1 /*
   2  * Copyright 1994-2006 Sun Microsystems, Inc.  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.  Sun designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  22  * CA 95054 USA or visit www.sun.com if you need additional information or
  23  * have any questions.
  24  */
  25 
  26 package java.lang;
  27 
  28 import java.io.ObjectStreamClass;
  29 import java.io.ObjectStreamField;
  30 import java.io.UnsupportedEncodingException;
  31 import java.nio.charset.Charset;
  32 import java.util.ArrayList;
  33 import java.util.Arrays;
  34 import java.util.Comparator;
  35 import java.util.Formatter;
  36 import java.util.Locale;
  37 import java.util.regex.Matcher;
  38 import java.util.regex.Pattern;
  39 import java.util.regex.PatternSyntaxException;
  40 
  41 
  42 /**
  43  * The <code>String</code> class represents character strings. All
  44  * string literals in Java programs, such as <code>"abc"</code>, are
  45  * implemented as instances of this class.
  46  * <p>
  47  * Strings are constant; their values cannot be changed after they
  48  * are created. String buffers support mutable strings.
  49  * Because String objects are immutable they can be shared. For example:
  50  * <p><blockquote><pre>
  51  *     String str = "abc";
  52  * </pre></blockquote><p>
  53  * is equivalent to:
  54  * <p><blockquote><pre>
  55  *     char data[] = {'a', 'b', 'c'};
  56  *     String str = new String(data);
  57  * </pre></blockquote><p>
  58  * Here are some more examples of how strings can be used:
  59  * <p><blockquote><pre>
  60  *     System.out.println("abc");
  61  *     String cde = "cde";
  62  *     System.out.println("abc" + cde);
  63  *     String c = "abc".substring(2,3);
  64  *     String d = cde.substring(1, 2);
  65  * </pre></blockquote>
  66  * <p>
  67  * The class <code>String</code> includes methods for examining
  68  * individual characters of the sequence, for comparing strings, for
  69  * searching strings, for extracting substrings, and for creating a
  70  * copy of a string with all characters translated to uppercase or to
  71  * lowercase. Case mapping is based on the Unicode Standard version
  72  * specified by the {@link java.lang.Character Character} class.
  73  * <p>
  74  * The Java language provides special support for the string
  75  * concatenation operator (&nbsp;+&nbsp;), and for conversion of
  76  * other objects to strings. String concatenation is implemented
  77  * through the <code>StringBuilder</code>(or <code>StringBuffer</code>)
  78  * class and its <code>append</code> method.
  79  * String conversions are implemented through the method
  80  * <code>toString</code>, defined by <code>Object</code> and
  81  * inherited by all classes in Java. For additional information on
  82  * string concatenation and conversion, see Gosling, Joy, and Steele,
  83  * <i>The Java Language Specification</i>.
  84  *
  85  * <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
  86  * or method in this class will cause a {@link NullPointerException} to be
  87  * thrown.
  88  *
  89  * <p>A <code>String</code> represents a string in the UTF-16 format
  90  * in which <em>supplementary characters</em> are represented by <em>surrogate
  91  * pairs</em> (see the section <a href="Character.html#unicode">Unicode
  92  * Character Representations</a> in the <code>Character</code> class for
  93  * more information).
  94  * Index values refer to <code>char</code> code units, so a supplementary
  95  * character uses two positions in a <code>String</code>.
  96  * <p>The <code>String</code> class provides methods for dealing with
  97  * Unicode code points (i.e., characters), in addition to those for
  98  * dealing with Unicode code units (i.e., <code>char</code> values).
  99  *
 100  * @author  Lee Boynton
 101  * @author  Arthur van Hoff
 102  * @see     java.lang.Object#toString()
 103  * @see     java.lang.StringBuffer
 104  * @see     java.lang.StringBuilder
 105  * @see     java.nio.charset.Charset
 106  * @since   JDK1.0
 107  */
 108 
 109 public final class String
 110     implements java.io.Serializable, Comparable<String>, CharSequence
 111 {
 112     /** The value is used for character storage. */
 113     private final char value[];
 114 
 115     /** The offset is the first index of the storage that is used. */
 116     private final int offset;
 117 
 118     /** The count is the number of characters in the String. */
 119     private final int count;
 120 
 121     /** Cache the hash code for the string */
 122     private int hash; // Default to 0
 123 
 124     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 125     private static final long serialVersionUID = -6849794470754667710L;
 126 
 127     /**
 128      * Class String is special cased within the Serialization Stream Protocol.
 129      *
 130      * A String instance is written initially into an ObjectOutputStream in the
 131      * following format:
 132      * <pre>
 133      *      <code>TC_STRING</code> (utf String)
 134      * </pre>
 135      * The String is written by method <code>DataOutput.writeUTF</code>.
 136      * A new handle is generated to  refer to all future references to the
 137      * string instance within the stream.
 138      */
 139     private static final ObjectStreamField[] serialPersistentFields =
 140         new ObjectStreamField[0];
 141 
 142     /**
 143      * Initializes a newly created {@code String} object so that it represents
 144      * an empty character sequence.  Note that use of this constructor is
 145      * unnecessary since Strings are immutable.
 146      */
 147     public String() {
 148         this.offset = 0;
 149         this.count = 0;
 150         this.value = new char[0];
 151     }
 152 
 153     /**
 154      * Initializes a newly created {@code String} object so that it represents
 155      * the same sequence of characters as the argument; in other words, the
 156      * newly created string is a copy of the argument string. Unless an
 157      * explicit copy of {@code original} is needed, use of this constructor is
 158      * unnecessary since Strings are immutable.
 159      *
 160      * @param  original
 161      *         A {@code String}
 162      */
 163     public String(String original) {
 164         int size = original.count;
 165         char[] originalValue = original.value;
 166         char[] v;
 167         if (originalValue.length > size) {
 168             // The array representing the String is bigger than the new
 169             // String itself.  Perhaps this constructor is being called
 170             // in order to trim the baggage, so make a copy of the array.
 171             int off = original.offset;
 172             v = Arrays.copyOfRange(originalValue, off, off+size);
 173         } else {
 174             // The array representing the String is the same
 175             // size as the String, so no point in making a copy.
 176             v = originalValue;
 177         }
 178         this.offset = 0;
 179         this.count = size;
 180         this.value = v;
 181     }
 182 
 183     /**
 184      * Allocates a new {@code String} so that it represents the sequence of
 185      * characters currently contained in the character array argument. The
 186      * contents of the character array are copied; subsequent modification of
 187      * the character array does not affect the newly created string.
 188      *
 189      * @param  value
 190      *         The initial value of the string
 191      */
 192     public String(char value[]) {
 193         int size = value.length;
 194         this.offset = 0;
 195         this.count = size;
 196         this.value = Arrays.copyOf(value, size);
 197     }
 198 
 199     /**
 200      * Allocates a new {@code String} that contains characters from a subarray
 201      * of the character array argument. The {@code offset} argument is the
 202      * index of the first character of the subarray and the {@code count}
 203      * argument specifies the length of the subarray. The contents of the
 204      * subarray are copied; subsequent modification of the character array does
 205      * not affect the newly created string.
 206      *
 207      * @param  value
 208      *         Array that is the source of characters
 209      *
 210      * @param  offset
 211      *         The initial offset
 212      *
 213      * @param  count
 214      *         The length
 215      *
 216      * @throws  IndexOutOfBoundsException
 217      *          If the {@code offset} and {@code count} arguments index
 218      *          characters outside the bounds of the {@code value} array
 219      */
 220     public String(char value[], int offset, int count) {
 221         if (offset < 0) {
 222             throw new StringIndexOutOfBoundsException(offset);
 223         }
 224         if (count < 0) {
 225             throw new StringIndexOutOfBoundsException(count);
 226         }
 227         // Note: offset or count might be near -1>>>1.
 228         if (offset > value.length - count) {
 229             throw new StringIndexOutOfBoundsException(offset + count);
 230         }
 231         this.offset = 0;
 232         this.count = count;
 233         this.value = Arrays.copyOfRange(value, offset, offset+count);
 234     }
 235 
 236     /**
 237      * Allocates a new {@code String} that contains characters from a subarray
 238      * of the <a href="Character.html#unicode">Unicode code point</a> array
 239      * argument.  The {@code offset} argument is the index of the first code
 240      * point of the subarray and the {@code count} argument specifies the
 241      * length of the subarray.  The contents of the subarray are converted to
 242      * {@code char}s; subsequent modification of the {@code int} array does not
 243      * affect the newly created string.
 244      *
 245      * @param  codePoints
 246      *         Array that is the source of Unicode code points
 247      *
 248      * @param  offset
 249      *         The initial offset
 250      *
 251      * @param  count
 252      *         The length
 253      *
 254      * @throws  IllegalArgumentException
 255      *          If any invalid Unicode code point is found in {@code
 256      *          codePoints}
 257      *
 258      * @throws  IndexOutOfBoundsException
 259      *          If the {@code offset} and {@code count} arguments index
 260      *          characters outside the bounds of the {@code codePoints} array
 261      *
 262      * @since  1.5
 263      */
 264     public String(int[] codePoints, int offset, int count) {
 265         if (offset < 0) {
 266             throw new StringIndexOutOfBoundsException(offset);
 267         }
 268         if (count < 0) {
 269             throw new StringIndexOutOfBoundsException(count);
 270         }
 271         // Note: offset or count might be near -1>>>1.
 272         if (offset > codePoints.length - count) {
 273             throw new StringIndexOutOfBoundsException(offset + count);
 274         }
 275 
 276         // Pass 1: Compute precise size of char[]
 277         int n = 0;
 278         for (int i = offset; i < offset + count; i++) {
 279             int c = codePoints[i];
 280             if (c >= Character.MIN_CODE_POINT &&
 281                 c <  Character.MIN_SUPPLEMENTARY_CODE_POINT)
 282                 n += 1;
 283             else if (Character.isSupplementaryCodePoint(c))
 284                 n += 2;
 285             else throw new IllegalArgumentException(Integer.toString(c));
 286         }
 287 
 288         // Pass 2: Allocate and fill in char[]
 289         char[] v = new char[n];
 290         for (int i = offset, j = 0; i < offset + count; i++) {
 291             int c = codePoints[i];
 292             if (c < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
 293                 v[j++] = (char) c;
 294             } else {
 295                 Character.toSurrogates(c, v, j);
 296                 j += 2;
 297             }
 298         }
 299 
 300         this.value  = v;
 301         this.count  = v.length;
 302         this.offset = 0;
 303     }
 304 
 305     /**
 306      * Allocates a new {@code String} constructed from a subarray of an array
 307      * of 8-bit integer values.
 308      *
 309      * <p> The {@code offset} argument is the index of the first byte of the
 310      * subarray, and the {@code count} argument specifies the length of the
 311      * subarray.
 312      *
 313      * <p> Each {@code byte} in the subarray is converted to a {@code char} as
 314      * specified in the method above.
 315      *
 316      * @deprecated This method does not properly convert bytes into characters.
 317      * As of JDK&nbsp;1.1, the preferred way to do this is via the
 318      * {@code String} constructors that take a {@link
 319      * java.nio.charset.Charset}, charset name, or that use the platform's
 320      * default charset.
 321      *
 322      * @param  ascii
 323      *         The bytes to be converted to characters
 324      *
 325      * @param  hibyte
 326      *         The top 8 bits of each 16-bit Unicode code unit
 327      *
 328      * @param  offset
 329      *         The initial offset
 330      * @param  count
 331      *         The length
 332      *
 333      * @throws  IndexOutOfBoundsException
 334      *          If the {@code offset} or {@code count} argument is invalid
 335      *
 336      * @see  #String(byte[], int)
 337      * @see  #String(byte[], int, int, java.lang.String)
 338      * @see  #String(byte[], int, int, java.nio.charset.Charset)
 339      * @see  #String(byte[], int, int)
 340      * @see  #String(byte[], java.lang.String)
 341      * @see  #String(byte[], java.nio.charset.Charset)
 342      * @see  #String(byte[])
 343      */
 344     @Deprecated
 345     public String(byte ascii[], int hibyte, int offset, int count) {
 346         checkBounds(ascii, offset, count);
 347         char value[] = new char[count];
 348 
 349         if (hibyte == 0) {
 350             for (int i = count ; i-- > 0 ;) {
 351                 value[i] = (char) (ascii[i + offset] & 0xff);
 352             }
 353         } else {
 354             hibyte <<= 8;
 355             for (int i = count ; i-- > 0 ;) {
 356                 value[i] = (char) (hibyte | (ascii[i + offset] & 0xff));
 357             }
 358         }
 359         this.offset = 0;
 360         this.count = count;
 361         this.value = value;
 362     }
 363 
 364     /**
 365      * Allocates a new {@code String} containing characters constructed from
 366      * an array of 8-bit integer values. Each character <i>c</i>in the
 367      * resulting string is constructed from the corresponding component
 368      * <i>b</i> in the byte array such that:
 369      *
 370      * <blockquote><pre>
 371      *     <b><i>c</i></b> == (char)(((hibyte &amp; 0xff) &lt;&lt; 8)
 372      *                         | (<b><i>b</i></b> &amp; 0xff))
 373      * </pre></blockquote>
 374      *
 375      * @deprecated  This method does not properly convert bytes into
 376      * characters.  As of JDK&nbsp;1.1, the preferred way to do this is via the
 377      * {@code String} constructors that take a {@link
 378      * java.nio.charset.Charset}, charset name, or that use the platform's
 379      * default charset.
 380      *
 381      * @param  ascii
 382      *         The bytes to be converted to characters
 383      *
 384      * @param  hibyte
 385      *         The top 8 bits of each 16-bit Unicode code unit
 386      *
 387      * @see  #String(byte[], int, int, java.lang.String)
 388      * @see  #String(byte[], int, int, java.nio.charset.Charset)
 389      * @see  #String(byte[], int, int)
 390      * @see  #String(byte[], java.lang.String)
 391      * @see  #String(byte[], java.nio.charset.Charset)
 392      * @see  #String(byte[])
 393      */
 394     @Deprecated
 395     public String(byte ascii[], int hibyte) {
 396         this(ascii, hibyte, 0, ascii.length);
 397     }
 398 
 399     /* Common private utility method used to bounds check the byte array
 400      * and requested offset & length values used by the String(byte[],..)
 401      * constructors.
 402      */
 403     private static void checkBounds(byte[] bytes, int offset, int length) {
 404         if (length < 0)
 405             throw new StringIndexOutOfBoundsException(length);
 406         if (offset < 0)
 407             throw new StringIndexOutOfBoundsException(offset);
 408         if (offset > bytes.length - length)
 409             throw new StringIndexOutOfBoundsException(offset + length);
 410     }
 411 
 412     /**
 413      * Constructs a new {@code String} by decoding the specified subarray of
 414      * bytes using the specified charset.  The length of the new {@code String}
 415      * is a function of the charset, and hence may not be equal to the length
 416      * of the subarray.
