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    2    * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
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   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
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   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.lang;
   27   
   28   import 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    * The <code>String</code> class represents character strings. All
   43    * string literals in Java programs, such as <code>"abc"</code>, are
   44    * implemented as instances of this class.
   45    * <p>
   46    * Strings are constant; their values cannot be changed after they
   47    * are created. String buffers support mutable strings.
   48    * Because String objects are immutable they can be shared. For example:
   49    * <p><blockquote><pre>
   50    *     String str = "abc";
   51    * </pre></blockquote><p>
   52    * is equivalent to:
   53    * <p><blockquote><pre>
   54    *     char data[] = {'a', 'b', 'c'};
   55    *     String str = new String(data);
   56    * </pre></blockquote><p>
   57    * Here are some more examples of how strings can be used:
   58    * <p><blockquote><pre>
   59    *     System.out.println("abc");
   60    *     String cde = "cde";
   61    *     System.out.println("abc" + cde);
   62    *     String c = "abc".substring(2,3);
   63    *     String d = cde.substring(1, 2);
   64    * </pre></blockquote>
   65    * <p>
   66    * The class <code>String</code> includes methods for examining
   67    * individual characters of the sequence, for comparing strings, for
   68    * searching strings, for extracting substrings, and for creating a
   69    * copy of a string with all characters translated to uppercase or to
   70    * lowercase. Case mapping is based on the Unicode Standard version
   71    * specified by the {@link java.lang.Character Character} class.
   72    * <p>
   73    * The Java language provides special support for the string
   74    * concatenation operator (&nbsp;+&nbsp;), and for conversion of
   75    * other objects to strings. String concatenation is implemented
   76    * through the <code>StringBuilder</code>(or <code>StringBuffer</code>)
   77    * class and its <code>append</code> method.
   78    * String conversions are implemented through the method
   79    * <code>toString</code>, defined by <code>Object</code> and
   80    * inherited by all classes in Java. For additional information on
   81    * string concatenation and conversion, see Gosling, Joy, and Steele,
   82    * <i>The Java Language Specification</i>.
   83    *
   84    * <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
   85    * or method in this class will cause a {@link NullPointerException} to be
   86    * thrown.
   87    *
   88    * <p>A <code>String</code> represents a string in the UTF-16 format
   89    * in which <em>supplementary characters</em> are represented by <em>surrogate
   90    * pairs</em> (see the section <a href="Character.html#unicode">Unicode
   91    * Character Representations</a> in the <code>Character</code> class for
   92    * more information).
   93    * Index values refer to <code>char</code> code units, so a supplementary
   94    * character uses two positions in a <code>String</code>.
   95    * <p>The <code>String</code> class provides methods for dealing with
   96    * Unicode code points (i.e., characters), in addition to those for
   97    * dealing with Unicode code units (i.e., <code>char</code> values).
   98    *
   99    * @author  Lee Boynton
  100    * @author  Arthur van Hoff
  101    * @author  Martin Buchholz
  102    * @author  Ulf Zibis
  103    * @see     java.lang.Object#toString()
  104    * @see     java.lang.StringBuffer
  105    * @see     java.lang.StringBuilder
  106    * @see     java.nio.charset.Charset
  107    * @since   JDK1.0
  108    */
  109   
  110   public final class String
  111       implements java.io.Serializable, Comparable<String>, CharSequence
  112   {
  113       /** The value is used for character storage. */
  114       private final char value[];
  115   
  116       /** The offset is the first index of the storage that is used. */
  117       private final int offset;
  118   
  119       /** The count is the number of characters in the String. */
  120       private final int count;
  121   
  122       /** Cache the hash code for the string */
  123       private int hash; // Default to 0
  124   
  125       /** use serialVersionUID from JDK 1.0.2 for interoperability */
  126       private static final long serialVersionUID = -6849794470754667710L;
  127   
  128       /**
  129        * Class String is special cased within the Serialization Stream Protocol.
  130        *
  131        * A String instance is written initially into an ObjectOutputStream in the
  132        * following format:
  133        * <pre>
  134        *      <code>TC_STRING</code> (utf String)
  135        * </pre>
  136        * The String is written by method <code>DataOutput.writeUTF</code>.
  137        * A new handle is generated to  refer to all future references to the
  138        * string instance within the stream.
  139        */
  140       private static final ObjectStreamField[] serialPersistentFields =
  141           new ObjectStreamField[0];
  142   
  143       /**
  144        * Initializes a newly created {@code String} object so that it represents
  145        * an empty character sequence.  Note that use of this constructor is
  146        * unnecessary since Strings are immutable.
  147        */
  148       public String() {
  149           this.offset = 0;
  150           this.count = 0;
  151           this.value = new char[0];
  152       }
  153   
  154       /**
  155        * Initializes a newly created {@code String} object so that it represents
  156        * the same sequence of characters as the argument; in other words, the
  157        * newly created string is a copy of the argument string. Unless an
  158        * explicit copy of {@code original} is needed, use of this constructor is
  159        * unnecessary since Strings are immutable.
  160        *
  161        * @param  original
  162        *         A {@code String}
  163        */
  164       public String(String original) {
  165           int size = original.count;
  166           char[] originalValue = original.value;
  167           char[] v;
  168           if (originalValue.length > size) {
  169               // The array representing the String is bigger than the new
  170               // String itself.  Perhaps this constructor is being called
  171               // in order to trim the baggage, so make a copy of the array.
  172               int off = original.offset;
  173               v = Arrays.copyOfRange(originalValue, off, off+size);
  174           } else {
  175               // The array representing the String is the same
  176               // size as the String, so no point in making a copy.
  177               v = originalValue;
  178           }
  179           this.offset = 0;
  180           this.count = size;
  181           this.value = v;
  182       }
  183   
  184       /**
  185        * Allocates a new {@code String} so that it represents the sequence of
  186        * characters currently contained in the character array argument. The
  187        * contents of the character array are copied; subsequent modification of
  188        * the character array does not affect the newly created string.
  189        *
  190        * @param  value
  191        *         The initial value of the string
  192        */
  193       public String(char value[]) {
  194           int size = value.length;
  195           this.offset = 0;
  196           this.count = size;
  197           this.value = Arrays.copyOf(value, size);
  198       }
  199   
  200       /**
  201        * Allocates a new {@code String} that contains characters from a subarray
  202        * of the character array argument. The {@code offset} argument is the
  203        * index of the first character of the subarray and the {@code count}
  204        * argument specifies the length of the subarray. The contents of the
  205        * subarray are copied; subsequent modification of the character array does
  206        * not affect the newly created string.
  207        *
  208        * @param  value
  209        *         Array that is the source of characters
  210        *
  211        * @param  offset
  212        *         The initial offset
  213        *
  214        * @param  count
  215        *         The length
  216        *
  217        * @throws  IndexOutOfBoundsException
  218        *          If the {@code offset} and {@code count} arguments index
  219        *          characters outside the bounds of the {@code value} array
  220        */
  221       public String(char value[], int offset, int count) {
  222           if (offset < 0) {
  223               throw new StringIndexOutOfBoundsException(offset);
  224           }
  225           if (count < 0) {
  226               throw new StringIndexOutOfBoundsException(count);
  227           }
  228           // Note: offset or count might be near -1>>>1.
  229           if (offset > value.length - count) {
  230               throw new StringIndexOutOfBoundsException(offset + count);
  231           }
  232           this.offset = 0;
  233           this.count = count;
  234           this.value = Arrays.copyOfRange(value, offset, offset+count);
  235       }
  236   
  237       /**
  238        * Allocates a new {@code String} that contains characters from a subarray
  239        * of the <a href="Character.html#unicode">Unicode code point</a> array
  240        * argument.  The {@code offset} argument is the index of the first code
  241        * point of the subarray and the {@code count} argument specifies the
  242        * length of the subarray.  The contents of the subarray are converted to
  243        * {@code char}s; subsequent modification of the {@code int} array does not
  244        * affect the newly created string.
  245        *
  246        * @param  codePoints
  247        *         Array that is the source of Unicode code points
  248        *
  249        * @param  offset
  250        *         The initial offset
  251        *
  252        * @param  count
  253        *         The length
  254        *
  255        * @throws  IllegalArgumentException
  256        *          If any invalid Unicode code point is found in {@code
  257        *          codePoints}
  258        *
  259        * @throws  IndexOutOfBoundsException
  260        *          If the {@code offset} and {@code count} arguments index
  261        *          characters outside the bounds of the {@code codePoints} array
  262        *
  263        * @since  1.5
  264        */
  265       public String(int[] codePoints, int offset, int count) {
  266           if (offset < 0) {
  267               throw new StringIndexOutOfBoundsException(offset);
  268           }
  269           if (count < 0) {
  270               throw new StringIndexOutOfBoundsException(count);
  271           }
  272           // Note: offset or count might be near -1>>>1.
  273           if (offset > codePoints.length - count) {
  274               throw new StringIndexOutOfBoundsException(offset + count);
  275           }
  276   
  277           final int end = offset + count;
  278   
  279           // Pass 1: Compute precise size of char[]
  280           int n = count;
  281           for (int i = offset; i < end; i++) {
  282               int c = codePoints[i];
  283               if (Character.isBmpCodePoint(c))
  284                   continue;
  285               else if (Character.isValidCodePoint(c))
  286                   n++;
  287               else throw new IllegalArgumentException(Integer.toString(c));
  288           }
  289   
  290           // Pass 2: Allocate and fill in char[]
  291           final char[] v = new char[n];
  292   
  293           for (int i = offset, j = 0; i < end; i++, j++) {
  294               int c = codePoints[i];
  295               if (Character.isBmpCodePoint(c))
  296                   v[j] = (char) c;
  297               else
  298                   Character.toSurrogates(c, v, j++);
  299           }
  300   
  301           this.value  = v;
  302           this.count  = n;
  303           this.offset = 0;
  304       }
  305   
  306       /**
  307        * Allocates a new {@code String} constructed from a subarray of an array
  308        * of 8-bit integer values.
  309        *
  310        * <p> The {@code offset} argument is the index of the first byte of the
  311        * subarray, and the {@code count} argument specifies the length of the
  312        * subarray.
  313        *
  314        * <p> Each {@code byte} in the subarray is converted to a {@code char} as
  315        * specified in the method above.
  316        *
  317        * @deprecated This method does not properly convert bytes into characters.
  318        * As of JDK&nbsp;1.1, the preferred way to do this is via the
  319        * {@code String} constructors that take a {@link
  320        * java.nio.charset.Charset}, charset name, or that use the platform's
  321        * default charset.
  322        *
  323        * @param  ascii
  324        *         The bytes to be converted to characters
  325        *
  326        * @param  hibyte
  327        *         The top 8 bits of each 16-bit Unicode code unit
  328        *
  329        * @param  offset
  330        *         The initial offset
  331        * @param  count
  332        *         The length
  333        *
  334        * @throws  IndexOutOfBoundsException
  335        *          If the {@code offset} or {@code count} argument is invalid
  336        *
  337        * @see  #String(byte[], int)
  338        * @see  #String(byte[], int, int, java.lang.String)
  339        * @see  #String(byte[], int, int, java.nio.charset.Charset)
  340        * @see  #String(byte[], int, int)
  341        * @see  #String(byte[], java.lang.String)
  342        * @see  #String(byte[], java.nio.charset.Charset)
  343        * @see  #String(byte[])
  344        */
  345       @Deprecated
  346       public String(byte ascii[], int hibyte, int offset, int count) {
  347           checkBounds(ascii, offset, count);
  348           char value[] = new char[count];
  349   
  350           if (hibyte == 0) {
  351               for (int i = count ; i-- > 0 ;) {
  352                   value[i] = (char) (ascii[i + offset] & 0xff);
  353               }
  354           } else {
  355               hibyte <<= 8;
  356               for (int i = count ; i-- > 0 ;) {
  357                   value[i] = (char) (hibyte | (ascii[i + offset] & 0xff));
  358               }
  359           }
  360           this.offset = 0;
  361           this.count = count;
  362           this.value = value;
  363       }
  364   
  365       /**
  366        * Allocates a new {@code String} containing characters constructed from
  367        * an array of 8-bit integer values. Each character <i>c</i>in the
  368        * resulting string is constructed from the corresponding component
  369        * <i>b</i> in the byte array such that:
  370        *
  371        * <blockquote><pre>
  372        *     <b><i>c</i></b> == (char)(((hibyte &amp; 0xff) &lt;&lt; 8)
  373        *                         | (<b><i>b</i></b> &amp; 0xff))
  374        * </pre></blockquote>
  375        *
  376        * @deprecated  This method does not properly convert bytes into
  377        * characters.  As of JDK&nbsp;1.1, the preferred way to do this is via the
  378        * {@code String} constructors that take a {@link
  379        * java.nio.charset.Charset}, charset name, or that use the platform's
  380        * default charset.
  381        *
  382        * @param  ascii
  383        *         The bytes to be converted to characters
  384        *
  385        * @param  hibyte
  386        *         The top 8 bits of each 16-bit Unicode code unit
  387        *
  388        * @see  #String(byte[], int, int, java.lang.String)
  389        * @see  #String(byte[], int, int, java.nio.charset.Charset)
  390        * @see  #String(byte[], int, int)
  391        * @see  #String(byte[], java.lang.String)
  392        * @see  #String(byte[], java.nio.charset.Charset)
  393        * @see  #String(byte[])
  394        */
  395       @Deprecated
  396       public String(byte ascii[], int hibyte) {
  397           this(ascii, hibyte, 0, ascii.length);
  398       }
  399   
  400       /* Common private utility method used to bounds check the byte array
  401        * and requested offset & length values used by the String(byte[],..)
  402        * constructors.
  403        */
  404       private static void checkBounds(byte[] bytes, int offset, int length) {
  405           if (length < 0)
  406               throw new StringIndexOutOfBoundsException(length);
  407           if (offset < 0)
  408               throw new StringIndexOutOfBoundsException(offset);
  409           if (offset > bytes.length - length)
  410               throw new StringIndexOutOfBoundsException(offset + length);
  411       }
  412   
  413       /**
  414        * Constructs a new {@code String} by decoding the specified subarray of
  415        * bytes using the specified charset.  The length of the new {@code String}
  416        * is a function of the charset, and hence may not be equal to the length
  417        * of the subarray.
  418        *
  419        * <p> The behavior of this constructor when the given bytes are not valid
  420        * in the given charset is unspecified.  The {@link
  421        * java.nio.charset.CharsetDecoder} class should be used when more control
  422        * over the decoding process is required.
  423        *
  424        * @param  bytes
  425        *         The bytes to be decoded into characters
  426        *
  427        * @param  offset
  428        *         The index of the first byte to decode
  429        *
  430        * @param  length
  431        *         The number of bytes to decode
  432   
  433        * @param  charsetName
  434        *         The name of a supported {@linkplain java.nio.charset.Charset
  435        *         charset}
  436        *
  437        * @throws  UnsupportedEncodingException
  438        *          If the named charset is not supported
  439        *
  440        * @throws  IndexOutOfBoundsException
  441        *          If the {@code offset} and {@code length} arguments index
  442        *          characters outside the bounds of the {@code bytes} array
  443        *
  444        * @since  JDK1.1
  445        */
  446       public String(byte bytes[], int offset, int length, String charsetName)
  447           throws UnsupportedEncodingException
  448       {
  449           if (charsetName == null)
  450               throw new NullPointerException("charsetName");
  451           checkBounds(bytes, offset, length);
  452           char[] v = StringCoding.decode(charsetName, bytes, offset, length);
  453           this.offset = 0;
  454           this.count = v.length;
  455           this.value = v;
  456       }
  457   
  458       /**
  459        * Constructs a new {@code String} by decoding the specified subarray of
  460        * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
  461        * The length of the new {@code String} is a function of the charset, and
  462        * hence may not be equal to the length of the subarray.
