336      * <pre>{@code
1337      *     k >= Math.min(fromIndex, this.length()) &&
1338      *                   this.toString().startsWith(str, k)
1339      * }</pre>
1340      * If no such value of <i>k</i> exists, then -1 is returned.
1341      *
1342      * @param   str         the substring for which to search.
1343      * @param   fromIndex   the index from which to start the search.
1344      * @return  the index within this string of the first occurrence of the
1345      *          specified substring, starting at the specified index.
1346      */
1347     public int indexOf(String str, int fromIndex) {
1348         return String.indexOf(value, 0, count, str, fromIndex);
1349     }
1350 
1351     /**
1352      * Returns the index within this string of the rightmost occurrence
1353      * of the specified substring.  The rightmost empty string "" is
1354      * considered to occur at the index value {@code this.length()}.
1355      * The returned index is the largest value <i>k</i> such that
1356      * <pre>{@code
1357      * this.toString().startsWith(str, k)
1358      * }</pre>
1359      * is true.
1360      *
1361      * @param   str   the substring to search for.
1362      * @return  if the string argument occurs one or more times as a substring
1363      *          within this object, then the index of the first character of
1364      *          the last such substring is returned. If it does not occur as
1365      *          a substring, {@code -1} is returned.
1366      */
1367     public int lastIndexOf(String str) {
1368         return lastIndexOf(str, count);
1369     }
1370 
1371     /**
1372      * Returns the index within this string of the last occurrence of the
1373      * specified substring. The integer returned is the largest value <i>k</i>
1374      * such that:
1375      * <pre>{@code
1376      *     k <= Math.min(fromIndex, this.length()) &&
1377      *                   this.toString().startsWith(str, k)
1378      * }</pre>
1379      * If no such value of <i>k</i> exists, then -1 is returned.
1380      *
1381      * @param   str         the substring to search for.
1382      * @param   fromIndex   the index to start the search from.
1383      * @return  the index within this sequence of the last occurrence of the
1384      *          specified substring.
1385      */
1386     public int lastIndexOf(String str, int fromIndex) {
1387         return String.lastIndexOf(value, 0, count, str, fromIndex);
1388     }
1389 
1390     /**
1391      * Causes this character sequence to be replaced by the reverse of
1392      * the sequence. If there are any surrogate pairs included in the
1393      * sequence, these are treated as single characters for the
1394      * reverse operation. Thus, the order of the high-low surrogates
1395      * is never reversed.
1396      *
1397      * Let <i>n</i> be the character length of this character sequence
1398      * (not the length in {@code char} values) just prior to
1399      * execution of the {@code reverse} method. Then the
1400      * character at index <i>k</i> in the new character sequence is
1401      * equal to the character at index <i>n-k-1</i> in the old
1402      * character sequence.
1403      *
1404      * <p>Note that the reverse operation may result in producing
1405      * surrogate pairs that were unpaired low-surrogates and
1406      * high-surrogates before the operation. For example, reversing
1407      * "\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
1408      * a valid surrogate pair.
1409      *
1410      * @return  a reference to this object.
1411      */
1412     public AbstractStringBuilder reverse() {
1413         boolean hasSurrogates = false;
1414         int n = count - 1;
1415         for (int j = (n-1) >> 1; j >= 0; j--) {
1416             int k = n - j;
1417             char cj = value[j];
1418             char ck = value[k];
1419             value[j] = ck;
1420             value[k] = cj;
1421             if (Character.isSurrogate(cj) ||
1422                 Character.isSurrogate(ck)) {
1423                 hasSurrogates = true;
1424             }
1425         }
1426         if (hasSurrogates) {
1427             reverseAllValidSurrogatePairs();
1428         }
1429         return this;
1430     }
1431 
1432     /** Outlined helper method for reverse() */
1433     private void reverseAllValidSurrogatePairs() {
1434         for (int i = 0; i < count - 1; i++) {
1435             char c2 = value[i];
1436             if (Character.isLowSurrogate(c2)) {
1437                 char c1 = value[i + 1];
1438                 if (Character.isHighSurrogate(c1)) {
1439                     value[i++] = c1;
1440                     value[i] = c2;
1441                 }
1442             }
1443         }
1444     }
1445 
1446     /**
1447      * Returns a string representing the data in this sequence.
1448      * A new {@code String} object is allocated and initialized to
1449      * contain the character sequence currently represented by this
1450      * object. This {@code String} is then returned. Subsequent
1451      * changes to this sequence do not affect the contents of the
1452      * {@code String}.
1453      *
1454      * @return  a string representation of this sequence of characters.
1455      */
1456     @Override
1457     public abstract String toString();
1458 
1459     /**
1460      * Needed by {@code String} for the contentEquals method.
1461      */
1462     final char[] getValue() {
1463         return value;
1464     }
1465 
1466 }