 417      *
 418      * <p> The behavior of this constructor when the given bytes are not valid
 419      * in the given charset is unspecified.  The {@link
 420      * java.nio.charset.CharsetDecoder} class should be used when more control
 421      * over the decoding process is required.
 422      *
 423      * @param  bytes
 424      *         The bytes to be decoded into characters
 425      *
 426      * @param  offset
 427      *         The index of the first byte to decode
 428      *
 429      * @param  length
 430      *         The number of bytes to decode
 431 
 432      * @param  charsetName
 433      *         The name of a supported {@linkplain java.nio.charset.Charset
 434      *         charset}
 435      *
 436      * @throws  UnsupportedEncodingException
 437      *          If the named charset is not supported
 438      *
 439      * @throws  IndexOutOfBoundsException
 440      *          If the {@code offset} and {@code length} arguments index
 441      *          characters outside the bounds of the {@code bytes} array
 442      *
 443      * @since  JDK1.1
 444      */
 445     public String(byte bytes[], int offset, int length, String charsetName)
 446         throws UnsupportedEncodingException
 447     {
 448         if (charsetName == null)
 449             throw new NullPointerException("charsetName");
 450         checkBounds(bytes, offset, length);
 451         char[] v = StringCoding.decode(charsetName, bytes, offset, length);
 452         this.offset = 0;
 453         this.count = v.length;
 454         this.value = v;
 455     }
 456 
 457     /**
 458      * Constructs a new {@code String} by decoding the specified subarray of
 459      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
 460      * The length of the new {@code String} is a function of the charset, and
 461      * hence may not be equal to the length of the subarray.
 462      *
 463      * <p> This method always replaces malformed-input and unmappable-character
 464      * sequences with this charset's default replacement string.  The {@link
 465      * java.nio.charset.CharsetDecoder} class should be used when more control
 466      * over the decoding process is required.
 467      *
 468      * @param  bytes
 469      *         The bytes to be decoded into characters
 470      *
 471      * @param  offset
 472      *         The index of the first byte to decode
 473      *
 474      * @param  length
 475      *         The number of bytes to decode
 476      *
 477      * @param  charset
 478      *         The {@linkplain java.nio.charset.Charset charset} to be used to
 479      *         decode the {@code bytes}
 480      *
 481      * @throws  IndexOutOfBoundsException
 482      *          If the {@code offset} and {@code length} arguments index
 483      *          characters outside the bounds of the {@code bytes} array
 484      *
 485      * @since  1.6
 486      */
 487     public String(byte bytes[], int offset, int length, Charset charset) {
 488         if (charset == null)
 489             throw new NullPointerException("charset");
 490         checkBounds(bytes, offset, length);
 491         char[] v = StringCoding.decode(charset, bytes, offset, length);
 492         this.offset = 0;
 493         this.count = v.length;
 494         this.value = v;
 495     }
 496 
 497     /**
 498      * Constructs a new {@code String} by decoding the specified array of bytes
 499      * using the specified {@linkplain java.nio.charset.Charset charset}.  The
 500      * length of the new {@code String} is a function of the charset, and hence
 501      * may not be equal to the length of the byte array.
 502      *
 503      * <p> The behavior of this constructor when the given bytes are not valid
 504      * in the given charset is unspecified.  The {@link
 505      * java.nio.charset.CharsetDecoder} class should be used when more control
 506      * over the decoding process is required.
 507      *
 508      * @param  bytes
 509      *         The bytes to be decoded into characters
 510      *
 511      * @param  charsetName
 512      *         The name of a supported {@linkplain java.nio.charset.Charset
 513      *         charset}
 514      *
 515      * @throws  UnsupportedEncodingException
 516      *          If the named charset is not supported
 517      *
 518      * @since  JDK1.1
 519      */
 520     public String(byte bytes[], String charsetName)
 521         throws UnsupportedEncodingException
 522     {
 523         this(bytes, 0, bytes.length, charsetName);
 524     }
 525 
 526     /**
 527      * Constructs a new {@code String} by decoding the specified array of
 528      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
 529      * The length of the new {@code String} is a function of the charset, and
 530      * hence may not be equal to the length of the byte array.
 531      *
 532      * <p> This method always replaces malformed-input and unmappable-character
 533      * sequences with this charset's default replacement string.  The {@link
 534      * java.nio.charset.CharsetDecoder} class should be used when more control
 535      * over the decoding process is required.
 536      *
 537      * @param  bytes
 538      *         The bytes to be decoded into characters
 539      *
 540      * @param  charset
 541      *         The {@linkplain java.nio.charset.Charset charset} to be used to
 542      *         decode the {@code bytes}
 543      *
 544      * @since  1.6
 545      */
 546     public String(byte bytes[], Charset charset) {
 547         this(bytes, 0, bytes.length, charset);
 548     }
 549 
 550     /**
 551      * Constructs a new {@code String} by decoding the specified subarray of
 552      * bytes using the platform's default charset.  The length of the new
 553      * {@code String} is a function of the charset, and hence may not be equal
 554      * to the length of the subarray.
 555      *
 556      * <p> The behavior of this constructor when the given bytes are not valid
 557      * in the default charset is unspecified.  The {@link
 558      * java.nio.charset.CharsetDecoder} class should be used when more control
 559      * over the decoding process is required.
 560      *
 561      * @param  bytes
 562      *         The bytes to be decoded into characters
 563      *
 564      * @param  offset
 565      *         The index of the first byte to decode
 566      *
 567      * @param  length
 568      *         The number of bytes to decode
 569      *
 570      * @throws  IndexOutOfBoundsException
 571      *          If the {@code offset} and the {@code length} arguments index
 572      *          characters outside the bounds of the {@code bytes} array
 573      *
 574      * @since  JDK1.1
 575      */
 576     public String(byte bytes[], int offset, int length) {
 577         checkBounds(bytes, offset, length);
 578         char[] v  = StringCoding.decode(bytes, offset, length);
 579         this.offset = 0;
 580         this.count = v.length;
 581         this.value = v;
 582     }
 583 
 584     /**
 585      * Constructs a new {@code String} by decoding the specified array of bytes
 586      * using the platform's default charset.  The length of the new {@code
 587      * String} is a function of the charset, and hence may not be equal to the
 588      * length of the byte array.
 589      *
 590      * <p> The behavior of this constructor when the given bytes are not valid
 591      * in the default charset is unspecified.  The {@link
 592      * java.nio.charset.CharsetDecoder} class should be used when more control
 593      * over the decoding process is required.
 594      *
 595      * @param  bytes
 596      *         The bytes to be decoded into characters
 597      *
 598      * @since  JDK1.1
 599      */
 600     public String(byte bytes[]) {
 601         this(bytes, 0, bytes.length);
 602     }
 603 
 604     /**
 605      * Allocates a new string that contains the sequence of characters
 606      * currently contained in the string buffer argument. The contents of the
 607      * string buffer are copied; subsequent modification of the string buffer
 608      * does not affect the newly created string.
 609      *
 610      * @param  buffer
 611      *         A {@code StringBuffer}
 612      */
 613     public String(StringBuffer buffer) {
 614         String result = buffer.toString();
 615         this.value = result.value;
 616         this.count = result.count;
 617         this.offset = result.offset;
 618     }
 619 
 620     /**
 621      * Allocates a new string that contains the sequence of characters
 622      * currently contained in the string builder argument. The contents of the
 623      * string builder are copied; subsequent modification of the string builder
 624      * does not affect the newly created string.
 625      *
 626      * <p> This constructor is provided to ease migration to {@code
 627      * StringBuilder}. Obtaining a string from a string builder via the {@code
 628      * toString} method is likely to run faster and is generally preferred.
 629      *
 630      * @param   builder
 631      *          A {@code StringBuilder}
 632      *
 633      * @since  1.5
 634      */
 635     public String(StringBuilder builder) {
 636         String result = builder.toString();
 637         this.value = result.value;
 638         this.count = result.count;
 639         this.offset = result.offset;
 640     }
 641 
 642 
 643     // Package private constructor which shares value array for speed.
 644     String(int offset, int count, char value[]) {
 645         this.value = value;
 646         this.offset = offset;
 647         this.count = count;
 648     }
 649 
 650     /**
 651      * Returns the length of this string.
 652      * The length is equal to the number of <a href="Character.html#unicode">Unicode
 653      * code units</a> in the string.
 654      *
 655      * @return  the length of the sequence of characters represented by this
 656      *          object.
 657      */
 658     public int length() {
 659         return count;
 660     }
 661 
 662     /**
 663      * Returns <tt>true</tt> if, and only if, {@link #length()} is <tt>0</tt>.
 664      *
 665      * @return <tt>true</tt> if {@link #length()} is <tt>0</tt>, otherwise
 666      * <tt>false</tt>
 667      *
 668      * @since 1.6
 669      */
 670     public boolean isEmpty() {
 671         return count == 0;
 672     }
 673 
 674     /**
 675      * Returns the <code>char</code> value at the
 676      * specified index. An index ranges from <code>0</code> to
 677      * <code>length() - 1</code>. The first <code>char</code> value of the sequence
 678      * is at index <code>0</code>, the next at index <code>1</code>,
 679      * and so on, as for array indexing.
 680      *
 681      * <p>If the <code>char</code> value specified by the index is a
 682      * <a href="Character.html#unicode">surrogate</a>, the surrogate
 683      * value is returned.
 684      *
 685      * @param      index   the index of the <code>char</code> value.
 686      * @return     the <code>char</code> value at the specified index of this string.
 687      *             The first <code>char</code> value is at index <code>0</code>.
 688      * @exception  IndexOutOfBoundsException  if the <code>index</code>
 689      *             argument is negative or not less than the length of this
 690      *             string.
 691      */
 692     public char charAt(int index) {
 693         if ((index < 0) || (index >= count)) {
 694             throw new StringIndexOutOfBoundsException(index);
 695         }
 696         return value[index + offset];
 697     }
 698 
 699     /**
 700      * Returns the character (Unicode code point) at the specified
 701      * index. The index refers to <code>char</code> values
 702      * (Unicode code units) and ranges from <code>0</code> to
 703      * {@link #length()}<code> - 1</code>.
 704      *
 705      * <p> If the <code>char</code> value specified at the given index
 706      * is in the high-surrogate range, the following index is less
 707      * than the length of this <code>String</code>, and the
 708      * <code>char</code> value at the following index is in the
 709      * low-surrogate range, then the supplementary code point
 710      * corresponding to this surrogate pair is returned. Otherwise,
 711      * the <code>char</code> value at the given index is returned.
 712      *
 713      * @param      index the index to the <code>char</code> values
 714      * @return     the code point value of the character at the
 715      *             <code>index</code>
 716      * @exception  IndexOutOfBoundsException  if the <code>index</code>
 717      *             argument is negative or not less than the length of this
 718      *             string.
 719      * @since      1.5
 720      */
 721     public int codePointAt(int index) {
 722         if ((index < 0) || (index >= count)) {
 723             throw new StringIndexOutOfBoundsException(index);
 724         }
 725         return Character.codePointAtImpl(value, offset + index, offset + count);
 726     }
 727 
 728     /**
 729      * Returns the character (Unicode code point) before the specified
 730      * index. The index refers to <code>char</code> values
 731      * (Unicode code units) and ranges from <code>1</code> to {@link
 732      * CharSequence#length() length}.
 733      *
 734      * <p> If the <code>char</code> value at <code>(index - 1)</code>
 735      * is in the low-surrogate range, <code>(index - 2)</code> is not
 736      * negative, and the <code>char</code> value at <code>(index -
 737      * 2)</code> is in the high-surrogate range, then the
 738      * supplementary code point value of the surrogate pair is
 739      * returned. If the <code>char</code> value at <code>index -
 740      * 1</code> is an unpaired low-surrogate or a high-surrogate, the
 741      * surrogate value is returned.
 742      *
 743      * @param     index the index following the code point that should be returned
 744      * @return    the Unicode code point value before the given index.
 745      * @exception IndexOutOfBoundsException if the <code>index</code>
 746      *            argument is less than 1 or greater than the length
 747      *            of this string.
 748      * @since     1.5
 749      */
 750     public int codePointBefore(int index) {
 751         int i = index - 1;
 752         if ((i < 0) || (i >= count)) {
 753             throw new StringIndexOutOfBoundsException(index);
 754         }
 755         return Character.codePointBeforeImpl(value, offset + index, offset);
 756     }
 757 
 758     /**
 759      * Returns the number of Unicode code points in the specified text
 760      * range of this <code>String</code>. The text range begins at the
 761      * specified <code>beginIndex</code> and extends to the
 762      * <code>char</code> at index <code>endIndex - 1</code>. Thus the
 763      * length (in <code>char</code>s) of the text range is
 764      * <code>endIndex-beginIndex</code>. Unpaired surrogates within
 765      * the text range count as one code point each.
 766      *
 767      * @param beginIndex the index to the first <code>char</code> of
 768      * the text range.
 769      * @param endIndex the index after the last <code>char</code> of
 770      * the text range.
 771      * @return the number of Unicode code points in the specified text
 772      * range
 773      * @exception IndexOutOfBoundsException if the
 774      * <code>beginIndex</code> is negative, or <code>endIndex</code>
 775      * is larger than the length of this <code>String</code>, or
 776      * <code>beginIndex</code> is larger than <code>endIndex</code>.
 777      * @since  1.5
 778      */
 779     public int codePointCount(int beginIndex, int endIndex) {
 780         if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
 781             throw new IndexOutOfBoundsException();
 782         }
 783         return Character.codePointCountImpl(value, offset+beginIndex, endIndex-beginIndex);
 784     }
 785 
 786     /**
 787      * Returns the index within this <code>String</code> that is
 788      * offset from the given <code>index</code> by
 789      * <code>codePointOffset</code> code points. Unpaired surrogates
 790      * within the text range given by <code>index</code> and
 791      * <code>codePointOffset</code> count as one code point each.
 792      *
 793      * @param index the index to be offset
 794      * @param codePointOffset the offset in code points
 795      * @return the index within this <code>String</code>
 796      * @exception IndexOutOfBoundsException if <code>index</code>
 797      *   is negative or larger then the length of this
 798      *   <code>String</code>, or if <code>codePointOffset</code> is positive
 799      *   and the substring starting with <code>index</code> has fewer
 800      *   than <code>codePointOffset</code> code points,
 801      *   or if <code>codePointOffset</code> is negative and the substring
 802      *   before <code>index</code> has fewer than the absolute value
 803      *   of <code>codePointOffset</code> code points.