  463        *
  464        * <p> This method always replaces malformed-input and unmappable-character
  465        * sequences with this charset's default replacement string.  The {@link
  466        * java.nio.charset.CharsetDecoder} class should be used when more control
  467        * over the decoding process is required.
  468        *
  469        * @param  bytes
  470        *         The bytes to be decoded into characters
  471        *
  472        * @param  offset
  473        *         The index of the first byte to decode
  474        *
  475        * @param  length
  476        *         The number of bytes to decode
  477        *
  478        * @param  charset
  479        *         The {@linkplain java.nio.charset.Charset charset} to be used to
  480        *         decode the {@code bytes}
  481        *
  482        * @throws  IndexOutOfBoundsException
  483        *          If the {@code offset} and {@code length} arguments index
  484        *          characters outside the bounds of the {@code bytes} array
  485        *
  486        * @since  1.6
  487        */
  488       public String(byte bytes[], int offset, int length, Charset charset) {
  489           if (charset == null)
  490               throw new NullPointerException("charset");
  491           checkBounds(bytes, offset, length);
  492           char[] v = StringCoding.decode(charset, bytes, offset, length);
  493           this.offset = 0;
  494           this.count = v.length;
  495           this.value = v;
  496       }
  497   
  498       /**
  499        * Constructs a new {@code String} by decoding the specified array of bytes
  500        * using the specified {@linkplain java.nio.charset.Charset charset}.  The
  501        * length of the new {@code String} is a function of the charset, and hence
  502        * may not be equal to the length of the byte array.
  503        *
  504        * <p> The behavior of this constructor when the given bytes are not valid
  505        * in the given charset is unspecified.  The {@link
  506        * java.nio.charset.CharsetDecoder} class should be used when more control
  507        * over the decoding process is required.
  508        *
  509        * @param  bytes
  510        *         The bytes to be decoded into characters
  511        *
  512        * @param  charsetName
  513        *         The name of a supported {@linkplain java.nio.charset.Charset
  514        *         charset}
  515        *
  516        * @throws  UnsupportedEncodingException
  517        *          If the named charset is not supported
  518        *
  519        * @since  JDK1.1
  520        */
  521       public String(byte bytes[], String charsetName)
  522           throws UnsupportedEncodingException
  523       {
  524           this(bytes, 0, bytes.length, charsetName);
  525       }
  526   
  527       /**
  528        * Constructs a new {@code String} by decoding the specified array of
  529        * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
  530        * The length of the new {@code String} is a function of the charset, and
  531        * hence may not be equal to the length of the byte array.
  532        *
  533        * <p> This method always replaces malformed-input and unmappable-character
  534        * sequences with this charset's default replacement string.  The {@link
  535        * java.nio.charset.CharsetDecoder} class should be used when more control
  536        * over the decoding process is required.
  537        *
  538        * @param  bytes
  539        *         The bytes to be decoded into characters
  540        *
  541        * @param  charset
  542        *         The {@linkplain java.nio.charset.Charset charset} to be used to
  543        *         decode the {@code bytes}
  544        *
  545        * @since  1.6
  546        */
  547       public String(byte bytes[], Charset charset) {
  548           this(bytes, 0, bytes.length, charset);
  549       }
  550   
  551       /**
  552        * Constructs a new {@code String} by decoding the specified subarray of
  553        * bytes using the platform's default charset.  The length of the new
  554        * {@code String} is a function of the charset, and hence may not be equal
  555        * to the length of the subarray.
  556        *
  557        * <p> The behavior of this constructor when the given bytes are not valid
  558        * in the default charset is unspecified.  The {@link
  559        * java.nio.charset.CharsetDecoder} class should be used when more control
  560        * over the decoding process is required.
  561        *
  562        * @param  bytes
  563        *         The bytes to be decoded into characters
  564        *
  565        * @param  offset
  566        *         The index of the first byte to decode
  567        *
  568        * @param  length
  569        *         The number of bytes to decode
  570        *
  571        * @throws  IndexOutOfBoundsException
  572        *          If the {@code offset} and the {@code length} arguments index
  573        *          characters outside the bounds of the {@code bytes} array
  574        *
  575        * @since  JDK1.1
  576        */
  577       public String(byte bytes[], int offset, int length) {
  578           checkBounds(bytes, offset, length);
  579           char[] v  = StringCoding.decode(bytes, offset, length);
  580           this.offset = 0;
  581           this.count = v.length;
  582           this.value = v;
  583       }
  584   
  585       /**
  586        * Constructs a new {@code String} by decoding the specified array of bytes
  587        * using the platform's default charset.  The length of the new {@code
  588        * String} is a function of the charset, and hence may not be equal to the
  589        * length of the byte array.
  590        *
  591        * <p> The behavior of this constructor when the given bytes are not valid
  592        * in the default charset is unspecified.  The {@link
  593        * java.nio.charset.CharsetDecoder} class should be used when more control
  594        * over the decoding process is required.
  595        *
  596        * @param  bytes
  597        *         The bytes to be decoded into characters
  598        *
  599        * @since  JDK1.1
  600        */
  601       public String(byte bytes[]) {
  602           this(bytes, 0, bytes.length);
  603       }
  604   
  605       /**
  606        * Allocates a new string that contains the sequence of characters
  607        * currently contained in the string buffer argument. The contents of the
  608        * string buffer are copied; subsequent modification of the string buffer
  609        * does not affect the newly created string.
  610        *
  611        * @param  buffer
  612        *         A {@code StringBuffer}
  613        */
  614       public String(StringBuffer buffer) {
  615           String result = buffer.toString();
  616           this.value = result.value;
  617           this.count = result.count;
  618           this.offset = result.offset;
  619       }
  620   
  621       /**
  622        * Allocates a new string that contains the sequence of characters
  623        * currently contained in the string builder argument. The contents of the
  624        * string builder are copied; subsequent modification of the string builder
  625        * does not affect the newly created string.
  626        *
  627        * <p> This constructor is provided to ease migration to {@code
  628        * StringBuilder}. Obtaining a string from a string builder via the {@code
  629        * toString} method is likely to run faster and is generally preferred.
  630        *
  631        * @param   builder
  632        *          A {@code StringBuilder}
  633        *
  634        * @since  1.5
  635        */
  636       public String(StringBuilder builder) {
  637           String result = builder.toString();
  638           this.value = result.value;
  639           this.count = result.count;
  640           this.offset = result.offset;
  641       }
  642   
  643   
  644       // Package private constructor which shares value array for speed.
  645       String(int offset, int count, char value[]) {
  646           this.value = value;
  647           this.offset = offset;
  648           this.count = count;
  649       }
  650   
  651       /**
  652        * Returns the length of this string.
  653        * The length is equal to the number of <a href="Character.html#unicode">Unicode
  654        * code units</a> in the string.
  655        *
  656        * @return  the length of the sequence of characters represented by this
  657        *          object.
  658        */
  659       public int length() {
  660           return count;
  661       }
  662   
  663       /**
  664        * Returns <tt>true</tt> if, and only if, {@link #length()} is <tt>0</tt>.
  665        *
  666        * @return <tt>true</tt> if {@link #length()} is <tt>0</tt>, otherwise
  667        * <tt>false</tt>
  668        *
  669        * @since 1.6
  670        */
  671       public boolean isEmpty() {
  672           return count == 0;
  673       }
  674   
  675       /**
  676        * Returns the <code>char</code> value at the
  677        * specified index. An index ranges from <code>0</code> to
  678        * <code>length() - 1</code>. The first <code>char</code> value of the sequence
  679        * is at index <code>0</code>, the next at index <code>1</code>,
  680        * and so on, as for array indexing.
  681        *
  682        * <p>If the <code>char</code> value specified by the index is a
  683        * <a href="Character.html#unicode">surrogate</a>, the surrogate
  684        * value is returned.
  685        *
  686        * @param      index   the index of the <code>char</code> value.
  687        * @return     the <code>char</code> value at the specified index of this string.
  688        *             The first <code>char</code> value is at index <code>0</code>.
  689        * @exception  IndexOutOfBoundsException  if the <code>index</code>
  690        *             argument is negative or not less than the length of this
  691        *             string.
  692        */
  693       public char charAt(int index) {
  694           if ((index < 0) || (index >= count)) {
  695               throw new StringIndexOutOfBoundsException(index);
  696           }
  697           return value[index + offset];
  698       }
  699   
  700       /**
  701        * Returns the character (Unicode code point) at the specified
  702        * index. The index refers to <code>char</code> values
  703        * (Unicode code units) and ranges from <code>0</code> to
  704        * {@link #length()}<code> - 1</code>.
  705        *
  706        * <p> If the <code>char</code> value specified at the given index
  707        * is in the high-surrogate range, the following index is less
  708        * than the length of this <code>String</code>, and the
  709        * <code>char</code> value at the following index is in the
  710        * low-surrogate range, then the supplementary code point
  711        * corresponding to this surrogate pair is returned. Otherwise,
  712        * the <code>char</code> value at the given index is returned.
  713        *
  714        * @param      index the index to the <code>char</code> values
  715        * @return     the code point value of the character at the
  716        *             <code>index</code>
  717        * @exception  IndexOutOfBoundsException  if the <code>index</code>
  718        *             argument is negative or not less than the length of this
  719        *             string.
  720        * @since      1.5
  721        */
  722       public int codePointAt(int index) {
  723           if ((index < 0) || (index >= count)) {
  724               throw new StringIndexOutOfBoundsException(index);
  725           }
  726           return Character.codePointAtImpl(value, offset + index, offset + count);
  727       }
  728   
  729       /**
  730        * Returns the character (Unicode code point) before the specified
  731        * index. The index refers to <code>char</code> values
  732        * (Unicode code units) and ranges from <code>1</code> to {@link
  733        * CharSequence#length() length}.
  734        *
  735        * <p> If the <code>char</code> value at <code>(index - 1)</code>
  736        * is in the low-surrogate range, <code>(index - 2)</code> is not
  737        * negative, and the <code>char</code> value at <code>(index -
  738        * 2)</code> is in the high-surrogate range, then the
  739        * supplementary code point value of the surrogate pair is
  740        * returned. If the <code>char</code> value at <code>index -
  741        * 1</code> is an unpaired low-surrogate or a high-surrogate, the
  742        * surrogate value is returned.
  743        *
  744        * @param     index the index following the code point that should be returned
  745        * @return    the Unicode code point value before the given index.
  746        * @exception IndexOutOfBoundsException if the <code>index</code>
  747        *            argument is less than 1 or greater than the length
  748        *            of this string.
  749        * @since     1.5
  750        */
  751       public int codePointBefore(int index) {
  752           int i = index - 1;
  753           if ((i < 0) || (i >= count)) {
  754               throw new StringIndexOutOfBoundsException(index);
  755           }
  756           return Character.codePointBeforeImpl(value, offset + index, offset);
  757       }
  758   
  759       /**
  760        * Returns the number of Unicode code points in the specified text
  761        * range of this <code>String</code>. The text range begins at the
  762        * specified <code>beginIndex</code> and extends to the
  763        * <code>char</code> at index <code>endIndex - 1</code>. Thus the
  764        * length (in <code>char</code>s) of the text range is
  765        * <code>endIndex-beginIndex</code>. Unpaired surrogates within
  766        * the text range count as one code point each.
  767        *
  768        * @param beginIndex the index to the first <code>char</code> of
  769        * the text range.
  770        * @param endIndex the index after the last <code>char</code> of
  771        * the text range.
  772        * @return the number of Unicode code points in the specified text
  773        * range
  774        * @exception IndexOutOfBoundsException if the
  775        * <code>beginIndex</code> is negative, or <code>endIndex</code>
  776        * is larger than the length of this <code>String</code>, or
  777        * <code>beginIndex</code> is larger than <code>endIndex</code>.
  778        * @since  1.5
  779        */
  780       public int codePointCount(int beginIndex, int endIndex) {
  781           if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
  782               throw new IndexOutOfBoundsException();
  783           }
  784           return Character.codePointCountImpl(value, offset+beginIndex, endIndex-beginIndex);
  785       }
  786   
  787       /**
  788        * Returns the index within this <code>String</code> that is
  789        * offset from the given <code>index</code> by
  790        * <code>codePointOffset</code> code points. Unpaired surrogates
  791        * within the text range given by <code>index</code> and
  792        * <code>codePointOffset</code> count as one code point each.
  793        *
  794        * @param index the index to be offset
  795        * @param codePointOffset the offset in code points
  796        * @return the index within this <code>String</code>
  797        * @exception IndexOutOfBoundsException if <code>index</code>
  798        *   is negative or larger then the length of this
  799        *   <code>String</code>, or if <code>codePointOffset</code> is positive
  800        *   and the substring starting with <code>index</code> has fewer
  801        *   than <code>codePointOffset</code> code points,
  802        *   or if <code>codePointOffset</code> is negative and the substring
  803        *   before <code>index</code> has fewer than the absolute value
  804        *   of <code>codePointOffset</code> code points.
  805        * @since 1.5
  806        */
  807       public int offsetByCodePoints(int index, int codePointOffset) {
  808           if (index < 0 || index > count) {
  809               throw new IndexOutOfBoundsException();
  810           }
  811           return Character.offsetByCodePointsImpl(value, offset, count,
  812                                                   offset+index, codePointOffset) - offset;
  813       }
  814   
  815       /**
  816        * Copy characters from this string into dst starting at dstBegin.
  817        * This method doesn't perform any range checking.
  818        */
  819       void getChars(char dst[], int dstBegin) {
  820           System.arraycopy(value, offset, dst, dstBegin, count);
  821       }
  822   
  823       /**
  824        * Copies characters from this string into the destination character
  825        * array.
  826        * <p>
  827        * The first character to be copied is at index <code>srcBegin</code>;
  828        * the last character to be copied is at index <code>srcEnd-1</code>
  829        * (thus the total number of characters to be copied is
  830        * <code>srcEnd-srcBegin</code>). The characters are copied into the
  831        * subarray of <code>dst</code> starting at index <code>dstBegin</code>
  832        * and ending at index:
  833        * <p><blockquote><pre>
  834        *     dstbegin + (srcEnd-srcBegin) - 1
  835        * </pre></blockquote>
  836        *
  837        * @param      srcBegin   index of the first character in the string
  838        *                        to copy.
  839        * @param      srcEnd     index after the last character in the string
  840        *                        to copy.
  841        * @param      dst        the destination array.
  842        * @param      dstBegin   the start offset in the destination array.
  843        * @exception IndexOutOfBoundsException If any of the following
  844        *            is true:
  845        *            <ul><li><code>srcBegin</code> is negative.
