1 /*
   2  * Copyright (c) 2003, 2012, 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      * This method has the same contract as ensureCapacity, but is
 116      * never synchronized.
 117      */
 118     private void ensureCapacityInternal(int minimumCapacity) {
 119         // overflow-conscious code
 120         if (minimumCapacity - value.length > 0)
 121             expandCapacity(minimumCapacity);
 122     }
 123 
 124     /**
 125      * This implements the expansion semantics of ensureCapacity with no
 126      * size check or synchronization.
 127      */
 128     void expandCapacity(int minimumCapacity) {
 129         int newCapacity = value.length * 2 + 2;
 130         if (newCapacity - minimumCapacity < 0)
 131             newCapacity = minimumCapacity;
 132         if (newCapacity < 0) {
 133             if (minimumCapacity < 0) // overflow
 134                 throw new OutOfMemoryError();
 135             newCapacity = Integer.MAX_VALUE;
 136         }
 137         value = Arrays.copyOf(value, newCapacity);
 138     }
 139 
 140     /**
 141      * Attempts to reduce storage used for the character sequence.
 142      * If the buffer is larger than necessary to hold its current sequence of
 143      * characters, then it may be resized to become more space efficient.
 144      * Calling this method may, but is not required to, affect the value
 145      * returned by a subsequent call to the {@link #capacity()} method.
 146      */
 147     public void trimToSize() {
 148         if (count < value.length) {
 149             value = Arrays.copyOf(value, count);
 150         }
 151     }
 152 
 153     /**
 154      * Sets the length of the character sequence.
 155      * The sequence is changed to a new character sequence
 156      * whose length is specified by the argument. For every nonnegative
 157      * index <i>k</i> less than {@code newLength}, the character at
 158      * index <i>k</i> in the new character sequence is the same as the
 159      * character at index <i>k</i> in the old sequence if <i>k</i> is less
 160      * than the length of the old character sequence; otherwise, it is the
 161      * null character {@code '\u005Cu0000'}.
 162      *
 163      * In other words, if the {@code newLength} argument is less than
 164      * the current length, the length is changed to the specified length.
 165      * <p>
 166      * If the {@code newLength} argument is greater than or equal
 167      * to the current length, sufficient null characters
 168      * ({@code '\u005Cu0000'}) are appended so that
 169      * length becomes the {@code newLength} argument.
 170      * <p>
 171      * The {@code newLength} argument must be greater than or equal
 172      * to {@code 0}.
 173      *
 174      * @param      newLength   the new length
 175      * @throws     IndexOutOfBoundsException  if the
 176      *               {@code newLength} argument is negative.
 177      */
 178     public void setLength(int newLength) {
 179         if (newLength < 0)
 180             throw new StringIndexOutOfBoundsException(newLength);
 181         ensureCapacityInternal(newLength);
 182 
 183         if (count < newLength) {
 184             Arrays.fill(value, count, newLength, '\0');
 185         }
 186 
 187         count = newLength;
 188     }
 189 
 190     /**
 191      * Returns the {@code char} value in this sequence at the specified index.
 192      * The first {@code char} value is at index {@code 0}, the next at index
 193      * {@code 1}, and so on, as in array indexing.
 194      * <p>
 195      * The index argument must be greater than or equal to
 196      * {@code 0}, and less than the length of this sequence.
 197      *
 198      * <p>If the {@code char} value specified by the index is a
 199      * <a href="Character.html#unicode">surrogate</a>, the surrogate
 200      * value is returned.
 201      *
 202      * @param      index   the index of the desired {@code char} value.
 203      * @return     the {@code char} value at the specified index.
 204      * @throws     IndexOutOfBoundsException  if {@code index} is
 205      *             negative or greater than or equal to {@code length()}.
 206      */
 207     @Override
 208     public char charAt(int index) {
 209         if ((index < 0) || (index >= count))
 210             throw new StringIndexOutOfBoundsException(index);
 211         return value[index];
 212     }
 213 
 214     /**
 215      * Returns the character (Unicode code point) at the specified
 216      * index. The index refers to {@code char} values
 217      * (Unicode code units) and ranges from {@code 0} to
 218      * {@link #length()}{@code  - 1}.
 219      *
 220      * <p> If the {@code char} value specified at the given index
 221      * is in the high-surrogate range, the following index is less
 222      * than the length of this sequence, and the
 223      * {@code char} value at the following index is in the
 224      * low-surrogate range, then the supplementary code point
 225      * corresponding to this surrogate pair is returned. Otherwise,
 226      * the {@code char} value at the given index is returned.
 227      *
 228      * @param      index the index to the {@code char} values
 229      * @return     the code point value of the character at the
 230      *             {@code index}
 231      * @exception  IndexOutOfBoundsException  if the {@code index}
 232      *             argument is negative or not less than the length of this
 233      *             sequence.
 234      */
 235     public int codePointAt(int index) {
 236         if ((index < 0) || (index >= count)) {
 237             throw new StringIndexOutOfBoundsException(index);
 238         }
 239         return Character.codePointAt(value, index);
 240     }
 241 
 242     /**
 243      * Returns the character (Unicode code point) before the specified
 244      * index. The index refers to {@code char} values
 245      * (Unicode code units) and ranges from {@code 1} to {@link
 246      * #length()}.
 247      *
 248      * <p> If the {@code char} value at {@code (index - 1)}
 249      * is in the low-surrogate range, {@code (index - 2)} is not
 250      * negative, and the {@code char} value at {@code (index -
 251      * 2)} is in the high-surrogate range, then the
 252      * supplementary code point value of the surrogate pair is
 253      * returned. If the {@code char} value at {@code index -
 254      * 1} is an unpaired low-surrogate or a high-surrogate, the
 255      * surrogate value is returned.
 256      *
 257      * @param     index the index following the code point that should be returned
 258      * @return    the Unicode code point value before the given index.
 259      * @exception IndexOutOfBoundsException if the {@code index}
 260      *            argument is less than 1 or greater than the length
 261      *            of this sequence.
