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1   /*
2    * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23   * questions.
24   */
25  
26  package java.lang;
27  
28  import java.io.ObjectStreamField;
29  import java.io.UnsupportedEncodingException;
30  import java.nio.charset.Charset;
31  import java.util.ArrayList;
32  import java.util.Arrays;
33  import java.util.Comparator;
34  import java.util.Formatter;
35  import java.util.Locale;
36  import java.util.Objects;
37  import java.util.StringJoiner;
38  import java.util.regex.Matcher;
39  import java.util.regex.Pattern;
40  import java.util.regex.PatternSyntaxException;
41  
42  /**
43   * The {@code String} class represents character strings. All
44   * string literals in Java programs, such as {@code "abc"}, are
45   * implemented as instances of this class.
46   * <p>
47   * Strings are constant; their values cannot be changed after they
48   * are created. String buffers support mutable strings.
49   * Because String objects are immutable they can be shared. For example:
50   * <blockquote><pre>
51   *     String str = "abc";
52   * </pre></blockquote><p>
53   * is equivalent to:
54   * <blockquote><pre>
55   *     char data[] = {'a', 'b', 'c'};
56   *     String str = new String(data);
57   * </pre></blockquote><p>
58   * Here are some more examples of how strings can be used:
59   * <blockquote><pre>
60   *     System.out.println("abc");
61   *     String cde = "cde";
62   *     System.out.println("abc" + cde);
63   *     String c = "abc".substring(2,3);
64   *     String d = cde.substring(1, 2);
65   * </pre></blockquote>
66   * <p>
67   * The class {@code String} includes methods for examining
68   * individual characters of the sequence, for comparing strings, for
69   * searching strings, for extracting substrings, and for creating a
70   * copy of a string with all characters translated to uppercase or to
71   * lowercase. Case mapping is based on the Unicode Standard version
72   * specified by the {@link java.lang.Character Character} class.
73   * <p>
74   * The Java language provides special support for the string
75   * concatenation operator (&nbsp;+&nbsp;), and for conversion of
76   * other objects to strings. String concatenation is implemented
77   * through the {@code StringBuilder}(or {@code StringBuffer})
78   * class and its {@code append} method.
79   * String conversions are implemented through the method
80   * {@code toString}, defined by {@code Object} and
81   * inherited by all classes in Java. For additional information on
82   * string concatenation and conversion, see Gosling, Joy, and Steele,
83   * <i>The Java Language Specification</i>.
84   *
85   * <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
86   * or method in this class will cause a {@link NullPointerException} to be
87   * thrown.
88   *
89   * <p>A {@code String} represents a string in the UTF-16 format
90   * in which <em>supplementary characters</em> are represented by <em>surrogate
91   * pairs</em> (see the section <a href="Character.html#unicode">Unicode
92   * Character Representations</a> in the {@code Character} class for
93   * more information).
94   * Index values refer to {@code char} code units, so a supplementary
95   * character uses two positions in a {@code String}.
96   * <p>The {@code String} class provides methods for dealing with
97   * Unicode code points (i.e., characters), in addition to those for
98   * dealing with Unicode code units (i.e., {@code char} values).
99   *
100  * @author  Lee Boynton
101  * @author  Arthur van Hoff
102  * @author  Martin Buchholz
103  * @author  Ulf Zibis
104  * @see     java.lang.Object#toString()
105  * @see     java.lang.StringBuffer
106  * @see     java.lang.StringBuilder
107  * @see     java.nio.charset.Charset
108  * @since   JDK1.0
109  */
110 
111 public final class String
112     implements java.io.Serializable, Comparable<String>, CharSequence {
113     /** The value is used for character storage. */
114     private final char value[];
115 
116     /** Cache the hash code for the string */
117     private int hash; // Default to 0
118 
119     /** use serialVersionUID from JDK 1.0.2 for interoperability */
120     private static final long serialVersionUID = -6849794470754667710L;
121 
122     /**
123      * Class String is special cased within the Serialization Stream Protocol.
124      *
125      * A String instance is written into an ObjectOutputStream according to
126      * <a href="{@docRoot}/../platform/serialization/spec/output.html">
127      * Object Serialization Specification, Section 6.2, "Stream Elements"</a>
128      */
129     private static final ObjectStreamField[] serialPersistentFields =
130         new ObjectStreamField[0];
131 
132     /**
133      * Initializes a newly created {@code String} object so that it represents
134      * an empty character sequence.  Note that use of this constructor is
135      * unnecessary since Strings are immutable.
136      */
137     public String() {
138         this.value = new char[0];
139     }
140 
141     /**
142      * Initializes a newly created {@code String} object so that it represents
143      * the same sequence of characters as the argument; in other words, the
144      * newly created string is a copy of the argument string. Unless an
145      * explicit copy of {@code original} is needed, use of this constructor is
146      * unnecessary since Strings are immutable.
147      *
148      * @param  original
149      *         A {@code String}
150      */
151     public String(String original) {
152         this.value = original.value;
153         this.hash = original.hash;
154     }
155 
156     /**
157      * Allocates a new {@code String} so that it represents the sequence of
158      * characters currently contained in the character array argument. The
159      * contents of the character array are copied; subsequent modification of
160      * the character array does not affect the newly created string.
161      *
162      * @param  value
163      *         The initial value of the string
164      */
165     public String(char value[]) {
166         this.value = Arrays.copyOf(value, value.length);
167     }
168 
169     /**
170      * Allocates a new {@code String} that contains characters from a subarray
171      * of the character array argument. The {@code offset} argument is the
172      * index of the first character of the subarray and the {@code count}
173      * argument specifies the length of the subarray. The contents of the
174      * subarray are copied; subsequent modification of the character array does
175      * not affect the newly created string.
176      *
177      * @param  value
178      *         Array that is the source of characters
179      *
180      * @param  offset
181      *         The initial offset
182      *
183      * @param  count
184      *         The length
185      *
186      * @throws  IndexOutOfBoundsException
187      *          If the {@code offset} and {@code count} arguments index
188      *          characters outside the bounds of the {@code value} array
189      */
190     public String(char value[], int offset, int count) {
191         if (offset < 0) {
192             throw new StringIndexOutOfBoundsException(offset);
193         }
194         if (count < 0) {
195             throw new StringIndexOutOfBoundsException(count);
196         }
197         // Note: offset or count might be near -1>>>1.
198         if (offset > value.length - count) {
199             throw new StringIndexOutOfBoundsException(offset + count);
200         }
201         this.value = Arrays.copyOfRange(value, offset, offset+count);
202     }
203 
204     /**
205      * Allocates a new {@code String} that contains characters from a subarray
206      * of the <a href="Character.html#unicode">Unicode code point</a> array
207      * argument.  The {@code offset} argument is the index of the first code
208      * point of the subarray and the {@code count} argument specifies the
209      * length of the subarray.  The contents of the subarray are converted to
210      * {@code char}s; subsequent modification of the {@code int} array does not
211      * affect the newly created string.
212      *
213      * @param  codePoints
214      *         Array that is the source of Unicode code points
215      *
216      * @param  offset
217      *         The initial offset
218      *
219      * @param  count
220      *         The length
221      *
222      * @throws  IllegalArgumentException
223      *          If any invalid Unicode code point is found in {@code
224      *          codePoints}
225      *
226      * @throws  IndexOutOfBoundsException
227      *          If the {@code offset} and {@code count} arguments index
228      *          characters outside the bounds of the {@code codePoints} array
229      *
230      * @since  1.5
231      */
232     public String(int[] codePoints, int offset, int count) {
233         if (offset < 0) {
234             throw new StringIndexOutOfBoundsException(offset);
235         }
236         if (count < 0) {
237             throw new StringIndexOutOfBoundsException(count);
238         }
239         // Note: offset or count might be near -1>>>1.
240         if (offset > codePoints.length - count) {
241             throw new StringIndexOutOfBoundsException(offset + count);
242         }
243 
244         final int end = offset + count;
245 
246         // Pass 1: Compute precise size of char[]
247         int n = count;
248         for (int i = offset; i < end; i++) {
249             int c = codePoints[i];
250             if (Character.isBmpCodePoint(c))
251                 continue;
252             else if (Character.isValidCodePoint(c))
253                 n++;
254             else throw new IllegalArgumentException(Integer.toString(c));
255         }
256 
257         // Pass 2: Allocate and fill in char[]
258         final char[] v = new char[n];
259 
260         for (int i = offset, j = 0; i < end; i++, j++) {
261             int c = codePoints[i];
262             if (Character.isBmpCodePoint(c))
263                 v[j] = (char)c;
264             else
265                 Character.toSurrogates(c, v, j++);
266         }
267 
268         this.value = v;
269     }
270 
271     /**
272      * Allocates a new {@code String} constructed from a subarray of an array
273      * of 8-bit integer values.
274      *
275      * <p> The {@code offset} argument is the index of the first byte of the
276      * subarray, and the {@code count} argument specifies the length of the
277      * subarray.
278      *
279      * <p> Each {@code byte} in the subarray is converted to a {@code char} as
280      * specified in the method above.
281      *
282      * @deprecated This method does not properly convert bytes into characters.
283      * As of JDK&nbsp;1.1, the preferred way to do this is via the
284      * {@code String} constructors that take a {@link
285      * java.nio.charset.Charset}, charset name, or that use the platform's
286      * default charset.
287      *
288      * @param  ascii
289      *         The bytes to be converted to characters
290      *
291      * @param  hibyte
292      *         The top 8 bits of each 16-bit Unicode code unit
293      *
294      * @param  offset
295      *         The initial offset
296      * @param  count
297      *         The length
298      *
299      * @throws  IndexOutOfBoundsException
300      *          If the {@code offset} or {@code count} argument is invalid
301      *
302      * @see  #String(byte[], int)
303      * @see  #String(byte[], int, int, java.lang.String)
304      * @see  #String(byte[], int, int, java.nio.charset.Charset)
305      * @see  #String(byte[], int, int)
306      * @see  #String(byte[], java.lang.String)
307      * @see  #String(byte[], java.nio.charset.Charset)
308      * @see  #String(byte[])
309      */
310     @Deprecated
311     public String(byte ascii[], int hibyte, int offset, int count) {
312         checkBounds(ascii, offset, count);
313         char value[] = new char[count];
314 
315         if (hibyte == 0) {
316             for (int i = count; i-- > 0;) {
317                 value[i] = (char)(ascii[i + offset] & 0xff);
318             }
319         } else {
320             hibyte <<= 8;
321             for (int i = count; i-- > 0;) {
322                 value[i] = (char)(hibyte | (ascii[i + offset] & 0xff));
323             }
324         }
325         this.value = value;
326     }
327 
328     /**
329      * Allocates a new {@code String} containing characters constructed from
330      * an array of 8-bit integer values. Each character <i>c</i>in the
331      * resulting string is constructed from the corresponding component
332      * <i>b</i> in the byte array such that:
333      *
334      * <blockquote><pre>
335      *     <b><i>c</i></b> == (char)(((hibyte &amp; 0xff) &lt;&lt; 8)
336      *                         | (<b><i>b</i></b> &amp; 0xff))
337      * </pre></blockquote>
338      *
339      * @deprecated  This method does not properly convert bytes into
340      * characters.  As of JDK&nbsp;1.1, the preferred way to do this is via the
341      * {@code String} constructors that take a {@link
342      * java.nio.charset.Charset}, charset name, or that use the platform's
343      * default charset.
344      *
345      * @param  ascii
346      *         The bytes to be converted to characters
347      *
348      * @param  hibyte
349      *         The top 8 bits of each 16-bit Unicode code unit
350      *
351      * @see  #String(byte[], int, int, java.lang.String)
352      * @see  #String(byte[], int, int, java.nio.charset.Charset)
353      * @see  #String(byte[], int, int)
354      * @see  #String(byte[], java.lang.String)
355      * @see  #String(byte[], java.nio.charset.Charset)
356      * @see  #String(byte[])
357      */
358     @Deprecated
359     public String(byte ascii[], int hibyte) {
360         this(ascii, hibyte, 0, ascii.length);
361     }
362 
363     /* Common private utility method used to bounds check the byte array
364      * and requested offset & length values used by the String(byte[],..)