  846        *            <li><code>srcBegin</code> is greater than <code>srcEnd</code>
  847        *            <li><code>srcEnd</code> is greater than the length of this
  848        *                string
  849        *            <li><code>dstBegin</code> is negative
  850        *            <li><code>dstBegin+(srcEnd-srcBegin)</code> is larger than
  851        *                <code>dst.length</code></ul>
  852        */
  853       public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
  854           if (srcBegin < 0) {
  855               throw new StringIndexOutOfBoundsException(srcBegin);
  856           }
  857           if (srcEnd > count) {
  858               throw new StringIndexOutOfBoundsException(srcEnd);
  859           }
  860           if (srcBegin > srcEnd) {
  861               throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
  862           }
  863           System.arraycopy(value, offset + srcBegin, dst, dstBegin,
  864                srcEnd - srcBegin);
  865       }
  866   
  867       /**
  868        * Copies characters from this string into the destination byte array. Each
  869        * byte receives the 8 low-order bits of the corresponding character. The
  870        * eight high-order bits of each character are not copied and do not
  871        * participate in the transfer in any way.
  872        *
  873        * <p> The first character to be copied is at index {@code srcBegin}; the
  874        * last character to be copied is at index {@code srcEnd-1}.  The total
  875        * number of characters to be copied is {@code srcEnd-srcBegin}. The
  876        * characters, converted to bytes, are copied into the subarray of {@code
  877        * dst} starting at index {@code dstBegin} and ending at index:
  878        *
  879        * <blockquote><pre>
  880        *     dstbegin + (srcEnd-srcBegin) - 1
  881        * </pre></blockquote>
  882        *
  883        * @deprecated  This method does not properly convert characters into
  884        * bytes.  As of JDK&nbsp;1.1, the preferred way to do this is via the
  885        * {@link #getBytes()} method, which uses the platform's default charset.
  886        *
  887        * @param  srcBegin
  888        *         Index of the first character in the string to copy
  889        *
  890        * @param  srcEnd
  891        *         Index after the last character in the string to copy
  892        *
  893        * @param  dst
  894        *         The destination array
  895        *
  896        * @param  dstBegin
  897        *         The start offset in the destination array
  898        *
  899        * @throws  IndexOutOfBoundsException
  900        *          If any of the following is true:
  901        *          <ul>
  902        *            <li> {@code srcBegin} is negative
  903        *            <li> {@code srcBegin} is greater than {@code srcEnd}
  904        *            <li> {@code srcEnd} is greater than the length of this String
  905        *            <li> {@code dstBegin} is negative
  906        *            <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
  907        *                 dst.length}
  908        *          </ul>
  909        */
  910       @Deprecated
  911       public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
  912           if (srcBegin < 0) {
  913               throw new StringIndexOutOfBoundsException(srcBegin);
  914           }
  915           if (srcEnd > count) {
  916               throw new StringIndexOutOfBoundsException(srcEnd);
  917           }
  918           if (srcBegin > srcEnd) {
  919               throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
  920           }
  921           int j = dstBegin;
  922           int n = offset + srcEnd;
  923           int i = offset + srcBegin;
  924           char[] val = value;   /* avoid getfield opcode */
  925   
  926           while (i < n) {
  927               dst[j++] = (byte)val[i++];
  928           }
  929       }
  930   
  931       /**
  932        * Encodes this {@code String} into a sequence of bytes using the named
  933        * charset, storing the result into a new byte array.
  934        *
  935        * <p> The behavior of this method when this string cannot be encoded in
  936        * the given charset is unspecified.  The {@link
  937        * java.nio.charset.CharsetEncoder} class should be used when more control
  938        * over the encoding process is required.
  939        *
  940        * @param  charsetName
  941        *         The name of a supported {@linkplain java.nio.charset.Charset
  942        *         charset}
  943        *
  944        * @return  The resultant byte array
  945        *
  946        * @throws  UnsupportedEncodingException
  947        *          If the named charset is not supported
  948        *
  949        * @since  JDK1.1
  950        */
  951       public byte[] getBytes(String charsetName)
  952           throws UnsupportedEncodingException
  953       {
  954           if (charsetName == null) throw new NullPointerException();
  955           return StringCoding.encode(charsetName, value, offset, count);
  956       }
  957   
  958       /**
  959        * Encodes this {@code String} into a sequence of bytes using the given
  960        * {@linkplain java.nio.charset.Charset charset}, storing the result into a
  961        * new byte array.
  962        *
  963        * <p> This method always replaces malformed-input and unmappable-character
  964        * sequences with this charset's default replacement byte array.  The
  965        * {@link java.nio.charset.CharsetEncoder} class should be used when more
  966        * control over the encoding process is required.
  967        *
  968        * @param  charset
  969        *         The {@linkplain java.nio.charset.Charset} to be used to encode
  970        *         the {@code String}
  971        *
  972        * @return  The resultant byte array
  973        *
  974        * @since  1.6
  975        */
  976       public byte[] getBytes(Charset charset) {
  977           if (charset == null) throw new NullPointerException();
  978           return StringCoding.encode(charset, value, offset, count);
  979       }
  980   
  981       /**
  982        * Encodes this {@code String} into a sequence of bytes using the
  983        * platform's default charset, storing the result into a new byte array.
  984        *
  985        * <p> The behavior of this method when this string cannot be encoded in
  986        * the default charset is unspecified.  The {@link
  987        * java.nio.charset.CharsetEncoder} class should be used when more control
  988        * over the encoding process is required.
  989        *
  990        * @return  The resultant byte array
  991        *
  992        * @since      JDK1.1
  993        */
  994       public byte[] getBytes() {
  995           return StringCoding.encode(value, offset, count);
  996       }
  997   
  998       /**
  999        * Compares this string to the specified object.  The result is {@code
 1000        * true} if and only if the argument is not {@code null} and is a {@code
 1001        * String} object that represents the same sequence of characters as this
 1002        * object.
 1003        *
 1004        * @param  anObject
 1005        *         The object to compare this {@code String} against
 1006        *
 1007        * @return  {@code true} if the given object represents a {@code String}
 1008        *          equivalent to this string, {@code false} otherwise
 1009        *
 1010        * @see  #compareTo(String)
 1011        * @see  #equalsIgnoreCase(String)
 1012        */
 1013       public boolean equals(Object anObject) {
 1014           if (this == anObject) {
 1015               return true;
 1016           }
 1017           if (anObject instanceof String) {
 1018               String anotherString = (String)anObject;
 1019               int n = count;
 1020               if (n == anotherString.count) {
 1021                   char v1[] = value;
 1022                   char v2[] = anotherString.value;
 1023                   int i = offset;
 1024                   int j = anotherString.offset;
 1025                   while (n-- != 0) {
 1026                       if (v1[i++] != v2[j++])
 1027                           return false;
 1028                   }
 1029                   return true;
 1030               }
 1031           }
 1032           return false;
 1033       }
 1034   
 1035       /**
 1036        * Compares this string to the specified {@code StringBuffer}.  The result
 1037        * is {@code true} if and only if this {@code String} represents the same
 1038        * sequence of characters as the specified {@code StringBuffer}.
 1039        *
 1040        * @param  sb
 1041        *         The {@code StringBuffer} to compare this {@code String} against
 1042        *
 1043        * @return  {@code true} if this {@code String} represents the same
 1044        *          sequence of characters as the specified {@code StringBuffer},
 1045        *          {@code false} otherwise
 1046        *
 1047        * @since  1.4
 1048        */
 1049       public boolean contentEquals(StringBuffer sb) {
 1050           synchronized(sb) {
 1051               return contentEquals((CharSequence)sb);
 1052           }
 1053       }
 1054   
 1055       /**
 1056        * Compares this string to the specified {@code CharSequence}.  The result
 1057        * is {@code true} if and only if this {@code String} represents the same
 1058        * sequence of char values as the specified sequence.
 1059        *
 1060        * @param  cs
 1061        *         The sequence to compare this {@code String} against
 1062        *
 1063        * @return  {@code true} if this {@code String} represents the same
 1064        *          sequence of char values as the specified sequence, {@code
 1065        *          false} otherwise
 1066        *
 1067        * @since  1.5
 1068        */
 1069       public boolean contentEquals(CharSequence cs) {
 1070           if (count != cs.length())
 1071               return false;
 1072           // Argument is a StringBuffer, StringBuilder
 1073           if (cs instanceof AbstractStringBuilder) {
 1074               char v1[] = value;
 1075               char v2[] = ((AbstractStringBuilder)cs).getValue();
 1076               int i = offset;
 1077               int j = 0;
 1078               int n = count;
 1079               while (n-- != 0) {
 1080                   if (v1[i++] != v2[j++])
 1081                       return false;
 1082               }
 1083               return true;
 1084           }
 1085           // Argument is a String
 1086           if (cs.equals(this))
 1087               return true;
 1088           // Argument is a generic CharSequence
 1089           char v1[] = value;
 1090           int i = offset;
 1091           int j = 0;
 1092           int n = count;
 1093           while (n-- != 0) {
 1094               if (v1[i++] != cs.charAt(j++))
 1095                   return false;
 1096           }
 1097           return true;
 1098       }
 1099   
 1100       /**
 1101        * Compares this {@code String} to another {@code String}, ignoring case
 1102        * considerations.  Two strings are considered equal ignoring case if they
 1103        * are of the same length and corresponding characters in the two strings
 1104        * are equal ignoring case.
 1105        *
 1106        * <p> Two characters {@code c1} and {@code c2} are considered the same
 1107        * ignoring case if at least one of the following is true:
 1108        * <ul>
 1109        *   <li> The two characters are the same (as compared by the
 1110        *        {@code ==} operator)
 1111        *   <li> Applying the method {@link
 1112        *        java.lang.Character#toUpperCase(char)} to each character
 1113        *        produces the same result
 1114        *   <li> Applying the method {@link
 1115        *        java.lang.Character#toLowerCase(char)} to each character
 1116        *        produces the same result
 1117        * </ul>
 1118        *
 1119        * @param  anotherString
 1120        *         The {@code String} to compare this {@code String} against
 1121        *
 1122        * @return  {@code true} if the argument is not {@code null} and it
 1123        *          represents an equivalent {@code String} ignoring case; {@code
 1124        *          false} otherwise
 1125        *
 1126        * @see  #equals(Object)
 1127        */
 1128       public boolean equalsIgnoreCase(String anotherString) {
 1129           return (this == anotherString) ? true :
 1130                  (anotherString != null) && (anotherString.count == count) &&
 1131                  regionMatches(true, 0, anotherString, 0, count);
 1132       }
 1133   
 1134       /**
 1135        * Compares two strings lexicographically.
 1136        * The comparison is based on the Unicode value of each character in
 1137        * the strings. The character sequence represented by this
 1138        * <code>String</code> object is compared lexicographically to the
 1139        * character sequence represented by the argument string. The result is
 1140        * a negative integer if this <code>String</code> object
 1141        * lexicographically precedes the argument string. The result is a
 1142        * positive integer if this <code>String</code> object lexicographically
 1143        * follows the argument string. The result is zero if the strings
 1144        * are equal; <code>compareTo</code> returns <code>0</code> exactly when
 1145        * the {@link #equals(Object)} method would return <code>true</code>.
 1146        * <p>
 1147        * This is the definition of lexicographic ordering. If two strings are
 1148        * different, then either they have different characters at some index
 1149        * that is a valid index for both strings, or their lengths are different,
 1150        * or both. If they have different characters at one or more index
 1151        * positions, let <i>k</i> be the smallest such index; then the string
 1152        * whose character at position <i>k</i> has the smaller value, as
 1153        * determined by using the &lt; operator, lexicographically precedes the
 1154        * other string. In this case, <code>compareTo</code> returns the
 1155        * difference of the two character values at position <code>k</code> in
 1156        * the two string -- that is, the value:
 1157        * <blockquote><pre>
 1158        * this.charAt(k)-anotherString.charAt(k)
 1159        * </pre></blockquote>
 1160        * If there is no index position at which they differ, then the shorter
 1161        * string lexicographically precedes the longer string. In this case,
 1162        * <code>compareTo</code> returns the difference of the lengths of the
 1163        * strings -- that is, the value:
 1164        * <blockquote><pre>
 1165        * this.length()-anotherString.length()
 1166        * </pre></blockquote>
 1167        *
 1168        * @param   anotherString   the <code>String</code> to be compared.
 1169        * @return  the value <code>0</code> if the argument string is equal to
 1170        *          this string; a value less than <code>0</code> if this string
 1171        *          is lexicographically less than the string argument; and a
 1172        *          value greater than <code>0</code> if this string is
 1173        *          lexicographically greater than the string argument.
 1174        */
 1175       public int compareTo(String anotherString) {
 1176           int len1 = count;
 1177           int len2 = anotherString.count;
 1178           int n = Math.min(len1, len2);
 1179           char v1[] = value;
 1180           char v2[] = anotherString.value;
 1181           int i = offset;
 1182           int j = anotherString.offset;
 1183   
 1184           if (i == j) {
 1185               int k = i;
 1186               int lim = n + i;
 1187               while (k < lim) {
 1188                   char c1 = v1[k];
 1189                   char c2 = v2[k];
 1190                   if (c1 != c2) {
 1191                       return c1 - c2;
 1192                   }
 1193                   k++;
 1194               }
 1195           } else {
 1196               while (n-- != 0) {
 1197                   char c1 = v1[i++];
 1198                   char c2 = v2[j++];
 1199                   if (c1 != c2) {
 1200                       return c1 - c2;
 1201                   }
 1202               }
 1203           }
 1204           return len1 - len2;
 1205       }
 1206   
 1207       /**
 1208        * A Comparator that orders <code>String</code> objects as by
 1209        * <code>compareToIgnoreCase</code>. This comparator is serializable.
 1210        * <p>
 1211        * Note that this Comparator does <em>not</em> take locale into account,
 1212        * and will result in an unsatisfactory ordering for certain locales.
 1213        * The java.text package provides <em>Collators</em> to allow
 1214        * locale-sensitive ordering.
 1215        *
 1216        * @see     java.text.Collator#compare(String, String)
 1217        * @since   1.2
 1218        */
 1219       public static final Comparator<String> CASE_INSENSITIVE_ORDER
 1220                                            = new CaseInsensitiveComparator();
 1221       private static class CaseInsensitiveComparator
 1222                            implements Comparator<String>, java.io.Serializable {
 1223           // use serialVersionUID from JDK 1.2.2 for interoperability
 1224           private static final long serialVersionUID = 8575799808933029326L;
 1225   
 1226           public int compare(String s1, String s2) {
 1227               int n1 = s1.length();
 1228               int n2 = s2.length();
 1229               int min = Math.min(n1, n2);
 1230               for (int i = 0; i < min; i++) {
 1231                   char c1 = s1.charAt(i);
 1232                   char c2 = s2.charAt(i);
 1233                   if (c1 != c2) {
 1234                       c1 = Character.toUpperCase(c1);
 1235                       c2 = Character.toUpperCase(c2);
 1236                       if (c1 != c2) {
 1237                           c1 = Character.toLowerCase(c1);
 1238                           c2 = Character.toLowerCase(c2);
 1239                           if (c1 != c2) {
 1240                               // No overflow because of numeric promotion
 1241                               return c1 - c2;
 1242                           }
 1243                       }
 1244                   }
 1245               }
 1246               return n1 - n2;
 1247           }
 1248       }
 1249   
 1250       /**
 1251        * Compares two strings lexicographically, ignoring case
 1252        * differences. This method returns an integer whose sign is that of
 1253        * calling <code>compareTo</code> with normalized versions of the strings
 1254        * where case differences have been eliminated by calling
 1255        * <code>Character.toLowerCase(Character.toUpperCase(character))</code> on
 1256        * each character.