 262      */
 263     public int codePointBefore(int index) {
 264         int i = index - 1;
 265         if ((i < 0) || (i >= count)) {
 266             throw new StringIndexOutOfBoundsException(index);
 267         }
 268         return Character.codePointBefore(value, index);
 269     }
 270 
 271     /**
 272      * Returns the number of Unicode code points in the specified text
 273      * range of this sequence. The text range begins at the specified
 274      * {@code beginIndex} and extends to the {@code char} at
 275      * index {@code endIndex - 1}. Thus the length (in
 276      * {@code char}s) of the text range is
 277      * {@code endIndex-beginIndex}. Unpaired surrogates within
 278      * this sequence count as one code point each.
 279      *
 280      * @param beginIndex the index to the first {@code char} of
 281      * the text range.
 282      * @param endIndex the index after the last {@code char} of
 283      * the text range.
 284      * @return the number of Unicode code points in the specified text
 285      * range
 286      * @exception IndexOutOfBoundsException if the
 287      * {@code beginIndex} is negative, or {@code endIndex}
 288      * is larger than the length of this sequence, or
 289      * {@code beginIndex} is larger than {@code endIndex}.
 290      */
 291     public int codePointCount(int beginIndex, int endIndex) {
 292         if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
 293             throw new IndexOutOfBoundsException();
 294         }
 295         return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex);
 296     }
 297 
 298     /**
 299      * Returns the index within this sequence that is offset from the
 300      * given {@code index} by {@code codePointOffset} code
 301      * points. Unpaired surrogates within the text range given by
 302      * {@code index} and {@code codePointOffset} count as
 303      * one code point each.
 304      *
 305      * @param index the index to be offset
 306      * @param codePointOffset the offset in code points
 307      * @return the index within this sequence
 308      * @exception IndexOutOfBoundsException if {@code index}
 309      *   is negative or larger then the length of this sequence,
 310      *   or if {@code codePointOffset} is positive and the subsequence
 311      *   starting with {@code index} has fewer than
 312      *   {@code codePointOffset} code points,
 313      *   or if {@code codePointOffset} is negative and the subsequence
 314      *   before {@code index} has fewer than the absolute value of
 315      *   {@code codePointOffset} code points.
 316      */
 317     public int offsetByCodePoints(int index, int codePointOffset) {
 318         if (index < 0 || index > count) {
 319             throw new IndexOutOfBoundsException();
 320         }
 321         return Character.offsetByCodePointsImpl(value, 0, count,
 322                                                 index, codePointOffset);
 323     }
 324 
 325     /**
 326      * Characters are copied from this sequence into the
 327      * destination character array {@code dst}. The first character to
 328      * be copied is at index {@code srcBegin}; the last character to
 329      * be copied is at index {@code srcEnd-1}. The total number of
 330      * characters to be copied is {@code srcEnd-srcBegin}. The
 331      * characters are copied into the subarray of {@code dst} starting
 332      * at index {@code dstBegin} and ending at index:
 333      * <p><blockquote><pre>
 334      * dstbegin + (srcEnd-srcBegin) - 1
 335      * </pre></blockquote>
 336      *
 337      * @param      srcBegin   start copying at this offset.
 338      * @param      srcEnd     stop copying at this offset.
 339      * @param      dst        the array to copy the data into.
 340      * @param      dstBegin   offset into {@code dst}.
 341      * @throws     IndexOutOfBoundsException  if any of the following is true:
 342      *             <ul>
 343      *             <li>{@code srcBegin} is negative
 344      *             <li>{@code dstBegin} is negative
 345      *             <li>the {@code srcBegin} argument is greater than
 346      *             the {@code srcEnd} argument.
 347      *             <li>{@code srcEnd} is greater than
 348      *             {@code this.length()}.
 349      *             <li>{@code dstBegin+srcEnd-srcBegin} is greater than
 350      *             {@code dst.length}
 351      *             </ul>
 352      */
 353     public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
 354     {
 355         if (srcBegin < 0)
 356             throw new StringIndexOutOfBoundsException(srcBegin);
 357         if ((srcEnd < 0) || (srcEnd > count))
 358             throw new StringIndexOutOfBoundsException(srcEnd);
 359         if (srcBegin > srcEnd)
 360             throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");
 361         System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
 362     }
 363 
 364     /**
 365      * The character at the specified index is set to {@code ch}. This
 366      * sequence is altered to represent a new character sequence that is
 367      * identical to the old character sequence, except that it contains the
 368      * character {@code ch} at position {@code index}.
 369      * <p>
 370      * The index argument must be greater than or equal to
 371      * {@code 0}, and less than the length of this sequence.
 372      *
 373      * @param      index   the index of the character to modify.
 374      * @param      ch      the new character.
 375      * @throws     IndexOutOfBoundsException  if {@code index} is
 376      *             negative or greater than or equal to {@code length()}.
 377      */
 378     public void setCharAt(int index, char ch) {
 379         if ((index < 0) || (index >= count))
 380             throw new StringIndexOutOfBoundsException(index);
 381         value[index] = ch;
 382     }
 383 
 384     /**
 385      * Appends the string representation of the {@code Object} argument.
 386      * <p>
 387      * The overall effect is exactly as if the argument were converted
 388      * to a string by the method {@link String#valueOf(Object)},
 389      * and the characters of that string were then
 390      * {@link #append(String) appended} to this character sequence.
 391      *
 392      * @param   obj   an {@code Object}.
 393      * @return  a reference to this object.
 394      */
 395     public AbstractStringBuilder append(Object obj) {
 396         return append(String.valueOf(obj));
 397     }
 398 
 399     /**
 400      * Appends the specified string to this character sequence.
 401      * <p>
 402      * The characters of the {@code String} argument are appended, in
 403      * order, increasing the length of this sequence by the length of the
 404      * argument. If {@code str} is {@code null}, then the four
 405      * characters {@code "null"} are appended.
 406      * <p>
 407      * Let <i>n</i> be the length of this character sequence just prior to
 408      * execution of the {@code append} method. Then the character at
 409      * index <i>k</i> in the new character sequence is equal to the character
 410      * at index <i>k</i> in the old character sequence, if <i>k</i> is less
 411      * than <i>n</i>; otherwise, it is equal to the character at index
 412      * <i>k-n</i> in the argument {@code str}.
 413      *
 414      * @param   str   a string.
 415      * @return  a reference to this object.