 804      * @since 1.5
 805      */
 806     public int offsetByCodePoints(int index, int codePointOffset) {
 807         if (index < 0 || index > count) {
 808             throw new IndexOutOfBoundsException();
 809         }
 810         return Character.offsetByCodePointsImpl(value, offset, count,
 811                                                 offset+index, codePointOffset) - offset;
 812     }
 813 
 814     /**
 815      * Copy characters from this string into dst starting at dstBegin.
 816      * This method doesn't perform any range checking.
 817      */
 818     void getChars(char dst[], int dstBegin) {
 819         System.arraycopy(value, offset, dst, dstBegin, count);
 820     }
 821 
 822     /**
 823      * Copies characters from this string into the destination character
 824      * array.
 825      * <p>
 826      * The first character to be copied is at index <code>srcBegin</code>;
 827      * the last character to be copied is at index <code>srcEnd-1</code>
 828      * (thus the total number of characters to be copied is
 829      * <code>srcEnd-srcBegin</code>). The characters are copied into the
 830      * subarray of <code>dst</code> starting at index <code>dstBegin</code>
 831      * and ending at index:
 832      * <p><blockquote><pre>
 833      *     dstbegin + (srcEnd-srcBegin) - 1
 834      * </pre></blockquote>
 835      *
 836      * @param      srcBegin   index of the first character in the string
 837      *                        to copy.
 838      * @param      srcEnd     index after the last character in the string
 839      *                        to copy.
 840      * @param      dst        the destination array.
 841      * @param      dstBegin   the start offset in the destination array.
 842      * @exception IndexOutOfBoundsException If any of the following
 843      *            is true:
 844      *            <ul><li><code>srcBegin</code> is negative.
 845      *            <li><code>srcBegin</code> is greater than <code>srcEnd</code>
 846      *            <li><code>srcEnd</code> is greater than the length of this
 847      *                string
 848      *            <li><code>dstBegin</code> is negative
 849      *            <li><code>dstBegin+(srcEnd-srcBegin)</code> is larger than
 850      *                <code>dst.length</code></ul>
 851      */
 852     public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
 853         if (srcBegin < 0) {
 854             throw new StringIndexOutOfBoundsException(srcBegin);
 855         }
 856         if (srcEnd > count) {
 857             throw new StringIndexOutOfBoundsException(srcEnd);
 858         }
 859         if (srcBegin > srcEnd) {
 860             throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
 861         }
 862         System.arraycopy(value, offset + srcBegin, dst, dstBegin,
 863              srcEnd - srcBegin);
 864     }
 865 
 866     /**
 867      * Copies characters from this string into the destination byte array. Each
 868      * byte receives the 8 low-order bits of the corresponding character. The
 869      * eight high-order bits of each character are not copied and do not
 870      * participate in the transfer in any way.
 871      *
 872      * <p> The first character to be copied is at index {@code srcBegin}; the
 873      * last character to be copied is at index {@code srcEnd-1}.  The total
 874      * number of characters to be copied is {@code srcEnd-srcBegin}. The
 875      * characters, converted to bytes, are copied into the subarray of {@code
 876      * dst} starting at index {@code dstBegin} and ending at index:
 877      *
 878      * <blockquote><pre>
 879      *     dstbegin + (srcEnd-srcBegin) - 1
 880      * </pre></blockquote>
 881      *
 882      * @deprecated  This method does not properly convert characters into
 883      * bytes.  As of JDK&nbsp;1.1, the preferred way to do this is via the
 884      * {@link #getBytes()} method, which uses the platform's default charset.
 885      *
 886      * @param  srcBegin
 887      *         Index of the first character in the string to copy
 888      *
 889      * @param  srcEnd
 890      *         Index after the last character in the string to copy
 891      *
 892      * @param  dst
 893      *         The destination array
 894      *
 895      * @param  dstBegin
 896      *         The start offset in the destination array
 897      *
 898      * @throws  IndexOutOfBoundsException
 899      *          If any of the following is true:
 900      *          <ul>
 901      *            <li> {@code srcBegin} is negative
 902      *            <li> {@code srcBegin} is greater than {@code srcEnd}
 903      *            <li> {@code srcEnd} is greater than the length of this String
 904      *            <li> {@code dstBegin} is negative
 905      *            <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
 906      *                 dst.length}
 907      *          </ul>
 908      */
 909     @Deprecated
 910     public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
 911         if (srcBegin < 0) {
 912             throw new StringIndexOutOfBoundsException(srcBegin);
 913         }
 914         if (srcEnd > count) {
 915             throw new StringIndexOutOfBoundsException(srcEnd);
 916         }
 917         if (srcBegin > srcEnd) {
 918             throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
 919         }
 920         int j = dstBegin;
 921         int n = offset + srcEnd;
 922         int i = offset + srcBegin;
 923         char[] val = value;   /* avoid getfield opcode */
 924 
 925         while (i < n) {
 926             dst[j++] = (byte)val[i++];
 927         }
 928     }
 929 
 930     /**
 931      * Encodes this {@code String} into a sequence of bytes using the named
 932      * charset, storing the result into a new byte array.
 933      *
 934      * <p> The behavior of this method when this string cannot be encoded in
 935      * the given charset is unspecified.  The {@link
 936      * java.nio.charset.CharsetEncoder} class should be used when more control
 937      * over the encoding process is required.
 938      *
 939      * @param  charsetName
 940      *         The name of a supported {@linkplain java.nio.charset.Charset
 941      *         charset}
 942      *
 943      * @return  The resultant byte array
 944      *
 945      * @throws  UnsupportedEncodingException
 946      *          If the named charset is not supported
 947      *
 948      * @since  JDK1.1
 949      */
 950     public byte[] getBytes(String charsetName)
 951         throws UnsupportedEncodingException
 952     {
 953         if (charsetName == null) throw new NullPointerException();
 954         return StringCoding.encode(charsetName, value, offset, count);
 955     }
 956 
 957     /**
 958      * Encodes this {@code String} into a sequence of bytes using the given
 959      * {@linkplain java.nio.charset.Charset charset}, storing the result into a
 960      * new byte array.
 961      *
 962      * <p> This method always replaces malformed-input and unmappable-character
 963      * sequences with this charset's default replacement byte array.  The
 964      * {@link java.nio.charset.CharsetEncoder} class should be used when more
 965      * control over the encoding process is required.
 966      *
 967      * @param  charset
 968      *         The {@linkplain java.nio.charset.Charset} to be used to encode
 969      *         the {@code String}
 970      *
 971      * @return  The resultant byte array
 972      *
 973      * @since  1.6
 974      */
 975     public byte[] getBytes(Charset charset) {
 976         if (charset == null) throw new NullPointerException();
 977         return StringCoding.encode(charset, value, offset, count);
 978     }
 979 
 980     /**
 981      * Encodes this {@code String} into a sequence of bytes using the
 982      * platform's default charset, storing the result into a new byte array.
 983      *
 984      * <p> The behavior of this method when this string cannot be encoded in
 985      * the default charset is unspecified.  The {@link
 986      * java.nio.charset.CharsetEncoder} class should be used when more control
 987      * over the encoding process is required.
 988      *
 989      * @return  The resultant byte array
 990      *
 991      * @since      JDK1.1
 992      */
 993     public byte[] getBytes() {
 994         return StringCoding.encode(value, offset, count);
 995     }
 996 
 997     /**
 998      * Compares this string to the specified object.  The result is {@code
 999      * true} if and only if the argument is not {@code null} and is a {@code
1000      * String} object that represents the same sequence of characters as this
1001      * object.
1002      *
1003      * @param  anObject
1004      *         The object to compare this {@code String} against
1005      *
1006      * @return  {@code true} if the given object represents a {@code String}
1007      *          equivalent to this string, {@code false} otherwise
1008      *
1009      * @see  #compareTo(String)
1010      * @see  #equalsIgnoreCase(String)
1011      */
1012     public boolean equals(Object anObject) {
1013         if (this == anObject) {
1014             return true;
1015         }
1016         if (anObject instanceof String) {
1017             String anotherString = (String)anObject;
1018             int n = count;
1019             if (n == anotherString.count) {
1020                 char v1[] = value;
1021                 char v2[] = anotherString.value;
1022                 int i = offset;
1023                 int j = anotherString.offset;
1024                 while (n-- != 0) {
1025                     if (v1[i++] != v2[j++])
1026                         return false;
1027                 }
1028                 return true;
1029             }
1030         }
1031         return false;
1032     }
1033 
1034     /**
1035      * Compares this string to the specified {@code StringBuffer}.  The result
1036      * is {@code true} if and only if this {@code String} represents the same
1037      * sequence of characters as the specified {@code StringBuffer}.
1038      *
1039      * @param  sb
1040      *         The {@code StringBuffer} to compare this {@code String} against
1041      *
1042      * @return  {@code true} if this {@code String} represents the same
1043      *          sequence of characters as the specified {@code StringBuffer},
1044      *          {@code false} otherwise
1045      *
1046      * @since  1.4
1047      */
1048     public boolean contentEquals(StringBuffer sb) {
1049         synchronized(sb) {
1050             return contentEquals((CharSequence)sb);
1051         }
1052     }
1053 
1054     /**
1055      * Compares this string to the specified {@code CharSequence}.  The result
1056      * is {@code true} if and only if this {@code String} represents the same
1057      * sequence of char values as the specified sequence.
1058      *
1059      * @param  cs
1060      *         The sequence to compare this {@code String} against
1061      *
1062      * @return  {@code true} if this {@code String} represents the same
1063      *          sequence of char values as the specified sequence, {@code
1064      *          false} otherwise
1065      *
1066      * @since  1.5
1067      */
1068     public boolean contentEquals(CharSequence cs) {
1069         if (count != cs.length())
1070             return false;
1071         // Argument is a StringBuffer, StringBuilder
1072         if (cs instanceof AbstractStringBuilder) {
1073             char v1[] = value;
1074             char v2[] = ((AbstractStringBuilder)cs).getValue();
1075             int i = offset;
1076             int j = 0;
1077             int n = count;
1078             while (n-- != 0) {
1079                 if (v1[i++] != v2[j++])
1080                     return false;
1081             }
1082             return true;
1083         }
1084         // Argument is a String
1085         if (cs.equals(this))
1086             return true;
1087         // Argument is a generic CharSequence
1088         char v1[] = value;
1089         int i = offset;
1090         int j = 0;
1091         int n = count;
1092         while (n-- != 0) {
1093             if (v1[i++] != cs.charAt(j++))
1094                 return false;
1095         }
1096         return true;
1097     }
1098 
1099     /**
1100      * Compares this {@code String} to another {@code String}, ignoring case
1101      * considerations.  Two strings are considered equal ignoring case if they
1102      * are of the same length and corresponding characters in the two strings
1103      * are equal ignoring case.
1104      *
1105      * <p> Two characters {@code c1} and {@code c2} are considered the same
1106      * ignoring case if at least one of the following is true:
1107      * <ul>
1108      *   <li> The two characters are the same (as compared by the
1109      *        {@code ==} operator)
1110      *   <li> Applying the method {@link
1111      *        java.lang.Character#toUpperCase(char)} to each character
1112      *        produces the same result
1113      *   <li> Applying the method {@link
1114      *        java.lang.Character#toLowerCase(char)} to each character
1115      *        produces the same result
1116      * </ul>
1117      *
1118      * @param  anotherString
1119      *         The {@code String} to compare this {@code String} against
1120      *
1121      * @return  {@code true} if the argument is not {@code null} and it
1122      *          represents an equivalent {@code String} ignoring case; {@code
1123      *          false} otherwise
1124      *
1125      * @see  #equals(Object)
1126      */
1127     public boolean equalsIgnoreCase(String anotherString) {
1128         return (this == anotherString) ? true :
1129                (anotherString != null) && (anotherString.count == count) &&
1130                regionMatches(true, 0, anotherString, 0, count);
1131     }
1132 
1133     /**
1134      * Compares two strings lexicographically.
1135      * The comparison is based on the Unicode value of each character in
1136      * the strings. The character sequence represented by this
1137      * <code>String</code> object is compared lexicographically to the
1138      * character sequence represented by the argument string. The result is
1139      * a negative integer if this <code>String</code> object
1140      * lexicographically precedes the argument string. The result is a
1141      * positive integer if this <code>String</code> object lexicographically
1142      * follows the argument string. The result is zero if the strings
1143      * are equal; <code>compareTo</code> returns <code>0</code> exactly when
1144      * the {@link #equals(Object)} method would return <code>true</code>.
1145      * <p>
1146      * This is the definition of lexicographic ordering. If two strings are
1147      * different, then either they have different characters at some index
1148      * that is a valid index for both strings, or their lengths are different,
1149      * or both. If they have different characters at one or more index
1150      * positions, let <i>k</i> be the smallest such index; then the string
1151      * whose character at position <i>k</i> has the smaller value, as
1152      * determined by using the &lt; operator, lexicographically precedes the
1153      * other string. In this case, <code>compareTo</code> returns the
1154      * difference of the two character values at position <code>k</code> in
1155      * the two string -- that is, the value:
1156      * <blockquote><pre>
1157      * this.charAt(k)-anotherString.charAt(k)
1158      * </pre></blockquote>
1159      * If there is no index position at which they differ, then the shorter
1160      * string lexicographically precedes the longer string. In this case,
1161      * <code>compareTo</code> returns the difference of the lengths of the
1162      * strings -- that is, the value:
1163      * <blockquote><pre>
1164      * this.length()-anotherString.length()
1165      * </pre></blockquote>
1166      *
1167      * @param   anotherString   the <code>String</code> to be compared.
1168      * @return  the value <code>0</code> if the argument string is equal to
1169      *          this string; a value less than <code>0</code> if this string
1170      *          is lexicographically less than the string argument; and a
1171      *          value greater than <code>0</code> if this string is
1172      *          lexicographically greater than the string argument.
1173      */
1174     public int compareTo(String anotherString) {
1175         int len1 = count;
1176         int len2 = anotherString.count;
1177         int n = Math.min(len1, len2);
1178         char v1[] = value;
1179         char v2[] = anotherString.value;
1180         int i = offset;
1181         int j = anotherString.offset;
1182 
1183         if (i == j) {
1184             int k = i;
1185             int lim = n + i;
1186             while (k < lim) {
1187                 char c1 = v1[k];
1188                 char c2 = v2[k];
1189                 if (c1 != c2) {
1190                     return c1 - c2;
1191                 }
1192                 k++;
1193             }
1194         } else {
1195             while (n-- != 0) {
1196                 char c1 = v1[i++];
1197                 char c2 = v2[j++];
1198                 if (c1 != c2) {
1199                     return c1 - c2;
1200                 }
1201             }
1202         }
1203         return len1 - len2;
1204     }
1205 
1206     /**
1207      * A Comparator that orders <code>String</code> objects as by
1208      * <code>compareToIgnoreCase</code>. This comparator is serializable.