365      * constructors.
366      */
367     private static void checkBounds(byte[] bytes, int offset, int length) {
368         if (length < 0)
369             throw new StringIndexOutOfBoundsException(length);
370         if (offset < 0)
371             throw new StringIndexOutOfBoundsException(offset);
372         if (offset > bytes.length - length)
373             throw new StringIndexOutOfBoundsException(offset + length);
374     }
375 
376     /**
377      * Constructs a new {@code String} by decoding the specified subarray of
378      * bytes using the specified charset.  The length of the new {@code String}
379      * is a function of the charset, and hence may not be equal to the length
380      * of the subarray.
381      *
382      * <p> The behavior of this constructor when the given bytes are not valid
383      * in the given charset is unspecified.  The {@link
384      * java.nio.charset.CharsetDecoder} class should be used when more control
385      * over the decoding process is required.
386      *
387      * @param  bytes
388      *         The bytes to be decoded into characters
389      *
390      * @param  offset
391      *         The index of the first byte to decode
392      *
393      * @param  length
394      *         The number of bytes to decode
395 
396      * @param  charsetName
397      *         The name of a supported {@linkplain java.nio.charset.Charset
398      *         charset}
399      *
400      * @throws  UnsupportedEncodingException
401      *          If the named charset is not supported
402      *
403      * @throws  IndexOutOfBoundsException
404      *          If the {@code offset} and {@code length} arguments index
405      *          characters outside the bounds of the {@code bytes} array
406      *
407      * @since  JDK1.1
408      */
409     public String(byte bytes[], int offset, int length, String charsetName)
410             throws UnsupportedEncodingException {
411         if (charsetName == null)
412             throw new NullPointerException("charsetName");
413         checkBounds(bytes, offset, length);
414         this.value = StringCoding.decode(charsetName, bytes, offset, length);
415     }
416 
417     /**
418      * Constructs a new {@code String} by decoding the specified subarray of
419      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
420      * The length of the new {@code String} is a function of the charset, and
421      * hence may not be equal to the length of the subarray.
422      *
423      * <p> This method always replaces malformed-input and unmappable-character
424      * sequences with this charset's default replacement string.  The {@link
425      * java.nio.charset.CharsetDecoder} class should be used when more control
426      * over the decoding process is required.
427      *
428      * @param  bytes
429      *         The bytes to be decoded into characters
430      *
431      * @param  offset
432      *         The index of the first byte to decode
433      *
434      * @param  length
435      *         The number of bytes to decode
436      *
437      * @param  charset
438      *         The {@linkplain java.nio.charset.Charset charset} to be used to
439      *         decode the {@code bytes}
440      *
441      * @throws  IndexOutOfBoundsException
442      *          If the {@code offset} and {@code length} arguments index
443      *          characters outside the bounds of the {@code bytes} array
444      *
445      * @since  1.6
446      */
447     public String(byte bytes[], int offset, int length, Charset charset) {
448         if (charset == null)
449             throw new NullPointerException("charset");
450         checkBounds(bytes, offset, length);
451         this.value =  StringCoding.decode(charset, bytes, offset, length);
452     }
453 
454     /**
455      * Constructs a new {@code String} by decoding the specified array of bytes
456      * using the specified {@linkplain java.nio.charset.Charset charset}.  The
457      * length of the new {@code String} is a function of the charset, and hence
458      * may not be equal to the length of the byte array.
459      *
460      * <p> The behavior of this constructor when the given bytes are not valid
461      * in the given charset is unspecified.  The {@link
462      * java.nio.charset.CharsetDecoder} class should be used when more control
463      * over the decoding process is required.
464      *
465      * @param  bytes
466      *         The bytes to be decoded into characters
467      *
468      * @param  charsetName
469      *         The name of a supported {@linkplain java.nio.charset.Charset
470      *         charset}
471      *
472      * @throws  UnsupportedEncodingException
473      *          If the named charset is not supported
474      *
475      * @since  JDK1.1
476      */
477     public String(byte bytes[], String charsetName)
478             throws UnsupportedEncodingException {
479         this(bytes, 0, bytes.length, charsetName);
480     }
481 
482     /**
483      * Constructs a new {@code String} by decoding the specified array of
484      * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
485      * The length of the new {@code String} is a function of the charset, and
486      * hence may not be equal to the length of the byte array.
487      *
488      * <p> This method always replaces malformed-input and unmappable-character
489      * sequences with this charset's default replacement string.  The {@link
490      * java.nio.charset.CharsetDecoder} class should be used when more control
491      * over the decoding process is required.
492      *
493      * @param  bytes
494      *         The bytes to be decoded into characters
495      *
496      * @param  charset
497      *         The {@linkplain java.nio.charset.Charset charset} to be used to
498      *         decode the {@code bytes}
499      *
500      * @since  1.6
501      */
502     public String(byte bytes[], Charset charset) {
503         this(bytes, 0, bytes.length, charset);
504     }
505 
506     /**
507      * Constructs a new {@code String} by decoding the specified subarray of
508      * bytes using the platform's default charset.  The length of the new
509      * {@code String} is a function of the charset, and hence may not be equal
510      * to the length of the subarray.
511      *
512      * <p> The behavior of this constructor when the given bytes are not valid
513      * in the default charset is unspecified.  The {@link
514      * java.nio.charset.CharsetDecoder} class should be used when more control
515      * over the decoding process is required.
516      *
517      * @param  bytes
518      *         The bytes to be decoded into characters
519      *
520      * @param  offset
521      *         The index of the first byte to decode
522      *
523      * @param  length
524      *         The number of bytes to decode
525      *
526      * @throws  IndexOutOfBoundsException
527      *          If the {@code offset} and the {@code length} arguments index
528      *          characters outside the bounds of the {@code bytes} array
529      *
530      * @since  JDK1.1
531      */
532     public String(byte bytes[], int offset, int length) {
533         checkBounds(bytes, offset, length);
534         this.value = StringCoding.decode(bytes, offset, length);
535     }
536 
537     /**
538      * Constructs a new {@code String} by decoding the specified array of bytes
539      * using the platform's default charset.  The length of the new {@code
540      * String} is a function of the charset, and hence may not be equal to the
541      * length of the byte array.
542      *
543      * <p> The behavior of this constructor when the given bytes are not valid
544      * in the default charset is unspecified.  The {@link
545      * java.nio.charset.CharsetDecoder} class should be used when more control
546      * over the decoding process is required.
547      *
548      * @param  bytes
549      *         The bytes to be decoded into characters
550      *
551      * @since  JDK1.1
552      */
553     public String(byte bytes[]) {
554         this(bytes, 0, bytes.length);
555     }
556 
557     /**
558      * Allocates a new string that contains the sequence of characters
559      * currently contained in the string buffer argument. The contents of the
560      * string buffer are copied; subsequent modification of the string buffer
561      * does not affect the newly created string.
562      *
563      * @param  buffer
564      *         A {@code StringBuffer}
565      */
566     public String(StringBuffer buffer) {
567         synchronized(buffer) {
568             this.value = Arrays.copyOf(buffer.getValue(), buffer.length());
569         }
570     }
571 
572     /**
573      * Allocates a new string that contains the sequence of characters
574      * currently contained in the string builder argument. The contents of the
575      * string builder are copied; subsequent modification of the string builder
576      * does not affect the newly created string.
577      *
578      * <p> This constructor is provided to ease migration to {@code
579      * StringBuilder}. Obtaining a string from a string builder via the {@code
580      * toString} method is likely to run faster and is generally preferred.
581      *
582      * @param   builder
583      *          A {@code StringBuilder}
584      *
585      * @since  1.5
586      */
587     public String(StringBuilder builder) {
588         this.value = Arrays.copyOf(builder.getValue(), builder.length());
589     }
590 
591     /*
592     * Package private constructor which shares value array for speed.
593     * this constructor is always expected to be called with share==true.
594     * a separate constructor is needed because we already have a public
595     * String(char[]) constructor that makes a copy of the given char[].
596     */
597     String(char[] value, boolean share) {
598         // assert share : "unshared not supported";
599         this.value = value;
600     }
601 
602     /**
603      * Returns the length of this string.
604      * The length is equal to the number of <a href="Character.html#unicode">Unicode
605      * code units</a> in the string.
606      *
607      * @return  the length of the sequence of characters represented by this
608      *          object.
609      */
610     public int length() {
611         return value.length;
612     }
613 
614     /**
615      * Returns {@code true} if, and only if, {@link #length()} is {@code 0}.
616      *
617      * @return {@code true} if {@link #length()} is {@code 0}, otherwise
618      * {@code false}
619      *
620      * @since 1.6
621      */
622     public boolean isEmpty() {
623         return value.length == 0;
624     }
625 
626     /**
627      * Returns the {@code char} value at the
628      * specified index. An index ranges from {@code 0} to
629      * {@code length() - 1}. The first {@code char} value of the sequence
630      * is at index {@code 0}, the next at index {@code 1},
631      * and so on, as for array indexing.
632      *
633      * <p>If the {@code char} value specified by the index is a
634      * <a href="Character.html#unicode">surrogate</a>, the surrogate
635      * value is returned.
636      *
637      * @param      index   the index of the {@code char} value.
638      * @return     the {@code char} value at the specified index of this string.
639      *             The first {@code char} value is at index {@code 0}.
640      * @exception  IndexOutOfBoundsException  if the {@code index}
641      *             argument is negative or not less than the length of this
642      *             string.
643      */
644     public char charAt(int index) {
645         if ((index < 0) || (index >= value.length)) {
646             throw new StringIndexOutOfBoundsException(index);
647         }
648         return value[index];
649     }
650 
651     /**
652      * Returns the character (Unicode code point) at the specified
653      * index. The index refers to {@code char} values
654      * (Unicode code units) and ranges from {@code 0} to
655      * {@link #length()}{@code  - 1}.
656      *
657      * <p> If the {@code char} value specified at the given index
658      * is in the high-surrogate range, the following index is less
659      * than the length of this {@code String}, and the
660      * {@code char} value at the following index is in the
661      * low-surrogate range, then the supplementary code point
662      * corresponding to this surrogate pair is returned. Otherwise,
663      * the {@code char} value at the given index is returned.
664      *
665      * @param      index the index to the {@code char} values
666      * @return     the code point value of the character at the
667      *             {@code index}
668      * @exception  IndexOutOfBoundsException  if the {@code index}
669      *             argument is negative or not less than the length of this
670      *             string.
671      * @since      1.5
672      */
673     public int codePointAt(int index) {
674         if ((index < 0) || (index >= value.length)) {
675             throw new StringIndexOutOfBoundsException(index);
676         }
677         return Character.codePointAtImpl(value, index, value.length);
678     }
679 
680     /**
681      * Returns the character (Unicode code point) before the specified
682      * index. The index refers to {@code char} values
683      * (Unicode code units) and ranges from {@code 1} to {@link
684      * CharSequence#length() length}.
685      *
686      * <p> If the {@code char} value at {@code (index - 1)}
687      * is in the low-surrogate range, {@code (index - 2)} is not
688      * negative, and the {@code char} value at {@code (index -
689      * 2)} is in the high-surrogate range, then the
690      * supplementary code point value of the surrogate pair is
691      * returned. If the {@code char} value at {@code index -
692      * 1} is an unpaired low-surrogate or a high-surrogate, the
693      * surrogate value is returned.
694      *
695      * @param     index the index following the code point that should be returned
696      * @return    the Unicode code point value before the given index.
697      * @exception IndexOutOfBoundsException if the {@code index}
698      *            argument is less than 1 or greater than the length
699      *            of this string.
700      * @since     1.5
701      */
702     public int codePointBefore(int index) {
703         int i = index - 1;
704         if ((i < 0) || (i >= value.length)) {
705             throw new StringIndexOutOfBoundsException(index);
706         }
707         return Character.codePointBeforeImpl(value, index, 0);
708     }
709 
710     /**
711      * Returns the number of Unicode code points in the specified text
712      * range of this {@code String}. The text range begins at the
713      * specified {@code beginIndex} and extends to the
714      * {@code char} at index {@code endIndex - 1}. Thus the
715      * length (in {@code char}s) of the text range is
716      * {@code endIndex-beginIndex}. Unpaired surrogates within
717      * the text range count as one code point each.