 416      */
 417     public AbstractStringBuilder append(String str) {
 418         if (str == null) str = "null";
 419         int len = str.length();
 420         ensureCapacityInternal(count + len);
 421         str.getChars(0, len, value, count);
 422         count += len;
 423         return this;
 424     }
 425 
 426     // Documentation in subclasses because of synchro difference
 427     public AbstractStringBuilder append(StringBuffer sb) {
 428         if (sb == null)
 429             return append("null");
 430         int len = sb.length();
 431         ensureCapacityInternal(count + len);
 432         sb.getChars(0, len, value, count);
 433         count += len;
 434         return this;
 435     }
 436 
 437     /**
 438      * @since 1.8
 439      */
 440     AbstractStringBuilder append(AbstractStringBuilder asb) {
 441         if (asb == null)
 442             return append("null");
 443         int len = asb.length();
 444         ensureCapacityInternal(count + len);
 445         asb.getChars(0, len, value, count);
 446         count += len;
 447         return this;
 448     }
 449 
 450     // Documentation in subclasses because of synchro difference
 451     @Override
 452     public AbstractStringBuilder append(CharSequence s) {
 453         if (s == null)
 454             s = "null";
 455         if (s instanceof String)
 456             return this.append((String)s);
 457         if (s instanceof AbstractStringBuilder)
 458             return this.append((AbstractStringBuilder)s);
 459 
 460         return this.append(s, 0, s.length());
 461     }
 462 
 463     /**
 464      * Appends a subsequence of the specified {@code CharSequence} to this
 465      * sequence.
 466      * <p>
 467      * Characters of the argument {@code s}, starting at
 468      * index {@code start}, are appended, in order, to the contents of
 469      * this sequence up to the (exclusive) index {@code end}. The length
 470      * of this sequence is increased by the value of {@code end - start}.
 471      * <p>
 472      * Let <i>n</i> be the length of this character sequence just prior to
 473      * execution of the {@code append} method. Then the character at
 474      * index <i>k</i> in this character sequence becomes equal to the
 475      * character at index <i>k</i> in this sequence, if <i>k</i> is less than
 476      * <i>n</i>; otherwise, it is equal to the character at index
 477      * <i>k+start-n</i> in the argument {@code s}.
 478      * <p>
 479      * If {@code s} is {@code null}, then this method appends
 480      * characters as if the s parameter was a sequence containing the four
 481      * characters {@code "null"}.
 482      *
 483      * @param   s the sequence to append.
 484      * @param   start   the starting index of the subsequence to be appended.
 485      * @param   end     the end index of the subsequence to be appended.
 486      * @return  a reference to this object.
 487      * @throws     IndexOutOfBoundsException if
 488      *             {@code start} is negative, or
 489      *             {@code start} is greater than {@code end} or
 490      *             {@code end} is greater than {@code s.length()}
 491      */
 492     @Override
 493     public AbstractStringBuilder append(CharSequence s, int start, int end) {
 494         if (s == null)
 495             s = "null";
 496         if ((start < 0) || (start > end) || (end > s.length()))
 497             throw new IndexOutOfBoundsException(
 498                 "start " + start + ", end " + end + ", s.length() "
 499                 + s.length());
 500         int len = end - start;
 501         ensureCapacityInternal(count + len);
 502         if (s instanceof String) {
 503             System.arraycopy(((String)s).value, start, value, count, len);
 504         } else if ((s instanceof StringBuilder) || (s instanceof StringBuffer)) {
 505             // two instanceof on leaf class is faster than instanceof check on AbstractStringBuilder.
 506             System.arraycopy(((AbstractStringBuilder)s).value, start, value, count, len);
 507         } else {
 508             // unspecialized path
 509             for (int i = start, j = count; i < end; i++, j++) {
 510                 value[j] = s.charAt(i);
 511             }
 512         }
 513         count += len;
 514         return this;
 515     }
 516 
 517     /**
 518      * Appends the string representation of the {@code char} array
 519      * argument to this sequence.
 520      * <p>
 521      * The characters of the array argument are appended, in order, to
 522      * the contents of this sequence. The length of this sequence
 523      * increases by the length of the argument.
 524      * <p>
 525      * The overall effect is exactly as if the argument were converted
 526      * to a string by the method {@link String#valueOf(char[])},
 527      * and the characters of that string were then
 528      * {@link #append(String) appended} to this character sequence.
 529      *
 530      * @param   str   the characters to be appended.
 531      * @return  a reference to this object.
 532      */
 533     public AbstractStringBuilder append(char[] str) {
 534         int len = str.length;
 535         ensureCapacityInternal(count + len);
 536         System.arraycopy(str, 0, value, count, len);
 537         count += len;
 538         return this;
 539     }
 540 
 541     /**
 542      * Appends the string representation of a subarray of the
 543      * {@code char} array argument to this sequence.
 544      * <p>
 545      * Characters of the {@code char} array {@code str}, starting at
 546      * index {@code offset}, are appended, in order, to the contents
 547      * of this sequence. The length of this sequence increases
 548      * by the value of {@code len}.
 549      * <p>
 550      * The overall effect is exactly as if the arguments were converted
 551      * to a string by the method {@link String#valueOf(char[],int,int)},
 552      * and the characters of that string were then
 553      * {@link #append(String) appended} to this character sequence.
 554      *
 555      * @param   str      the characters to be appended.
 556      * @param   offset   the index of the first {@code char} to append.
 557      * @param   len      the number of {@code char}s to append.
 558      * @return  a reference to this object.
 559      * @throws IndexOutOfBoundsException
 560      *         if {@code offset < 0} or {@code len < 0}
 561      *         or {@code offset+len > str.length}
 562      */
 563     public AbstractStringBuilder append(char str[], int offset, int len) {
 564         if (len > 0)                // let arraycopy report AIOOBE for len < 0
 565             ensureCapacityInternal(count + len);
 566         System.arraycopy(str, offset, value, count, len);
 567         count += len;
 568         return this;
 569     }
 570 
 571     /**
 572      * Appends the string representation of the {@code boolean}
 573      * argument to the sequence.
 574      * <p>
 575      * The overall effect is exactly as if the argument were converted
 576      * to a string by the method {@link String#valueOf(boolean)},
 577      * and the characters of that string were then
 578      * {@link #append(String) appended} to this character sequence.