1209      * <p>
1210      * Note that this Comparator does <em>not</em> take locale into account,
1211      * and will result in an unsatisfactory ordering for certain locales.
1212      * The java.text package provides <em>Collators</em> to allow
1213      * locale-sensitive ordering.
1214      *
1215      * @see     java.text.Collator#compare(String, String)
1216      * @since   1.2
1217      */
1218     public static final Comparator<String> CASE_INSENSITIVE_ORDER
1219                                          = new CaseInsensitiveComparator();
1220     private static class CaseInsensitiveComparator
1221                          implements Comparator<String>, java.io.Serializable {
1222         // use serialVersionUID from JDK 1.2.2 for interoperability
1223         private static final long serialVersionUID = 8575799808933029326L;
1224 
1225         public int compare(String s1, String s2) {
1226             int n1 = s1.length();
1227             int n2 = s2.length();
1228             int min = Math.min(n1, n2);
1229             for (int i = 0; i < min; i++) {
1230                 char c1 = s1.charAt(i);
1231                 char c2 = s2.charAt(i);
1232                 if (c1 != c2) {
1233                     c1 = Character.toUpperCase(c1);
1234                     c2 = Character.toUpperCase(c2);
1235                     if (c1 != c2) {
1236                         c1 = Character.toLowerCase(c1);
1237                         c2 = Character.toLowerCase(c2);
1238                         if (c1 != c2) {
1239                             // No overflow because of numeric promotion
1240                             return c1 - c2;
1241                         }
1242                     }
1243                 }
1244             }
1245             return n1 - n2;
1246         }
1247     }
1248 
1249     /**
1250      * Compares two strings lexicographically, ignoring case
1251      * differences. This method returns an integer whose sign is that of
1252      * calling <code>compareTo</code> with normalized versions of the strings
1253      * where case differences have been eliminated by calling
1254      * <code>Character.toLowerCase(Character.toUpperCase(character))</code> on
1255      * each character.
1256      * <p>
1257      * Note that this method does <em>not</em> take locale into account,
1258      * and will result in an unsatisfactory ordering for certain locales.
1259      * The java.text package provides <em>collators</em> to allow
1260      * locale-sensitive ordering.
1261      *
1262      * @param   str   the <code>String</code> to be compared.
1263      * @return  a negative integer, zero, or a positive integer as the
1264      *          specified String is greater than, equal to, or less
1265      *          than this String, ignoring case considerations.
1266      * @see     java.text.Collator#compare(String, String)
1267      * @since   1.2
1268      */
1269     public int compareToIgnoreCase(String str) {
1270         return CASE_INSENSITIVE_ORDER.compare(this, str);
1271     }
1272 
1273     /**
1274      * Tests if two string regions are equal.
1275      * <p>
1276      * A substring of this <tt>String</tt> object is compared to a substring
1277      * of the argument other. The result is true if these substrings
1278      * represent identical character sequences. The substring of this
1279      * <tt>String</tt> object to be compared begins at index <tt>toffset</tt>
1280      * and has length <tt>len</tt>. The substring of other to be compared
1281      * begins at index <tt>ooffset</tt> and has length <tt>len</tt>. The
1282      * result is <tt>false</tt> if and only if at least one of the following
1283      * is true:
1284      * <ul><li><tt>toffset</tt> is negative.
1285      * <li><tt>ooffset</tt> is negative.
1286      * <li><tt>toffset+len</tt> is greater than the length of this
1287      * <tt>String</tt> object.
1288      * <li><tt>ooffset+len</tt> is greater than the length of the other
1289      * argument.
1290      * <li>There is some nonnegative integer <i>k</i> less than <tt>len</tt>
1291      * such that:
1292      * <tt>this.charAt(toffset+<i>k</i>)&nbsp;!=&nbsp;other.charAt(ooffset+<i>k</i>)</tt>
1293      * </ul>
1294      *
1295      * @param   toffset   the starting offset of the subregion in this string.
1296      * @param   other     the string argument.
1297      * @param   ooffset   the starting offset of the subregion in the string
1298      *                    argument.
1299      * @param   len       the number of characters to compare.
1300      * @return  <code>true</code> if the specified subregion of this string
1301      *          exactly matches the specified subregion of the string argument;
1302      *          <code>false</code> otherwise.
1303      */
1304     public boolean regionMatches(int toffset, String other, int ooffset,
1305                                  int len) {
1306         char ta[] = value;
1307         int to = offset + toffset;
1308         char pa[] = other.value;
1309         int po = other.offset + ooffset;
1310         // Note: toffset, ooffset, or len might be near -1>>>1.
1311         if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len)
1312             || (ooffset > (long)other.count - len)) {
1313             return false;
1314         }
1315         while (len-- > 0) {
1316             if (ta[to++] != pa[po++]) {
1317                 return false;
1318             }
1319         }
1320         return true;
1321     }
1322 
1323     /**
1324      * Tests if two string regions are equal.
1325      * <p>
1326      * A substring of this <tt>String</tt> object is compared to a substring
1327      * of the argument <tt>other</tt>. The result is <tt>true</tt> if these
1328      * substrings represent character sequences that are the same, ignoring
1329      * case if and only if <tt>ignoreCase</tt> is true. The substring of
1330      * this <tt>String</tt> object to be compared begins at index
1331      * <tt>toffset</tt> and has length <tt>len</tt>. The substring of
1332      * <tt>other</tt> to be compared begins at index <tt>ooffset</tt> and
1333      * has length <tt>len</tt>. The result is <tt>false</tt> if and only if
1334      * at least one of the following is true:
1335      * <ul><li><tt>toffset</tt> is negative.
1336      * <li><tt>ooffset</tt> is negative.
1337      * <li><tt>toffset+len</tt> is greater than the length of this
1338      * <tt>String</tt> object.
1339      * <li><tt>ooffset+len</tt> is greater than the length of the other
1340      * argument.
1341      * <li><tt>ignoreCase</tt> is <tt>false</tt> and there is some nonnegative
1342      * integer <i>k</i> less than <tt>len</tt> such that:
1343      * <blockquote><pre>
1344      * this.charAt(toffset+k) != other.charAt(ooffset+k)
1345      * </pre></blockquote>
1346      * <li><tt>ignoreCase</tt> is <tt>true</tt> and there is some nonnegative
1347      * integer <i>k</i> less than <tt>len</tt> such that:
1348      * <blockquote><pre>
1349      * Character.toLowerCase(this.charAt(toffset+k)) !=
1350                Character.toLowerCase(other.charAt(ooffset+k))
1351      * </pre></blockquote>
1352      * and:
1353      * <blockquote><pre>
1354      * Character.toUpperCase(this.charAt(toffset+k)) !=
1355      *         Character.toUpperCase(other.charAt(ooffset+k))
1356      * </pre></blockquote>
1357      * </ul>
1358      *
1359      * @param   ignoreCase   if <code>true</code>, ignore case when comparing
1360      *                       characters.
1361      * @param   toffset      the starting offset of the subregion in this
1362      *                       string.
1363      * @param   other        the string argument.
1364      * @param   ooffset      the starting offset of the subregion in the string
1365      *                       argument.
1366      * @param   len          the number of characters to compare.
1367      * @return  <code>true</code> if the specified subregion of this string
1368      *          matches the specified subregion of the string argument;
1369      *          <code>false</code> otherwise. Whether the matching is exact
1370      *          or case insensitive depends on the <code>ignoreCase</code>
1371      *          argument.
1372      */
1373     public boolean regionMatches(boolean ignoreCase, int toffset,
1374                            String other, int ooffset, int len) {
1375         char ta[] = value;
1376         int to = offset + toffset;
1377         char pa[] = other.value;
1378         int po = other.offset + ooffset;
1379         // Note: toffset, ooffset, or len might be near -1>>>1.
1380         if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len) ||
1381                 (ooffset > (long)other.count - len)) {
1382             return false;
1383         }
1384         while (len-- > 0) {
1385             char c1 = ta[to++];
1386             char c2 = pa[po++];
1387             if (c1 == c2) {
1388                 continue;
1389             }
1390             if (ignoreCase) {
1391                 // If characters don't match but case may be ignored,
1392                 // try converting both characters to uppercase.
1393                 // If the results match, then the comparison scan should
1394                 // continue.
1395                 char u1 = Character.toUpperCase(c1);
1396                 char u2 = Character.toUpperCase(c2);
1397                 if (u1 == u2) {
1398                     continue;
1399                 }
1400                 // Unfortunately, conversion to uppercase does not work properly
1401                 // for the Georgian alphabet, which has strange rules about case
1402                 // conversion.  So we need to make one last check before
1403                 // exiting.
1404                 if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
1405                     continue;
1406                 }
1407             }
1408             return false;
1409         }
1410         return true;
1411     }
1412 
1413     /**
1414      * Tests if the substring of this string beginning at the
1415      * specified index starts with the specified prefix.
1416      *
1417      * @param   prefix    the prefix.
1418      * @param   toffset   where to begin looking in this string.
1419      * @return  <code>true</code> if the character sequence represented by the
1420      *          argument is a prefix of the substring of this object starting
1421      *          at index <code>toffset</code>; <code>false</code> otherwise.
1422      *          The result is <code>false</code> if <code>toffset</code> is
1423      *          negative or greater than the length of this
1424      *          <code>String</code> object; otherwise the result is the same
1425      *          as the result of the expression
1426      *          <pre>
1427      *          this.substring(toffset).startsWith(prefix)
1428      *          </pre>
1429      */
1430     public boolean startsWith(String prefix, int toffset) {
1431         char ta[] = value;
1432         int to = offset + toffset;
1433         char pa[] = prefix.value;
1434         int po = prefix.offset;
1435         int pc = prefix.count;
1436         // Note: toffset might be near -1>>>1.
1437         if ((toffset < 0) || (toffset > count - pc)) {
1438             return false;
1439         }
1440         while (--pc >= 0) {
1441             if (ta[to++] != pa[po++]) {
1442                 return false;
1443             }
1444         }
1445         return true;
1446     }
1447 
1448     /**
1449      * Tests if this string starts with the specified prefix.
1450      *
1451      * @param   prefix   the prefix.
1452      * @return  <code>true</code> if the character sequence represented by the
1453      *          argument is a prefix of the character sequence represented by
1454      *          this string; <code>false</code> otherwise.
1455      *          Note also that <code>true</code> will be returned if the
1456      *          argument is an empty string or is equal to this
1457      *          <code>String</code> object as determined by the
1458      *          {@link #equals(Object)} method.
1459      * @since   1. 0
1460      */
1461     public boolean startsWith(String prefix) {
1462         return startsWith(prefix, 0);
1463     }
1464 
1465     /**
1466      * Tests if this string ends with the specified suffix.
1467      *
1468      * @param   suffix   the suffix.
1469      * @return  <code>true</code> if the character sequence represented by the
1470      *          argument is a suffix of the character sequence represented by
1471      *          this object; <code>false</code> otherwise. Note that the
1472      *          result will be <code>true</code> if the argument is the
1473      *          empty string or is equal to this <code>String</code> object
1474      *          as determined by the {@link #equals(Object)} method.
1475      */
1476     public boolean endsWith(String suffix) {
1477         return startsWith(suffix, count - suffix.count);
1478     }
1479 
1480     /**
1481      * Returns a hash code for this string. The hash code for a
1482      * <code>String</code> object is computed as
1483      * <blockquote><pre>
1484      * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
1485      * </pre></blockquote>
1486      * using <code>int</code> arithmetic, where <code>s[i]</code> is the
1487      * <i>i</i>th character of the string, <code>n</code> is the length of
1488      * the string, and <code>^</code> indicates exponentiation.
1489      * (The hash value of the empty string is zero.)
1490      *
1491      * @return  a hash code value for this object.
1492      */
1493     public int hashCode() {
1494         int h = hash;
1495         if (h == 0) {
1496             int off = offset;
1497             char val[] = value;
1498             int len = count;
1499 
1500             for (int i = 0; i < len; i++) {
1501                 h = 31*h + val[off++];
1502             }
1503             hash = h;
1504         }
1505         return h;
1506     }
1507 
1508     /**
1509      * Returns the index within this string of the first occurrence of
1510      * the specified character. If a character with value
1511      * <code>ch</code> occurs in the character sequence represented by
1512      * this <code>String</code> object, then the index (in Unicode
1513      * code units) of the first such occurrence is returned. For
1514      * values of <code>ch</code> in the range from 0 to 0xFFFF
1515      * (inclusive), this is the smallest value <i>k</i> such that:
1516      * <blockquote><pre>
1517      * this.charAt(<i>k</i>) == ch
1518      * </pre></blockquote>
1519      * is true. For other values of <code>ch</code>, it is the
1520      * smallest value <i>k</i> such that:
1521      * <blockquote><pre>
1522      * this.codePointAt(<i>k</i>) == ch
1523      * </pre></blockquote>
1524      * is true. In either case, if no such character occurs in this
1525      * string, then <code>-1</code> is returned.
1526      *
1527      * @param   ch   a character (Unicode code point).
1528      * @return  the index of the first occurrence of the character in the
1529      *          character sequence represented by this object, or
1530      *          <code>-1</code> if the character does not occur.
1531      */
1532     public int indexOf(int ch) {
1533         return indexOf(ch, 0);
1534     }
1535 
1536     /**
1537      * Returns the index within this string of the first occurrence of the
1538      * specified character, starting the search at the specified index.
1539      * <p>
1540      * If a character with value <code>ch</code> occurs in the
1541      * character sequence represented by this <code>String</code>
1542      * object at an index no smaller than <code>fromIndex</code>, then
1543      * the index of the first such occurrence is returned. For values
1544      * of <code>ch</code> in the range from 0 to 0xFFFF (inclusive),
1545      * this is the smallest value <i>k</i> such that:
1546      * <blockquote><pre>
1547      * (this.charAt(<i>k</i>) == ch) && (<i>k</i> &gt;= fromIndex)
1548      * </pre></blockquote>
1549      * is true. For other values of <code>ch</code>, it is the
1550      * smallest value <i>k</i> such that:
1551      * <blockquote><pre>
1552      * (this.codePointAt(<i>k</i>) == ch) && (<i>k</i> &gt;= fromIndex)
1553      * </pre></blockquote>
1554      * is true. In either case, if no such character occurs in this
1555      * string at or after position <code>fromIndex</code>, then
1556      * <code>-1</code> is returned.
1557      *
1558      * <p>
1559      * There is no restriction on the value of <code>fromIndex</code>. If it
1560      * is negative, it has the same effect as if it were zero: this entire
1561      * string may be searched. If it is greater than the length of this
1562      * string, it has the same effect as if it were equal to the length of
1563      * this string: <code>-1</code> is returned.