 1257        * <p>
 1258        * Note that this method does <em>not</em> take locale into account,
 1259        * and will result in an unsatisfactory ordering for certain locales.
 1260        * The java.text package provides <em>collators</em> to allow
 1261        * locale-sensitive ordering.
 1262        *
 1263        * @param   str   the <code>String</code> to be compared.
 1264        * @return  a negative integer, zero, or a positive integer as the
 1265        *          specified String is greater than, equal to, or less
 1266        *          than this String, ignoring case considerations.
 1267        * @see     java.text.Collator#compare(String, String)
 1268        * @since   1.2
 1269        */
 1270       public int compareToIgnoreCase(String str) {
 1271           return CASE_INSENSITIVE_ORDER.compare(this, str);
 1272       }
 1273   
 1274       /**
 1275        * Tests if two string regions are equal.
 1276        * <p>
 1277        * A substring of this <tt>String</tt> object is compared to a substring
 1278        * of the argument other. The result is true if these substrings
 1279        * represent identical character sequences. The substring of this
 1280        * <tt>String</tt> object to be compared begins at index <tt>toffset</tt>
 1281        * and has length <tt>len</tt>. The substring of other to be compared
 1282        * begins at index <tt>ooffset</tt> and has length <tt>len</tt>. The
 1283        * result is <tt>false</tt> if and only if at least one of the following
 1284        * is true:
 1285        * <ul><li><tt>toffset</tt> is negative.
 1286        * <li><tt>ooffset</tt> is negative.
 1287        * <li><tt>toffset+len</tt> is greater than the length of this
 1288        * <tt>String</tt> object.
 1289        * <li><tt>ooffset+len</tt> is greater than the length of the other
 1290        * argument.
 1291        * <li>There is some nonnegative integer <i>k</i> less than <tt>len</tt>
 1292        * such that:
 1293        * <tt>this.charAt(toffset+<i>k</i>)&nbsp;!=&nbsp;other.charAt(ooffset+<i>k</i>)</tt>
 1294        * </ul>
 1295        *
 1296        * @param   toffset   the starting offset of the subregion in this string.
 1297        * @param   other     the string argument.
 1298        * @param   ooffset   the starting offset of the subregion in the string
 1299        *                    argument.
 1300        * @param   len       the number of characters to compare.
 1301        * @return  <code>true</code> if the specified subregion of this string
 1302        *          exactly matches the specified subregion of the string argument;
 1303        *          <code>false</code> otherwise.
 1304        */
 1305       public boolean regionMatches(int toffset, String other, int ooffset,
 1306                                    int len) {
 1307           char ta[] = value;
 1308           int to = offset + toffset;
 1309           char pa[] = other.value;
 1310           int po = other.offset + ooffset;
 1311           // Note: toffset, ooffset, or len might be near -1>>>1.
 1312           if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len)
 1313               || (ooffset > (long)other.count - len)) {
 1314               return false;
 1315           }
 1316           while (len-- > 0) {
 1317               if (ta[to++] != pa[po++]) {
 1318                   return false;
 1319               }
 1320           }
 1321           return true;
 1322       }
 1323   
 1324       /**
 1325        * Tests if two string regions are equal.
 1326        * <p>
 1327        * A substring of this <tt>String</tt> object is compared to a substring
 1328        * of the argument <tt>other</tt>. The result is <tt>true</tt> if these
 1329        * substrings represent character sequences that are the same, ignoring
 1330        * case if and only if <tt>ignoreCase</tt> is true. The substring of
 1331        * this <tt>String</tt> object to be compared begins at index
 1332        * <tt>toffset</tt> and has length <tt>len</tt>. The substring of
 1333        * <tt>other</tt> to be compared begins at index <tt>ooffset</tt> and
 1334        * has length <tt>len</tt>. The result is <tt>false</tt> if and only if
 1335        * at least one of the following is true:
 1336        * <ul><li><tt>toffset</tt> is negative.
 1337        * <li><tt>ooffset</tt> is negative.
 1338        * <li><tt>toffset+len</tt> is greater than the length of this
 1339        * <tt>String</tt> object.
 1340        * <li><tt>ooffset+len</tt> is greater than the length of the other
 1341        * argument.
 1342        * <li><tt>ignoreCase</tt> is <tt>false</tt> and there is some nonnegative
 1343        * integer <i>k</i> less than <tt>len</tt> such that:
 1344        * <blockquote><pre>
 1345        * this.charAt(toffset+k) != other.charAt(ooffset+k)
 1346        * </pre></blockquote>
 1347        * <li><tt>ignoreCase</tt> is <tt>true</tt> and there is some nonnegative
 1348        * integer <i>k</i> less than <tt>len</tt> such that:
 1349        * <blockquote><pre>
 1350        * Character.toLowerCase(this.charAt(toffset+k)) !=
 1351                  Character.toLowerCase(other.charAt(ooffset+k))
 1352        * </pre></blockquote>
 1353        * and:
 1354        * <blockquote><pre>
 1355        * Character.toUpperCase(this.charAt(toffset+k)) !=
 1356        *         Character.toUpperCase(other.charAt(ooffset+k))
 1357        * </pre></blockquote>
 1358        * </ul>
 1359        *
 1360        * @param   ignoreCase   if <code>true</code>, ignore case when comparing
 1361        *                       characters.
 1362        * @param   toffset      the starting offset of the subregion in this
 1363        *                       string.
 1364        * @param   other        the string argument.
 1365        * @param   ooffset      the starting offset of the subregion in the string
 1366        *                       argument.
 1367        * @param   len          the number of characters to compare.
 1368        * @return  <code>true</code> if the specified subregion of this string
 1369        *          matches the specified subregion of the string argument;
 1370        *          <code>false</code> otherwise. Whether the matching is exact
 1371        *          or case insensitive depends on the <code>ignoreCase</code>
 1372        *          argument.
 1373        */
 1374       public boolean regionMatches(boolean ignoreCase, int toffset,
 1375                              String other, int ooffset, int len) {
 1376           char ta[] = value;
 1377           int to = offset + toffset;
 1378           char pa[] = other.value;
 1379           int po = other.offset + ooffset;
 1380           // Note: toffset, ooffset, or len might be near -1>>>1.
 1381           if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len) ||
 1382                   (ooffset > (long)other.count - len)) {
 1383               return false;
 1384           }
 1385           while (len-- > 0) {
 1386               char c1 = ta[to++];
 1387               char c2 = pa[po++];
 1388               if (c1 == c2) {
 1389                   continue;
 1390               }
 1391               if (ignoreCase) {
 1392                   // If characters don't match but case may be ignored,
 1393                   // try converting both characters to uppercase.
 1394                   // If the results match, then the comparison scan should
 1395                   // continue.
 1396                   char u1 = Character.toUpperCase(c1);
 1397                   char u2 = Character.toUpperCase(c2);
 1398                   if (u1 == u2) {
 1399                       continue;
 1400                   }
 1401                   // Unfortunately, conversion to uppercase does not work properly
 1402                   // for the Georgian alphabet, which has strange rules about case
 1403                   // conversion.  So we need to make one last check before
 1404                   // exiting.
 1405                   if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
 1406                       continue;
 1407                   }
 1408               }
 1409               return false;
 1410           }
 1411           return true;
 1412       }
 1413   
 1414       /**
 1415        * Tests if the substring of this string beginning at the
 1416        * specified index starts with the specified prefix.
 1417        *
 1418        * @param   prefix    the prefix.
 1419        * @param   toffset   where to begin looking in this string.
 1420        * @return  <code>true</code> if the character sequence represented by the
 1421        *          argument is a prefix of the substring of this object starting
 1422        *          at index <code>toffset</code>; <code>false</code> otherwise.
 1423        *          The result is <code>false</code> if <code>toffset</code> is
 1424        *          negative or greater than the length of this
 1425        *          <code>String</code> object; otherwise the result is the same
 1426        *          as the result of the expression
 1427        *          <pre>
 1428        *          this.substring(toffset).startsWith(prefix)
 1429        *          </pre>
 1430        */
 1431       public boolean startsWith(String prefix, int toffset) {
 1432           char ta[] = value;
 1433           int to = offset + toffset;
 1434           char pa[] = prefix.value;
 1435           int po = prefix.offset;
 1436           int pc = prefix.count;
 1437           // Note: toffset might be near -1>>>1.
 1438           if ((toffset < 0) || (toffset > count - pc)) {
 1439               return false;
 1440           }
 1441           while (--pc >= 0) {
 1442               if (ta[to++] != pa[po++]) {
 1443                   return false;
 1444               }
 1445           }
 1446           return true;
 1447       }
 1448   
 1449       /**
 1450        * Tests if this string starts with the specified prefix.
 1451        *
 1452        * @param   prefix   the prefix.
 1453        * @return  <code>true</code> if the character sequence represented by the
 1454        *          argument is a prefix of the character sequence represented by
 1455        *          this string; <code>false</code> otherwise.
 1456        *          Note also that <code>true</code> will be returned if the
 1457        *          argument is an empty string or is equal to this
 1458        *          <code>String</code> object as determined by the
 1459        *          {@link #equals(Object)} method.
 1460        * @since   1. 0
 1461        */
 1462       public boolean startsWith(String prefix) {
 1463           return startsWith(prefix, 0);
 1464       }
 1465   
 1466       /**
 1467        * Tests if this string ends with the specified suffix.
 1468        *
 1469        * @param   suffix   the suffix.
 1470        * @return  <code>true</code> if the character sequence represented by the
 1471        *          argument is a suffix of the character sequence represented by
 1472        *          this object; <code>false</code> otherwise. Note that the
 1473        *          result will be <code>true</code> if the argument is the
 1474        *          empty string or is equal to this <code>String</code> object
 1475        *          as determined by the {@link #equals(Object)} method.
 1476        */
 1477       public boolean endsWith(String suffix) {
 1478           return startsWith(suffix, count - suffix.count);
 1479       }
 1480   
 1481       /**
 1482        * Returns a hash code for this string. The hash code for a
 1483        * <code>String</code> object is computed as
 1484        * <blockquote><pre>
 1485        * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
 1486        * </pre></blockquote>
 1487        * using <code>int</code> arithmetic, where <code>s[i]</code> is the
 1488        * <i>i</i>th character of the string, <code>n</code> is the length of
 1489        * the string, and <code>^</code> indicates exponentiation.
 1490        * (The hash value of the empty string is zero.)
 1491        *
 1492        * @return  a hash code value for this object.
 1493        */
 1494       public int hashCode() {
 1495           int h = hash;
 1496           if (h == 0 && count > 0) {
 1497               int off = offset;
 1498               char val[] = value;
 1499               int len = count;
 1500   
 1501               for (int i = 0; i < len; i++) {
 1502                   h = 31*h + val[off++];
 1503               }
 1504               hash = h;
 1505           }
 1506           return h;
 1507       }
 1508   
 1509       /**
 1510        * Returns the index within this string of the first occurrence of
 1511        * the specified character. If a character with value
 1512        * <code>ch</code> occurs in the character sequence represented by
 1513        * this <code>String</code> object, then the index (in Unicode
 1514        * code units) of the first such occurrence is returned. For
 1515        * values of <code>ch</code> in the range from 0 to 0xFFFF
 1516        * (inclusive), this is the smallest value <i>k</i> such that:
 1517        * <blockquote><pre>
 1518        * this.charAt(<i>k</i>) == ch
 1519        * </pre></blockquote>
 1520        * is true. For other values of <code>ch</code>, it is the
 1521        * smallest value <i>k</i> such that:
 1522        * <blockquote><pre>
 1523        * this.codePointAt(<i>k</i>) == ch
 1524        * </pre></blockquote>
 1525        * is true. In either case, if no such character occurs in this
 1526        * string, then <code>-1</code> is returned.
 1527        *
 1528        * @param   ch   a character (Unicode code point).
 1529        * @return  the index of the first occurrence of the character in the
 1530        *          character sequence represented by this object, or
 1531        *          <code>-1</code> if the character does not occur.
 1532        */
 1533       public int indexOf(int ch) {
 1534           return indexOf(ch, 0);
 1535       }
 1536   
 1537       /**
 1538        * Returns the index within this string of the first occurrence of the
 1539        * specified character, starting the search at the specified index.
 1540        * <p>
 1541        * If a character with value <code>ch</code> occurs in the
 1542        * character sequence represented by this <code>String</code>
 1543        * object at an index no smaller than <code>fromIndex</code>, then
 1544        * the index of the first such occurrence is returned. For values
 1545        * of <code>ch</code> in the range from 0 to 0xFFFF (inclusive),
 1546        * this is the smallest value <i>k</i> such that:
 1547        * <blockquote><pre>
 1548        * (this.charAt(<i>k</i>) == ch) && (<i>k</i> &gt;= fromIndex)
 1549        * </pre></blockquote>
 1550        * is true. For other values of <code>ch</code>, it is the
 1551        * smallest value <i>k</i> such that:
 1552        * <blockquote><pre>
 1553        * (this.codePointAt(<i>k</i>) == ch) && (<i>k</i> &gt;= fromIndex)
 1554        * </pre></blockquote>
 1555        * is true. In either case, if no such character occurs in this
 1556        * string at or after position <code>fromIndex</code>, then
 1557        * <code>-1</code> is returned.
 1558        *
 1559        * <p>
 1560        * There is no restriction on the value of <code>fromIndex</code>. If it
 1561        * is negative, it has the same effect as if it were zero: this entire
 1562        * string may be searched. If it is greater than the length of this
 1563        * string, it has the same effect as if it were equal to the length of
 1564        * this string: <code>-1</code> is returned.
 1565        *
 1566        * <p>All indices are specified in <code>char</code> values
 1567        * (Unicode code units).
 1568        *
 1569        * @param   ch          a character (Unicode code point).
 1570        * @param   fromIndex   the index to start the search from.
 1571        * @return  the index of the first occurrence of the character in the
 1572        *          character sequence represented by this object that is greater
 1573        *          than or equal to <code>fromIndex</code>, or <code>-1</code>
 1574        *          if the character does not occur.
 1575        */
 1576       public int indexOf(int ch, int fromIndex) {
 1577           if (fromIndex < 0) {
 1578               fromIndex = 0;
 1579           } else if (fromIndex >= count) {
 1580               // Note: fromIndex might be near -1>>>1.
 1581               return -1;
 1582           }
 1583   
 1584           if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
 1585               // handle most cases here (ch is a BMP code point or a
 1586               // negative value (invalid code point))
 1587               final char[] value = this.value;
 1588               final int offset = this.offset;
 1589               final int max = offset + count;
 1590               for (int i = offset + fromIndex; i < max ; i++) {
 1591                   if (value[i] == ch) {
 1592                       return i - offset;
 1593                   }
 1594               }
 1595               return -1;
 1596           } else {
 1597               return indexOfSupplementary(ch, fromIndex);
 1598           }
 1599       }
 1600   
 1601       /**
 1602        * Handles (rare) calls of indexOf with a supplementary character.