 579      *
 580      * @param   b   a {@code boolean}.
 581      * @return  a reference to this object.
 582      */
 583     public AbstractStringBuilder append(boolean b) {
 584         if (b) {
 585             ensureCapacityInternal(count + 4);
 586             value[count++] = 't';
 587             value[count++] = 'r';
 588             value[count++] = 'u';
 589             value[count++] = 'e';
 590         } else {
 591             ensureCapacityInternal(count + 5);
 592             value[count++] = 'f';
 593             value[count++] = 'a';
 594             value[count++] = 'l';
 595             value[count++] = 's';
 596             value[count++] = 'e';
 597         }
 598         return this;
 599     }
 600 
 601     /**
 602      * Appends the string representation of the {@code char}
 603      * argument to this sequence.
 604      * <p>
 605      * The argument is appended to the contents of this sequence.
 606      * The length of this sequence increases by {@code 1}.
 607      * <p>
 608      * The overall effect is exactly as if the argument were converted
 609      * to a string by the method {@link String#valueOf(char)},
 610      * and the character in that string were then
 611      * {@link #append(String) appended} to this character sequence.
 612      *
 613      * @param   c   a {@code char}.
 614      * @return  a reference to this object.
 615      */
 616     @Override
 617     public AbstractStringBuilder append(char c) {
 618         ensureCapacityInternal(count + 1);
 619         value[count++] = c;
 620         return this;
 621     }
 622 
 623     /**
 624      * Appends the string representation of the {@code int}
 625      * argument to this sequence.
 626      * <p>
 627      * The overall effect is exactly as if the argument were converted
 628      * to a string by the method {@link String#valueOf(int)},
 629      * and the characters of that string were then
 630      * {@link #append(String) appended} to this character sequence.
 631      *
 632      * @param   i   an {@code int}.
 633      * @return  a reference to this object.
 634      */
 635     public AbstractStringBuilder append(int i) {
 636         if (i == Integer.MIN_VALUE) {
 637             append("-2147483648");
 638             return this;
 639         }
 640         int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1
 641                                      : Integer.stringSize(i);
 642         int spaceNeeded = count + appendedLength;
 643         ensureCapacityInternal(spaceNeeded);
 644         Integer.getChars(i, spaceNeeded, value);
 645         count = spaceNeeded;
 646         return this;
 647     }
 648 
 649     /**
 650      * Appends the string representation of the {@code long}
 651      * argument to this sequence.
 652      * <p>
 653      * The overall effect is exactly as if the argument were converted
 654      * to a string by the method {@link String#valueOf(long)},
 655      * and the characters of that string were then
 656      * {@link #append(String) appended} to this character sequence.
 657      *
 658      * @param   l   a {@code long}.
 659      * @return  a reference to this object.
 660      */
 661     public AbstractStringBuilder append(long l) {
 662         if (l == Long.MIN_VALUE) {
 663             append("-9223372036854775808");
 664             return this;
 665         }
 666         int appendedLength = (l < 0) ? Long.stringSize(-l) + 1
 667                                      : Long.stringSize(l);
 668         int spaceNeeded = count + appendedLength;
 669         ensureCapacityInternal(spaceNeeded);
 670         Long.getChars(l, spaceNeeded, value);
 671         count = spaceNeeded;
 672         return this;
 673     }
 674 
 675     /**
 676      * Appends the string representation of the {@code float}
 677      * argument to this sequence.
 678      * <p>
 679      * The overall effect is exactly as if the argument were converted
 680      * to a string by the method {@link String#valueOf(float)},
 681      * and the characters of that string were then
 682      * {@link #append(String) appended} to this character sequence.
 683      *
 684      * @param   f   a {@code float}.
 685      * @return  a reference to this object.
 686      */
 687     public AbstractStringBuilder append(float f) {
 688         new FloatingDecimal(f).appendTo(this);
 689         return this;
 690     }
 691 
 692     /**
 693      * Appends the string representation of the {@code double}
 694      * argument to this sequence.
 695      * <p>
 696      * The overall effect is exactly as if the argument were converted
 697      * to a string by the method {@link String#valueOf(double)},
 698      * and the characters of that string were then
 699      * {@link #append(String) appended} to this character sequence.
 700      *
 701      * @param   d   a {@code double}.
 702      * @return  a reference to this object.
 703      */
 704     public AbstractStringBuilder append(double d) {
 705         new FloatingDecimal(d).appendTo(this);
 706         return this;
 707     }
 708 
 709     /**
 710      * Removes the characters in a substring of this sequence.
 711      * The substring begins at the specified {@code start} and extends to
 712      * the character at index {@code end - 1} or to the end of the
 713      * sequence if no such character exists. If
 714      * {@code start} is equal to {@code end}, no changes are made.
 715      *
 716      * @param      start  The beginning index, inclusive.
 717      * @param      end    The ending index, exclusive.
 718      * @return     This object.
 719      * @throws     StringIndexOutOfBoundsException  if {@code start}
 720      *             is negative, greater than {@code length()}, or
 721      *             greater than {@code end}.
 722      */
 723     public AbstractStringBuilder delete(int start, int end) {
 724         if (start < 0)
 725             throw new StringIndexOutOfBoundsException(start);
 726         if (end > count)
 727             end = count;
 728         if (start > end)
 729             throw new StringIndexOutOfBoundsException();
 730         int len = end - start;
 731         if (len > 0) {
 732             System.arraycopy(value, start+len, value, start, count-end);
 733             count -= len;
 734         }
 735         return this;
 736     }
 737 
 738     /**
 739      * Appends the string representation of the {@code codePoint}
 740      * argument to this sequence.
 741      *
 742      * <p> The argument is appended to the contents of this sequence.
 743      * The length of this sequence increases by
 744      * {@link Character#charCount(int) Character.charCount(codePoint)}.
 745      *
 746      * <p> The overall effect is exactly as if the argument were
 747      * converted to a {@code char} array by the method
 748      * {@link Character#toChars(int)} and the character in that array
 749      * were then {@link #append(char[]) appended} to this character
 750      * sequence.
 751      *
 752      * @param   codePoint   a Unicode code point
 753      * @return  a reference to this object.