1564      *
1565      * <p>All indices are specified in <code>char</code> values
1566      * (Unicode code units).
1567      *
1568      * @param   ch          a character (Unicode code point).
1569      * @param   fromIndex   the index to start the search from.
1570      * @return  the index of the first occurrence of the character in the
1571      *          character sequence represented by this object that is greater
1572      *          than or equal to <code>fromIndex</code>, or <code>-1</code>
1573      *          if the character does not occur.
1574      */
1575     public int indexOf(int ch, int fromIndex) {
1576         int max = offset + count;
1577         char v[] = value;
1578 
1579         if (fromIndex < 0) {
1580             fromIndex = 0;
1581         } else if (fromIndex >= count) {
1582             // Note: fromIndex might be near -1>>>1.
1583             return -1;
1584         }
1585 
1586         int i = offset + fromIndex;
1587         if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
1588             // handle most cases here (ch is a BMP code point or a
1589             // negative value (invalid code point))
1590             for (; i < max ; i++) {
1591                 if (v[i] == ch) {
1592                     return i - offset;
1593                 }
1594             }
1595             return -1;
1596         }
1597 
1598         if (ch <= Character.MAX_CODE_POINT) {
1599             // handle supplementary characters here
1600             char[] surrogates = Character.toChars(ch);
1601             for (; i < max; i++) {
1602                 if (v[i] == surrogates[0]) {
1603                     if (i + 1 == max) {
1604                         break;
1605                     }
1606                     if (v[i+1] == surrogates[1]) {
1607                         return i - offset;
1608                     }
1609                 }
1610             }
1611         }
1612         return -1;
1613     }
1614 
1615     /**
1616      * Returns the index within this string of the last occurrence of
1617      * the specified character. For values of <code>ch</code> in the
1618      * range from 0 to 0xFFFF (inclusive), the index (in Unicode code
1619      * units) returned is the largest value <i>k</i> such that:
1620      * <blockquote><pre>
1621      * this.charAt(<i>k</i>) == ch
1622      * </pre></blockquote>
1623      * is true. For other values of <code>ch</code>, it is the
1624      * largest value <i>k</i> such that:
1625      * <blockquote><pre>
1626      * this.codePointAt(<i>k</i>) == ch
1627      * </pre></blockquote>
1628      * is true.  In either case, if no such character occurs in this
1629      * string, then <code>-1</code> is returned.  The
1630      * <code>String</code> is searched backwards starting at the last
1631      * character.
1632      *
1633      * @param   ch   a character (Unicode code point).
1634      * @return  the index of the last occurrence of the character in the
1635      *          character sequence represented by this object, or
1636      *          <code>-1</code> if the character does not occur.
1637      */
1638     public int lastIndexOf(int ch) {
1639         return lastIndexOf(ch, count - 1);
1640     }
1641 
1642     /**
1643      * Returns the index within this string of the last occurrence of
1644      * the specified character, searching backward starting at the
1645      * specified index. For values of <code>ch</code> in the range
1646      * from 0 to 0xFFFF (inclusive), the index returned is the largest
1647      * value <i>k</i> such that:
1648      * <blockquote><pre>
1649      * (this.charAt(<i>k</i>) == ch) && (<i>k</i> &lt;= fromIndex)
1650      * </pre></blockquote>
1651      * is true. For other values of <code>ch</code>, it is the
1652      * largest value <i>k</i> such that:
1653      * <blockquote><pre>
1654      * (this.codePointAt(<i>k</i>) == ch) && (<i>k</i> &lt;= fromIndex)
1655      * </pre></blockquote>
1656      * is true. In either case, if no such character occurs in this
1657      * string at or before position <code>fromIndex</code>, then
1658      * <code>-1</code> is returned.
1659      *
1660      * <p>All indices are specified in <code>char</code> values
1661      * (Unicode code units).
1662      *
1663      * @param   ch          a character (Unicode code point).
1664      * @param   fromIndex   the index to start the search from. There is no
1665      *          restriction on the value of <code>fromIndex</code>. If it is
1666      *          greater than or equal to the length of this string, it has
1667      *          the same effect as if it were equal to one less than the
1668      *          length of this string: this entire string may be searched.
1669      *          If it is negative, it has the same effect as if it were -1:
1670      *          -1 is returned.
1671      * @return  the index of the last occurrence of the character in the
1672      *          character sequence represented by this object that is less
1673      *          than or equal to <code>fromIndex</code>, or <code>-1</code>
1674      *          if the character does not occur before that point.
1675      */
1676     public int lastIndexOf(int ch, int fromIndex) {
1677         int min = offset;
1678         char v[] = value;
1679 
1680         int i = offset + ((fromIndex >= count) ? count - 1 : fromIndex);
1681 
1682         if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
1683             // handle most cases here (ch is a BMP code point or a
1684             // negative value (invalid code point))
1685             for (; i >= min ; i--) {
1686                 if (v[i] == ch) {
1687                     return i - offset;
1688                 }
1689             }
1690             return -1;
1691         }
1692 
1693         int max = offset + count;
1694         if (ch <= Character.MAX_CODE_POINT) {
1695             // handle supplementary characters here
1696             char[] surrogates = Character.toChars(ch);
1697             for (; i >= min; i--) {
1698                 if (v[i] == surrogates[0]) {
1699                     if (i + 1 == max) {
1700                         break;
1701                     }
1702                     if (v[i+1] == surrogates[1]) {
1703                         return i - offset;
1704                     }
1705                 }
1706             }
1707         }
1708         return -1;
1709     }
1710 
1711     /**
1712      * Returns the index within this string of the first occurrence of the
1713      * specified substring. The integer returned is the smallest value
1714      * <i>k</i> such that:
1715      * <blockquote><pre>
1716      * this.startsWith(str, <i>k</i>)
1717      * </pre></blockquote>
1718      * is <code>true</code>.
1719      *
1720      * @param   str   any string.
1721      * @return  if the string argument occurs as a substring within this
1722      *          object, then the index of the first character of the first
1723      *          such substring is returned; if it does not occur as a
1724      *          substring, <code>-1</code> is returned.
1725      */
1726     public int indexOf(String str) {
1727         return indexOf(str, 0);
1728     }
1729 
1730     /**
1731      * Returns the index within this string of the first occurrence of the
1732      * specified substring, starting at the specified index.  The integer
1733      * returned is the smallest value <tt>k</tt> for which:
1734      * <blockquote><pre>
1735      *     k &gt;= Math.min(fromIndex, this.length()) && this.startsWith(str, k)
1736      * </pre></blockquote>
1737      * If no such value of <i>k</i> exists, then -1 is returned.
1738      *
1739      * @param   str         the substring for which to search.
1740      * @param   fromIndex   the index from which to start the search.
1741      * @return  the index within this string of the first occurrence of the
1742      *          specified substring, starting at the specified index.
1743      */
1744     public int indexOf(String str, int fromIndex) {
1745         return indexOf(value, offset, count,
1746                        str.value, str.offset, str.count, fromIndex);
1747     }
1748 
1749     /**
1750      * Code shared by String and StringBuffer to do searches. The
1751      * source is the character array being searched, and the target
1752      * is the string being searched for.
1753      *
1754      * @param   source       the characters being searched.
1755      * @param   sourceOffset offset of the source string.
1756      * @param   sourceCount  count of the source string.
1757      * @param   target       the characters being searched for.
1758      * @param   targetOffset offset of the target string.
1759      * @param   targetCount  count of the target string.
1760      * @param   fromIndex    the index to begin searching from.
1761      */
1762     static int indexOf(char[] source, int sourceOffset, int sourceCount,
1763                        char[] target, int targetOffset, int targetCount,
1764                        int fromIndex) {
1765         if (fromIndex >= sourceCount) {
1766             return (targetCount == 0 ? sourceCount : -1);
1767         }
1768         if (fromIndex < 0) {
1769             fromIndex = 0;
1770         }
1771         if (targetCount == 0) {
1772             return fromIndex;
1773         }
1774 
1775         char first  = target[targetOffset];
1776         int max = sourceOffset + (sourceCount - targetCount);
1777 
1778         for (int i = sourceOffset + fromIndex; i <= max; i++) {
1779             /* Look for first character. */
1780             if (source[i] != first) {
1781                 while (++i <= max && source[i] != first);
1782             }
1783 
1784             /* Found first character, now look at the rest of v2 */
1785             if (i <= max) {
1786                 int j = i + 1;
1787                 int end = j + targetCount - 1;
1788                 for (int k = targetOffset + 1; j < end && source[j] ==
1789                          target[k]; j++, k++);
1790 
1791                 if (j == end) {
1792                     /* Found whole string. */
1793                     return i - sourceOffset;
1794                 }
1795             }
1796         }
1797         return -1;
1798     }
1799 
1800     /**
1801      * Returns the index within this string of the rightmost occurrence
1802      * of the specified substring.  The rightmost empty string "" is
1803      * considered to occur at the index value <code>this.length()</code>.
1804      * The returned index is the largest value <i>k</i> such that
1805      * <blockquote><pre>
1806      * this.startsWith(str, k)
1807      * </pre></blockquote>
1808      * is true.
1809      *
1810      * @param   str   the substring to search for.
1811      * @return  if the string argument occurs one or more times as a substring
1812      *          within this object, then the index of the first character of
1813      *          the last such substring is returned. If it does not occur as
1814      *          a substring, <code>-1</code> is returned.
1815      */
1816     public int lastIndexOf(String str) {
1817         return lastIndexOf(str, count);
1818     }
1819 
1820     /**
1821      * Returns the index within this string of the last occurrence of the
1822      * specified substring, searching backward starting at the specified index.
1823      * The integer returned is the largest value <i>k</i> such that:
1824      * <blockquote><pre>
1825      *     k &lt;= Math.min(fromIndex, this.length()) && this.startsWith(str, k)
1826      * </pre></blockquote>
1827      * If no such value of <i>k</i> exists, then -1 is returned.
1828      *
1829      * @param   str         the substring to search for.
1830      * @param   fromIndex   the index to start the search from.
1831      * @return  the index within this string of the last occurrence of the
1832      *          specified substring.
1833      */
1834     public int lastIndexOf(String str, int fromIndex) {
1835         return lastIndexOf(value, offset, count,
1836                            str.value, str.offset, str.count, fromIndex);
1837     }
1838 
1839     /**
1840      * Code shared by String and StringBuffer to do searches. The
1841      * source is the character array being searched, and the target
1842      * is the string being searched for.
1843      *
1844      * @param   source       the characters being searched.
1845      * @param   sourceOffset offset of the source string.
1846      * @param   sourceCount  count of the source string.
1847      * @param   target       the characters being searched for.
1848      * @param   targetOffset offset of the target string.
1849      * @param   targetCount  count of the target string.
1850      * @param   fromIndex    the index to begin searching from.
1851      */
1852     static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,
1853                            char[] target, int targetOffset, int targetCount,
1854                            int fromIndex) {
1855         /*
1856          * Check arguments; return immediately where possible. For
1857          * consistency, don't check for null str.
1858          */
1859         int rightIndex = sourceCount - targetCount;
1860         if (fromIndex < 0) {
1861             return -1;
1862         }
1863         if (fromIndex > rightIndex) {
1864             fromIndex = rightIndex;
1865         }
1866         /* Empty string always matches. */
1867         if (targetCount == 0) {
1868             return fromIndex;
1869         }
1870 
1871         int strLastIndex = targetOffset + targetCount - 1;
1872         char strLastChar = target[strLastIndex];
1873         int min = sourceOffset + targetCount - 1;
1874         int i = min + fromIndex;
1875 
1876     startSearchForLastChar:
1877         while (true) {
1878             while (i >= min && source[i] != strLastChar) {
1879                 i--;
1880             }
1881             if (i < min) {
1882                 return -1;
1883             }
1884             int j = i - 1;
1885             int start = j - (targetCount - 1);
1886             int k = strLastIndex - 1;
1887 
1888             while (j > start) {
1889                 if (source[j--] != target[k--]) {
1890                     i--;
1891                     continue startSearchForLastChar;
1892                 }
1893             }
1894             return start - sourceOffset + 1;
1895         }
1896     }
1897 
1898     /**
1899      * Returns a new string that is a substring of this string. The
1900      * substring begins with the character at the specified index and
1901      * extends to the end of this string. <p>
1902      * Examples:
1903      * <blockquote><pre>
1904      * "unhappy".substring(2) returns "happy"
1905      * "Harbison".substring(3) returns "bison"
1906      * "emptiness".substring(9) returns "" (an empty string)
1907      * </pre></blockquote>
1908      *
1909      * @param      beginIndex   the beginning index, inclusive.
1910      * @return     the specified substring.
1911      * @exception  IndexOutOfBoundsException  if
1912      *             <code>beginIndex</code> is negative or larger than the
1913      *             length of this <code>String</code> object.
1914      */
1915     public String substring(int beginIndex) {
1916         return substring(beginIndex, count);
1917     }
1918 
1919     /**
1920      * Returns a new string that is a substring of this string. The
1921      * substring begins at the specified <code>beginIndex</code> and
1922      * extends to the character at index <code>endIndex - 1</code>.
1923      * Thus the length of the substring is <code>endIndex-beginIndex</code>.
1924      * <p>
1925      * Examples:
1926      * <blockquote><pre>
1927      * "hamburger".substring(4, 8) returns "urge"
1928      * "smiles".substring(1, 5) returns "mile"
1929      * </pre></blockquote>
1930      *
1931      * @param      beginIndex   the beginning index, inclusive.
1932      * @param      endIndex     the ending index, exclusive.
1933      * @return     the specified substring.
1934      * @exception  IndexOutOfBoundsException  if the
1935      *             <code>beginIndex</code> is negative, or
1936      *             <code>endIndex</code> is larger than the length of
1937      *             this <code>String</code> object, or
1938      *             <code>beginIndex</code> is larger than
1939      *             <code>endIndex</code>.
1940      */
1941     public String substring(int beginIndex, int endIndex) {
1942         if (beginIndex < 0) {
1943             throw new StringIndexOutOfBoundsException(beginIndex);
1944         }
1945         if (endIndex > count) {
1946             throw new StringIndexOutOfBoundsException(endIndex);
1947         }
1948         if (beginIndex > endIndex) {
1949             throw new StringIndexOutOfBoundsException(endIndex - beginIndex);
1950         }
1951         return ((beginIndex == 0) && (endIndex == count)) ? this :
1952             new String(offset + beginIndex, endIndex - beginIndex, value);
1953     }
1954 
1955     /**
1956      * Returns a new character sequence that is a subsequence of this sequence.