718      *
719      * @param beginIndex the index to the first {@code char} of
720      * the text range.
721      * @param endIndex the index after the last {@code char} of
722      * the text range.
723      * @return the number of Unicode code points in the specified text
724      * range
725      * @exception IndexOutOfBoundsException if the
726      * {@code beginIndex} is negative, or {@code endIndex}
727      * is larger than the length of this {@code String}, or
728      * {@code beginIndex} is larger than {@code endIndex}.
729      * @since  1.5
730      */
731     public int codePointCount(int beginIndex, int endIndex) {
732         if (beginIndex < 0 || endIndex > value.length || beginIndex > endIndex) {
733             throw new IndexOutOfBoundsException();
734         }
735         return Character.codePointCountImpl(value, beginIndex, endIndex - beginIndex);
736     }
737 
738     /**
739      * Returns the index within this {@code String} that is
740      * offset from the given {@code index} by
741      * {@code codePointOffset} code points. Unpaired surrogates
742      * within the text range given by {@code index} and
743      * {@code codePointOffset} count as one code point each.
744      *
745      * @param index the index to be offset
746      * @param codePointOffset the offset in code points
747      * @return the index within this {@code String}
748      * @exception IndexOutOfBoundsException if {@code index}
749      *   is negative or larger then the length of this
750      *   {@code String}, or if {@code codePointOffset} is positive
751      *   and the substring starting with {@code index} has fewer
752      *   than {@code codePointOffset} code points,
753      *   or if {@code codePointOffset} is negative and the substring
754      *   before {@code index} has fewer than the absolute value
755      *   of {@code codePointOffset} code points.
756      * @since 1.5
757      */
758     public int offsetByCodePoints(int index, int codePointOffset) {
759         if (index < 0 || index > value.length) {
760             throw new IndexOutOfBoundsException();
761         }
762         return Character.offsetByCodePointsImpl(value, 0, value.length,
763                 index, codePointOffset);
764     }
765 
766     /**
767      * Copy characters from this string into dst starting at dstBegin.
768      * This method doesn't perform any range checking.
769      */
770     void getChars(char dst[], int dstBegin) {
771         System.arraycopy(value, 0, dst, dstBegin, value.length);
772     }
773 
774     /**
775      * Copies characters from this string into the destination character
776      * array.
777      * <p>
778      * The first character to be copied is at index {@code srcBegin};
779      * the last character to be copied is at index {@code srcEnd-1}
780      * (thus the total number of characters to be copied is
781      * {@code srcEnd-srcBegin}). The characters are copied into the
782      * subarray of {@code dst} starting at index {@code dstBegin}
783      * and ending at index:
784      * <blockquote><pre>
785      *     dstbegin + (srcEnd-srcBegin) - 1
786      * </pre></blockquote>
787      *
788      * @param      srcBegin   index of the first character in the string
789      *                        to copy.
790      * @param      srcEnd     index after the last character in the string
791      *                        to copy.
792      * @param      dst        the destination array.
793      * @param      dstBegin   the start offset in the destination array.
794      * @exception IndexOutOfBoundsException If any of the following
795      *            is true:
796      *            <ul><li>{@code srcBegin} is negative.
797      *            <li>{@code srcBegin} is greater than {@code srcEnd}
798      *            <li>{@code srcEnd} is greater than the length of this
799      *                string
800      *            <li>{@code dstBegin} is negative
801      *            <li>{@code dstBegin+(srcEnd-srcBegin)} is larger than
802      *                {@code dst.length}</ul>
803      */
804     public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
805         if (srcBegin < 0) {
806             throw new StringIndexOutOfBoundsException(srcBegin);
807         }
808         if (srcEnd > value.length) {
809             throw new StringIndexOutOfBoundsException(srcEnd);
810         }
811         if (srcBegin > srcEnd) {
812             throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
813         }
814         System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
815     }
816 
817     /**
818      * Copies characters from this string into the destination byte array. Each
819      * byte receives the 8 low-order bits of the corresponding character. The
820      * eight high-order bits of each character are not copied and do not
821      * participate in the transfer in any way.
822      *
823      * <p> The first character to be copied is at index {@code srcBegin}; the
824      * last character to be copied is at index {@code srcEnd-1}.  The total
825      * number of characters to be copied is {@code srcEnd-srcBegin}. The
826      * characters, converted to bytes, are copied into the subarray of {@code
827      * dst} starting at index {@code dstBegin} and ending at index:
828      *
829      * <blockquote><pre>
830      *     dstbegin + (srcEnd-srcBegin) - 1
831      * </pre></blockquote>
832      *
833      * @deprecated  This method does not properly convert characters into
834      * bytes.  As of JDK&nbsp;1.1, the preferred way to do this is via the
835      * {@link #getBytes()} method, which uses the platform's default charset.
836      *
837      * @param  srcBegin
838      *         Index of the first character in the string to copy
839      *
840      * @param  srcEnd
841      *         Index after the last character in the string to copy
842      *
843      * @param  dst
844      *         The destination array
845      *
846      * @param  dstBegin
847      *         The start offset in the destination array
848      *
849      * @throws  IndexOutOfBoundsException
850      *          If any of the following is true:
851      *          <ul>
852      *            <li> {@code srcBegin} is negative
853      *            <li> {@code srcBegin} is greater than {@code srcEnd}
854      *            <li> {@code srcEnd} is greater than the length of this String
855      *            <li> {@code dstBegin} is negative
856      *            <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
857      *                 dst.length}
858      *          </ul>
859      */
860     @Deprecated
861     public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
862         if (srcBegin < 0) {
863             throw new StringIndexOutOfBoundsException(srcBegin);
864         }
865         if (srcEnd > value.length) {
866             throw new StringIndexOutOfBoundsException(srcEnd);
867         }
868         if (srcBegin > srcEnd) {
869             throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
870         }
871         Objects.requireNonNull(dst);
872 
873         int j = dstBegin;
874         int n = srcEnd;
875         int i = srcBegin;
876         char[] val = value;   /* avoid getfield opcode */
877 
878         while (i < n) {
879             dst[j++] = (byte)val[i++];
880         }
881     }
882 
883     /**
884      * Encodes this {@code String} into a sequence of bytes using the named
885      * charset, storing the result into a new byte array.
886      *
887      * <p> The behavior of this method when this string cannot be encoded in
888      * the given charset is unspecified.  The {@link
889      * java.nio.charset.CharsetEncoder} class should be used when more control
890      * over the encoding process is required.
891      *
892      * @param  charsetName
893      *         The name of a supported {@linkplain java.nio.charset.Charset
894      *         charset}
895      *
896      * @return  The resultant byte array
897      *
898      * @throws  UnsupportedEncodingException
899      *          If the named charset is not supported
900      *
901      * @since  JDK1.1
902      */
903     public byte[] getBytes(String charsetName)
904             throws UnsupportedEncodingException {
905         if (charsetName == null) throw new NullPointerException();
906         return StringCoding.encode(charsetName, value, 0, value.length);
907     }
908 
909     /**
910      * Encodes this {@code String} into a sequence of bytes using the given
911      * {@linkplain java.nio.charset.Charset charset}, storing the result into a
912      * new byte array.
913      *
914      * <p> This method always replaces malformed-input and unmappable-character
915      * sequences with this charset's default replacement byte array.  The
916      * {@link java.nio.charset.CharsetEncoder} class should be used when more
917      * control over the encoding process is required.
918      *
919      * @param  charset
920      *         The {@linkplain java.nio.charset.Charset} to be used to encode
921      *         the {@code String}
922      *
923      * @return  The resultant byte array
924      *
925      * @since  1.6
926      */
927     public byte[] getBytes(Charset charset) {
928         if (charset == null) throw new NullPointerException();
929         return StringCoding.encode(charset, value, 0, value.length);
930     }
931 
932     /**
933      * Encodes this {@code String} into a sequence of bytes using the
934      * platform's default charset, storing the result into a new byte array.
935      *
936      * <p> The behavior of this method when this string cannot be encoded in
937      * the default charset is unspecified.  The {@link
938      * java.nio.charset.CharsetEncoder} class should be used when more control
939      * over the encoding process is required.
940      *
941      * @return  The resultant byte array
942      *
943      * @since      JDK1.1
944      */
945     public byte[] getBytes() {
946         return StringCoding.encode(value, 0, value.length);
947     }
948 
949     /**
950      * Compares this string to the specified object.  The result is {@code
951      * true} if and only if the argument is not {@code null} and is a {@code
952      * String} object that represents the same sequence of characters as this
953      * object.
954      *
955      * @param  anObject
956      *         The object to compare this {@code String} against
957      *
958      * @return  {@code true} if the given object represents a {@code String}
959      *          equivalent to this string, {@code false} otherwise
960      *
961      * @see  #compareTo(String)
962      * @see  #equalsIgnoreCase(String)
963      */
964     public boolean equals(Object anObject) {
965         if (this == anObject) {
966             return true;
967         }
968         if (anObject instanceof String) {
969             String anotherString = (String)anObject;
970             int n = value.length;
971             if (n == anotherString.value.length) {
972                 char v1[] = value;
973                 char v2[] = anotherString.value;
974                 int i = 0;
975                 while (n-- != 0) {
976                     if (v1[i] != v2[i])
977                         return false;
978                     i++;
979                 }
980                 return true;
981             }
982         }
983         return false;
984     }
985 
986     /**
987      * Compares this string to the specified {@code StringBuffer}.  The result
988      * is {@code true} if and only if this {@code String} represents the same
989      * sequence of characters as the specified {@code StringBuffer}. This method
990      * synchronizes on the {@code StringBuffer}.
991      *
992      * @param  sb
993      *         The {@code StringBuffer} to compare this {@code String} against
994      *
995      * @return  {@code true} if this {@code String} represents the same
996      *          sequence of characters as the specified {@code StringBuffer},
997      *          {@code false} otherwise
998      *
999      * @since  1.4
1000      */
1001     public boolean contentEquals(StringBuffer sb) {
1002         return contentEquals((CharSequence)sb);
1003     }
1004 
1005     private boolean nonSyncContentEquals(AbstractStringBuilder sb) {
1006         char v1[] = value;
1007         char v2[] = sb.getValue();
1008         int n = v1.length;
1009         if (n != sb.length()) {
1010             return false;
1011         }
1012         for (int i = 0; i < n; i++) {
1013             if (v1[i] != v2[i]) {
1014                 return false;
1015             }
1016         }
1017         return true;
1018     }
1019 
1020     /**
1021      * Compares this string to the specified {@code CharSequence}.  The
1022      * result is {@code true} if and only if this {@code String} represents the
1023      * same sequence of char values as the specified sequence. Note that if the
1024      * {@code CharSequence} is a {@code StringBuffer} then the method
1025      * synchronizes on it.
1026      *
1027      * @param  cs
1028      *         The sequence to compare this {@code String} against
1029      *
1030      * @return  {@code true} if this {@code String} represents the same
1031      *          sequence of char values as the specified sequence, {@code
1032      *          false} otherwise
1033      *
1034      * @since  1.5
1035      */
1036     public boolean contentEquals(CharSequence cs) {
1037         // Argument is a StringBuffer, StringBuilder
1038         if (cs instanceof AbstractStringBuilder) {
1039             if (cs instanceof StringBuffer) {
1040                 synchronized(cs) {
1041                    return nonSyncContentEquals((AbstractStringBuilder)cs);
1042                 }
1043             } else {
1044                 return nonSyncContentEquals((AbstractStringBuilder)cs);
1045             }
1046         }
1047         // Argument is a String
1048         if (cs.equals(this))
1049             return true;
1050         // Argument is a generic CharSequence
1051         char v1[] = value;
1052         int n = v1.length;
1053         if (n != cs.length()) {
1054             return false;
1055         }
1056         for (int i = 0; i < n; i++) {
1057             if (v1[i] != cs.charAt(i)) {
1058                 return false;
1059             }
1060         }
1061         return true;
1062     }
1063 
1064     /**
1065      * Compares this {@code String} to another {@code String}, ignoring case
1066      * considerations.  Two strings are considered equal ignoring case if they
1067      * are of the same length and corresponding characters in the two strings
1068      * are equal ignoring case.