 754      * @exception IllegalArgumentException if the specified
 755      * {@code codePoint} isn't a valid Unicode code point
 756      */
 757     public AbstractStringBuilder appendCodePoint(int codePoint) {
 758         final int count = this.count;
 759 
 760         if (Character.isBmpCodePoint(codePoint)) {
 761             ensureCapacityInternal(count + 1);
 762             value[count] = (char) codePoint;
 763             this.count = count + 1;
 764         } else if (Character.isValidCodePoint(codePoint)) {
 765             ensureCapacityInternal(count + 2);
 766             Character.toSurrogates(codePoint, value, count);
 767             this.count = count + 2;
 768         } else {
 769             throw new IllegalArgumentException();
 770         }
 771         return this;
 772     }
 773 
 774     /**
 775      * Removes the {@code char} at the specified position in this
 776      * sequence. This sequence is shortened by one {@code char}.
 777      *
 778      * <p>Note: If the character at the given index is a supplementary
 779      * character, this method does not remove the entire character. If
 780      * correct handling of supplementary characters is required,
 781      * determine the number of {@code char}s to remove by calling
 782      * {@code Character.charCount(thisSequence.codePointAt(index))},
 783      * where {@code thisSequence} is this sequence.
 784      *
 785      * @param       index  Index of {@code char} to remove
 786      * @return      This object.
 787      * @throws      StringIndexOutOfBoundsException  if the {@code index}
 788      *              is negative or greater than or equal to
 789      *              {@code length()}.
 790      */
 791     public AbstractStringBuilder deleteCharAt(int index) {
 792         if ((index < 0) || (index >= count))
 793             throw new StringIndexOutOfBoundsException(index);
 794         System.arraycopy(value, index+1, value, index, count-index-1);
 795         count--;
 796         return this;
 797     }
 798 
 799     /**
 800      * Replaces the characters in a substring of this sequence
 801      * with characters in the specified {@code String}. The substring
 802      * begins at the specified {@code start} and extends to the character
 803      * at index {@code end - 1} or to the end of the
 804      * sequence if no such character exists. First the
 805      * characters in the substring are removed and then the specified
 806      * {@code String} is inserted at {@code start}. (This
 807      * sequence will be lengthened to accommodate the
 808      * specified String if necessary.)
 809      *
 810      * @param      start    The beginning index, inclusive.
 811      * @param      end      The ending index, exclusive.
 812      * @param      str   String that will replace previous contents.
 813      * @return     This object.
 814      * @throws     StringIndexOutOfBoundsException  if {@code start}
 815      *             is negative, greater than {@code length()}, or
 816      *             greater than {@code end}.
 817      */
 818     public AbstractStringBuilder replace(int start, int end, String str) {
 819         if (start < 0)
 820             throw new StringIndexOutOfBoundsException(start);
 821         if (start > count)
 822             throw new StringIndexOutOfBoundsException("start > length()");
 823         if (start > end)
 824             throw new StringIndexOutOfBoundsException("start > end");
 825 
 826         if (end > count)
 827             end = count;
 828         int len = str.length();
 829         int newCount = count + len - (end - start);
 830         ensureCapacityInternal(newCount);
 831 
 832         System.arraycopy(value, end, value, start + len, count - end);
 833         str.getChars(value, start);
 834         count = newCount;
 835         return this;
 836     }
 837 
 838     /**
 839      * Returns a new {@code String} that contains a subsequence of
 840      * characters currently contained in this character sequence. The
 841      * substring begins at the specified index and extends to the end of
 842      * this sequence.
 843      *
 844      * @param      start    The beginning index, inclusive.
 845      * @return     The new string.
 846      * @throws     StringIndexOutOfBoundsException  if {@code start} is
 847      *             less than zero, or greater than the length of this object.
 848      */
 849     public String substring(int start) {
 850         return substring(start, count);
 851     }
 852 
 853     /**
 854      * Returns a new character sequence that is a subsequence of this sequence.
 855      *
 856      * <p> An invocation of this method of the form
 857      *
 858      * <blockquote><pre>
 859      * sb.subSequence(begin,&nbsp;end)</pre></blockquote>
 860      *
 861      * behaves in exactly the same way as the invocation
 862      *
 863      * <blockquote><pre>
 864      * sb.substring(begin,&nbsp;end)</pre></blockquote>
 865      *
 866      * This method is provided so that this class can
 867      * implement the {@link CharSequence} interface. </p>
 868      *
 869      * @param      start   the start index, inclusive.
 870      * @param      end     the end index, exclusive.
 871      * @return     the specified subsequence.
 872      *
 873      * @throws  IndexOutOfBoundsException
 874      *          if {@code start} or {@code end} are negative,
 875      *          if {@code end} is greater than {@code length()},
 876      *          or if {@code start} is greater than {@code end}
 877      * @spec JSR-51
 878      */
 879     @Override
 880     public CharSequence subSequence(int start, int end) {
 881         return substring(start, end);
 882     }
 883 
 884     /**
 885      * Returns a new {@code String} that contains a subsequence of
 886      * characters currently contained in this sequence. The
 887      * substring begins at the specified {@code start} and
 888      * extends to the character at index {@code end - 1}.
 889      *
 890      * @param      start    The beginning index, inclusive.
 891      * @param      end      The ending index, exclusive.
 892      * @return     The new string.
 893      * @throws     StringIndexOutOfBoundsException  if {@code start}
 894      *             or {@code end} are negative or greater than
 895      *             {@code length()}, or {@code start} is
 896      *             greater than {@code end}.
 897      */
 898     public String substring(int start, int end) {
 899         if (start < 0)
 900             throw new StringIndexOutOfBoundsException(start);
 901         if (end > count)
 902             throw new StringIndexOutOfBoundsException(end);
 903         if (start > end)
 904             throw new StringIndexOutOfBoundsException(end - start);
 905         return new String(value, start, end - start);
 906     }
 907 
 908     /**
 909      * Inserts the string representation of a subarray of the {@code str}
 910      * array argument into this sequence. The subarray begins at the
 911      * specified {@code offset} and extends {@code len} {@code char}s.
 912      * The characters of the subarray are inserted into this sequence at
 913      * the position indicated by {@code index}. The length of this
 914      * sequence increases by {@code len} {@code char}s.