1957      *
1958      * <p> An invocation of this method of the form
1959      *
1960      * <blockquote><pre>
1961      * str.subSequence(begin,&nbsp;end)</pre></blockquote>
1962      *
1963      * behaves in exactly the same way as the invocation
1964      *
1965      * <blockquote><pre>
1966      * str.substring(begin,&nbsp;end)</pre></blockquote>
1967      *
1968      * This method is defined so that the <tt>String</tt> class can implement
1969      * the {@link CharSequence} interface. </p>
1970      *
1971      * @param      beginIndex   the begin index, inclusive.
1972      * @param      endIndex     the end index, exclusive.
1973      * @return     the specified subsequence.
1974      *
1975      * @throws  IndexOutOfBoundsException
1976      *          if <tt>beginIndex</tt> or <tt>endIndex</tt> are negative,
1977      *          if <tt>endIndex</tt> is greater than <tt>length()</tt>,
1978      *          or if <tt>beginIndex</tt> is greater than <tt>startIndex</tt>
1979      *
1980      * @since 1.4
1981      * @spec JSR-51
1982      */
1983     public CharSequence subSequence(int beginIndex, int endIndex) {
1984         return this.substring(beginIndex, endIndex);
1985     }
1986 
1987     /**
1988      * Concatenates the specified string to the end of this string.
1989      * <p>
1990      * If the length of the argument string is <code>0</code>, then this
1991      * <code>String</code> object is returned. Otherwise, a new
1992      * <code>String</code> object is created, representing a character
1993      * sequence that is the concatenation of the character sequence
1994      * represented by this <code>String</code> object and the character
1995      * sequence represented by the argument string.<p>
1996      * Examples:
1997      * <blockquote><pre>
1998      * "cares".concat("s") returns "caress"
1999      * "to".concat("get").concat("her") returns "together"
2000      * </pre></blockquote>
2001      *
2002      * @param   str   the <code>String</code> that is concatenated to the end
2003      *                of this <code>String</code>.
2004      * @return  a string that represents the concatenation of this object's
2005      *          characters followed by the string argument's characters.
2006      */
2007     public String concat(String str) {
2008         int otherLen = str.length();
2009         if (otherLen == 0) {
2010             return this;
2011         }
2012         char buf[] = new char[count + otherLen];
2013         getChars(0, count, buf, 0);
2014         str.getChars(0, otherLen, buf, count);
2015         return new String(0, count + otherLen, buf);
2016     }
2017 
2018     /**
2019      * Returns a new string resulting from replacing all occurrences of
2020      * <code>oldChar</code> in this string with <code>newChar</code>.
2021      * <p>
2022      * If the character <code>oldChar</code> does not occur in the
2023      * character sequence represented by this <code>String</code> object,
2024      * then a reference to this <code>String</code> object is returned.
2025      * Otherwise, a new <code>String</code> object is created that
2026      * represents a character sequence identical to the character sequence
2027      * represented by this <code>String</code> object, except that every
2028      * occurrence of <code>oldChar</code> is replaced by an occurrence
2029      * of <code>newChar</code>.
2030      * <p>
2031      * Examples:
2032      * <blockquote><pre>
2033      * "mesquite in your cellar".replace('e', 'o')
2034      *         returns "mosquito in your collar"
2035      * "the war of baronets".replace('r', 'y')
2036      *         returns "the way of bayonets"
2037      * "sparring with a purple porpoise".replace('p', 't')
2038      *         returns "starring with a turtle tortoise"
2039      * "JonL".replace('q', 'x') returns "JonL" (no change)
2040      * </pre></blockquote>
2041      *
2042      * @param   oldChar   the old character.
2043      * @param   newChar   the new character.
2044      * @return  a string derived from this string by replacing every
2045      *          occurrence of <code>oldChar</code> with <code>newChar</code>.
2046      */
2047     public String replace(char oldChar, char newChar) {
2048         if (oldChar != newChar) {
2049             int len = count;
2050             int i = -1;
2051             char[] val = value; /* avoid getfield opcode */
2052             int off = offset;   /* avoid getfield opcode */
2053 
2054             while (++i < len) {
2055                 if (val[off + i] == oldChar) {
2056                     break;
2057                 }
2058             }
2059             if (i < len) {
2060                 char buf[] = new char[len];
2061                 for (int j = 0 ; j < i ; j++) {
2062                     buf[j] = val[off+j];
2063                 }
2064                 while (i < len) {
2065                     char c = val[off + i];
2066                     buf[i] = (c == oldChar) ? newChar : c;
2067                     i++;
2068                 }
2069                 return new String(0, len, buf);
2070             }
2071         }
2072         return this;
2073     }
2074 
2075     /**
2076      * Tells whether or not this string matches the given <a
2077      * href="../util/regex/Pattern.html#sum">regular expression</a>.
2078      *
2079      * <p> An invocation of this method of the form
2080      * <i>str</i><tt>.matches(</tt><i>regex</i><tt>)</tt> yields exactly the
2081      * same result as the expression
2082      *
2083      * <blockquote><tt> {@link java.util.regex.Pattern}.{@link
2084      * java.util.regex.Pattern#matches(String,CharSequence)
2085      * matches}(</tt><i>regex</i><tt>,</tt> <i>str</i><tt>)</tt></blockquote>
2086      *
2087      * @param   regex
2088      *          the regular expression to which this string is to be matched
2089      *
2090      * @return  <tt>true</tt> if, and only if, this string matches the
2091      *          given regular expression
2092      *
2093      * @throws  PatternSyntaxException
2094      *          if the regular expression's syntax is invalid
2095      *
2096      * @see java.util.regex.Pattern
2097      *
2098      * @since 1.4
2099      * @spec JSR-51
2100      */
2101     public boolean matches(String regex) {
2102         return Pattern.matches(regex, this);
2103     }
2104 
2105     /**
2106      * Returns true if and only if this string contains the specified
2107      * sequence of char values.
2108      *
2109      * @param s the sequence to search for
2110      * @return true if this string contains <code>s</code>, false otherwise
2111      * @throws NullPointerException if <code>s</code> is <code>null</code>
2112      * @since 1.5
2113      */
2114     public boolean contains(CharSequence s) {
2115         return indexOf(s.toString()) > -1;
2116     }
2117 
2118     /**
2119      * Replaces the first substring of this string that matches the given <a
2120      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
2121      * given replacement.
2122      *
2123      * <p> An invocation of this method of the form
2124      * <i>str</i><tt>.replaceFirst(</tt><i>regex</i><tt>,</tt> <i>repl</i><tt>)</tt>
2125      * yields exactly the same result as the expression
2126      *
2127      * <blockquote><tt>
2128      * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
2129      * compile}(</tt><i>regex</i><tt>).{@link
2130      * java.util.regex.Pattern#matcher(java.lang.CharSequence)
2131      * matcher}(</tt><i>str</i><tt>).{@link java.util.regex.Matcher#replaceFirst
2132      * replaceFirst}(</tt><i>repl</i><tt>)</tt></blockquote>
2133      *
2134      *<p>
2135      * Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in the
2136      * replacement string may cause the results to be different than if it were
2137      * being treated as a literal replacement string; see
2138      * {@link java.util.regex.Matcher#replaceFirst}.
2139      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
2140      * meaning of these characters, if desired.
2141      *
2142      * @param   regex
2143      *          the regular expression to which this string is to be matched
2144      * @param   replacement
2145      *          the string to be substituted for the first match
2146      *
2147      * @return  The resulting <tt>String</tt>
2148      *
2149      * @throws  PatternSyntaxException
2150      *          if the regular expression's syntax is invalid
2151      *
2152      * @see java.util.regex.Pattern
2153      *
2154      * @since 1.4
2155      * @spec JSR-51
2156      */
2157     public String replaceFirst(String regex, String replacement) {
2158         return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
2159     }
2160 
2161     /**
2162      * Replaces each substring of this string that matches the given <a
2163      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
2164      * given replacement.
2165      *
2166      * <p> An invocation of this method of the form
2167      * <i>str</i><tt>.replaceAll(</tt><i>regex</i><tt>,</tt> <i>repl</i><tt>)</tt>
2168      * yields exactly the same result as the expression
2169      *
2170      * <blockquote><tt>
2171      * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
2172      * compile}(</tt><i>regex</i><tt>).{@link
2173      * java.util.regex.Pattern#matcher(java.lang.CharSequence)
2174      * matcher}(</tt><i>str</i><tt>).{@link java.util.regex.Matcher#replaceAll
2175      * replaceAll}(</tt><i>repl</i><tt>)</tt></blockquote>
2176      *
2177      *<p>
2178      * Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in the
2179      * replacement string may cause the results to be different than if it were
2180      * being treated as a literal replacement string; see
2181      * {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
2182      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
2183      * meaning of these characters, if desired.
2184      *
2185      * @param   regex
2186      *          the regular expression to which this string is to be matched
2187      * @param   replacement
2188      *          the string to be substituted for each match
2189      *
2190      * @return  The resulting <tt>String</tt>
2191      *
2192      * @throws  PatternSyntaxException
2193      *          if the regular expression's syntax is invalid
2194      *
2195      * @see java.util.regex.Pattern
2196      *
2197      * @since 1.4
2198      * @spec JSR-51
2199      */
2200     public String replaceAll(String regex, String replacement) {
2201         return Pattern.compile(regex).matcher(this).replaceAll(replacement);
2202     }
2203 
2204     /**
2205      * Replaces each substring of this string that matches the literal target
2206      * sequence with the specified literal replacement sequence. The
2207      * replacement proceeds from the beginning of the string to the end, for
2208      * example, replacing "aa" with "b" in the string "aaa" will result in
2209      * "ba" rather than "ab".
2210      *
2211      * @param  target The sequence of char values to be replaced
2212      * @param  replacement The replacement sequence of char values
2213      * @return  The resulting string
2214      * @throws NullPointerException if <code>target</code> or
2215      *         <code>replacement</code> is <code>null</code>.
2216      * @since 1.5
2217      */
2218     public String replace(CharSequence target, CharSequence replacement) {
2219         return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
2220             this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
2221     }
2222 
2223     /**
2224      * Splits this string around matches of the given
2225      * <a href="../util/regex/Pattern.html#sum">regular expression</a>.
2226      *
2227      * <p> The array returned by this method contains each substring of this
2228      * string that is terminated by another substring that matches the given
2229      * expression or is terminated by the end of the string.  The substrings in
2230      * the array are in the order in which they occur in this string.  If the
2231      * expression does not match any part of the input then the resulting array
2232      * has just one element, namely this string.
2233      *
2234      * <p> The <tt>limit</tt> parameter controls the number of times the
2235      * pattern is applied and therefore affects the length of the resulting
2236      * array.  If the limit <i>n</i> is greater than zero then the pattern
2237      * will be applied at most <i>n</i>&nbsp;-&nbsp;1 times, the array's
2238      * length will be no greater than <i>n</i>, and the array's last entry
2239      * will contain all input beyond the last matched delimiter.  If <i>n</i>
2240      * is non-positive then the pattern will be applied as many times as
2241      * possible and the array can have any length.  If <i>n</i> is zero then
2242      * the pattern will be applied as many times as possible, the array can
2243      * have any length, and trailing empty strings will be discarded.
2244      *
2245      * <p> The string <tt>"boo:and:foo"</tt>, for example, yields the
2246      * following results with these parameters:
2247      *
2248      * <blockquote><table cellpadding=1 cellspacing=0 summary="Split example showing regex, limit, and result">
2249      * <tr>
2250      *     <th>Regex</th>
2251      *     <th>Limit</th>
2252      *     <th>Result</th>
2253      * </tr>
2254      * <tr><td align=center>:</td>
2255      *     <td align=center>2</td>
2256      *     <td><tt>{ "boo", "and:foo" }</tt></td></tr>
2257      * <tr><td align=center>:</td>
2258      *     <td align=center>5</td>
2259      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
2260      * <tr><td align=center>:</td>
2261      *     <td align=center>-2</td>
2262      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
2263      * <tr><td align=center>o</td>
2264      *     <td align=center>5</td>
2265      *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
2266      * <tr><td align=center>o</td>
2267      *     <td align=center>-2</td>
2268      *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
2269      * <tr><td align=center>o</td>
2270      *     <td align=center>0</td>
2271      *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
2272      * </table></blockquote>
2273      *
2274      * <p> An invocation of this method of the form
2275      * <i>str.</i><tt>split(</tt><i>regex</i><tt>,</tt>&nbsp;<i>n</i><tt>)</tt>
2276      * yields the same result as the expression
2277      *
2278      * <blockquote>
2279      * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
2280      * compile}<tt>(</tt><i>regex</i><tt>)</tt>.{@link
2281      * java.util.regex.Pattern#split(java.lang.CharSequence,int)
2282      * split}<tt>(</tt><i>str</i><tt>,</tt>&nbsp;<i>n</i><tt>)</tt>
2283      * </blockquote>
2284      *
2285      *
2286      * @param  regex
2287      *         the delimiting regular expression
2288      *
2289      * @param  limit
2290      *         the result threshold, as described above
2291      *
2292      * @return  the array of strings computed by splitting this string
2293      *          around matches of the given regular expression
2294      *
2295      * @throws  PatternSyntaxException
2296      *          if the regular expression's syntax is invalid
2297      *
2298      * @see java.util.regex.Pattern
2299      *
2300      * @since 1.4
2301      * @spec JSR-51
2302      */
2303     public String[] split(String regex, int limit) {
2304         return Pattern.compile(regex).split(this, limit);
2305     }
2306 
2307     /**
2308      * Splits this string around matches of the given <a
2309      * href="../util/regex/Pattern.html#sum">regular expression</a>.
2310      *
2311      * <p> This method works as if by invoking the two-argument {@link
2312      * #split(String, int) split} method with the given expression and a limit
2313      * argument of zero.  Trailing empty strings are therefore not included in
2314      * the resulting array.
2315      *
2316      * <p> The string <tt>"boo:and:foo"</tt>, for example, yields the following
2317      * results with these expressions:
2318      *
2319      * <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
2320      * <tr>
2321      *  <th>Regex</th>
2322      *  <th>Result</th>
2323      * </tr>
2324      * <tr><td align=center>:</td>
2325      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
2326      * <tr><td align=center>o</td>
2327      *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
2328      * </table></blockquote>
2329      *
2330      *
2331      * @param  regex
2332      *         the delimiting regular expression
2333      *
2334      * @return  the array of strings computed by splitting this string
2335      *          around matches of the given regular expression
2336      *
2337      * @throws  PatternSyntaxException
2338      *          if the regular expression's syntax is invalid
2339      *
2340      * @see java.util.regex.Pattern
2341      *
2342      * @since 1.4
2343      * @spec JSR-51
2344      */
2345     public String[] split(String regex) {
2346         return split(regex, 0);
2347     }
2348 
2349     /**
2350      * Converts all of the characters in this <code>String</code> to lower
2351      * case using the rules of the given <code>Locale</code>.  Case mapping is based
2352      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
2353      * class. Since case mappings are not always 1:1 char mappings, the resulting
2354      * <code>String</code> may be a different length than the original <code>String</code>.