1069      *
1070      * <p> Two characters {@code c1} and {@code c2} are considered the same
1071      * ignoring case if at least one of the following is true:
1072      * <ul>
1073      *   <li> The two characters are the same (as compared by the
1074      *        {@code ==} operator)
1075      *   <li> Applying the method {@link
1076      *        java.lang.Character#toUpperCase(char)} to each character
1077      *        produces the same result
1078      *   <li> Applying the method {@link
1079      *        java.lang.Character#toLowerCase(char)} to each character
1080      *        produces the same result
1081      * </ul>
1082      *
1083      * @param  anotherString
1084      *         The {@code String} to compare this {@code String} against
1085      *
1086      * @return  {@code true} if the argument is not {@code null} and it
1087      *          represents an equivalent {@code String} ignoring case; {@code
1088      *          false} otherwise
1089      *
1090      * @see  #equals(Object)
1091      */
1092     public boolean equalsIgnoreCase(String anotherString) {
1093         return (this == anotherString) ? true
1094                 : (anotherString != null)
1095                 && (anotherString.value.length == value.length)
1096                 && regionMatches(true, 0, anotherString, 0, value.length);
1097     }
1098 
1099     /**
1100      * Compares two strings lexicographically.
1101      * The comparison is based on the Unicode value of each character in
1102      * the strings. The character sequence represented by this
1103      * {@code String} object is compared lexicographically to the
1104      * character sequence represented by the argument string. The result is
1105      * a negative integer if this {@code String} object
1106      * lexicographically precedes the argument string. The result is a
1107      * positive integer if this {@code String} object lexicographically
1108      * follows the argument string. The result is zero if the strings
1109      * are equal; {@code compareTo} returns {@code 0} exactly when
1110      * the {@link #equals(Object)} method would return {@code true}.
1111      * <p>
1112      * This is the definition of lexicographic ordering. If two strings are
1113      * different, then either they have different characters at some index
1114      * that is a valid index for both strings, or their lengths are different,
1115      * or both. If they have different characters at one or more index
1116      * positions, let <i>k</i> be the smallest such index; then the string
1117      * whose character at position <i>k</i> has the smaller value, as
1118      * determined by using the &lt; operator, lexicographically precedes the
1119      * other string. In this case, {@code compareTo} returns the
1120      * difference of the two character values at position {@code k} in
1121      * the two string -- that is, the value:
1122      * <blockquote><pre>
1123      * this.charAt(k)-anotherString.charAt(k)
1124      * </pre></blockquote>
1125      * If there is no index position at which they differ, then the shorter
1126      * string lexicographically precedes the longer string. In this case,
1127      * {@code compareTo} returns the difference of the lengths of the
1128      * strings -- that is, the value:
1129      * <blockquote><pre>
1130      * this.length()-anotherString.length()
1131      * </pre></blockquote>
1132      *
1133      * @param   anotherString   the {@code String} to be compared.
1134      * @return  the value {@code 0} if the argument string is equal to
1135      *          this string; a value less than {@code 0} if this string
1136      *          is lexicographically less than the string argument; and a
1137      *          value greater than {@code 0} if this string is
1138      *          lexicographically greater than the string argument.
1139      */
1140     public int compareTo(String anotherString) {
1141         int len1 = value.length;
1142         int len2 = anotherString.value.length;
1143         int lim = Math.min(len1, len2);
1144         char v1[] = value;
1145         char v2[] = anotherString.value;
1146 
1147         int k = 0;
1148         while (k < lim) {
1149             char c1 = v1[k];
1150             char c2 = v2[k];
1151             if (c1 != c2) {
1152                 return c1 - c2;
1153             }
1154             k++;
1155         }
1156         return len1 - len2;
1157     }
1158 
1159     /**
1160      * A Comparator that orders {@code String} objects as by
1161      * {@code compareToIgnoreCase}. This comparator is serializable.
1162      * <p>
1163      * Note that this Comparator does <em>not</em> take locale into account,
1164      * and will result in an unsatisfactory ordering for certain locales.
1165      * The java.text package provides <em>Collators</em> to allow
1166      * locale-sensitive ordering.
1167      *
1168      * @see     java.text.Collator#compare(String, String)
1169      * @since   1.2
1170      */
1171     public static final Comparator<String> CASE_INSENSITIVE_ORDER
1172                                          = new CaseInsensitiveComparator();
1173     private static class CaseInsensitiveComparator
1174             implements Comparator<String>, java.io.Serializable {
1175         // use serialVersionUID from JDK 1.2.2 for interoperability
1176         private static final long serialVersionUID = 8575799808933029326L;
1177 
1178         public int compare(String s1, String s2) {
1179             int n1 = s1.length();
1180             int n2 = s2.length();
1181             int min = Math.min(n1, n2);
1182             for (int i = 0; i < min; i++) {
1183                 char c1 = s1.charAt(i);
1184                 char c2 = s2.charAt(i);
1185                 if (c1 != c2) {
1186                     c1 = Character.toUpperCase(c1);
1187                     c2 = Character.toUpperCase(c2);
1188                     if (c1 != c2) {
1189                         c1 = Character.toLowerCase(c1);
1190                         c2 = Character.toLowerCase(c2);
1191                         if (c1 != c2) {
1192                             // No overflow because of numeric promotion
1193                             return c1 - c2;
1194                         }
1195                     }
1196                 }
1197             }
1198             return n1 - n2;
1199         }
1200 
1201         /** Replaces the de-serialized object. */
1202         private Object readResolve() { return CASE_INSENSITIVE_ORDER; }
1203     }
1204 
1205     /**
1206      * Compares two strings lexicographically, ignoring case
1207      * differences. This method returns an integer whose sign is that of
1208      * calling {@code compareTo} with normalized versions of the strings
1209      * where case differences have been eliminated by calling
1210      * {@code Character.toLowerCase(Character.toUpperCase(character))} on
1211      * each character.
1212      * <p>
1213      * Note that this method does <em>not</em> take locale into account,
1214      * and will result in an unsatisfactory ordering for certain locales.
1215      * The java.text package provides <em>collators</em> to allow
1216      * locale-sensitive ordering.
1217      *
1218      * @param   str   the {@code String} to be compared.
1219      * @return  a negative integer, zero, or a positive integer as the
1220      *          specified String is greater than, equal to, or less
1221      *          than this String, ignoring case considerations.
1222      * @see     java.text.Collator#compare(String, String)
1223      * @since   1.2
1224      */
1225     public int compareToIgnoreCase(String str) {
1226         return CASE_INSENSITIVE_ORDER.compare(this, str);
1227     }
1228 
1229     /**
1230      * Tests if two string regions are equal.
1231      * <p>
1232      * A substring of this {@code String} object is compared to a substring
1233      * of the argument other. The result is true if these substrings
1234      * represent identical character sequences. The substring of this
1235      * {@code String} object to be compared begins at index {@code toffset}
1236      * and has length {@code len}. The substring of other to be compared
1237      * begins at index {@code ooffset} and has length {@code len}. The
1238      * result is {@code false} if and only if at least one of the following
1239      * is true:
1240      * <ul><li>{@code toffset} is negative.
1241      * <li>{@code ooffset} is negative.
1242      * <li>{@code toffset+len} is greater than the length of this
1243      * {@code String} object.
1244      * <li>{@code ooffset+len} is greater than the length of the other
1245      * argument.
1246      * <li>There is some nonnegative integer <i>k</i> less than {@code len}
1247      * such that:
1248      * {@code this.charAt(toffset + }<i>k</i>{@code ) != other.charAt(ooffset + }
1249      * <i>k</i>{@code )}
1250      * </ul>
1251      *
1252      * @param   toffset   the starting offset of the subregion in this string.
1253      * @param   other     the string argument.
1254      * @param   ooffset   the starting offset of the subregion in the string
1255      *                    argument.
1256      * @param   len       the number of characters to compare.
1257      * @return  {@code true} if the specified subregion of this string
1258      *          exactly matches the specified subregion of the string argument;
1259      *          {@code false} otherwise.
1260      */
1261     public boolean regionMatches(int toffset, String other, int ooffset,
1262             int len) {
1263         char ta[] = value;
1264         int to = toffset;
1265         char pa[] = other.value;
1266         int po = ooffset;
1267         // Note: toffset, ooffset, or len might be near -1>>>1.
1268         if ((ooffset < 0) || (toffset < 0)
1269                 || (toffset > (long)value.length - len)
1270                 || (ooffset > (long)other.value.length - len)) {
1271             return false;
1272         }
1273         while (len-- > 0) {
1274             if (ta[to++] != pa[po++]) {
1275                 return false;
1276             }
1277         }
1278         return true;
1279     }
1280 
1281     /**
1282      * Tests if two string regions are equal.
1283      * <p>
1284      * A substring of this {@code String} object is compared to a substring
1285      * of the argument {@code other}. The result is {@code true} if these
1286      * substrings represent character sequences that are the same, ignoring
1287      * case if and only if {@code ignoreCase} is true. The substring of
1288      * this {@code String} object to be compared begins at index
1289      * {@code toffset} and has length {@code len}. The substring of
1290      * {@code other} to be compared begins at index {@code ooffset} and
1291      * has length {@code len}. The result is {@code false} if and only if
1292      * at least one of the following is true:
1293      * <ul><li>{@code toffset} is negative.
1294      * <li>{@code ooffset} is negative.
1295      * <li>{@code toffset+len} is greater than the length of this
1296      * {@code String} object.
1297      * <li>{@code ooffset+len} is greater than the length of the other
1298      * argument.
1299      * <li>{@code ignoreCase} is {@code false} and there is some nonnegative
1300      * integer <i>k</i> less than {@code len} such that:
1301      * <blockquote><pre>
1302      * this.charAt(toffset+k) != other.charAt(ooffset+k)
1303      * </pre></blockquote>
1304      * <li>{@code ignoreCase} is {@code true} and there is some nonnegative
1305      * integer <i>k</i> less than {@code len} such that:
1306      * <blockquote><pre>
1307      * Character.toLowerCase(this.charAt(toffset+k)) !=
1308      Character.toLowerCase(other.charAt(ooffset+k))
1309      * </pre></blockquote>
1310      * and:
1311      * <blockquote><pre>
1312      * Character.toUpperCase(this.charAt(toffset+k)) !=
1313      *         Character.toUpperCase(other.charAt(ooffset+k))
1314      * </pre></blockquote>
1315      * </ul>
1316      *
1317      * @param   ignoreCase   if {@code true}, ignore case when comparing
1318      *                       characters.
1319      * @param   toffset      the starting offset of the subregion in this
1320      *                       string.
1321      * @param   other        the string argument.
1322      * @param   ooffset      the starting offset of the subregion in the string
1323      *                       argument.
1324      * @param   len          the number of characters to compare.
1325      * @return  {@code true} if the specified subregion of this string
1326      *          matches the specified subregion of the string argument;
1327      *          {@code false} otherwise. Whether the matching is exact
1328      *          or case insensitive depends on the {@code ignoreCase}
1329      *          argument.
1330      */
1331     public boolean regionMatches(boolean ignoreCase, int toffset,
1332             String other, int ooffset, int len) {
1333         char ta[] = value;
1334         int to = toffset;
1335         char pa[] = other.value;
1336         int po = ooffset;
1337         // Note: toffset, ooffset, or len might be near -1>>>1.
1338         if ((ooffset < 0) || (toffset < 0)
1339                 || (toffset > (long)value.length - len)
1340                 || (ooffset > (long)other.value.length - len)) {
1341             return false;
1342         }
1343         while (len-- > 0) {
1344             char c1 = ta[to++];
1345             char c2 = pa[po++];
1346             if (c1 == c2) {
1347                 continue;
1348             }
1349             if (ignoreCase) {
1350                 // If characters don't match but case may be ignored,
1351                 // try converting both characters to uppercase.
1352                 // If the results match, then the comparison scan should
1353                 // continue.