 1603        */
 1604       private int indexOfSupplementary(int ch, int fromIndex) {
 1605           if (Character.isValidCodePoint(ch)) {
 1606               final char[] value = this.value;
 1607               final int offset = this.offset;
 1608               final char hi = Character.highSurrogate(ch);
 1609               final char lo = Character.lowSurrogate(ch);
 1610               final int max = offset + count - 1;
 1611               for (int i = offset + fromIndex; i < max; i++) {
 1612                   if (value[i] == hi && value[i+1] == lo) {
 1613                       return i - offset;
 1614                   }
 1615               }
 1616           }
 1617           return -1;
 1618       }
 1619   
 1620       /**
 1621        * Returns the index within this string of the last occurrence of
 1622        * the specified character. For values of <code>ch</code> in the
 1623        * range from 0 to 0xFFFF (inclusive), the index (in Unicode code
 1624        * units) returned is the largest value <i>k</i> such that:
 1625        * <blockquote><pre>
 1626        * this.charAt(<i>k</i>) == ch
 1627        * </pre></blockquote>
 1628        * is true. For other values of <code>ch</code>, it is the
 1629        * largest value <i>k</i> such that:
 1630        * <blockquote><pre>
 1631        * this.codePointAt(<i>k</i>) == ch
 1632        * </pre></blockquote>
 1633        * is true.  In either case, if no such character occurs in this
 1634        * string, then <code>-1</code> is returned.  The
 1635        * <code>String</code> is searched backwards starting at the last
 1636        * character.
 1637        *
 1638        * @param   ch   a character (Unicode code point).
 1639        * @return  the index of the last occurrence of the character in the
 1640        *          character sequence represented by this object, or
 1641        *          <code>-1</code> if the character does not occur.
 1642        */
 1643       public int lastIndexOf(int ch) {
 1644           return lastIndexOf(ch, count - 1);
 1645       }
 1646   
 1647       /**
 1648        * Returns the index within this string of the last occurrence of
 1649        * the specified character, searching backward starting at the
 1650        * specified index. For values of <code>ch</code> in the range
 1651        * from 0 to 0xFFFF (inclusive), the index returned is the largest
 1652        * value <i>k</i> such that:
 1653        * <blockquote><pre>
 1654        * (this.charAt(<i>k</i>) == ch) && (<i>k</i> &lt;= fromIndex)
 1655        * </pre></blockquote>
 1656        * is true. For other values of <code>ch</code>, it is the
 1657        * largest value <i>k</i> such that:
 1658        * <blockquote><pre>
 1659        * (this.codePointAt(<i>k</i>) == ch) && (<i>k</i> &lt;= fromIndex)
 1660        * </pre></blockquote>
 1661        * is true. In either case, if no such character occurs in this
 1662        * string at or before position <code>fromIndex</code>, then
 1663        * <code>-1</code> is returned.
 1664        *
 1665        * <p>All indices are specified in <code>char</code> values
 1666        * (Unicode code units).
 1667        *
 1668        * @param   ch          a character (Unicode code point).
 1669        * @param   fromIndex   the index to start the search from. There is no
 1670        *          restriction on the value of <code>fromIndex</code>. If it is
 1671        *          greater than or equal to the length of this string, it has
 1672        *          the same effect as if it were equal to one less than the
 1673        *          length of this string: this entire string may be searched.
 1674        *          If it is negative, it has the same effect as if it were -1:
 1675        *          -1 is returned.
 1676        * @return  the index of the last occurrence of the character in the
 1677        *          character sequence represented by this object that is less
 1678        *          than or equal to <code>fromIndex</code>, or <code>-1</code>
 1679        *          if the character does not occur before that point.
 1680        */
 1681       public int lastIndexOf(int ch, int fromIndex) {
 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               final char[] value = this.value;
 1686               final int offset = this.offset;
 1687               int i = offset + Math.min(fromIndex, count - 1);
 1688               for (; i >= offset ; i--) {
 1689                   if (value[i] == ch) {
 1690                       return i - offset;
 1691                   }
 1692               }
 1693               return -1;
 1694           } else {
 1695               return lastIndexOfSupplementary(ch, fromIndex);
 1696           }
 1697       }
 1698   
 1699       /**
 1700        * Handles (rare) calls of lastIndexOf with a supplementary character.
 1701        */
 1702       private int lastIndexOfSupplementary(int ch, int fromIndex) {
 1703           if (Character.isValidCodePoint(ch)) {
 1704               final char[] value = this.value;
 1705               final int offset = this.offset;
 1706               char hi = Character.highSurrogate(ch);
 1707               char lo = Character.lowSurrogate(ch);
 1708               int i = offset + Math.min(fromIndex, count - 2);
 1709               for (; i >= offset; i--) {
 1710                   if (value[i] == hi && value[i+1] == lo) {
 1711                       return i - offset;
 1712                   }
 1713               }
 1714           }
 1715           return -1;
 1716       }
 1717   
 1718       /**
 1719        * Returns the index within this string of the first occurrence of the
 1720        * specified substring.
 1721        *
 1722        * <p>The returned index is the smallest value <i>k</i> for which:
 1723        * <blockquote><pre>
 1724        * this.startsWith(str, <i>k</i>)
 1725        * </pre></blockquote>
 1726        * If no such value of <i>k</i> exists, then {@code -1} is returned.
 1727        *
 1728        * @param   str   the substring to search for.
 1729        * @return  the index of the first occurrence of the specified substring,
 1730        *          or {@code -1} if there is no such occurrence.
 1731        */
 1732       public int indexOf(String str) {
 1733           return indexOf(str, 0);
 1734       }
 1735   
 1736       /**
 1737        * Returns the index within this string of the first occurrence of the
 1738        * specified substring, starting at the specified index.
 1739        *
 1740        * <p>The returned index is the smallest value <i>k</i> for which:
 1741        * <blockquote><pre>
 1742        * <i>k</i> &gt;= fromIndex && this.startsWith(str, <i>k</i>)
 1743        * </pre></blockquote>
 1744        * If no such value of <i>k</i> exists, then {@code -1} is returned.
 1745        *
 1746        * @param   str         the substring to search for.
 1747        * @param   fromIndex   the index from which to start the search.
 1748        * @return  the index of the first occurrence of the specified substring,
 1749        *          starting at the specified index,
 1750        *          or {@code -1} if there is no such occurrence.
 1751        */
 1752       public int indexOf(String str, int fromIndex) {
 1753           return indexOf(value, offset, count,
 1754                          str.value, str.offset, str.count, fromIndex);
 1755       }
 1756   
 1757       /**
 1758        * Code shared by String and StringBuffer to do searches. The
 1759        * source is the character array being searched, and the target
 1760        * is the string being searched for.
 1761        *
 1762        * @param   source       the characters being searched.
 1763        * @param   sourceOffset offset of the source string.
 1764        * @param   sourceCount  count of the source string.
 1765        * @param   target       the characters being searched for.
 1766        * @param   targetOffset offset of the target string.
 1767        * @param   targetCount  count of the target string.
 1768        * @param   fromIndex    the index to begin searching from.
 1769        */
 1770       static int indexOf(char[] source, int sourceOffset, int sourceCount,
 1771                          char[] target, int targetOffset, int targetCount,
 1772                          int fromIndex) {
 1773           if (fromIndex >= sourceCount) {
 1774               return (targetCount == 0 ? sourceCount : -1);
 1775           }
 1776           if (fromIndex < 0) {
 1777               fromIndex = 0;
 1778           }
 1779           if (targetCount == 0) {
 1780               return fromIndex;
 1781           }
 1782   
 1783           char first  = target[targetOffset];
 1784           int max = sourceOffset + (sourceCount - targetCount);
 1785   
 1786           for (int i = sourceOffset + fromIndex; i <= max; i++) {
 1787               /* Look for first character. */
 1788               if (source[i] != first) {
 1789                   while (++i <= max && source[i] != first);
 1790               }
 1791   
 1792               /* Found first character, now look at the rest of v2 */
 1793               if (i <= max) {
 1794                   int j = i + 1;
 1795                   int end = j + targetCount - 1;
 1796                   for (int k = targetOffset + 1; j < end && source[j] ==
 1797                            target[k]; j++, k++);
 1798   
 1799                   if (j == end) {
 1800                       /* Found whole string. */
 1801                       return i - sourceOffset;
 1802                   }
 1803               }
 1804           }
 1805           return -1;
 1806       }
 1807   
 1808       /**
 1809        * Returns the index within this string of the last occurrence of the
 1810        * specified substring.  The last occurrence of the empty string ""
 1811        * is considered to occur at the index value {@code this.length()}.
 1812        *
 1813        * <p>The returned index is the largest value <i>k</i> for which:
 1814        * <blockquote><pre>
 1815        * this.startsWith(str, <i>k</i>)
 1816        * </pre></blockquote>
 1817        * If no such value of <i>k</i> exists, then {@code -1} is returned.
 1818        *
 1819        * @param   str   the substring to search for.
 1820        * @return  the index of the last occurrence of the specified substring,
 1821        *          or {@code -1} if there is no such occurrence.
 1822        */
 1823       public int lastIndexOf(String str) {
 1824           return lastIndexOf(str, count);
 1825       }
 1826   
 1827       /**
 1828        * Returns the index within this string of the last occurrence of the
 1829        * specified substring, searching backward starting at the specified index.
 1830        *
 1831        * <p>The returned index is the largest value <i>k</i> for which:
 1832        * <blockquote><pre>
 1833        * <i>k</i> &lt;= fromIndex && this.startsWith(str, <i>k</i>)
 1834        * </pre></blockquote>
 1835        * If no such value of <i>k</i> exists, then {@code -1} is returned.
 1836        *
 1837        * @param   str         the substring to search for.
 1838        * @param   fromIndex   the index to start the search from.
 1839        * @return  the index of the last occurrence of the specified substring,
 1840        *          searching backward from the specified index,
 1841        *          or {@code -1} if there is no such occurrence.
 1842        */
 1843       public int lastIndexOf(String str, int fromIndex) {
 1844           return lastIndexOf(value, offset, count,
 1845                              str.value, str.offset, str.count, fromIndex);
 1846       }
 1847   
 1848       /**
 1849        * Code shared by String and StringBuffer to do searches. The
 1850        * source is the character array being searched, and the target
 1851        * is the string being searched for.
 1852        *
 1853        * @param   source       the characters being searched.
 1854        * @param   sourceOffset offset of the source string.
 1855        * @param   sourceCount  count of the source string.
 1856        * @param   target       the characters being searched for.
 1857        * @param   targetOffset offset of the target string.
 1858        * @param   targetCount  count of the target string.
 1859        * @param   fromIndex    the index to begin searching from.
 1860        */
 1861       static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,
 1862                              char[] target, int targetOffset, int targetCount,
 1863                              int fromIndex) {
 1864           /*
 1865            * Check arguments; return immediately where possible. For
 1866            * consistency, don't check for null str.
 1867            */
 1868           int rightIndex = sourceCount - targetCount;
 1869           if (fromIndex < 0) {
 1870               return -1;
 1871           }
 1872           if (fromIndex > rightIndex) {
 1873               fromIndex = rightIndex;
 1874           }
 1875           /* Empty string always matches. */
 1876           if (targetCount == 0) {
 1877               return fromIndex;
 1878           }
 1879   
 1880           int strLastIndex = targetOffset + targetCount - 1;
 1881           char strLastChar = target[strLastIndex];
 1882           int min = sourceOffset + targetCount - 1;
 1883           int i = min + fromIndex;
 1884   
 1885       startSearchForLastChar:
 1886           while (true) {
 1887               while (i >= min && source[i] != strLastChar) {
 1888                   i--;
 1889               }
 1890               if (i < min) {
 1891                   return -1;
 1892               }
 1893               int j = i - 1;
 1894               int start = j - (targetCount - 1);
 1895               int k = strLastIndex - 1;
 1896   
 1897               while (j > start) {
 1898                   if (source[j--] != target[k--]) {
 1899                       i--;
 1900                       continue startSearchForLastChar;
 1901                   }
 1902               }
 1903               return start - sourceOffset + 1;
 1904           }
 1905       }
 1906   
 1907       /**
 1908        * Returns a new string that is a substring of this string. The
 1909        * substring begins with the character at the specified index and
 1910        * extends to the end of this string. <p>
 1911        * Examples:
 1912        * <blockquote><pre>
 1913        * "unhappy".substring(2) returns "happy"
 1914        * "Harbison".substring(3) returns "bison"
 1915        * "emptiness".substring(9) returns "" (an empty string)
 1916        * </pre></blockquote>
 1917        *
 1918        * @param      beginIndex   the beginning index, inclusive.
 1919        * @return     the specified substring.
 1920        * @exception  IndexOutOfBoundsException  if
 1921        *             <code>beginIndex</code> is negative or larger than the
 1922        *             length of this <code>String</code> object.
 1923        */
 1924       public String substring(int beginIndex) {
 1925           return substring(beginIndex, count);
 1926       }
 1927   
 1928       /**
 1929        * Returns a new string that is a substring of this string. The
 1930        * substring begins at the specified <code>beginIndex</code> and
 1931        * extends to the character at index <code>endIndex - 1</code>.
 1932        * Thus the length of the substring is <code>endIndex-beginIndex</code>.
 1933        * <p>
 1934        * Examples:
 1935        * <blockquote><pre>
 1936        * "hamburger".substring(4, 8) returns "urge"
 1937        * "smiles".substring(1, 5) returns "mile"
 1938        * </pre></blockquote>
 1939        *
 1940        * @param      beginIndex   the beginning index, inclusive.
 1941        * @param      endIndex     the ending index, exclusive.
 1942        * @return     the specified substring.
 1943        * @exception  IndexOutOfBoundsException  if the
 1944        *             <code>beginIndex</code> is negative, or
 1945        *             <code>endIndex</code> is larger than the length of
 1946        *             this <code>String</code> object, or
 1947        *             <code>beginIndex</code> is larger than
 1948        *             <code>endIndex</code>.
 1949        */
 1950       public String substring(int beginIndex, int endIndex) {
 1951           if (beginIndex < 0) {
 1952               throw new StringIndexOutOfBoundsException(beginIndex);
 1953           }
 1954           if (endIndex > count) {
 1955               throw new StringIndexOutOfBoundsException(endIndex);
 1956           }
 1957           if (beginIndex > endIndex) {
 1958               throw new StringIndexOutOfBoundsException(endIndex - beginIndex);
 1959           }
 1960           return ((beginIndex == 0) && (endIndex == count)) ? this :
 1961               new String(offset + beginIndex, endIndex - beginIndex, value);
 1962       }
 1963   
 1964       /**
 1965        * Returns a new character sequence that is a subsequence of this sequence.
 1966        *
 1967        * <p> An invocation of this method of the form
 1968        *
 1969        * <blockquote><pre>
 1970        * str.subSequence(begin,&nbsp;end)</pre></blockquote>
 1971        *
 1972        * behaves in exactly the same way as the invocation
 1973        *
 1974        * <blockquote><pre>
 1975        * str.substring(begin,&nbsp;end)</pre></blockquote>
 1976        *
 1977        * This method is defined so that the <tt>String</tt> class can implement
 1978        * the {@link CharSequence} interface. </p>
 1979        *
 1980        * @param      beginIndex   the begin index, inclusive.