2355      * <p>
2356      * Examples of lowercase  mappings are in the following table:
2357      * <table border="1" summary="Lowercase mapping examples showing language code of locale, upper case, lower case, and description">
2358      * <tr>
2359      *   <th>Language Code of Locale</th>
2360      *   <th>Upper Case</th>
2361      *   <th>Lower Case</th>
2362      *   <th>Description</th>
2363      * </tr>
2364      * <tr>
2365      *   <td>tr (Turkish)</td>
2366      *   <td>&#92;u0130</td>
2367      *   <td>&#92;u0069</td>
2368      *   <td>capital letter I with dot above -&gt; small letter i</td>
2369      * </tr>
2370      * <tr>
2371      *   <td>tr (Turkish)</td>
2372      *   <td>&#92;u0049</td>
2373      *   <td>&#92;u0131</td>
2374      *   <td>capital letter I -&gt; small letter dotless i </td>
2375      * </tr>
2376      * <tr>
2377      *   <td>(all)</td>
2378      *   <td>French Fries</td>
2379      *   <td>french fries</td>
2380      *   <td>lowercased all chars in String</td>
2381      * </tr>
2382      * <tr>
2383      *   <td>(all)</td>
2384      *   <td><img src="doc-files/capiota.gif" alt="capiota"><img src="doc-files/capchi.gif" alt="capchi">
2385      *       <img src="doc-files/captheta.gif" alt="captheta"><img src="doc-files/capupsil.gif" alt="capupsil">
2386      *       <img src="doc-files/capsigma.gif" alt="capsigma"></td>
2387      *   <td><img src="doc-files/iota.gif" alt="iota"><img src="doc-files/chi.gif" alt="chi">
2388      *       <img src="doc-files/theta.gif" alt="theta"><img src="doc-files/upsilon.gif" alt="upsilon">
2389      *       <img src="doc-files/sigma1.gif" alt="sigma"></td>
2390      *   <td>lowercased all chars in String</td>
2391      * </tr>
2392      * </table>
2393      *
2394      * @param locale use the case transformation rules for this locale
2395      * @return the <code>String</code>, converted to lowercase.
2396      * @see     java.lang.String#toLowerCase()
2397      * @see     java.lang.String#toUpperCase()
2398      * @see     java.lang.String#toUpperCase(Locale)
2399      * @since   1.1
2400      */
2401     public String toLowerCase(Locale locale) {
2402         if (locale == null) {
2403             throw new NullPointerException();
2404         }
2405 
2406         int     firstUpper;
2407 
2408         /* Now check if there are any characters that need to be changed. */
2409         scan: {
2410             for (firstUpper = 0 ; firstUpper < count; ) {
2411                 char c = value[offset+firstUpper];
2412                 if ((c >= Character.MIN_HIGH_SURROGATE) &&
2413                     (c <= Character.MAX_HIGH_SURROGATE)) {
2414                     int supplChar = codePointAt(firstUpper);
2415                     if (supplChar != Character.toLowerCase(supplChar)) {
2416                         break scan;
2417                     }
2418                     firstUpper += Character.charCount(supplChar);
2419                 } else {
2420                     if (c != Character.toLowerCase(c)) {
2421                         break scan;
2422                     }
2423                     firstUpper++;
2424                 }
2425             }
2426             return this;
2427         }
2428 
2429         char[]  result = new char[count];
2430         int     resultOffset = 0;  /* result may grow, so i+resultOffset
2431                                     * is the write location in result */
2432 
2433         /* Just copy the first few lowerCase characters. */
2434         System.arraycopy(value, offset, result, 0, firstUpper);
2435 
2436         String lang = locale.getLanguage();
2437         boolean localeDependent =
2438             (lang == "tr" || lang == "az" || lang == "lt");
2439         char[] lowerCharArray;
2440         int lowerChar;
2441         int srcChar;
2442         int srcCount;
2443         for (int i = firstUpper; i < count; i += srcCount) {
2444             srcChar = (int)value[offset+i];
2445             if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
2446                 (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
2447                 srcChar = codePointAt(i);
2448                 srcCount = Character.charCount(srcChar);
2449             } else {
2450                 srcCount = 1;
2451             }
2452             if (localeDependent || srcChar == '\u03A3') { // GREEK CAPITAL LETTER SIGMA
2453                 lowerChar = ConditionalSpecialCasing.toLowerCaseEx(this, i, locale);
2454             } else {
2455                 lowerChar = Character.toLowerCase(srcChar);
2456             }
2457             if ((lowerChar == Character.ERROR) ||
2458                 (lowerChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
2459                 if (lowerChar == Character.ERROR) {
2460                     lowerCharArray =
2461                         ConditionalSpecialCasing.toLowerCaseCharArray(this, i, locale);
2462                 } else if (srcCount == 2) {
2463                     resultOffset += Character.toChars(lowerChar, result, i + resultOffset) - srcCount;
2464                     continue;
2465                 } else {
2466                     lowerCharArray = Character.toChars(lowerChar);
2467                 }
2468 
2469                 /* Grow result if needed */
2470                 int mapLen = lowerCharArray.length;
2471                 if (mapLen > srcCount) {
2472                     char[] result2 = new char[result.length + mapLen - srcCount];
2473                     System.arraycopy(result, 0, result2, 0,
2474                         i + resultOffset);
2475                     result = result2;
2476                 }
2477                 for (int x=0; x<mapLen; ++x) {
2478                     result[i+resultOffset+x] = lowerCharArray[x];
2479                 }
2480                 resultOffset += (mapLen - srcCount);
2481             } else {
2482                 result[i+resultOffset] = (char)lowerChar;
2483             }
2484         }
2485         return new String(0, count+resultOffset, result);
2486     }
2487 
2488     /**
2489      * Converts all of the characters in this <code>String</code> to lower
2490      * case using the rules of the default locale. This is equivalent to calling
2491      * <code>toLowerCase(Locale.getDefault())</code>.
2492      * <p>
2493      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
2494      * results if used for strings that are intended to be interpreted locale
2495      * independently.
2496      * Examples are programming language identifiers, protocol keys, and HTML
2497      * tags.
2498      * For instance, <code>"TITLE".toLowerCase()</code> in a Turkish locale
2499      * returns <code>"t\u0131tle"</code>, where '\u0131' is the LATIN SMALL
2500      * LETTER DOTLESS I character.
2501      * To obtain correct results for locale insensitive strings, use
2502      * <code>toLowerCase(Locale.ENGLISH)</code>.
2503      * <p>
2504      * @return  the <code>String</code>, converted to lowercase.
2505      * @see     java.lang.String#toLowerCase(Locale)
2506      */
2507     public String toLowerCase() {
2508         return toLowerCase(Locale.getDefault());
2509     }
2510 
2511     /**
2512      * Converts all of the characters in this <code>String</code> to upper
2513      * case using the rules of the given <code>Locale</code>. Case mapping is based
2514      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
2515      * class. Since case mappings are not always 1:1 char mappings, the resulting
2516      * <code>String</code> may be a different length than the original <code>String</code>.
2517      * <p>
2518      * Examples of locale-sensitive and 1:M case mappings are in the following table.
2519      * <p>
2520      * <table border="1" summary="Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.">
2521      * <tr>
2522      *   <th>Language Code of Locale</th>
2523      *   <th>Lower Case</th>
2524      *   <th>Upper Case</th>
2525      *   <th>Description</th>
2526      * </tr>
2527      * <tr>
2528      *   <td>tr (Turkish)</td>
2529      *   <td>&#92;u0069</td>
2530      *   <td>&#92;u0130</td>
2531      *   <td>small letter i -&gt; capital letter I with dot above</td>
2532      * </tr>
2533      * <tr>
2534      *   <td>tr (Turkish)</td>
2535      *   <td>&#92;u0131</td>
2536      *   <td>&#92;u0049</td>
2537      *   <td>small letter dotless i -&gt; capital letter I</td>
2538      * </tr>
2539      * <tr>
2540      *   <td>(all)</td>
2541      *   <td>&#92;u00df</td>
2542      *   <td>&#92;u0053 &#92;u0053</td>
2543      *   <td>small letter sharp s -&gt; two letters: SS</td>
2544      * </tr>
2545      * <tr>
2546      *   <td>(all)</td>
2547      *   <td>Fahrvergn&uuml;gen</td>
2548      *   <td>FAHRVERGN&Uuml;GEN</td>
2549      *   <td></td>
2550      * </tr>
2551      * </table>
2552      * @param locale use the case transformation rules for this locale
2553      * @return the <code>String</code>, converted to uppercase.
2554      * @see     java.lang.String#toUpperCase()
2555      * @see     java.lang.String#toLowerCase()
2556      * @see     java.lang.String#toLowerCase(Locale)
2557      * @since   1.1
2558      */
2559     public String toUpperCase(Locale locale) {
2560         if (locale == null) {
2561             throw new NullPointerException();
2562         }
2563 
2564         int     firstLower;
2565 
2566         /* Now check if there are any characters that need to be changed. */
2567         scan: {
2568             for (firstLower = 0 ; firstLower < count; ) {
2569                 int c = (int)value[offset+firstLower];
2570                 int srcCount;
2571                 if ((c >= Character.MIN_HIGH_SURROGATE) &&
2572                     (c <= Character.MAX_HIGH_SURROGATE)) {
2573                     c = codePointAt(firstLower);
2574                     srcCount = Character.charCount(c);
2575                 } else {
2576                     srcCount = 1;
2577                 }
2578                 int upperCaseChar = Character.toUpperCaseEx(c);
2579                 if ((upperCaseChar == Character.ERROR) ||
2580                     (c != upperCaseChar)) {
2581                     break scan;
2582                 }
2583                 firstLower += srcCount;
2584             }
2585             return this;
2586         }
2587 
2588         char[]  result       = new char[count]; /* may grow */
2589         int     resultOffset = 0;  /* result may grow, so i+resultOffset
2590                                     * is the write location in result */
2591 
2592         /* Just copy the first few upperCase characters. */
2593         System.arraycopy(value, offset, result, 0, firstLower);
2594 
2595         String lang = locale.getLanguage();
2596         boolean localeDependent =
2597             (lang == "tr" || lang == "az" || lang == "lt");
2598         char[] upperCharArray;
2599         int upperChar;
2600         int srcChar;
2601         int srcCount;
2602         for (int i = firstLower; i < count; i += srcCount) {
2603             srcChar = (int)value[offset+i];
2604             if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
2605                 (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
2606                 srcChar = codePointAt(i);
2607                 srcCount = Character.charCount(srcChar);
2608             } else {
2609                 srcCount = 1;
2610             }
2611             if (localeDependent) {
2612                 upperChar = ConditionalSpecialCasing.toUpperCaseEx(this, i, locale);
2613             } else {
2614                 upperChar = Character.toUpperCaseEx(srcChar);
2615             }
2616             if ((upperChar == Character.ERROR) ||
2617                 (upperChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
2618                 if (upperChar == Character.ERROR) {
2619                     if (localeDependent) {
2620                         upperCharArray =
2621                             ConditionalSpecialCasing.toUpperCaseCharArray(this, i, locale);
2622                     } else {
2623                         upperCharArray = Character.toUpperCaseCharArray(srcChar);
2624                     }
2625                 } else if (srcCount == 2) {
2626                     resultOffset += Character.toChars(upperChar, result, i + resultOffset) - srcCount;
2627                     continue;
2628                 } else {
2629                     upperCharArray = Character.toChars(upperChar);
2630                 }
2631 
2632                 /* Grow result if needed */
2633                 int mapLen = upperCharArray.length;
2634                 if (mapLen > srcCount) {
2635                     char[] result2 = new char[result.length + mapLen - srcCount];
2636                     System.arraycopy(result, 0, result2, 0,
2637                         i + resultOffset);
2638                     result = result2;
2639                 }
2640                 for (int x=0; x<mapLen; ++x) {
2641                     result[i+resultOffset+x] = upperCharArray[x];
2642                 }
2643                 resultOffset += (mapLen - srcCount);
2644             } else {
2645                 result[i+resultOffset] = (char)upperChar;
2646             }
2647         }
2648         return new String(0, count+resultOffset, result);
2649     }
2650 
2651     /**
2652      * Converts all of the characters in this <code>String</code> to upper
2653      * case using the rules of the default locale. This method is equivalent to
2654      * <code>toUpperCase(Locale.getDefault())</code>.
2655      * <p>
2656      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
2657      * results if used for strings that are intended to be interpreted locale
2658      * independently.
2659      * Examples are programming language identifiers, protocol keys, and HTML
2660      * tags.
2661      * For instance, <code>"title".toUpperCase()</code> in a Turkish locale
2662      * returns <code>"T\u0130TLE"</code>, where '\u0130' is the LATIN CAPITAL
2663      * LETTER I WITH DOT ABOVE character.
2664      * To obtain correct results for locale insensitive strings, use
2665      * <code>toUpperCase(Locale.ENGLISH)</code>.
2666      * <p>
2667      * @return  the <code>String</code>, converted to uppercase.
2668      * @see     java.lang.String#toUpperCase(Locale)
2669      */
2670     public String toUpperCase() {
2671         return toUpperCase(Locale.getDefault());
2672     }
2673 
2674     /**
2675      * Returns a copy of the string, with leading and trailing whitespace
2676      * omitted.
2677      * <p>
2678      * If this <code>String</code> object represents an empty character
2679      * sequence, or the first and last characters of character sequence
2680      * represented by this <code>String</code> object both have codes
2681      * greater than <code>'&#92;u0020'</code> (the space character), then a
2682      * reference to this <code>String</code> object is returned.
2683      * <p>
2684      * Otherwise, if there is no character with a code greater than
2685      * <code>'&#92;u0020'</code> in the string, then a new
2686      * <code>String</code> object representing an empty string is created
2687      * and returned.
2688      * <p>
2689      * Otherwise, let <i>k</i> be the index of the first character in the
2690      * string whose code is greater than <code>'&#92;u0020'</code>, and let
2691      * <i>m</i> be the index of the last character in the string whose code
2692      * is greater than <code>'&#92;u0020'</code>. A new <code>String</code>
2693      * object is created, representing the substring of this string that
2694      * begins with the character at index <i>k</i> and ends with the
2695      * character at index <i>m</i>-that is, the result of
2696      * <code>this.substring(<i>k</i>,&nbsp;<i>m</i>+1)</code>.