1354                 char u1 = Character.toUpperCase(c1);
1355                 char u2 = Character.toUpperCase(c2);
1356                 if (u1 == u2) {
1357                     continue;
1358                 }
1359                 // Unfortunately, conversion to uppercase does not work properly
1360                 // for the Georgian alphabet, which has strange rules about case
1361                 // conversion.  So we need to make one last check before
1362                 // exiting.
1363                 if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
1364                     continue;
1365                 }
1366             }
1367             return false;
1368         }
1369         return true;
1370     }
1371 
1372     /**
1373      * Tests if the substring of this string beginning at the
1374      * specified index starts with the specified prefix.
1375      *
1376      * @param   prefix    the prefix.
1377      * @param   toffset   where to begin looking in this string.
1378      * @return  {@code true} if the character sequence represented by the
1379      *          argument is a prefix of the substring of this object starting
1380      *          at index {@code toffset}; {@code false} otherwise.
1381      *          The result is {@code false} if {@code toffset} is
1382      *          negative or greater than the length of this
1383      *          {@code String} object; otherwise the result is the same
1384      *          as the result of the expression
1385      *          <pre>
1386      *          this.substring(toffset).startsWith(prefix)
1387      *          </pre>
1388      */
1389     public boolean startsWith(String prefix, int toffset) {
1390         char ta[] = value;
1391         int to = toffset;
1392         char pa[] = prefix.value;
1393         int po = 0;
1394         int pc = prefix.value.length;
1395         // Note: toffset might be near -1>>>1.
1396         if ((toffset < 0) || (toffset > value.length - pc)) {
1397             return false;
1398         }
1399         while (--pc >= 0) {
1400             if (ta[to++] != pa[po++]) {
1401                 return false;
1402             }
1403         }
1404         return true;
1405     }
1406 
1407     /**
1408      * Tests if this string starts with the specified prefix.
1409      *
1410      * @param   prefix   the prefix.
1411      * @return  {@code true} if the character sequence represented by the
1412      *          argument is a prefix of the character sequence represented by
1413      *          this string; {@code false} otherwise.
1414      *          Note also that {@code true} will be returned if the
1415      *          argument is an empty string or is equal to this
1416      *          {@code String} object as determined by the
1417      *          {@link #equals(Object)} method.
1418      * @since   1. 0
1419      */
1420     public boolean startsWith(String prefix) {
1421         return startsWith(prefix, 0);
1422     }
1423 
1424     /**
1425      * Tests if this string ends with the specified suffix.
1426      *
1427      * @param   suffix   the suffix.
1428      * @return  {@code true} if the character sequence represented by the
1429      *          argument is a suffix of the character sequence represented by
1430      *          this object; {@code false} otherwise. Note that the
1431      *          result will be {@code true} if the argument is the
1432      *          empty string or is equal to this {@code String} object
1433      *          as determined by the {@link #equals(Object)} method.
1434      */
1435     public boolean endsWith(String suffix) {
1436         return startsWith(suffix, value.length - suffix.value.length);
1437     }
1438 
1439     /**
1440      * Returns a hash code for this string. The hash code for a
1441      * {@code String} object is computed as
1442      * <blockquote><pre>
1443      * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
1444      * </pre></blockquote>
1445      * using {@code int} arithmetic, where {@code s[i]} is the
1446      * <i>i</i>th character of the string, {@code n} is the length of
1447      * the string, and {@code ^} indicates exponentiation.
1448      * (The hash value of the empty string is zero.)
1449      *
1450      * @return  a hash code value for this object.
1451      */
1452     public int hashCode() {
1453         int h = hash;
1454         if (h == 0 && value.length > 0) {
1455             char val[] = value;
1456 
1457             for (int i = 0; i < value.length; i++) {
1458                 h = 31 * h + val[i];
1459             }
1460             hash = h;
1461         }
1462         return h;
1463     }
1464 
1465     /**
1466      * Returns the index within this string of the first occurrence of
1467      * the specified character. If a character with value
1468      * {@code ch} occurs in the character sequence represented by
1469      * this {@code String} object, then the index (in Unicode
1470      * code units) of the first such occurrence is returned. For
1471      * values of {@code ch} in the range from 0 to 0xFFFF
1472      * (inclusive), this is the smallest value <i>k</i> such that:
1473      * <blockquote><pre>
1474      * this.charAt(<i>k</i>) == ch
1475      * </pre></blockquote>
1476      * is true. For other values of {@code ch}, it is the
1477      * smallest value <i>k</i> such that:
1478      * <blockquote><pre>
1479      * this.codePointAt(<i>k</i>) == ch
1480      * </pre></blockquote>
1481      * is true. In either case, if no such character occurs in this
1482      * string, then {@code -1} is returned.
1483      *
1484      * @param   ch   a character (Unicode code point).
1485      * @return  the index of the first occurrence of the character in the
1486      *          character sequence represented by this object, or
1487      *          {@code -1} if the character does not occur.
1488      */
1489     public int indexOf(int ch) {
1490         return indexOf(ch, 0);
1491     }
1492 
1493     /**
1494      * Returns the index within this string of the first occurrence of the
1495      * specified character, starting the search at the specified index.
1496      * <p>
1497      * If a character with value {@code ch} occurs in the
1498      * character sequence represented by this {@code String}
1499      * object at an index no smaller than {@code fromIndex}, then
1500      * the index of the first such occurrence is returned. For values
1501      * of {@code ch} in the range from 0 to 0xFFFF (inclusive),
1502      * this is the smallest value <i>k</i> such that:
1503      * <blockquote><pre>
1504      * (this.charAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &gt;= fromIndex)
1505      * </pre></blockquote>
1506      * is true. For other values of {@code ch}, it is the
1507      * smallest value <i>k</i> such that:
1508      * <blockquote><pre>
1509      * (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &gt;= fromIndex)
1510      * </pre></blockquote>
1511      * is true. In either case, if no such character occurs in this
1512      * string at or after position {@code fromIndex}, then
1513      * {@code -1} is returned.
1514      *
1515      * <p>
1516      * There is no restriction on the value of {@code fromIndex}. If it
1517      * is negative, it has the same effect as if it were zero: this entire
1518      * string may be searched. If it is greater than the length of this
1519      * string, it has the same effect as if it were equal to the length of
1520      * this string: {@code -1} is returned.
1521      *
1522      * <p>All indices are specified in {@code char} values
1523      * (Unicode code units).
1524      *
1525      * @param   ch          a character (Unicode code point).
1526      * @param   fromIndex   the index to start the search from.
1527      * @return  the index of the first occurrence of the character in the
1528      *          character sequence represented by this object that is greater
1529      *          than or equal to {@code fromIndex}, or {@code -1}
1530      *          if the character does not occur.
1531      */
1532     public int indexOf(int ch, int fromIndex) {
1533         final int max = value.length;
1534         if (fromIndex < 0) {
1535             fromIndex = 0;
1536         } else if (fromIndex >= max) {
1537             // Note: fromIndex might be near -1>>>1.
1538             return -1;
1539         }
1540 
1541         if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
1542             // handle most cases here (ch is a BMP code point or a
1543             // negative value (invalid code point))
1544             final char[] value = this.value;
1545             for (int i = fromIndex; i < max; i++) {
1546                 if (value[i] == ch) {
1547                     return i;
1548                 }
1549             }
1550             return -1;
1551         } else {
1552             return indexOfSupplementary(ch, fromIndex);
1553         }
1554     }
1555 
1556     /**
1557      * Handles (rare) calls of indexOf with a supplementary character.
1558      */
1559     private int indexOfSupplementary(int ch, int fromIndex) {
1560         if (Character.isValidCodePoint(ch)) {
1561             final char[] value = this.value;
1562             final char hi = Character.highSurrogate(ch);
1563             final char lo = Character.lowSurrogate(ch);
1564             final int max = value.length - 1;
1565             for (int i = fromIndex; i < max; i++) {
1566                 if (value[i] == hi && value[i + 1] == lo) {
1567                     return i;
1568                 }
1569             }
1570         }
1571         return -1;
1572     }
1573 
1574     /**
1575      * Returns the index within this string of the last occurrence of
1576      * the specified character. For values of {@code ch} in the
1577      * range from 0 to 0xFFFF (inclusive), the index (in Unicode code
1578      * units) returned is the largest value <i>k</i> such that:
1579      * <blockquote><pre>
1580      * this.charAt(<i>k</i>) == ch
1581      * </pre></blockquote>
1582      * is true. For other values of {@code ch}, it is the
1583      * largest value <i>k</i> such that:
1584      * <blockquote><pre>
1585      * this.codePointAt(<i>k</i>) == ch
1586      * </pre></blockquote>
1587      * is true.  In either case, if no such character occurs in this
1588      * string, then {@code -1} is returned.  The
1589      * {@code String} is searched backwards starting at the last
1590      * character.
1591      *
1592      * @param   ch   a character (Unicode code point).
1593      * @return  the index of the last occurrence of the character in the
1594      *          character sequence represented by this object, or
1595      *          {@code -1} if the character does not occur.
1596      */
1597     public int lastIndexOf(int ch) {
1598         return lastIndexOf(ch, value.length - 1);
1599     }
1600 
1601     /**
1602      * Returns the index within this string of the last occurrence of
1603      * the specified character, searching backward starting at the
1604      * specified index. For values of {@code ch} in the range
1605      * from 0 to 0xFFFF (inclusive), the index returned is the largest
1606      * value <i>k</i> such that:
1607      * <blockquote><pre>
1608      * (this.charAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &lt;= fromIndex)
1609      * </pre></blockquote>
1610      * is true. For other values of {@code ch}, it is the
1611      * largest value <i>k</i> such that:
1612      * <blockquote><pre>
1613      * (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> &lt;= fromIndex)
1614      * </pre></blockquote>
1615      * is true. In either case, if no such character occurs in this
1616      * string at or before position {@code fromIndex}, then
1617      * {@code -1} is returned.
1618      *
1619      * <p>All indices are specified in {@code char} values
1620      * (Unicode code units).
1621      *
1622      * @param   ch          a character (Unicode code point).
1623      * @param   fromIndex   the index to start the search from. There is no
1624      *          restriction on the value of {@code fromIndex}. If it is
1625      *          greater than or equal to the length of this string, it has
1626      *          the same effect as if it were equal to one less than the
1627      *          length of this string: this entire string may be searched.
1628      *          If it is negative, it has the same effect as if it were -1:
1629      *          -1 is returned.
1630      * @return  the index of the last occurrence of the character in the
1631      *          character sequence represented by this object that is less
1632      *          than or equal to {@code fromIndex}, or {@code -1}
1633      *          if the character does not occur before that point.
1634      */
1635     public int lastIndexOf(int ch, int fromIndex) {
1636         if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
1637             // handle most cases here (ch is a BMP code point or a
1638             // negative value (invalid code point))
1639             final char[] value = this.value;
1640             int i = Math.min(fromIndex, value.length - 1);
1641             for (; i >= 0; i--) {
1642                 if (value[i] == ch) {
1643                     return i;
1644                 }
1645             }
1646             return -1;
1647         } else {
1648             return lastIndexOfSupplementary(ch, fromIndex);
1649         }
1650     }
1651 
1652     /**
1653      * Handles (rare) calls of lastIndexOf with a supplementary character.
1654      */
1655     private int lastIndexOfSupplementary(int ch, int fromIndex) {
1656         if (Character.isValidCodePoint(ch)) {
1657             final char[] value = this.value;
1658             char hi = Character.highSurrogate(ch);
1659             char lo = Character.lowSurrogate(ch);
1660             int i = Math.min(fromIndex, value.length - 2);
1661             for (; i >= 0; i--) {
1662                 if (value[i] == hi && value[i + 1] == lo) {
1663                     return i;
1664                 }
1665             }
1666         }
1667         return -1;
1668     }
1669 
1670     /**
1671      * Returns the index within this string of the first occurrence of the
1672      * specified substring.
1673      *
1674      * <p>The returned index is the smallest value <i>k</i> for which:
1675      * <blockquote><pre>
1676      * this.startsWith(str, <i>k</i>)
1677      * </pre></blockquote>
1678      * If no such value of <i>k</i> exists, then {@code -1} is returned.