 915      *
 916      * @param      index    position at which to insert subarray.
 917      * @param      str       A {@code char} array.
 918      * @param      offset   the index of the first {@code char} in subarray to
 919      *             be inserted.
 920      * @param      len      the number of {@code char}s in the subarray to
 921      *             be inserted.
 922      * @return     This object
 923      * @throws     StringIndexOutOfBoundsException  if {@code index}
 924      *             is negative or greater than {@code length()}, or
 925      *             {@code offset} or {@code len} are negative, or
 926      *             {@code (offset+len)} is greater than
 927      *             {@code str.length}.
 928      */
 929     public AbstractStringBuilder insert(int index, char[] str, int offset,
 930                                         int len)
 931     {
 932         if ((index < 0) || (index > length()))
 933             throw new StringIndexOutOfBoundsException(index);
 934         if ((offset < 0) || (len < 0) || (offset > str.length - len))
 935             throw new StringIndexOutOfBoundsException(
 936                 "offset " + offset + ", len " + len + ", str.length "
 937                 + str.length);
 938         ensureCapacityInternal(count + len);
 939         System.arraycopy(value, index, value, index + len, count - index);
 940         System.arraycopy(str, offset, value, index, len);
 941         count += len;
 942         return this;
 943     }
 944 
 945     /**
 946      * Inserts the string representation of the {@code Object}
 947      * argument into this character sequence.
 948      * <p>
 949      * The overall effect is exactly as if the second argument were
 950      * converted to a string by the method {@link String#valueOf(Object)},
 951      * and the characters of that string were then
 952      * {@link #insert(int,String) inserted} into this character
 953      * sequence at the indicated offset.
 954      * <p>
 955      * The {@code offset} argument must be greater than or equal to
 956      * {@code 0}, and less than or equal to the {@linkplain #length() length}
 957      * of this sequence.
 958      *
 959      * @param      offset   the offset.
 960      * @param      obj      an {@code Object}.
 961      * @return     a reference to this object.
 962      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
 963      */
 964     public AbstractStringBuilder insert(int offset, Object obj) {
 965         return insert(offset, String.valueOf(obj));
 966     }
 967 
 968     /**
 969      * Inserts the string into this character sequence.
 970      * <p>
 971      * The characters of the {@code String} argument are inserted, in
 972      * order, into this sequence at the indicated offset, moving up any
 973      * characters originally above that position and increasing the length
 974      * of this sequence by the length of the argument. If
 975      * {@code str} is {@code null}, then the four characters
 976      * {@code "null"} are inserted into this sequence.
 977      * <p>
 978      * The character at index <i>k</i> in the new character sequence is
 979      * equal to:
 980      * <ul>
 981      * <li>the character at index <i>k</i> in the old character sequence, if
 982      * <i>k</i> is less than {@code offset}
 983      * <li>the character at index <i>k</i>{@code -offset} in the
 984      * argument {@code str}, if <i>k</i> is not less than
 985      * {@code offset} but is less than {@code offset+str.length()}
 986      * <li>the character at index <i>k</i>{@code -str.length()} in the
 987      * old character sequence, if <i>k</i> is not less than
 988      * {@code offset+str.length()}
 989      * </ul><p>
 990      * The {@code offset} argument must be greater than or equal to
 991      * {@code 0}, and less than or equal to the {@linkplain #length() length}
 992      * of this sequence.
 993      *
 994      * @param      offset   the offset.
 995      * @param      str      a string.
 996      * @return     a reference to this object.
 997      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
 998      */
 999     public AbstractStringBuilder insert(int offset, String str) {
1000         if ((offset < 0) || (offset > length()))
1001             throw new StringIndexOutOfBoundsException(offset);
1002         if (str == null)
1003             str = "null";
1004         int len = str.length();
1005         ensureCapacityInternal(count + len);
1006         System.arraycopy(value, offset, value, offset + len, count - offset);
1007         str.getChars(value, offset);
1008         count += len;
1009         return this;
1010     }
1011 
1012     /**
1013      * Inserts the string representation of the {@code char} array
1014      * argument into this sequence.
1015      * <p>
1016      * The characters of the array argument are inserted into the
1017      * contents of this sequence at the position indicated by
1018      * {@code offset}. The length of this sequence increases by
1019      * the length of the argument.
1020      * <p>
1021      * The overall effect is exactly as if the second argument were
1022      * converted to a string by the method {@link String#valueOf(char[])},
1023      * and the characters of that string were then
1024      * {@link #insert(int,String) inserted} into this character
1025      * sequence at the indicated offset.
1026      * <p>
1027      * The {@code offset} argument must be greater than or equal to
1028      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1029      * of this sequence.
1030      *
1031      * @param      offset   the offset.
1032      * @param      str      a character array.
1033      * @return     a reference to this object.
1034      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1035      */
1036     public AbstractStringBuilder insert(int offset, char[] str) {
1037         if ((offset < 0) || (offset > length()))
1038             throw new StringIndexOutOfBoundsException(offset);
1039         int len = str.length;
1040         ensureCapacityInternal(count + len);
1041         System.arraycopy(value, offset, value, offset + len, count - offset);
1042         System.arraycopy(str, 0, value, offset, len);
1043         count += len;
1044         return this;
1045     }
1046 
1047     /**
1048      * Inserts the specified {@code CharSequence} into this sequence.
1049      * <p>
1050      * The characters of the {@code CharSequence} argument are inserted,
1051      * in order, into this sequence at the indicated offset, moving up
1052      * any characters originally above that position and increasing the length
1053      * of this sequence by the length of the argument s.
1054      * <p>
1055      * The result of this method is exactly the same as if it were an
1056      * invocation of this object's
1057      * {@link #insert(int,CharSequence,int,int) insert}(dstOffset, s, 0, s.length())
1058      * method.
1059      *
1060      * <p>If {@code s} is {@code null}, then the four characters
1061      * {@code "null"} are inserted into this sequence.
1062      *
1063      * @param      dstOffset   the offset.
1064      * @param      s the sequence to be inserted
1065      * @return     a reference to this object.
1066      * @throws     IndexOutOfBoundsException  if the offset is invalid.