 1981        * @param      endIndex     the end index, exclusive.
 1982        * @return     the specified subsequence.
 1983        *
 1984        * @throws  IndexOutOfBoundsException
 1985        *          if <tt>beginIndex</tt> or <tt>endIndex</tt> are negative,
 1986        *          if <tt>endIndex</tt> is greater than <tt>length()</tt>,
 1987        *          or if <tt>beginIndex</tt> is greater than <tt>startIndex</tt>
 1988        *
 1989        * @since 1.4
 1990        * @spec JSR-51
 1991        */
 1992       public CharSequence subSequence(int beginIndex, int endIndex) {
 1993           return this.substring(beginIndex, endIndex);
 1994       }
 1995   
 1996       /**
 1997        * Concatenates the specified string to the end of this string.
 1998        * <p>
 1999        * If the length of the argument string is <code>0</code>, then this
 2000        * <code>String</code> object is returned. Otherwise, a new
 2001        * <code>String</code> object is created, representing a character
 2002        * sequence that is the concatenation of the character sequence
 2003        * represented by this <code>String</code> object and the character
 2004        * sequence represented by the argument string.<p>
 2005        * Examples:
 2006        * <blockquote><pre>
 2007        * "cares".concat("s") returns "caress"
 2008        * "to".concat("get").concat("her") returns "together"
 2009        * </pre></blockquote>
 2010        *
 2011        * @param   str   the <code>String</code> that is concatenated to the end
 2012        *                of this <code>String</code>.
 2013        * @return  a string that represents the concatenation of this object's
 2014        *          characters followed by the string argument's characters.
 2015        */
 2016       public String concat(String str) {
 2017           int otherLen = str.length();
 2018           if (otherLen == 0) {
 2019               return this;
 2020           }
 2021           char buf[] = new char[count + otherLen];
 2022           getChars(0, count, buf, 0);
 2023           str.getChars(0, otherLen, buf, count);
 2024           return new String(0, count + otherLen, buf);
 2025       }
 2026   
 2027       /**
 2028        * Returns a new string resulting from replacing all occurrences of
 2029        * <code>oldChar</code> in this string with <code>newChar</code>.
 2030        * <p>
 2031        * If the character <code>oldChar</code> does not occur in the
 2032        * character sequence represented by this <code>String</code> object,
 2033        * then a reference to this <code>String</code> object is returned.
 2034        * Otherwise, a new <code>String</code> object is created that
 2035        * represents a character sequence identical to the character sequence
 2036        * represented by this <code>String</code> object, except that every
 2037        * occurrence of <code>oldChar</code> is replaced by an occurrence
 2038        * of <code>newChar</code>.
 2039        * <p>
 2040        * Examples:
 2041        * <blockquote><pre>
 2042        * "mesquite in your cellar".replace('e', 'o')
 2043        *         returns "mosquito in your collar"
 2044        * "the war of baronets".replace('r', 'y')
 2045        *         returns "the way of bayonets"
 2046        * "sparring with a purple porpoise".replace('p', 't')
 2047        *         returns "starring with a turtle tortoise"
 2048        * "JonL".replace('q', 'x') returns "JonL" (no change)
 2049        * </pre></blockquote>
 2050        *
 2051        * @param   oldChar   the old character.
 2052        * @param   newChar   the new character.
 2053        * @return  a string derived from this string by replacing every
 2054        *          occurrence of <code>oldChar</code> with <code>newChar</code>.
 2055        */
 2056       public String replace(char oldChar, char newChar) {
 2057           if (oldChar != newChar) {
 2058               int len = count;
 2059               int i = -1;
 2060               char[] val = value; /* avoid getfield opcode */
 2061               int off = offset;   /* avoid getfield opcode */
 2062   
 2063               while (++i < len) {
 2064                   if (val[off + i] == oldChar) {
 2065                       break;
 2066                   }
 2067               }
 2068               if (i < len) {
 2069                   char buf[] = new char[len];
 2070                   for (int j = 0 ; j < i ; j++) {
 2071                       buf[j] = val[off+j];
 2072                   }
 2073                   while (i < len) {
 2074                       char c = val[off + i];
 2075                       buf[i] = (c == oldChar) ? newChar : c;
 2076                       i++;
 2077                   }
 2078                   return new String(0, len, buf);
 2079               }
 2080           }
 2081           return this;
 2082       }
 2083   
 2084       /**
 2085        * Tells whether or not this string matches the given <a
 2086        * href="../util/regex/Pattern.html#sum">regular expression</a>.
 2087        *
 2088        * <p> An invocation of this method of the form
 2089        * <i>str</i><tt>.matches(</tt><i>regex</i><tt>)</tt> yields exactly the
 2090        * same result as the expression
 2091        *
 2092        * <blockquote><tt> {@link java.util.regex.Pattern}.{@link
 2093        * java.util.regex.Pattern#matches(String,CharSequence)
 2094        * matches}(</tt><i>regex</i><tt>,</tt> <i>str</i><tt>)</tt></blockquote>
 2095        *
 2096        * @param   regex
 2097        *          the regular expression to which this string is to be matched
 2098        *
 2099        * @return  <tt>true</tt> if, and only if, this string matches the
 2100        *          given regular expression
 2101        *
 2102        * @throws  PatternSyntaxException
 2103        *          if the regular expression's syntax is invalid
 2104        *
 2105        * @see java.util.regex.Pattern
 2106        *
 2107        * @since 1.4
 2108        * @spec JSR-51
 2109        */
 2110       public boolean matches(String regex) {
 2111           return Pattern.matches(regex, this);
 2112       }
 2113   
 2114       /**
 2115        * Returns true if and only if this string contains the specified
 2116        * sequence of char values.
 2117        *
 2118        * @param s the sequence to search for
 2119        * @return true if this string contains <code>s</code>, false otherwise
 2120        * @throws NullPointerException if <code>s</code> is <code>null</code>
 2121        * @since 1.5
 2122        */
 2123       public boolean contains(CharSequence s) {
 2124           return indexOf(s.toString()) > -1;
 2125       }
 2126   
 2127       /**
 2128        * Replaces the first substring of this string that matches the given <a
 2129        * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 2130        * given replacement.
 2131        *
 2132        * <p> An invocation of this method of the form
 2133        * <i>str</i><tt>.replaceFirst(</tt><i>regex</i><tt>,</tt> <i>repl</i><tt>)</tt>
 2134        * yields exactly the same result as the expression
 2135        *
 2136        * <blockquote><tt>
 2137        * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
 2138        * compile}(</tt><i>regex</i><tt>).{@link
 2139        * java.util.regex.Pattern#matcher(java.lang.CharSequence)
 2140        * matcher}(</tt><i>str</i><tt>).{@link java.util.regex.Matcher#replaceFirst
 2141        * replaceFirst}(</tt><i>repl</i><tt>)</tt></blockquote>
 2142        *
 2143        *<p>
 2144        * Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in the
 2145        * replacement string may cause the results to be different than if it were
 2146        * being treated as a literal replacement string; see
 2147        * {@link java.util.regex.Matcher#replaceFirst}.
 2148        * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
 2149        * meaning of these characters, if desired.
 2150        *
 2151        * @param   regex
 2152        *          the regular expression to which this string is to be matched
 2153        * @param   replacement
 2154        *          the string to be substituted for the first match
 2155        *
 2156        * @return  The resulting <tt>String</tt>
 2157        *
 2158        * @throws  PatternSyntaxException
 2159        *          if the regular expression's syntax is invalid
 2160        *
 2161        * @see java.util.regex.Pattern
 2162        *
 2163        * @since 1.4
 2164        * @spec JSR-51
 2165        */
 2166       public String replaceFirst(String regex, String replacement) {
 2167           return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
 2168       }
 2169   
 2170       /**
 2171        * Replaces each substring of this string that matches the given <a
 2172        * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 2173        * given replacement.
 2174        *
 2175        * <p> An invocation of this method of the form
 2176        * <i>str</i><tt>.replaceAll(</tt><i>regex</i><tt>,</tt> <i>repl</i><tt>)</tt>
 2177        * yields exactly the same result as the expression
 2178        *
 2179        * <blockquote><tt>
 2180        * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
 2181        * compile}(</tt><i>regex</i><tt>).{@link
 2182        * java.util.regex.Pattern#matcher(java.lang.CharSequence)
 2183        * matcher}(</tt><i>str</i><tt>).{@link java.util.regex.Matcher#replaceAll
 2184        * replaceAll}(</tt><i>repl</i><tt>)</tt></blockquote>
 2185        *
 2186        *<p>
 2187        * Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in the
 2188        * replacement string may cause the results to be different than if it were
 2189        * being treated as a literal replacement string; see
 2190        * {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
 2191        * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
 2192        * meaning of these characters, if desired.
 2193        *
 2194        * @param   regex
 2195        *          the regular expression to which this string is to be matched
 2196        * @param   replacement
 2197        *          the string to be substituted for each match
 2198        *
 2199        * @return  The resulting <tt>String</tt>
 2200        *
 2201        * @throws  PatternSyntaxException
 2202        *          if the regular expression's syntax is invalid
 2203        *
 2204        * @see java.util.regex.Pattern
 2205        *
 2206        * @since 1.4
 2207        * @spec JSR-51
 2208        */
 2209       public String replaceAll(String regex, String replacement) {
 2210           return Pattern.compile(regex).matcher(this).replaceAll(replacement);
 2211       }
 2212   
 2213       /**
 2214        * Replaces each substring of this string that matches the literal target
 2215        * sequence with the specified literal replacement sequence. The
 2216        * replacement proceeds from the beginning of the string to the end, for
 2217        * example, replacing "aa" with "b" in the string "aaa" will result in
 2218        * "ba" rather than "ab".
 2219        *
 2220        * @param  target The sequence of char values to be replaced
 2221        * @param  replacement The replacement sequence of char values
 2222        * @return  The resulting string
 2223        * @throws NullPointerException if <code>target</code> or
 2224        *         <code>replacement</code> is <code>null</code>.
 2225        * @since 1.5
 2226        */
 2227       public String replace(CharSequence target, CharSequence replacement) {
 2228           return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
 2229               this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
 2230       }
 2231   
 2232       /**
 2233        * Splits this string around matches of the given
 2234        * <a href="../util/regex/Pattern.html#sum">regular expression</a>.
 2235        *
 2236        * <p> The array returned by this method contains each substring of this
 2237        * string that is terminated by another substring that matches the given
 2238        * expression or is terminated by the end of the string.  The substrings in
 2239        * the array are in the order in which they occur in this string.  If the
 2240        * expression does not match any part of the input then the resulting array
 2241        * has just one element, namely this string.
 2242        *
 2243        * <p> The <tt>limit</tt> parameter controls the number of times the
 2244        * pattern is applied and therefore affects the length of the resulting
 2245        * array.  If the limit <i>n</i> is greater than zero then the pattern
 2246        * will be applied at most <i>n</i>&nbsp;-&nbsp;1 times, the array's
 2247        * length will be no greater than <i>n</i>, and the array's last entry
 2248        * will contain all input beyond the last matched delimiter.  If <i>n</i>
 2249        * is non-positive then the pattern will be applied as many times as
 2250        * possible and the array can have any length.  If <i>n</i> is zero then
 2251        * the pattern will be applied as many times as possible, the array can
 2252        * have any length, and trailing empty strings will be discarded.
 2253        *
 2254        * <p> The string <tt>"boo:and:foo"</tt>, for example, yields the
 2255        * following results with these parameters:
 2256        *
 2257        * <blockquote><table cellpadding=1 cellspacing=0 summary="Split example showing regex, limit, and result">
 2258        * <tr>
 2259        *     <th>Regex</th>
 2260        *     <th>Limit</th>
 2261        *     <th>Result</th>
 2262        * </tr>
 2263        * <tr><td align=center>:</td>
 2264        *     <td align=center>2</td>
 2265        *     <td><tt>{ "boo", "and:foo" }</tt></td></tr>
 2266        * <tr><td align=center>:</td>
 2267        *     <td align=center>5</td>
 2268        *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
 2269        * <tr><td align=center>:</td>
 2270        *     <td align=center>-2</td>
 2271        *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
 2272        * <tr><td align=center>o</td>
 2273        *     <td align=center>5</td>
 2274        *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
 2275        * <tr><td align=center>o</td>
 2276        *     <td align=center>-2</td>
 2277        *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
 2278        * <tr><td align=center>o</td>
 2279        *     <td align=center>0</td>
 2280        *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
 2281        * </table></blockquote>
 2282        *
 2283        * <p> An invocation of this method of the form
 2284        * <i>str.</i><tt>split(</tt><i>regex</i><tt>,</tt>&nbsp;<i>n</i><tt>)</tt>
 2285        * yields the same result as the expression
 2286        *
 2287        * <blockquote>
 2288        * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
 2289        * compile}<tt>(</tt><i>regex</i><tt>)</tt>.{@link
 2290        * java.util.regex.Pattern#split(java.lang.CharSequence,int)
 2291        * split}<tt>(</tt><i>str</i><tt>,</tt>&nbsp;<i>n</i><tt>)</tt>
 2292        * </blockquote>
 2293        *
 2294        *
 2295        * @param  regex
 2296        *         the delimiting regular expression
 2297        *
 2298        * @param  limit
 2299        *         the result threshold, as described above
 2300        *
 2301        * @return  the array of strings computed by splitting this string
 2302        *          around matches of the given regular expression
 2303        *
 2304        * @throws  PatternSyntaxException
 2305        *          if the regular expression's syntax is invalid
 2306        *
 2307        * @see java.util.regex.Pattern
 2308        *
 2309        * @since 1.4
 2310        * @spec JSR-51
 2311        */
 2312       public String[] split(String regex, int limit) {
 2313           /* fastpath if the regex is a
 2314              (1)one-char String and this character is not one of the
 2315                 RegEx's meta characters ".$|()[{^?*+\\", or
 2316              (2)two-char String and the first char is the backslash and
 2317                 the second is not the ascii digit or ascii letter.
 2318           */
 2319           char ch = 0;
 2320           if (((regex.count == 1 &&
 2321                ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||
 2322                (regex.length() == 2 &&
 2323                 regex.charAt(0) == '\\' &&
 2324                 (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
 2325                 ((ch-'a')|('z'-ch)) < 0 &&
 2326                 ((ch-'A')|('Z'-ch)) < 0)) &&
 2327               (ch < Character.MIN_HIGH_SURROGATE ||
 2328                ch > Character.MAX_LOW_SURROGATE))
 2329           {
 2330               int off = 0;
 2331               int next = 0;
 2332               boolean limited = limit > 0;
 2333               ArrayList<String> list = new ArrayList<>();
 2334               while ((next = indexOf(ch, off)) != -1) {
 2335                   if (!limited || list.size() < limit - 1) {
 2336                       list.add(substring(off, next));
 2337                       off = next + 1;
 2338                   } else {    // last one
 2339                       //assert (list.size() == limit - 1);
 2340                       list.add(substring(off, count));
 2341                       off = count;
 2342                       break;
 2343                   }
 2344               }
 2345               // If no match was found, return this
 2346               if (off == 0)
 2347                   return new String[] { this };
 2348   
 2349               // Add remaining segment
 2350               if (!limited || list.size() < limit)
 2351                   list.add(substring(off, count));
 2352   
 2353               // Construct result
 2354               int resultSize = list.size();
 2355               if (limit == 0)
 2356                   while (resultSize > 0 && list.get(resultSize-1).length() == 0)
 2357                       resultSize--;
 2358               String[] result = new String[resultSize];
 2359               return list.subList(0, resultSize).toArray(result);
 2360           }
 2361           return Pattern.compile(regex).split(this, limit);
 2362       }
 2363   
 2364       /**
 2365        * Splits this string around matches of the given <a
 2366        * href="../util/regex/Pattern.html#sum">regular expression</a>.