1679      *
1680      * @param   str   the substring to search for.
1681      * @return  the index of the first occurrence of the specified substring,
1682      *          or {@code -1} if there is no such occurrence.
1683      */
1684     public int indexOf(String str) {
1685         return indexOf(str, 0);
1686     }
1687 
1688     /**
1689      * Returns the index within this string of the first occurrence of the
1690      * specified substring, starting at the specified index.
1691      *
1692      * <p>The returned index is the smallest value <i>k</i> for which:
1693      * <blockquote><pre>
1694      * <i>k</i> &gt;= fromIndex {@code &&} this.startsWith(str, <i>k</i>)
1695      * </pre></blockquote>
1696      * If no such value of <i>k</i> exists, then {@code -1} is returned.
1697      *
1698      * @param   str         the substring to search for.
1699      * @param   fromIndex   the index from which to start the search.
1700      * @return  the index of the first occurrence of the specified substring,
1701      *          starting at the specified index,
1702      *          or {@code -1} if there is no such occurrence.
1703      */
1704     public int indexOf(String str, int fromIndex) {
1705         return indexOf(value, 0, value.length,
1706                 str.value, 0, str.value.length, fromIndex);
1707     }
1708 
1709     /**
1710      * Code shared by String and AbstractStringBuilder to do searches. The
1711      * source is the character array being searched, and the target
1712      * is the string being searched for.
1713      *
1714      * @param   source       the characters being searched.
1715      * @param   sourceOffset offset of the source string.
1716      * @param   sourceCount  count of the source string.
1717      * @param   target       the characters being searched for.
1718      * @param   fromIndex    the index to begin searching from.
1719      */
1720     static int indexOf(char[] source, int sourceOffset, int sourceCount,
1721             String target, int fromIndex) {
1722         return indexOf(source, sourceOffset, sourceCount,
1723                        target.value, 0, target.value.length,
1724                        fromIndex);
1725     }
1726 
1727     /**
1728      * Code shared by String and StringBuffer to do searches. The
1729      * source is the character array being searched, and the target
1730      * is the string being searched for.
1731      *
1732      * @param   source       the characters being searched.
1733      * @param   sourceOffset offset of the source string.
1734      * @param   sourceCount  count of the source string.
1735      * @param   target       the characters being searched for.
1736      * @param   targetOffset offset of the target string.
1737      * @param   targetCount  count of the target string.
1738      * @param   fromIndex    the index to begin searching from.
1739      */
1740     static int indexOf(char[] source, int sourceOffset, int sourceCount,
1741             char[] target, int targetOffset, int targetCount,
1742             int fromIndex) {
1743         if (fromIndex >= sourceCount) {
1744             return (targetCount == 0 ? sourceCount : -1);
1745         }
1746         if (fromIndex < 0) {
1747             fromIndex = 0;
1748         }
1749         if (targetCount == 0) {
1750             return fromIndex;
1751         }
1752 
1753         char first = target[targetOffset];
1754         int max = sourceOffset + (sourceCount - targetCount);
1755 
1756         for (int i = sourceOffset + fromIndex; i <= max; i++) {
1757             /* Look for first character. */
1758             if (source[i] != first) {
1759                 while (++i <= max && source[i] != first);
1760             }
1761 
1762             /* Found first character, now look at the rest of v2 */
1763             if (i <= max) {
1764                 int j = i + 1;
1765                 int end = j + targetCount - 1;
1766                 for (int k = targetOffset + 1; j < end && source[j]
1767                         == target[k]; j++, k++);
1768 
1769                 if (j == end) {
1770                     /* Found whole string. */
1771                     return i - sourceOffset;
1772                 }
1773             }
1774         }
1775         return -1;
1776     }
1777 
1778     /**
1779      * Returns the index within this string of the last occurrence of the
1780      * specified substring.  The last occurrence of the empty string ""
1781      * is considered to occur at the index value {@code this.length()}.
1782      *
1783      * <p>The returned index is the largest value <i>k</i> for which:
1784      * <blockquote><pre>
1785      * this.startsWith(str, <i>k</i>)
1786      * </pre></blockquote>
1787      * If no such value of <i>k</i> exists, then {@code -1} is returned.
1788      *
1789      * @param   str   the substring to search for.
1790      * @return  the index of the last occurrence of the specified substring,
1791      *          or {@code -1} if there is no such occurrence.
1792      */
1793     public int lastIndexOf(String str) {
1794         return lastIndexOf(str, value.length);
1795     }
1796 
1797     /**
1798      * Returns the index within this string of the last occurrence of the
1799      * specified substring, searching backward starting at the specified index.
1800      *
1801      * <p>The returned index is the largest value <i>k</i> for which:
1802      * <blockquote><pre>
1803      * <i>k</i> {@code <=} fromIndex {@code &&} this.startsWith(str, <i>k</i>)
1804      * </pre></blockquote>
1805      * If no such value of <i>k</i> exists, then {@code -1} is returned.
1806      *
1807      * @param   str         the substring to search for.
1808      * @param   fromIndex   the index to start the search from.
1809      * @return  the index of the last occurrence of the specified substring,
1810      *          searching backward from the specified index,
1811      *          or {@code -1} if there is no such occurrence.
1812      */
1813     public int lastIndexOf(String str, int fromIndex) {
1814         return lastIndexOf(value, 0, value.length,
1815                 str.value, 0, str.value.length, fromIndex);
1816     }
1817 
1818     /**
1819      * Code shared by String and AbstractStringBuilder to do searches. The
1820      * source is the character array being searched, and the target
1821      * is the string being searched for.
1822      *
1823      * @param   source       the characters being searched.
1824      * @param   sourceOffset offset of the source string.
1825      * @param   sourceCount  count of the source string.
1826      * @param   target       the characters being searched for.
1827      * @param   fromIndex    the index to begin searching from.
1828      */
1829     static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,
1830             String target, int fromIndex) {
1831         return lastIndexOf(source, sourceOffset, sourceCount,
1832                        target.value, 0, target.value.length,
1833                        fromIndex);
1834     }
1835 
1836     /**
1837      * Code shared by String and StringBuffer to do searches. The
1838      * source is the character array being searched, and the target
1839      * is the string being searched for.
1840      *
1841      * @param   source       the characters being searched.
1842      * @param   sourceOffset offset of the source string.
1843      * @param   sourceCount  count of the source string.
1844      * @param   target       the characters being searched for.
1845      * @param   targetOffset offset of the target string.
1846      * @param   targetCount  count of the target string.
1847      * @param   fromIndex    the index to begin searching from.
1848      */
1849     static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,
1850             char[] target, int targetOffset, int targetCount,
1851             int fromIndex) {
1852         /*
1853          * Check arguments; return immediately where possible. For
1854          * consistency, don't check for null str.
1855          */
1856         int rightIndex = sourceCount - targetCount;
1857         if (fromIndex < 0) {
1858             return -1;
1859         }
1860         if (fromIndex > rightIndex) {
1861             fromIndex = rightIndex;
1862         }
1863         /* Empty string always matches. */
1864         if (targetCount == 0) {
1865             return fromIndex;
1866         }
1867 
1868         int strLastIndex = targetOffset + targetCount - 1;
1869         char strLastChar = target[strLastIndex];
1870         int min = sourceOffset + targetCount - 1;
1871         int i = min + fromIndex;
1872 
1873     startSearchForLastChar:
1874         while (true) {
1875             while (i >= min && source[i] != strLastChar) {
1876                 i--;
1877             }
1878             if (i < min) {
1879                 return -1;
1880             }
1881             int j = i - 1;
1882             int start = j - (targetCount - 1);
1883             int k = strLastIndex - 1;
1884 
1885             while (j > start) {
1886                 if (source[j--] != target[k--]) {
1887                     i--;
1888                     continue startSearchForLastChar;
1889                 }
1890             }
1891             return start - sourceOffset + 1;
1892         }
1893     }
1894 
1895     /**
1896      * Returns a string that is a substring of this string. The
1897      * substring begins with the character at the specified index and
1898      * extends to the end of this string. <p>
1899      * Examples:
1900      * <blockquote><pre>
1901      * "unhappy".substring(2) returns "happy"
1902      * "Harbison".substring(3) returns "bison"
1903      * "emptiness".substring(9) returns "" (an empty string)
1904      * </pre></blockquote>
1905      *
1906      * @param      beginIndex   the beginning index, inclusive.
1907      * @return     the specified substring.
1908      * @exception  IndexOutOfBoundsException  if
1909      *             {@code beginIndex} is negative or larger than the
1910      *             length of this {@code String} object.
1911      */
1912     public String substring(int beginIndex) {
1913         if (beginIndex < 0) {
1914             throw new StringIndexOutOfBoundsException(beginIndex);
1915         }
1916         int subLen = value.length - beginIndex;
1917         if (subLen < 0) {
1918             throw new StringIndexOutOfBoundsException(subLen);
1919         }
1920         return (beginIndex == 0) ? this : new String(value, beginIndex, subLen);
1921     }
1922 
1923     /**
1924      * Returns a string that is a substring of this string. The
1925      * substring begins at the specified {@code beginIndex} and
1926      * extends to the character at index {@code endIndex - 1}.
1927      * Thus the length of the substring is {@code endIndex-beginIndex}.
1928      * <p>
1929      * Examples:
1930      * <blockquote><pre>
1931      * "hamburger".substring(4, 8) returns "urge"
1932      * "smiles".substring(1, 5) returns "mile"
1933      * </pre></blockquote>
1934      *
1935      * @param      beginIndex   the beginning index, inclusive.
1936      * @param      endIndex     the ending index, exclusive.
1937      * @return     the specified substring.
1938      * @exception  IndexOutOfBoundsException  if the
1939      *             {@code beginIndex} is negative, or
1940      *             {@code endIndex} is larger than the length of
1941      *             this {@code String} object, or
1942      *             {@code beginIndex} is larger than
1943      *             {@code endIndex}.
1944      */
1945     public String substring(int beginIndex, int endIndex) {
1946         if (beginIndex < 0) {
1947             throw new StringIndexOutOfBoundsException(beginIndex);
1948         }
1949         if (endIndex > value.length) {
1950             throw new StringIndexOutOfBoundsException(endIndex);
1951         }
1952         int subLen = endIndex - beginIndex;
1953         if (subLen < 0) {
1954             throw new StringIndexOutOfBoundsException(subLen);
1955         }
1956         return ((beginIndex == 0) && (endIndex == value.length)) ? this
1957                 : new String(value, beginIndex, subLen);
1958     }
1959 
1960     /**
1961      * Returns a character sequence that is a subsequence of this sequence.
1962      *
1963      * <p> An invocation of this method of the form
1964      *
1965      * <blockquote><pre>
1966      * str.subSequence(begin,&nbsp;end)</pre></blockquote>
1967      *
1968      * behaves in exactly the same way as the invocation
1969      *
1970      * <blockquote><pre>
1971      * str.substring(begin,&nbsp;end)</pre></blockquote>
1972      *
1973      * @apiNote
1974      * This method is defined so that the {@code String} class can implement
1975      * the {@link CharSequence} interface.
1976      *
1977      * @param   beginIndex   the begin index, inclusive.
1978      * @param   endIndex     the end index, exclusive.
1979      * @return  the specified subsequence.
1980      *
1981      * @throws  IndexOutOfBoundsException
1982      *          if {@code beginIndex} or {@code endIndex} is negative,
1983      *          if {@code endIndex} is greater than {@code length()},
1984      *          or if {@code beginIndex} is greater than {@code endIndex}
1985      *
1986      * @since 1.4
1987      * @spec JSR-51
1988      */
1989     public CharSequence subSequence(int beginIndex, int endIndex) {
1990         return this.substring(beginIndex, endIndex);
1991     }
1992 
1993     /**
1994      * Concatenates the specified string to the end of this string.