1067      */
1068     public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
1069         if (s == null)
1070             s = "null";
1071         if (s instanceof String)
1072             return this.insert(dstOffset, (String)s);
1073         return this.insert(dstOffset, s, 0, s.length());
1074     }
1075 
1076     /**
1077      * Inserts a subsequence of the specified {@code CharSequence} into
1078      * this sequence.
1079      * <p>
1080      * The subsequence of the argument {@code s} specified by
1081      * {@code start} and {@code end} are inserted,
1082      * in order, into this sequence at the specified destination offset, moving
1083      * up any characters originally above that position. The length of this
1084      * sequence is increased by {@code end - start}.
1085      * <p>
1086      * The character at index <i>k</i> in this sequence becomes equal to:
1087      * <ul>
1088      * <li>the character at index <i>k</i> in this sequence, if
1089      * <i>k</i> is less than {@code dstOffset}
1090      * <li>the character at index <i>k</i>{@code +start-dstOffset} in
1091      * the argument {@code s}, if <i>k</i> is greater than or equal to
1092      * {@code dstOffset} but is less than {@code dstOffset+end-start}
1093      * <li>the character at index <i>k</i>{@code -(end-start)} in this
1094      * sequence, if <i>k</i> is greater than or equal to
1095      * {@code dstOffset+end-start}
1096      * </ul><p>
1097      * The {@code dstOffset} argument must be greater than or equal to
1098      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1099      * of this sequence.
1100      * <p>The start argument must be nonnegative, and not greater than
1101      * {@code end}.
1102      * <p>The end argument must be greater than or equal to
1103      * {@code start}, and less than or equal to the length of s.
1104      *
1105      * <p>If {@code s} is {@code null}, then this method inserts
1106      * characters as if the s parameter was a sequence containing the four
1107      * characters {@code "null"}.
1108      *
1109      * @param      dstOffset   the offset in this sequence.
1110      * @param      s       the sequence to be inserted.
1111      * @param      start   the starting index of the subsequence to be inserted.
1112      * @param      end     the end index of the subsequence to be inserted.
1113      * @return     a reference to this object.
1114      * @throws     IndexOutOfBoundsException  if {@code dstOffset}
1115      *             is negative or greater than {@code this.length()}, or
1116      *              {@code start} or {@code end} are negative, or
1117      *              {@code start} is greater than {@code end} or
1118      *              {@code end} is greater than {@code s.length()}
1119      */
1120      public AbstractStringBuilder insert(int dstOffset, CharSequence s,
1121                                          int start, int end) {
1122         if (s == null)
1123             s = "null";
1124         if ((dstOffset < 0) || (dstOffset > this.length()))
1125             throw new IndexOutOfBoundsException("dstOffset "+dstOffset);
1126         if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))
1127             throw new IndexOutOfBoundsException(
1128                 "start " + start + ", end " + end + ", s.length() "
1129                 + s.length());
1130         int len = end - start;
1131         ensureCapacityInternal(count + len);
1132         System.arraycopy(value, dstOffset, value, dstOffset + len,
1133                          count - dstOffset);
1134         if (s instanceof String) {
1135             System.arraycopy(((String)s).value, start, value, dstOffset, len);
1136         } else if ((s instanceof StringBuilder) || (s instanceof StringBuffer)) {
1137             // two instanceof on leaf class is faster than instanceof check on AbstractStringBuilder.
1138             System.arraycopy(((AbstractStringBuilder)s).value, start, value, dstOffset, len);
1139         } else {
1140             // unspecialized path
1141             for (int i=start; i<end; i++)
1142                 value[dstOffset++] = s.charAt(i);
1143         }
1144         count += len;
1145         return this;
1146     }
1147 
1148     /**
1149      * Inserts the string representation of the {@code boolean}
1150      * argument into this sequence.
1151      * <p>
1152      * The overall effect is exactly as if the second argument were
1153      * converted to a string by the method {@link String#valueOf(boolean)},
1154      * and the characters of that string were then
1155      * {@link #insert(int,String) inserted} into this character
1156      * sequence at the indicated offset.
1157      * <p>
1158      * The {@code offset} argument must be greater than or equal to
1159      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1160      * of this sequence.
1161      *
1162      * @param      offset   the offset.
1163      * @param      b        a {@code boolean}.
1164      * @return     a reference to this object.
1165      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1166      */
1167     public AbstractStringBuilder insert(int offset, boolean b) {
1168         return insert(offset, String.valueOf(b));
1169     }
1170 
1171     /**
1172      * Inserts the string representation of the {@code char}
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(char)},
1177      * and the character in 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      c        a {@code char}.
1187      * @return     a reference to this object.
1188      * @throws     IndexOutOfBoundsException  if the offset is invalid.
1189      */
1190     public AbstractStringBuilder insert(int offset, char c) {
1191         ensureCapacityInternal(count + 1);
1192         System.arraycopy(value, offset, value, offset + 1, count - offset);
1193         value[offset] = c;
1194         count += 1;
1195         return this;
1196     }
1197 
1198     /**
1199      * Inserts the string representation of the second {@code int}
1200      * argument into this sequence.
1201      * <p>
1202      * The overall effect is exactly as if the second argument were
1203      * converted to a string by the method {@link String#valueOf(int)},
1204      * and the characters of that string were then
1205      * {@link #insert(int,String) inserted} into this character
1206      * sequence at the indicated offset.
1207      * <p>
1208      * The {@code offset} argument must be greater than or equal to
1209      * {@code 0}, and less than or equal to the {@linkplain #length() length}
1210      * of this sequence.
1211      *
1212      * @param      offset   the offset.
1213      * @param      i        an {@code int}.
1214      * @return     a reference to this object.
1215      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1216      */
1217     public AbstractStringBuilder insert(int offset, int i) {
1218         return insert(offset, String.valueOf(i));
1219     }
1220 
1221     /**
1222      * Inserts the string representation of the {@code long}
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(long)},
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      l        a {@code long}.
1237      * @return     a reference to this object.
1238      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1239      */
1240     public AbstractStringBuilder insert(int offset, long l) {
1241         return insert(offset, String.valueOf(l));
1242     }
1243 
1244     /**
1245      * Inserts the string representation of the {@code float}
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(float)},
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      f        a {@code float}.