 2367        *
 2368        * <p> This method works as if by invoking the two-argument {@link
 2369        * #split(String, int) split} method with the given expression and a limit
 2370        * argument of zero.  Trailing empty strings are therefore not included in
 2371        * the resulting array.
 2372        *
 2373        * <p> The string <tt>"boo:and:foo"</tt>, for example, yields the following
 2374        * results with these expressions:
 2375        *
 2376        * <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
 2377        * <tr>
 2378        *  <th>Regex</th>
 2379        *  <th>Result</th>
 2380        * </tr>
 2381        * <tr><td align=center>:</td>
 2382        *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
 2383        * <tr><td align=center>o</td>
 2384        *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
 2385        * </table></blockquote>
 2386        *
 2387        *
 2388        * @param  regex
 2389        *         the delimiting regular expression
 2390        *
 2391        * @return  the array of strings computed by splitting this string
 2392        *          around matches of the given regular expression
 2393        *
 2394        * @throws  PatternSyntaxException
 2395        *          if the regular expression's syntax is invalid
 2396        *
 2397        * @see java.util.regex.Pattern
 2398        *
 2399        * @since 1.4
 2400        * @spec JSR-51
 2401        */
 2402       public String[] split(String regex) {
 2403           return split(regex, 0);
 2404       }
 2405   
 2406       /**
 2407        * Converts all of the characters in this <code>String</code> to lower
 2408        * case using the rules of the given <code>Locale</code>.  Case mapping is based
 2409        * on the Unicode Standard version specified by the {@link java.lang.Character Character}
 2410        * class. Since case mappings are not always 1:1 char mappings, the resulting
 2411        * <code>String</code> may be a different length than the original <code>String</code>.
 2412        * <p>
 2413        * Examples of lowercase  mappings are in the following table:
 2414        * <table border="1" summary="Lowercase mapping examples showing language code of locale, upper case, lower case, and description">
 2415        * <tr>
 2416        *   <th>Language Code of Locale</th>
 2417        *   <th>Upper Case</th>
 2418        *   <th>Lower Case</th>
 2419        *   <th>Description</th>
 2420        * </tr>
 2421        * <tr>
 2422        *   <td>tr (Turkish)</td>
 2423        *   <td>&#92;u0130</td>
 2424        *   <td>&#92;u0069</td>
 2425        *   <td>capital letter I with dot above -&gt; small letter i</td>
 2426        * </tr>
 2427        * <tr>
 2428        *   <td>tr (Turkish)</td>
 2429        *   <td>&#92;u0049</td>
 2430        *   <td>&#92;u0131</td>
 2431        *   <td>capital letter I -&gt; small letter dotless i </td>
 2432        * </tr>
 2433        * <tr>
 2434        *   <td>(all)</td>
 2435        *   <td>French Fries</td>
 2436        *   <td>french fries</td>
 2437        *   <td>lowercased all chars in String</td>
 2438        * </tr>
 2439        * <tr>
 2440        *   <td>(all)</td>
 2441        *   <td><img src="doc-files/capiota.gif" alt="capiota"><img src="doc-files/capchi.gif" alt="capchi">
 2442        *       <img src="doc-files/captheta.gif" alt="captheta"><img src="doc-files/capupsil.gif" alt="capupsil">
 2443        *       <img src="doc-files/capsigma.gif" alt="capsigma"></td>
 2444        *   <td><img src="doc-files/iota.gif" alt="iota"><img src="doc-files/chi.gif" alt="chi">
 2445        *       <img src="doc-files/theta.gif" alt="theta"><img src="doc-files/upsilon.gif" alt="upsilon">
 2446        *       <img src="doc-files/sigma1.gif" alt="sigma"></td>
 2447        *   <td>lowercased all chars in String</td>
 2448        * </tr>
 2449        * </table>
 2450        *
 2451        * @param locale use the case transformation rules for this locale
 2452        * @return the <code>String</code>, converted to lowercase.
 2453        * @see     java.lang.String#toLowerCase()
 2454        * @see     java.lang.String#toUpperCase()
 2455        * @see     java.lang.String#toUpperCase(Locale)
 2456        * @since   1.1
 2457        */
 2458       public String toLowerCase(Locale locale) {
 2459           if (locale == null) {
 2460               throw new NullPointerException();
 2461           }
 2462   
 2463           int     firstUpper;
 2464   
 2465           /* Now check if there are any characters that need to be changed. */
 2466           scan: {
 2467               for (firstUpper = 0 ; firstUpper < count; ) {
 2468                   char c = value[offset+firstUpper];
 2469                   if ((c >= Character.MIN_HIGH_SURROGATE) &&
 2470                       (c <= Character.MAX_HIGH_SURROGATE)) {
 2471                       int supplChar = codePointAt(firstUpper);
 2472                       if (supplChar != Character.toLowerCase(supplChar)) {
 2473                           break scan;
 2474                       }
 2475                       firstUpper += Character.charCount(supplChar);
 2476                   } else {
 2477                       if (c != Character.toLowerCase(c)) {
 2478                           break scan;
 2479                       }
 2480                       firstUpper++;
 2481                   }
 2482               }
 2483               return this;
 2484           }
 2485   
 2486           char[]  result = new char[count];
 2487           int     resultOffset = 0;  /* result may grow, so i+resultOffset
 2488                                       * is the write location in result */
 2489   
 2490           /* Just copy the first few lowerCase characters. */
 2491           System.arraycopy(value, offset, result, 0, firstUpper);
 2492   
 2493           String lang = locale.getLanguage();
 2494           boolean localeDependent =
 2495               (lang == "tr" || lang == "az" || lang == "lt");
 2496           char[] lowerCharArray;
 2497           int lowerChar;
 2498           int srcChar;
 2499           int srcCount;
 2500           for (int i = firstUpper; i < count; i += srcCount) {
 2501               srcChar = (int)value[offset+i];
 2502               if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
 2503                   (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
 2504                   srcChar = codePointAt(i);
 2505                   srcCount = Character.charCount(srcChar);
 2506               } else {
 2507                   srcCount = 1;
 2508               }
 2509               if (localeDependent || srcChar == '\u03A3') { // GREEK CAPITAL LETTER SIGMA
 2510                   lowerChar = ConditionalSpecialCasing.toLowerCaseEx(this, i, locale);
 2511               } else if (srcChar == '\u0130') { // LATIN CAPITAL LETTER I DOT
 2512                   lowerChar = Character.ERROR;
 2513               } else {
 2514                   lowerChar = Character.toLowerCase(srcChar);
 2515               }
 2516               if ((lowerChar == Character.ERROR) ||
 2517                   (lowerChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
 2518                   if (lowerChar == Character.ERROR) {
 2519                        if (!localeDependent && srcChar == '\u0130') {
 2520                            lowerCharArray =
 2521                                ConditionalSpecialCasing.toLowerCaseCharArray(this, i, Locale.ENGLISH);
 2522                        } else {
 2523                           lowerCharArray =
 2524                               ConditionalSpecialCasing.toLowerCaseCharArray(this, i, locale);
 2525                        }
 2526                   } else if (srcCount == 2) {
 2527                       resultOffset += Character.toChars(lowerChar, result, i + resultOffset) - srcCount;
 2528                       continue;
 2529                   } else {
 2530                       lowerCharArray = Character.toChars(lowerChar);
 2531                   }
 2532   
 2533                   /* Grow result if needed */
 2534                   int mapLen = lowerCharArray.length;
 2535                   if (mapLen > srcCount) {
 2536                       char[] result2 = new char[result.length + mapLen - srcCount];
 2537                       System.arraycopy(result, 0, result2, 0,
 2538                           i + resultOffset);
 2539                       result = result2;
 2540                   }
 2541                   for (int x=0; x<mapLen; ++x) {
 2542                       result[i+resultOffset+x] = lowerCharArray[x];
 2543                   }
 2544                   resultOffset += (mapLen - srcCount);
 2545               } else {
 2546                   result[i+resultOffset] = (char)lowerChar;
 2547               }
 2548           }
 2549           return new String(0, count+resultOffset, result);
 2550       }
 2551   
 2552       /**
 2553        * Converts all of the characters in this <code>String</code> to lower
 2554        * case using the rules of the default locale. This is equivalent to calling
 2555        * <code>toLowerCase(Locale.getDefault())</code>.
 2556        * <p>
 2557        * <b>Note:</b> This method is locale sensitive, and may produce unexpected
 2558        * results if used for strings that are intended to be interpreted locale
 2559        * independently.
 2560        * Examples are programming language identifiers, protocol keys, and HTML
 2561        * tags.
 2562        * For instance, <code>"TITLE".toLowerCase()</code> in a Turkish locale
 2563        * returns <code>"t\u005Cu0131tle"</code>, where '\u005Cu0131' is the
 2564        * LATIN SMALL LETTER DOTLESS I character.
 2565        * To obtain correct results for locale insensitive strings, use
 2566        * <code>toLowerCase(Locale.ENGLISH)</code>.
 2567        * <p>
 2568        * @return  the <code>String</code>, converted to lowercase.
 2569        * @see     java.lang.String#toLowerCase(Locale)
 2570        */
 2571       public String toLowerCase() {
 2572           return toLowerCase(Locale.getDefault());
 2573       }
 2574   
 2575       /**
 2576        * Converts all of the characters in this <code>String</code> to upper
 2577        * case using the rules of the given <code>Locale</code>. Case mapping is based
 2578        * on the Unicode Standard version specified by the {@link java.lang.Character Character}
 2579        * class. Since case mappings are not always 1:1 char mappings, the resulting
 2580        * <code>String</code> may be a different length than the original <code>String</code>.
 2581        * <p>
 2582        * Examples of locale-sensitive and 1:M case mappings are in the following table.
 2583        * <p>
 2584        * <table border="1" summary="Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.">
 2585        * <tr>
 2586        *   <th>Language Code of Locale</th>
 2587        *   <th>Lower Case</th>
 2588        *   <th>Upper Case</th>
 2589        *   <th>Description</th>
 2590        * </tr>
 2591        * <tr>
 2592        *   <td>tr (Turkish)</td>
 2593        *   <td>&#92;u0069</td>
 2594        *   <td>&#92;u0130</td>
 2595        *   <td>small letter i -&gt; capital letter I with dot above</td>
 2596        * </tr>
 2597        * <tr>
 2598        *   <td>tr (Turkish)</td>
 2599        *   <td>&#92;u0131</td>
 2600        *   <td>&#92;u0049</td>
 2601        *   <td>small letter dotless i -&gt; capital letter I</td>
 2602        * </tr>
 2603        * <tr>
 2604        *   <td>(all)</td>
 2605        *   <td>&#92;u00df</td>
 2606        *   <td>&#92;u0053 &#92;u0053</td>
 2607        *   <td>small letter sharp s -&gt; two letters: SS</td>
 2608        * </tr>
 2609        * <tr>
 2610        *   <td>(all)</td>
 2611        *   <td>Fahrvergn&uuml;gen</td>
 2612        *   <td>FAHRVERGN&Uuml;GEN</td>
 2613        *   <td></td>
 2614        * </tr>
 2615        * </table>
 2616        * @param locale use the case transformation rules for this locale
 2617        * @return the <code>String</code>, converted to uppercase.
 2618        * @see     java.lang.String#toUpperCase()
 2619        * @see     java.lang.String#toLowerCase()
 2620        * @see     java.lang.String#toLowerCase(Locale)
 2621        * @since   1.1
 2622        */
 2623       public String toUpperCase(Locale locale) {
 2624           if (locale == null) {
 2625               throw new NullPointerException();
 2626           }
 2627   
 2628           int     firstLower;
 2629   
 2630           /* Now check if there are any characters that need to be changed. */
 2631           scan: {
 2632               for (firstLower = 0 ; firstLower < count; ) {
 2633                   int c = (int)value[offset+firstLower];
 2634                   int srcCount;
 2635                   if ((c >= Character.MIN_HIGH_SURROGATE) &&
 2636                       (c <= Character.MAX_HIGH_SURROGATE)) {
 2637                       c = codePointAt(firstLower);
 2638                       srcCount = Character.charCount(c);
 2639                   } else {
 2640                       srcCount = 1;
 2641                   }
 2642                   int upperCaseChar = Character.toUpperCaseEx(c);
 2643                   if ((upperCaseChar == Character.ERROR) ||
 2644                       (c != upperCaseChar)) {
 2645                       break scan;
 2646                   }
 2647                   firstLower += srcCount;
 2648               }
 2649               return this;
 2650           }
 2651   
 2652           char[]  result       = new char[count]; /* may grow */
 2653           int     resultOffset = 0;  /* result may grow, so i+resultOffset
 2654                                       * is the write location in result */
 2655   
 2656           /* Just copy the first few upperCase characters. */
 2657           System.arraycopy(value, offset, result, 0, firstLower);
 2658   
 2659           String lang = locale.getLanguage();
 2660           boolean localeDependent =
 2661               (lang == "tr" || lang == "az" || lang == "lt");
 2662           char[] upperCharArray;
 2663           int upperChar;
 2664           int srcChar;
 2665           int srcCount;
 2666           for (int i = firstLower; i < count; i += srcCount) {
 2667               srcChar = (int)value[offset+i];
 2668               if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
 2669                   (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
 2670                   srcChar = codePointAt(i);
 2671                   srcCount = Character.charCount(srcChar);
 2672               } else {
 2673                   srcCount = 1;
 2674               }
 2675               if (localeDependent) {
 2676                   upperChar = ConditionalSpecialCasing.toUpperCaseEx(this, i, locale);
 2677               } else {
 2678                   upperChar = Character.toUpperCaseEx(srcChar);
 2679               }
 2680               if ((upperChar == Character.ERROR) ||
 2681                   (upperChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
 2682                   if (upperChar == Character.ERROR) {
 2683                       if (localeDependent) {
 2684                           upperCharArray =
 2685                               ConditionalSpecialCasing.toUpperCaseCharArray(this, i, locale);
 2686                       } else {
 2687                           upperCharArray = Character.toUpperCaseCharArray(srcChar);
 2688                       }
 2689                   } else if (srcCount == 2) {
 2690                       resultOffset += Character.toChars(upperChar, result, i + resultOffset) - srcCount;
 2691                       continue;
 2692                   } else {
 2693                       upperCharArray = Character.toChars(upperChar);
 2694                   }
 2695   
 2696                   /* Grow result if needed */
 2697                   int mapLen = upperCharArray.length;
 2698                   if (mapLen > srcCount) {
 2699                       char[] result2 = new char[result.length + mapLen - srcCount];
 2700                       System.arraycopy(result, 0, result2, 0,
 2701                           i + resultOffset);
 2702                       result = result2;
 2703                   }
 2704                   for (int x=0; x<mapLen; ++x) {
 2705                       result[i+resultOffset+x] = upperCharArray[x];
 2706                   }
 2707                   resultOffset += (mapLen - srcCount);
 2708               } else {
 2709                   result[i+resultOffset] = (char)upperChar;
 2710               }
 2711           }
 2712           return new String(0, count+resultOffset, result);
 2713       }
 2714   
 2715       /**
 2716        * Converts all of the characters in this <code>String</code> to upper
 2717        * case using the rules of the default locale. This method is equivalent to
 2718        * <code>toUpperCase(Locale.getDefault())</code>.