1995      * <p>
1996      * If the length of the argument string is {@code 0}, then this
1997      * {@code String} object is returned. Otherwise, a
1998      * {@code String} object is returned that represents a character
1999      * sequence that is the concatenation of the character sequence
2000      * represented by this {@code String} object and the character
2001      * sequence represented by the argument string.<p>
2002      * Examples:
2003      * <blockquote><pre>
2004      * "cares".concat("s") returns "caress"
2005      * "to".concat("get").concat("her") returns "together"
2006      * </pre></blockquote>
2007      *
2008      * @param   str   the {@code String} that is concatenated to the end
2009      *                of this {@code String}.
2010      * @return  a string that represents the concatenation of this object's
2011      *          characters followed by the string argument's characters.
2012      */
2013     public String concat(String str) {
2014         int otherLen = str.length();
2015         if (otherLen == 0) {
2016             return this;
2017         }
2018         int len = value.length;
2019         char buf[] = Arrays.copyOf(value, len + otherLen);
2020         str.getChars(buf, len);
2021         return new String(buf, true);
2022     }
2023 
2024     /**
2025      * Returns a string resulting from replacing all occurrences of
2026      * {@code oldChar} in this string with {@code newChar}.
2027      * <p>
2028      * If the character {@code oldChar} does not occur in the
2029      * character sequence represented by this {@code String} object,
2030      * then a reference to this {@code String} object is returned.
2031      * Otherwise, a {@code String} object is returned that
2032      * represents a character sequence identical to the character sequence
2033      * represented by this {@code String} object, except that every
2034      * occurrence of {@code oldChar} is replaced by an occurrence
2035      * of {@code newChar}.
2036      * <p>
2037      * Examples:
2038      * <blockquote><pre>
2039      * "mesquite in your cellar".replace('e', 'o')
2040      *         returns "mosquito in your collar"
2041      * "the war of baronets".replace('r', 'y')
2042      *         returns "the way of bayonets"
2043      * "sparring with a purple porpoise".replace('p', 't')
2044      *         returns "starring with a turtle tortoise"
2045      * "JonL".replace('q', 'x') returns "JonL" (no change)
2046      * </pre></blockquote>
2047      *
2048      * @param   oldChar   the old character.
2049      * @param   newChar   the new character.
2050      * @return  a string derived from this string by replacing every
2051      *          occurrence of {@code oldChar} with {@code newChar}.
2052      */
2053     public String replace(char oldChar, char newChar) {
2054         if (oldChar != newChar) {
2055             int len = value.length;
2056             int i = -1;
2057             char[] val = value; /* avoid getfield opcode */
2058 
2059             while (++i < len) {
2060                 if (val[i] == oldChar) {
2061                     break;
2062                 }
2063             }
2064             if (i < len) {
2065                 char buf[] = new char[len];
2066                 for (int j = 0; j < i; j++) {
2067                     buf[j] = val[j];
2068                 }
2069                 while (i < len) {
2070                     char c = val[i];
2071                     buf[i] = (c == oldChar) ? newChar : c;
2072                     i++;
2073                 }
2074                 return new String(buf, true);
2075             }
2076         }
2077         return this;
2078     }
2079 
2080     /**
2081      * Tells whether or not this string matches the given <a
2082      * href="../util/regex/Pattern.html#sum">regular expression</a>.
2083      *
2084      * <p> An invocation of this method of the form
2085      * <i>str</i>{@code .matches(}<i>regex</i>{@code )} yields exactly the
2086      * same result as the expression
2087      *
2088      * <blockquote>
2089      * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#matches(String,CharSequence)
2090      * matches(<i>regex</i>, <i>str</i>)}
2091      * </blockquote>
2092      *
2093      * @param   regex
2094      *          the regular expression to which this string is to be matched
2095      *
2096      * @return  {@code true} if, and only if, this string matches the
2097      *          given regular expression
2098      *
2099      * @throws  PatternSyntaxException
2100      *          if the regular expression's syntax is invalid
2101      *
2102      * @see java.util.regex.Pattern
2103      *
2104      * @since 1.4
2105      * @spec JSR-51
2106      */
2107     public boolean matches(String regex) {
2108         return Pattern.matches(regex, this);
2109     }
2110 
2111     /**
2112      * Returns true if and only if this string contains the specified
2113      * sequence of char values.
2114      *
2115      * @param s the sequence to search for
2116      * @return true if this string contains {@code s}, false otherwise
2117      * @since 1.5
2118      */
2119     public boolean contains(CharSequence s) {
2120         return indexOf(s.toString()) > -1;
2121     }
2122 
2123     /**
2124      * Replaces the first substring of this string that matches the given <a
2125      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
2126      * given replacement.
2127      *
2128      * <p> An invocation of this method of the form
2129      * <i>str</i>{@code .replaceFirst(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
2130      * yields exactly the same result as the expression
2131      *
2132      * <blockquote>
2133      * <code>
2134      * {@link java.util.regex.Pattern}.{@link
2135      * java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
2136      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
2137      * java.util.regex.Matcher#replaceFirst replaceFirst}(<i>repl</i>)
2138      * </code>
2139      * </blockquote>
2140      *
2141      *<p>
2142      * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
2143      * replacement string may cause the results to be different than if it were
2144      * being treated as a literal replacement string; see
2145      * {@link java.util.regex.Matcher#replaceFirst}.
2146      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
2147      * meaning of these characters, if desired.
2148      *
2149      * @param   regex
2150      *          the regular expression to which this string is to be matched
2151      * @param   replacement
2152      *          the string to be substituted for the first match
2153      *
2154      * @return  The resulting {@code String}
2155      *
2156      * @throws  PatternSyntaxException
2157      *          if the regular expression's syntax is invalid
2158      *
2159      * @see java.util.regex.Pattern
2160      *
2161      * @since 1.4
2162      * @spec JSR-51
2163      */
2164     public String replaceFirst(String regex, String replacement) {
2165         return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
2166     }
2167 
2168     /**
2169      * Replaces each substring of this string that matches the given <a
2170      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
2171      * given replacement.
2172      *
2173      * <p> An invocation of this method of the form
2174      * <i>str</i>{@code .replaceAll(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
2175      * yields exactly the same result as the expression
2176      *
2177      * <blockquote>
2178      * <code>
2179      * {@link java.util.regex.Pattern}.{@link
2180      * java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
2181      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
2182      * java.util.regex.Matcher#replaceAll replaceAll}(<i>repl</i>)
2183      * </code>
2184      * </blockquote>
2185      *
2186      *<p>
2187      * Note that backslashes ({@code \}) and dollar signs ({@code $}) 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 {@code String}
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      * @since 1.5
2224      */
2225     public String replace(CharSequence target, CharSequence replacement) {
2226         return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
2227                 this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
2228     }
2229 
2230     /**
2231      * Splits this string around matches of the given
2232      * <a href="../util/regex/Pattern.html#sum">regular expression</a>.
2233      *
2234      * <p> The array returned by this method contains each substring of this
2235      * string that is terminated by another substring that matches the given
2236      * expression or is terminated by the end of the string.  The substrings in
2237      * the array are in the order in which they occur in this string.  If the
2238      * expression does not match any part of the input then the resulting array
2239      * has just one element, namely this string.
2240      *
2241      * <p> When there is a positive-width match at the beginning of this
2242      * string then an empty leading substring is included at the beginning
2243      * of the resulting array. A zero-width match at the beginning however
2244      * never produces such empty leading substring.
2245      *
2246      * <p> The {@code limit} parameter controls the number of times the
2247      * pattern is applied and therefore affects the length of the resulting
2248      * array.  If the limit <i>n</i> is greater than zero then the pattern
2249      * will be applied at most <i>n</i>&nbsp;-&nbsp;1 times, the array's
2250      * length will be no greater than <i>n</i>, and the array's last entry
2251      * will contain all input beyond the last matched delimiter.  If <i>n</i>
2252      * is non-positive then the pattern will be applied as many times as
2253      * possible and the array can have any length.  If <i>n</i> is zero then
2254      * the pattern will be applied as many times as possible, the array can
2255      * have any length, and trailing empty strings will be discarded.
2256      *
2257      * <p> The string {@code "boo:and:foo"}, for example, yields the
2258      * following results with these parameters:
2259      *
2260      * <blockquote><table cellpadding=1 cellspacing=0 summary="Split example showing regex, limit, and result">
2261      * <tr>
2262      *     <th>Regex</th>
2263      *     <th>Limit</th>
2264      *     <th>Result</th>
2265      * </tr>
2266      * <tr><td align=center>:</td>
2267      *     <td align=center>2</td>
2268      *     <td>{@code { "boo", "and:foo" }}</td></tr>
2269      * <tr><td align=center>:</td>
2270      *     <td align=center>5</td>
2271      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
2272      * <tr><td align=center>:</td>
2273      *     <td align=center>-2</td>
2274      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
2275      * <tr><td align=center>o</td>
2276      *     <td align=center>5</td>
2277      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
2278      * <tr><td align=center>o</td>
2279      *     <td align=center>-2</td>
2280      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
2281      * <tr><td align=center>o</td>
2282      *     <td align=center>0</td>
2283      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
2284      * </table></blockquote>
2285      *
2286      * <p> An invocation of this method of the form
2287      * <i>str.</i>{@code split(}<i>regex</i>{@code ,}&nbsp;<i>n</i>{@code )}
2288      * yields the same result as the expression
2289      *
2290      * <blockquote>
2291      * <code>
2292      * {@link java.util.regex.Pattern}.{@link
2293      * java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
2294      * java.util.regex.Pattern#split(java.lang.CharSequence,int) split}(<i>str</i>,&nbsp;<i>n</i>)
2295      * </code>
2296      * </blockquote>
2297      *
2298      *
2299      * @param  regex
2300      *         the delimiting regular expression
2301      *
2302      * @param  limit
2303      *         the result threshold, as described above
2304      *
2305      * @return  the array of strings computed by splitting this string
2306      *          around matches of the given regular expression
2307      *
2308      * @throws  PatternSyntaxException
2309      *          if the regular expression's syntax is invalid
2310      *
2311      * @see java.util.regex.Pattern
2312      *
2313      * @since 1.4
2314      * @spec JSR-51
2315      */
2316     public String[] split(String regex, int limit) {
2317         /* fastpath if the regex is a
2318          (1)one-char String and this character is not one of the
2319             RegEx's meta characters ".$|()[{^?*+\\", or
2320          (2)two-char String and the first char is the backslash and
2321             the second is not the ascii digit or ascii letter.
2322          */
2323         char ch = 0;
2324         if (((regex.value.length == 1 &&
2325              ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||
2326              (regex.length() == 2 &&
2327               regex.charAt(0) == '\\' &&
2328               (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
2329               ((ch-'a')|('z'-ch)) < 0 &&
2330               ((ch-'A')|('Z'-ch)) < 0)) &&
2331             (ch < Character.MIN_HIGH_SURROGATE ||
2332              ch > Character.MAX_LOW_SURROGATE))
2333         {
2334             int off = 0;
2335             int next = 0;
2336             boolean limited = limit > 0;
2337             ArrayList<String> list = new ArrayList<>();
2338             while ((next = indexOf(ch, off)) != -1) {
2339                 if (!limited || list.size() < limit - 1) {
2340                     list.add(substring(off, next));
2341                     off = next + 1;
2342                 } else {    // last one
2343                     //assert (list.size() == limit - 1);
2344                     list.add(substring(off, value.length));
2345                     off = value.length;
2346                     break;
2347                 }
2348             }
2349             // If no match was found, return this
2350             if (off == 0)
2351                 return new String[]{this};
2352 
2353             // Add remaining segment
2354             if (!limited || list.size() < limit)
2355                 list.add(substring(off, value.length));
2356 
2357             // Construct result
2358             int resultSize = list.size();
2359             if (limit == 0) {
2360                 while (resultSize > 0 && list.get(resultSize - 1).length() == 0) {
2361                     resultSize--;
2362                 }
2363             }
2364             String[] result = new String[resultSize];
2365             return list.subList(0, resultSize).toArray(result);
2366         }
2367         return Pattern.compile(regex).split(this, limit);
2368     }
2369 
2370     /**
2371      * Splits this string around matches of the given <a
2372      * href="../util/regex/Pattern.html#sum">regular expression</a>.
2373      *
2374      * <p> This method works as if by invoking the two-argument {@link
2375      * #split(String, int) split} method with the given expression and a limit
2376      * argument of zero.  Trailing empty strings are therefore not included in
2377      * the resulting array.