1260      * @return     a reference to this object.
1261      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1262      */
1263     public AbstractStringBuilder insert(int offset, float f) {
1264         return insert(offset, String.valueOf(f));
1265     }
1266 
1267     /**
1268      * Inserts the string representation of the {@code double}
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(double)},
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      d        a {@code double}.
1283      * @return     a reference to this object.
1284      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
1285      */
1286     public AbstractStringBuilder insert(int offset, double d) {
1287         return insert(offset, String.valueOf(d));
1288     }
1289 
1290     /**
1291      * Returns the index within this string of the first occurrence of the
1292      * specified substring. The integer returned is the smallest value
1293      * <i>k</i> such that:
1294      * <blockquote><pre>
1295      * this.toString().startsWith(str, <i>k</i>)
1296      * </pre></blockquote>
1297      * is {@code true}.
1298      *
1299      * @param   str   any string.
1300      * @return  if the string argument occurs as a substring within this
1301      *          object, then the index of the first character of the first
1302      *          such substring is returned; if it does not occur as a
1303      *          substring, {@code -1} is returned.
1304      */
1305     public int indexOf(String str) {
1306         return indexOf(str, 0);
1307     }
1308 
1309     /**
1310      * Returns the index within this string of the first occurrence of the
1311      * specified substring, starting at the specified index.  The integer
1312      * returned is the smallest value {@code k} for which:
1313      * <blockquote><pre>
1314      *     k >= Math.min(fromIndex, str.length()) &&
1315      *                   this.toString().startsWith(str, k)
1316      * </pre></blockquote>
1317      * If no such value of <i>k</i> exists, then -1 is returned.
1318      *
1319      * @param   str         the substring for which to search.
1320      * @param   fromIndex   the index from which to start the search.
1321      * @return  the index within this string of the first occurrence of the
1322      *          specified substring, starting at the specified index.
1323      */
1324     public int indexOf(String str, int fromIndex) {
1325         return String.indexOf(value, 0, count, str, fromIndex);
1326     }
1327 
1328     /**
1329      * Returns the index within this string of the rightmost occurrence
1330      * of the specified substring.  The rightmost empty string "" is
1331      * considered to occur at the index value {@code this.length()}.
1332      * The returned index is the largest value <i>k</i> such that
1333      * <blockquote><pre>
1334      * this.toString().startsWith(str, k)
1335      * </pre></blockquote>
1336      * is true.
1337      *
1338      * @param   str   the substring to search for.
1339      * @return  if the string argument occurs one or more times as a substring
1340      *          within this object, then the index of the first character of
1341      *          the last such substring is returned. If it does not occur as
1342      *          a substring, {@code -1} is returned.
1343      */
1344     public int lastIndexOf(String str) {
1345         return lastIndexOf(str, count);
1346     }
1347 
1348     /**
1349      * Returns the index within this string of the last occurrence of the
1350      * specified substring. The integer returned is the largest value <i>k</i>
1351      * such that:
1352      * <blockquote><pre>
1353      *     k <= Math.min(fromIndex, str.length()) &&
1354      *                   this.toString().startsWith(str, k)
1355      * </pre></blockquote>
1356      * If no such value of <i>k</i> exists, then -1 is returned.
1357      *
1358      * @param   str         the substring to search for.
1359      * @param   fromIndex   the index to start the search from.
1360      * @return  the index within this sequence of the last occurrence of the
1361      *          specified substring.
1362      */
1363     public int lastIndexOf(String str, int fromIndex) {
1364         return String.lastIndexOf(value, 0, count, str, fromIndex);
1365     }
1366 
1367     /**
1368      * Causes this character sequence to be replaced by the reverse of
1369      * the sequence. If there are any surrogate pairs included in the
1370      * sequence, these are treated as single characters for the
1371      * reverse operation. Thus, the order of the high-low surrogates
1372      * is never reversed.
1373      *
1374      * Let <i>n</i> be the character length of this character sequence
1375      * (not the length in {@code char} values) just prior to
1376      * execution of the {@code reverse} method. Then the
1377      * character at index <i>k</i> in the new character sequence is
1378      * equal to the character at index <i>n-k-1</i> in the old
1379      * character sequence.
1380      *
1381      * <p>Note that the reverse operation may result in producing
1382      * surrogate pairs that were unpaired low-surrogates and
1383      * high-surrogates before the operation. For example, reversing
1384      * "\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
1385      * a valid surrogate pair.
1386      *
1387      * @return  a reference to this object.
1388      */
1389     public AbstractStringBuilder reverse() {
1390         boolean hasSurrogate = false;
1391         int n = count - 1;
1392         for (int j = (n-1) >> 1; j >= 0; --j) {
1393             char temp = value[j];
1394             char temp2 = value[n - j];
1395             if (!hasSurrogate) {
1396                 hasSurrogate = (temp >= Character.MIN_SURROGATE && temp <= Character.MAX_SURROGATE)
1397                     || (temp2 >= Character.MIN_SURROGATE && temp2 <= Character.MAX_SURROGATE);
1398             }
1399             value[j] = temp2;
1400             value[n - j] = temp;
1401         }
1402         if (hasSurrogate) {
1403             // Reverse back all valid surrogate pairs
1404             for (int i = 0; i < count - 1; i++) {
1405                 char c2 = value[i];
1406                 if (Character.isLowSurrogate(c2)) {
1407                     char c1 = value[i + 1];
1408                     if (Character.isHighSurrogate(c1)) {
1409                         value[i++] = c1;
1410                         value[i] = c2;
1411                     }
1412                 }
1413             }
1414         }
1415         return this;
1416     }
1417 
1418     /**
1419      * Returns a string representing the data in this sequence.
1420      * A new {@code String} object is allocated and initialized to
1421      * contain the character sequence currently represented by this
1422      * object. This {@code String} is then returned. Subsequent
1423      * changes to this sequence do not affect the contents of the
1424      * {@code String}.
1425      *
1426      * @return  a string representation of this sequence of characters.
1427      */
1428     @Override
1429     public abstract String toString();
1430 
1431     /**
1432      * Needed by {@code String} for the contentEquals method.
1433      */
1434     final char[] getValue() {
1435         return value;
1436     }
1437 
1438 }