 2719        * <p>
 2720        * <b>Note:</b> This method is locale sensitive, and may produce unexpected
 2721        * results if used for strings that are intended to be interpreted locale
 2722        * independently.
 2723        * Examples are programming language identifiers, protocol keys, and HTML
 2724        * tags.
 2725        * For instance, <code>"title".toUpperCase()</code> in a Turkish locale
 2726        * returns <code>"T\u005Cu0130TLE"</code>, where '\u005Cu0130' is the
 2727        * LATIN CAPITAL LETTER I WITH DOT ABOVE character.
 2728        * To obtain correct results for locale insensitive strings, use
 2729        * <code>toUpperCase(Locale.ENGLISH)</code>.
 2730        * <p>
 2731        * @return  the <code>String</code>, converted to uppercase.
 2732        * @see     java.lang.String#toUpperCase(Locale)
 2733        */
 2734       public String toUpperCase() {
 2735           return toUpperCase(Locale.getDefault());
 2736       }
 2737   
 2738       /**
 2739        * Returns a copy of the string, with leading and trailing whitespace
 2740        * omitted.
 2741        * <p>
 2742        * If this <code>String</code> object represents an empty character
 2743        * sequence, or the first and last characters of character sequence
 2744        * represented by this <code>String</code> object both have codes
 2745        * greater than <code>'&#92;u0020'</code> (the space character), then a
 2746        * reference to this <code>String</code> object is returned.
 2747        * <p>
 2748        * Otherwise, if there is no character with a code greater than
 2749        * <code>'&#92;u0020'</code> in the string, then a new
 2750        * <code>String</code> object representing an empty string is created
 2751        * and returned.
 2752        * <p>
 2753        * Otherwise, let <i>k</i> be the index of the first character in the
 2754        * string whose code is greater than <code>'&#92;u0020'</code>, and let
 2755        * <i>m</i> be the index of the last character in the string whose code
 2756        * is greater than <code>'&#92;u0020'</code>. A new <code>String</code>
 2757        * object is created, representing the substring of this string that
 2758        * begins with the character at index <i>k</i> and ends with the
 2759        * character at index <i>m</i>-that is, the result of
 2760        * <code>this.substring(<i>k</i>,&nbsp;<i>m</i>+1)</code>.
 2761        * <p>
 2762        * This method may be used to trim whitespace (as defined above) from
 2763        * the beginning and end of a string.
 2764        *
 2765        * @return  A copy of this string with leading and trailing white
 2766        *          space removed, or this string if it has no leading or
 2767        *          trailing white space.
 2768        */
 2769       public String trim() {
 2770           int len = count;
 2771           int st = 0;
 2772           int off = offset;      /* avoid getfield opcode */
 2773           char[] val = value;    /* avoid getfield opcode */
 2774   
 2775           while ((st < len) && (val[off + st] <= ' ')) {
 2776               st++;
 2777           }
 2778           while ((st < len) && (val[off + len - 1] <= ' ')) {
 2779               len--;
 2780           }
 2781           return ((st > 0) || (len < count)) ? substring(st, len) : this;
 2782       }
 2783   
 2784       /**
 2785        * This object (which is already a string!) is itself returned.
 2786        *
 2787        * @return  the string itself.
 2788        */
 2789       public String toString() {
 2790           return this;
 2791       }
 2792   
 2793       /**
 2794        * Converts this string to a new character array.
 2795        *
 2796        * @return  a newly allocated character array whose length is the length
 2797        *          of this string and whose contents are initialized to contain
 2798        *          the character sequence represented by this string.
 2799        */
 2800       public char[] toCharArray() {
 2801           char result[] = new char[count];
 2802           getChars(0, count, result, 0);
 2803           return result;
 2804       }
 2805   
 2806       /**
 2807        * Returns a formatted string using the specified format string and
 2808        * arguments.
 2809        *
 2810        * <p> The locale always used is the one returned by {@link
 2811        * java.util.Locale#getDefault() Locale.getDefault()}.
 2812        *
 2813        * @param  format
 2814        *         A <a href="../util/Formatter.html#syntax">format string</a>
 2815        *
 2816        * @param  args
 2817        *         Arguments referenced by the format specifiers in the format
 2818        *         string.  If there are more arguments than format specifiers, the
 2819        *         extra arguments are ignored.  The number of arguments is
 2820        *         variable and may be zero.  The maximum number of arguments is
 2821        *         limited by the maximum dimension of a Java array as defined by
 2822        *         <cite>The Java&trade; Virtual Machine Specification</cite>.
 2823        *         The behaviour on a
 2824        *         <tt>null</tt> argument depends on the <a
 2825        *         href="../util/Formatter.html#syntax">conversion</a>.
 2826        *
 2827        * @throws  IllegalFormatException
 2828        *          If a format string contains an illegal syntax, a format
 2829        *          specifier that is incompatible with the given arguments,
 2830        *          insufficient arguments given the format string, or other
 2831        *          illegal conditions.  For specification of all possible
 2832        *          formatting errors, see the <a
 2833        *          href="../util/Formatter.html#detail">Details</a> section of the
 2834        *          formatter class specification.
 2835        *
 2836        * @throws  NullPointerException
 2837        *          If the <tt>format</tt> is <tt>null</tt>
 2838        *
 2839        * @return  A formatted string
 2840        *
 2841        * @see  java.util.Formatter
 2842        * @since  1.5
 2843        */
 2844       public static String format(String format, Object ... args) {
 2845           return new Formatter().format(format, args).toString();
 2846       }
 2847   
 2848       /**
 2849        * Returns a formatted string using the specified locale, format string,
 2850        * and arguments.
 2851        *
 2852        * @param  l
 2853        *         The {@linkplain java.util.Locale locale} to apply during
 2854        *         formatting.  If <tt>l</tt> is <tt>null</tt> then no localization
 2855        *         is applied.
 2856        *
 2857        * @param  format
 2858        *         A <a href="../util/Formatter.html#syntax">format string</a>
 2859        *
 2860        * @param  args
 2861        *         Arguments referenced by the format specifiers in the format
 2862        *         string.  If there are more arguments than format specifiers, the
 2863        *         extra arguments are ignored.  The number of arguments is
 2864        *         variable and may be zero.  The maximum number of arguments is
 2865        *         limited by the maximum dimension of a Java array as defined by
 2866        *         <cite>The Java&trade; Virtual Machine Specification</cite>.
 2867        *         The behaviour on a
 2868        *         <tt>null</tt> argument depends on the <a
 2869        *         href="../util/Formatter.html#syntax">conversion</a>.
 2870        *
 2871        * @throws  IllegalFormatException
 2872        *          If a format string contains an illegal syntax, a format
 2873        *          specifier that is incompatible with the given arguments,
 2874        *          insufficient arguments given the format string, or other
 2875        *          illegal conditions.  For specification of all possible
 2876        *          formatting errors, see the <a
 2877        *          href="../util/Formatter.html#detail">Details</a> section of the
 2878        *          formatter class specification
 2879        *
 2880        * @throws  NullPointerException
 2881        *          If the <tt>format</tt> is <tt>null</tt>
 2882        *
 2883        * @return  A formatted string
 2884        *
 2885        * @see  java.util.Formatter
 2886        * @since  1.5
 2887        */
 2888       public static String format(Locale l, String format, Object ... args) {
 2889           return new Formatter(l).format(format, args).toString();
 2890       }
 2891   
 2892       /**
 2893        * Returns the string representation of the <code>Object</code> argument.
 2894        *
 2895        * @param   obj   an <code>Object</code>.
 2896        * @return  if the argument is <code>null</code>, then a string equal to
 2897        *          <code>"null"</code>; otherwise, the value of
 2898        *          <code>obj.toString()</code> is returned.
 2899        * @see     java.lang.Object#toString()
 2900        */
 2901       public static String valueOf(Object obj) {
 2902           return (obj == null) ? "null" : obj.toString();
 2903       }
 2904   
 2905       /**
 2906        * Returns the string representation of the <code>char</code> array
 2907        * argument. The contents of the character array are copied; subsequent
 2908        * modification of the character array does not affect the newly
 2909        * created string.
 2910        *
 2911        * @param   data   a <code>char</code> array.
 2912        * @return  a newly allocated string representing the same sequence of
 2913        *          characters contained in the character array argument.
 2914        */
 2915       public static String valueOf(char data[]) {
 2916           return new String(data);
 2917       }
 2918   
 2919       /**
 2920        * Returns the string representation of a specific subarray of the
 2921        * <code>char</code> array argument.
 2922        * <p>
 2923        * The <code>offset</code> argument is the index of the first
 2924        * character of the subarray. The <code>count</code> argument
 2925        * specifies the length of the subarray. The contents of the subarray
 2926        * are copied; subsequent modification of the character array does not
 2927        * affect the newly created string.
 2928        *
 2929        * @param   data     the character array.
 2930        * @param   offset   the initial offset into the value of the
 2931        *                  <code>String</code>.
 2932        * @param   count    the length of the value of the <code>String</code>.
 2933        * @return  a string representing the sequence of characters contained
 2934        *          in the subarray of the character array argument.
 2935        * @exception IndexOutOfBoundsException if <code>offset</code> is
 2936        *          negative, or <code>count</code> is negative, or
 2937        *          <code>offset+count</code> is larger than
 2938        *          <code>data.length</code>.
 2939        */
 2940       public static String valueOf(char data[], int offset, int count) {
 2941           return new String(data, offset, count);
 2942       }
 2943   
 2944       /**
 2945        * Returns a String that represents the character sequence in the
 2946        * array specified.
 2947        *
 2948        * @param   data     the character array.
 2949        * @param   offset   initial offset of the subarray.
 2950        * @param   count    length of the subarray.
 2951        * @return  a <code>String</code> that contains the characters of the
 2952        *          specified subarray of the character array.
 2953        */
 2954       public static String copyValueOf(char data[], int offset, int count) {
 2955           // All public String constructors now copy the data.
 2956           return new String(data, offset, count);
 2957       }
 2958   
 2959       /**
 2960        * Returns a String that represents the character sequence in the
 2961        * array specified.
 2962        *
 2963        * @param   data   the character array.
 2964        * @return  a <code>String</code> that contains the characters of the
 2965        *          character array.
 2966        */
 2967       public static String copyValueOf(char data[]) {
 2968           return copyValueOf(data, 0, data.length);
 2969       }
 2970   
 2971       /**
 2972        * Returns the string representation of the <code>boolean</code> argument.
 2973        *
 2974        * @param   b   a <code>boolean</code>.
 2975        * @return  if the argument is <code>true</code>, a string equal to
 2976        *          <code>"true"</code> is returned; otherwise, a string equal to
 2977        *          <code>"false"</code> is returned.
 2978        */
 2979       public static String valueOf(boolean b) {
 2980           return b ? "true" : "false";
 2981       }
 2982   
 2983       /**
 2984        * Returns the string representation of the <code>char</code>
 2985        * argument.
 2986        *
 2987        * @param   c   a <code>char</code>.
 2988        * @return  a string of length <code>1</code> containing
 2989        *          as its single character the argument <code>c</code>.
 2990        */
 2991       public static String valueOf(char c) {
 2992           char data[] = {c};
 2993           return new String(0, 1, data);
 2994       }
 2995   
 2996       /**
 2997        * Returns the string representation of the <code>int</code> argument.
 2998        * <p>
 2999        * The representation is exactly the one returned by the
 3000        * <code>Integer.toString</code> method of one argument.
 3001        *
 3002        * @param   i   an <code>int</code>.
 3003        * @return  a string representation of the <code>int</code> argument.
 3004        * @see     java.lang.Integer#toString(int, int)
 3005        */
 3006       public static String valueOf(int i) {
 3007           return Integer.toString(i);
 3008       }
 3009   
 3010       /**
 3011        * Returns the string representation of the <code>long</code> argument.
 3012        * <p>
 3013        * The representation is exactly the one returned by the
 3014        * <code>Long.toString</code> method of one argument.
 3015        *
 3016        * @param   l   a <code>long</code>.
 3017        * @return  a string representation of the <code>long</code> argument.
 3018        * @see     java.lang.Long#toString(long)
 3019        */
 3020       public static String valueOf(long l) {
 3021           return Long.toString(l);
 3022       }
 3023   
 3024       /**
 3025        * Returns the string representation of the <code>float</code> argument.
 3026        * <p>
 3027        * The representation is exactly the one returned by the
 3028        * <code>Float.toString</code> method of one argument.
 3029        *
 3030        * @param   f   a <code>float</code>.
 3031        * @return  a string representation of the <code>float</code> argument.
 3032        * @see     java.lang.Float#toString(float)
 3033        */
 3034       public static String valueOf(float f) {
 3035           return Float.toString(f);
 3036       }
 3037   
 3038       /**
 3039        * Returns the string representation of the <code>double</code> argument.
 3040        * <p>
 3041        * The representation is exactly the one returned by the
 3042        * <code>Double.toString</code> method of one argument.
 3043        *
 3044        * @param   d   a <code>double</code>.
 3045        * @return  a  string representation of the <code>double</code> argument.
 3046        * @see     java.lang.Double#toString(double)
 3047        */
 3048       public static String valueOf(double d) {
 3049           return Double.toString(d);
 3050       }
 3051   
 3052       /**
 3053        * Returns a canonical representation for the string object.
 3054        * <p>
 3055        * A pool of strings, initially empty, is maintained privately by the
 3056        * class <code>String</code>.
 3057        * <p>
 3058        * When the intern method is invoked, if the pool already contains a
 3059        * string equal to this <code>String</code> object as determined by
 3060        * the {@link #equals(Object)} method, then the string from the pool is
 3061        * returned. Otherwise, this <code>String</code> object is added to the
 3062        * pool and a reference to this <code>String</code> object is returned.
 3063        * <p>
 3064        * It follows that for any two strings <code>s</code> and <code>t</code>,
 3065        * <code>s.intern()&nbsp;==&nbsp;t.intern()</code> is <code>true</code>
 3066        * if and only if <code>s.equals(t)</code> is <code>true</code>.
 3067        * <p>
 3068        * All literal strings and string-valued constant expressions are
 3069        * interned. String literals are defined in section 3.10.5 of the
 3070        * <cite>The Java&trade; Language Specification</cite>.
 3071        *
 3072        * @return  a string that has the same contents as this string, but is
 3073        *          guaranteed to be from a pool of unique strings.
 3074        */
 3075       public native String intern();
 3076   
 3077   }

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