2697      * <p>
2698      * This method may be used to trim whitespace (as defined above) from
2699      * the beginning and end of a string.
2700      *
2701      * @return  A copy of this string with leading and trailing white
2702      *          space removed, or this string if it has no leading or
2703      *          trailing white space.
2704      */
2705     public String trim() {
2706         int len = count;
2707         int st = 0;
2708         int off = offset;      /* avoid getfield opcode */
2709         char[] val = value;    /* avoid getfield opcode */
2710 
2711         while ((st < len) && (val[off + st] <= ' ')) {
2712             st++;
2713         }
2714         while ((st < len) && (val[off + len - 1] <= ' ')) {
2715             len--;
2716         }
2717         return ((st > 0) || (len < count)) ? substring(st, len) : this;
2718     }
2719 
2720     /**
2721      * This object (which is already a string!) is itself returned.
2722      *
2723      * @return  the string itself.
2724      */
2725     public String toString() {
2726         return this;
2727     }
2728 
2729     /**
2730      * Converts this string to a new character array.
2731      *
2732      * @return  a newly allocated character array whose length is the length
2733      *          of this string and whose contents are initialized to contain
2734      *          the character sequence represented by this string.
2735      */
2736     public char[] toCharArray() {
2737         char result[] = new char[count];
2738         getChars(0, count, result, 0);
2739         return result;
2740     }
2741 
2742     /**
2743      * Returns a formatted string using the specified format string and
2744      * arguments.
2745      *
2746      * <p> The locale always used is the one returned by {@link
2747      * java.util.Locale#getDefault() Locale.getDefault()}.
2748      *
2749      * @param  format
2750      *         A <a href="../util/Formatter.html#syntax">format string</a>
2751      *
2752      * @param  args
2753      *         Arguments referenced by the format specifiers in the format
2754      *         string.  If there are more arguments than format specifiers, the
2755      *         extra arguments are ignored.  The number of arguments is
2756      *         variable and may be zero.  The maximum number of arguments is
2757      *         limited by the maximum dimension of a Java array as defined by
2758      *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
2759      *         Virtual Machine Specification</a>.  The behaviour on a
2760      *         <tt>null</tt> argument depends on the <a
2761      *         href="../util/Formatter.html#syntax">conversion</a>.
2762      *
2763      * @throws  IllegalFormatException
2764      *          If a format string contains an illegal syntax, a format
2765      *          specifier that is incompatible with the given arguments,
2766      *          insufficient arguments given the format string, or other
2767      *          illegal conditions.  For specification of all possible
2768      *          formatting errors, see the <a
2769      *          href="../util/Formatter.html#detail">Details</a> section of the
2770      *          formatter class specification.
2771      *
2772      * @throws  NullPointerException
2773      *          If the <tt>format</tt> is <tt>null</tt>
2774      *
2775      * @return  A formatted string
2776      *
2777      * @see  java.util.Formatter
2778      * @since  1.5
2779      */
2780     public static String format(String format, Object ... args) {
2781         return new Formatter().format(format, args).toString();
2782     }
2783 
2784     /**
2785      * Returns a formatted string using the specified locale, format string,
2786      * and arguments.
2787      *
2788      * @param  l
2789      *         The {@linkplain java.util.Locale locale} to apply during
2790      *         formatting.  If <tt>l</tt> is <tt>null</tt> then no localization
2791      *         is applied.
2792      *
2793      * @param  format
2794      *         A <a href="../util/Formatter.html#syntax">format string</a>
2795      *
2796      * @param  args
2797      *         Arguments referenced by the format specifiers in the format
2798      *         string.  If there are more arguments than format specifiers, the
2799      *         extra arguments are ignored.  The number of arguments is
2800      *         variable and may be zero.  The maximum number of arguments is
2801      *         limited by the maximum dimension of a Java array as defined by
2802      *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
2803      *         Virtual Machine Specification</a>.  The behaviour on a
2804      *         <tt>null</tt> argument depends on the <a
2805      *         href="../util/Formatter.html#syntax">conversion</a>.
2806      *
2807      * @throws  IllegalFormatException
2808      *          If a format string contains an illegal syntax, a format
2809      *          specifier that is incompatible with the given arguments,
2810      *          insufficient arguments given the format string, or other
2811      *          illegal conditions.  For specification of all possible
2812      *          formatting errors, see the <a
2813      *          href="../util/Formatter.html#detail">Details</a> section of the
2814      *          formatter class specification
2815      *
2816      * @throws  NullPointerException
2817      *          If the <tt>format</tt> is <tt>null</tt>
2818      *
2819      * @return  A formatted string
2820      *
2821      * @see  java.util.Formatter
2822      * @since  1.5
2823      */
2824     public static String format(Locale l, String format, Object ... args) {
2825         return new Formatter(l).format(format, args).toString();
2826     }
2827 
2828     /**
2829      * Returns a new String that is a composition of the values returned
2830      * by calling {@link String#valueOf(Object)} on each element and joining them together
2831      * with the current String instance.
2832      *
2833      * <blockquote>An example:
2834      * <pre>
2835      * String message = " ".join("Java", "is", "cool" );
2836      * // message returned is: "Java is cool"
2837      * </pre></blockquote>
2838      *
2839      * @param first the first element to join
2840      * @param elements  the other Object elements to join together with the first one.
2841      * @return a new String that is composed from the first and the elements parameters and
2842      *         the String instance used as delimiter.
2843      *
2844      * @see StringBuilder#join(String,Object,Object[])
2845      *
2846      * @throws  NullPointerException
2847      *          If <tt>elements</tt> is <tt>null</tt>
2848      *
2849      * @since 1.7
2850      */
2851     public String join(Object first, Object... elements) {
2852         if (elements.length==0)
2853           return String.valueOf(first);
2854         return new StringBuilder().join(this, first, elements).toString();
2855     }
2856 
2857     /**
2858      * Returns a new String that is a composition of the values returned
2859      * by calling {@link String#valueOf(Object)} on each array element
2860      * and joining them together with the current String instance.
2861      *
2862      * <blockquote>An example:
2863      * <pre>
2864      * String[] strings = new String[]{ "Java", "is", "cool" };
2865      * String message = " ".join( strings );
2866      * // message returned is: "Java is cool"
2867      * </pre></blockquote>
2868      *
2869      * @param elements an array of Object element to join together.
2870      * @return a new String that is composed from the elements parameters joining
2871      *         with the current String instance.
2872      *
2873      * @see #join(Object[])
2874      * @see StringBuilder#join(String,Object[])
2875      *
2876      * @throws  NullPointerException
2877      *          If <tt>elements</tt> is <tt>null</tt>
2878      *
2879      * @since 1.7
2880      */
2881     public String join(Object[] elements) {
2882         return new StringBuilder().join(this, elements).toString();
2883     }
2884     
2885     /**
2886      * Returns a new String that is a composition of the values returned by
2887      * calling {@link String#valueOf(Object)} on each of the elements
2888      * parameter and joining them together with the current String instance.
2889      *
2890      * <blockquote>Two examples:
2891      * <pre>
2892      * List&lt;String&gt; strings = new LinkedList&lt;String&gt;();
2893      * strings.add( "Java" ); strings.add( "is" ); strings.add( "cool" );
2894      * String message = " ".join( strings );
2895      * //message returned is: "Java is cool"
2896      * Set&lt;String&gt; strings = new HashSet&lt;String&gt;();
2897      * strings.add( "Java" ); strings.add( "is" ); strings.add( "cool" );
2898      * String message = " ".join( strings );
2899      * //message returned is: "Java is cool"
2900      * </pre></blockquote>
2901      *
2902      * @param elements an Iterable that will have its elements joined together.
2903      * @return a new String that is composed from the elements parameters
2904      *         and the current String instance.
2905      *
2906      * @see #join(Object[])
2907      * @see StringBuilder#join(String,Iterable)
2908      *
2909      * @throws  NullPointerException
2910      *          If <tt>elements</tt> is <tt>null</tt>
2911      *
2912      * @since 1.7
2913      */
2914     public String join(Iterable<?> elements) {
2915       return new StringBuilder().join(this, elements).toString();
2916     } 
2917     
2918     /**
2919      * Returns the string representation of the <code>Object</code> argument.
2920      *
2921      * @param   obj   an <code>Object</code>.
2922      * @return  if the argument is <code>null</code>, then a string equal to
2923      *          <code>"null"</code>; otherwise, the value of
2924      *          <code>obj.toString()</code> is returned.
2925      * @see     java.lang.Object#toString()
2926      */
2927     public static String valueOf(Object obj) {
2928         return (obj == null) ? "null" : obj.toString();
2929     }
2930 
2931     /**
2932      * Returns the string representation of the <code>char</code> array
2933      * argument. The contents of the character array are copied; subsequent
2934      * modification of the character array does not affect the newly
2935      * created string.
2936      *
2937      * @param   data   a <code>char</code> array.
2938      * @return  a newly allocated string representing the same sequence of
2939      *          characters contained in the character array argument.
2940      */
2941     public static String valueOf(char data[]) {
2942         return new String(data);
2943     }
2944 
2945     /**
2946      * Returns the string representation of a specific subarray of the
2947      * <code>char</code> array argument.
2948      * <p>
2949      * The <code>offset</code> argument is the index of the first
2950      * character of the subarray. The <code>count</code> argument
2951      * specifies the length of the subarray. The contents of the subarray
2952      * are copied; subsequent modification of the character array does not
2953      * affect the newly created string.
2954      *
2955      * @param   data     the character array.
2956      * @param   offset   the initial offset into the value of the
2957      *                  <code>String</code>.
2958      * @param   count    the length of the value of the <code>String</code>.
2959      * @return  a string representing the sequence of characters contained
2960      *          in the subarray of the character array argument.
2961      * @exception IndexOutOfBoundsException if <code>offset</code> is
2962      *          negative, or <code>count</code> is negative, or
2963      *          <code>offset+count</code> is larger than
2964      *          <code>data.length</code>.
2965      */
2966     public static String valueOf(char data[], int offset, int count) {
2967         return new String(data, offset, count);
2968     }
2969 
2970     /**
2971      * Returns a String that represents the character sequence in the
2972      * array specified.
2973      *
2974      * @param   data     the character array.
2975      * @param   offset   initial offset of the subarray.
2976      * @param   count    length of the subarray.
2977      * @return  a <code>String</code> that contains the characters of the
2978      *          specified subarray of the character array.
2979      */
2980     public static String copyValueOf(char data[], int offset, int count) {
2981         // All public String constructors now copy the data.
2982         return new String(data, offset, count);
2983     }
2984 
2985     /**
2986      * Returns a String that represents the character sequence in the
2987      * array specified.
2988      *
2989      * @param   data   the character array.
2990      * @return  a <code>String</code> that contains the characters of the
2991      *          character array.
2992      */
2993     public static String copyValueOf(char data[]) {
2994         return copyValueOf(data, 0, data.length);
2995     }
2996 
2997     /**
2998      * Returns the string representation of the <code>boolean</code> argument.
2999      *
3000      * @param   b   a <code>boolean</code>.
3001      * @return  if the argument is <code>true</code>, a string equal to
3002      *          <code>"true"</code> is returned; otherwise, a string equal to
3003      *          <code>"false"</code> is returned.
3004      */
3005     public static String valueOf(boolean b) {
3006         return b ? "true" : "false";
3007     }
3008 
3009     /**
3010      * Returns the string representation of the <code>char</code>
3011      * argument.
3012      *
3013      * @param   c   a <code>char</code>.
3014      * @return  a string of length <code>1</code> containing
3015      *          as its single character the argument <code>c</code>.
3016      */
3017     public static String valueOf(char c) {
3018         char data[] = {c};
3019         return new String(0, 1, data);
3020     }
3021 
3022     /**
3023      * Returns the string representation of the <code>int</code> argument.
3024      * <p>
3025      * The representation is exactly the one returned by the
3026      * <code>Integer.toString</code> method of one argument.
3027      *
3028      * @param   i   an <code>int</code>.
3029      * @return  a string representation of the <code>int</code> argument.
3030      * @see     java.lang.Integer#toString(int, int)
3031      */
3032     public static String valueOf(int i) {
3033         return Integer.toString(i, 10);
3034     }
3035 
3036     /**
3037      * Returns the string representation of the <code>long</code> argument.
3038      * <p>
3039      * The representation is exactly the one returned by the
3040      * <code>Long.toString</code> method of one argument.
3041      *
3042      * @param   l   a <code>long</code>.
3043      * @return  a string representation of the <code>long</code> argument.
3044      * @see     java.lang.Long#toString(long)
3045      */
3046     public static String valueOf(long l) {
3047         return Long.toString(l, 10);
3048     }
3049 
3050     /**
3051      * Returns the string representation of the <code>float</code> argument.
3052      * <p>
3053      * The representation is exactly the one returned by the
3054      * <code>Float.toString</code> method of one argument.
3055      *
3056      * @param   f   a <code>float</code>.
3057      * @return  a string representation of the <code>float</code> argument.
3058      * @see     java.lang.Float#toString(float)
3059      */
3060     public static String valueOf(float f) {
3061         return Float.toString(f);
3062     }
3063 
3064     /**
3065      * Returns the string representation of the <code>double</code> argument.
3066      * <p>
3067      * The representation is exactly the one returned by the
3068      * <code>Double.toString</code> method of one argument.
3069      *
3070      * @param   d   a <code>double</code>.
3071      * @return  a  string representation of the <code>double</code> argument.
3072      * @see     java.lang.Double#toString(double)
3073      */
3074     public static String valueOf(double d) {
3075         return Double.toString(d);
3076     }
3077 
3078     /**
3079      * Returns a canonical representation for the string object.
3080      * <p>
3081      * A pool of strings, initially empty, is maintained privately by the
3082      * class <code>String</code>.
3083      * <p>
3084      * When the intern method is invoked, if the pool already contains a
3085      * string equal to this <code>String</code> object as determined by
3086      * the {@link #equals(Object)} method, then the string from the pool is
3087      * returned. Otherwise, this <code>String</code> object is added to the
3088      * pool and a reference to this <code>String</code> object is returned.
3089      * <p>
3090      * It follows that for any two strings <code>s</code> and <code>t</code>,
3091      * <code>s.intern()&nbsp;==&nbsp;t.intern()</code> is <code>true</code>
3092      * if and only if <code>s.equals(t)</code> is <code>true</code>.
3093      * <p>
3094      * All literal strings and string-valued constant expressions are
3095      * interned. String literals are defined in &sect;3.10.5 of the
3096      * <a href="http://java.sun.com/docs/books/jls/html/">Java Language
3097      * Specification</a>
3098      *
3099      * @return  a string that has the same contents as this string, but is
3100      *          guaranteed to be from a pool of unique strings.
3101      */
3102     public native String intern();
3103 
3104 }