2378      *
2379      * <p> The string {@code "boo:and:foo"}, for example, yields the following
2380      * results with these expressions:
2381      *
2382      * <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
2383      * <tr>
2384      *  <th>Regex</th>
2385      *  <th>Result</th>
2386      * </tr>
2387      * <tr><td align=center>:</td>
2388      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
2389      * <tr><td align=center>o</td>
2390      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
2391      * </table></blockquote>
2392      *
2393      *
2394      * @param  regex
2395      *         the delimiting regular expression
2396      *
2397      * @return  the array of strings computed by splitting this string
2398      *          around matches of the given regular expression
2399      *
2400      * @throws  PatternSyntaxException
2401      *          if the regular expression's syntax is invalid
2402      *
2403      * @see java.util.regex.Pattern
2404      *
2405      * @since 1.4
2406      * @spec JSR-51
2407      */
2408     public String[] split(String regex) {
2409         return split(regex, 0);
2410     }
2411 
2412     /**
2413      * Returns a new String composed of copies of the
2414      * {@code CharSequence elements} joined together with a copy of
2415      * the specified {@code delimiter}.
2416      *
2417      * <blockquote>For example,
2418      * <pre>{@code
2419      *     String message = String.join("-", "Java", "is", "cool");
2420      *     // message returned is: "Java-is-cool"
2421      * }</pre></blockquote>
2422      *
2423      * Note that if an element is null, then {@code "null"} is added.
2424      *
2425      * @param  delimiter the delimiter that separates each element
2426      * @param  elements the elements to join together.
2427      *
2428      * @return a new {@code String} that is composed of the {@code elements}
2429      *         separated by the {@code delimiter}
2430      *
2431      * @throws NullPointerException If {@code delimiter} or {@code elements}
2432      *         is {@code null}
2433      *
2434      * @see java.util.StringJoiner
2435      * @since 1.8
2436      */
2437     public static String join(CharSequence delimiter, CharSequence... elements) {
2438         Objects.requireNonNull(delimiter);
2439         Objects.requireNonNull(elements);
2440         // Number of elements not likely worth Arrays.stream overhead.
2441         StringJoiner joiner = new StringJoiner(delimiter);
2442         for (CharSequence cs: elements) {
2443             joiner.add(cs);
2444         }
2445         return joiner.toString();
2446     }
2447 
2448     /**
2449      * Returns a new {@code String} composed of copies of the
2450      * {@code CharSequence elements} joined together with a copy of the
2451      * specified {@code delimiter}.
2452      *
2453      * <blockquote>For example,
2454      * <pre>{@code
2455      *     List<String> strings = new LinkedList<>();
2456      *     strings.add("Java");strings.add("is");
2457      *     strings.add("cool");
2458      *     String message = String.join(" ", strings);
2459      *     //message returned is: "Java is cool"
2460      *
2461      *     Set<String> strings = new LinkedHashSet<>();
2462      *     strings.add("Java"); strings.add("is");
2463      *     strings.add("very"); strings.add("cool");
2464      *     String message = String.join("-", strings);
2465      *     //message returned is: "Java-is-very-cool"
2466      * }</pre></blockquote>
2467      *
2468      * Note that if an individual element is {@code null}, then {@code "null"} is added.
2469      *
2470      * @param  delimiter a sequence of characters that is used to separate each
2471      *         of the {@code elements} in the resulting {@code String}
2472      * @param  elements an {@code Iterable} that will have its {@code elements}
2473      *         joined together.
2474      *
2475      * @return a new {@code String} that is composed from the {@code elements}
2476      *         argument
2477      *
2478      * @throws NullPointerException If {@code delimiter} or {@code elements}
2479      *         is {@code null}
2480      *
2481      * @see    #join(CharSequence,CharSequence...)
2482      * @see    java.util.StringJoiner
2483      * @since 1.8
2484      */
2485     public static String join(CharSequence delimiter,
2486             Iterable<? extends CharSequence> elements) {
2487         Objects.requireNonNull(delimiter);
2488         Objects.requireNonNull(elements);
2489         StringJoiner joiner = new StringJoiner(delimiter);
2490         for (CharSequence cs: elements) {
2491             joiner.add(cs);
2492         }
2493         return joiner.toString();
2494     }
2495 
2496     /**
2497      * Converts all of the characters in this {@code String} to lower
2498      * case using the rules of the given {@code Locale}.  Case mapping is based
2499      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
2500      * class. Since case mappings are not always 1:1 char mappings, the resulting
2501      * {@code String} may be a different length than the original {@code String}.
2502      * <p>
2503      * Examples of lowercase  mappings are in the following table:
2504      * <table border="1" summary="Lowercase mapping examples showing language code of locale, upper case, lower case, and description">
2505      * <tr>
2506      *   <th>Language Code of Locale</th>
2507      *   <th>Upper Case</th>
2508      *   <th>Lower Case</th>
2509      *   <th>Description</th>
2510      * </tr>
2511      * <tr>
2512      *   <td>tr (Turkish)</td>
2513      *   <td>&#92;u0130</td>
2514      *   <td>&#92;u0069</td>
2515      *   <td>capital letter I with dot above -&gt; small letter i</td>
2516      * </tr>
2517      * <tr>
2518      *   <td>tr (Turkish)</td>
2519      *   <td>&#92;u0049</td>
2520      *   <td>&#92;u0131</td>
2521      *   <td>capital letter I -&gt; small letter dotless i </td>
2522      * </tr>
2523      * <tr>
2524      *   <td>(all)</td>
2525      *   <td>French Fries</td>
2526      *   <td>french fries</td>
2527      *   <td>lowercased all chars in String</td>
2528      * </tr>
2529      * <tr>
2530      *   <td>(all)</td>
2531      *   <td><img src="doc-files/capiota.gif" alt="capiota"><img src="doc-files/capchi.gif" alt="capchi">
2532      *       <img src="doc-files/captheta.gif" alt="captheta"><img src="doc-files/capupsil.gif" alt="capupsil">
2533      *       <img src="doc-files/capsigma.gif" alt="capsigma"></td>
2534      *   <td><img src="doc-files/iota.gif" alt="iota"><img src="doc-files/chi.gif" alt="chi">
2535      *       <img src="doc-files/theta.gif" alt="theta"><img src="doc-files/upsilon.gif" alt="upsilon">
2536      *       <img src="doc-files/sigma1.gif" alt="sigma"></td>
2537      *   <td>lowercased all chars in String</td>
2538      * </tr>
2539      * </table>
2540      *
2541      * @param locale use the case transformation rules for this locale
2542      * @return the {@code String}, converted to lowercase.
2543      * @see     java.lang.String#toLowerCase()
2544      * @see     java.lang.String#toUpperCase()
2545      * @see     java.lang.String#toUpperCase(Locale)
2546      * @since   1.1
2547      */
2548     public String toLowerCase(Locale locale) {
2549         if (locale == null) {
2550             throw new NullPointerException();
2551         }
2552 
2553         int firstUpper;
2554         final int len = value.length;
2555 
2556         /* Now check if there are any characters that need to be changed. */
2557         scan: {
2558             for (firstUpper = 0 ; firstUpper < len; ) {
2559                 char c = value[firstUpper];
2560                 if ((c >= Character.MIN_HIGH_SURROGATE)
2561                         && (c <= Character.MAX_HIGH_SURROGATE)) {
2562                     int supplChar = codePointAt(firstUpper);
2563                     if (supplChar != Character.toLowerCase(supplChar)) {
2564                         break scan;
2565                     }
2566                     firstUpper += Character.charCount(supplChar);
2567                 } else {
2568                     if (c != Character.toLowerCase(c)) {
2569                         break scan;
2570                     }
2571                     firstUpper++;
2572                 }
2573             }
2574             return this;
2575         }
2576 
2577         char[] result = new char[len];
2578         int resultOffset = 0;  /* result may grow, so i+resultOffset
2579                                 * is the write location in result */
2580 
2581         /* Just copy the first few lowerCase characters. */
2582         System.arraycopy(value, 0, result, 0, firstUpper);
2583 
2584         String lang = locale.getLanguage();
2585         boolean localeDependent =
2586                 (lang == "tr" || lang == "az" || lang == "lt");
2587         char[] lowerCharArray;
2588         int lowerChar;
2589         int srcChar;
2590         int srcCount;
2591         for (int i = firstUpper; i < len; i += srcCount) {
2592             srcChar = (int)value[i];
2593             if ((char)srcChar >= Character.MIN_HIGH_SURROGATE
2594                     && (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
2595                 srcChar = codePointAt(i);
2596                 srcCount = Character.charCount(srcChar);
2597             } else {
2598                 srcCount = 1;
2599             }
2600             if (localeDependent || srcChar == '\u03A3') { // GREEK CAPITAL LETTER SIGMA
2601                 lowerChar = ConditionalSpecialCasing.toLowerCaseEx(this, i, locale);
2602             } else {
2603                 lowerChar = Character.toLowerCase(srcChar);
2604             }
2605             if ((lowerChar == Character.ERROR)
2606                     || (lowerChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
2607                 if (lowerChar == Character.ERROR) {
2608                     lowerCharArray =
2609                             ConditionalSpecialCasing.toLowerCaseCharArray(this, i, locale);
2610                 } else if (srcCount == 2) {
2611                     resultOffset += Character.toChars(lowerChar, result, i + resultOffset) - srcCount;
2612                     continue;
2613                 } else {
2614                     lowerCharArray = Character.toChars(lowerChar);
2615                 }
2616 
2617                 /* Grow result if needed */
2618                 int mapLen = lowerCharArray.length;
2619                 if (mapLen > srcCount) {
2620                     char[] result2 = new char[result.length + mapLen - srcCount];
2621                     System.arraycopy(result, 0, result2, 0, i + resultOffset);
2622                     result = result2;
2623                 }
2624                 for (int x = 0; x < mapLen; ++x) {
2625                     result[i + resultOffset + x] = lowerCharArray[x];
2626                 }
2627                 resultOffset += (mapLen - srcCount);
2628             } else {
2629                 result[i + resultOffset] = (char)lowerChar;
2630             }
2631         }
2632         return new String(result, 0, len + resultOffset);
2633     }
2634 
2635     /**
2636      * Converts all of the characters in this {@code String} to lower
2637      * case using the rules of the default locale. This is equivalent to calling
2638      * {@code toLowerCase(Locale.getDefault())}.
2639      * <p>
2640      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
2641      * results if used for strings that are intended to be interpreted locale
2642      * independently.
2643      * Examples are programming language identifiers, protocol keys, and HTML
2644      * tags.
2645      * For instance, {@code "TITLE".toLowerCase()} in a Turkish locale
2646      * returns {@code "t\u005Cu0131tle"}, where '\u005Cu0131' is the
2647      * LATIN SMALL LETTER DOTLESS I character.
2648      * To obtain correct results for locale insensitive strings, use
2649      * {@code toLowerCase(Locale.ROOT)}.
2650      * <p>
2651      * @return  the {@code String}, converted to lowercase.
2652      * @see     java.lang.String#toLowerCase(Locale)
2653      */
2654     public String toLowerCase() {
2655         return toLowerCase(Locale.getDefault());
2656     }
2657 
2658     /**
2659      * Converts all of the characters in this {@code String} to upper
2660      * case using the rules of the given {@code Locale}. Case mapping is based
2661      * on the Unicode Standard version specified by the {@link java.lang.Character Character}
2662      * class. Since case mappings are not always 1:1 char mappings, the resulting
2663      * {@code String} may be a different length than the original {@code String}.
2664      * <p>
2665      * Examples of locale-sensitive and 1:M case mappings are in the following table.
2666      *
2667      * <table border="1" summary="Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.">
2668      * <tr>
2669      *   <th>Language Code of Locale</th>
2670      *   <th>Lower Case</th>
2671      *   <th>Upper Case</th>
2672      *   <th>Description</th>
2673      * </tr>
2674      * <tr>
2675      *   <td>tr (Turkish)</td>
2676      *   <td>&#92;u0069</td>
2677      *   <td>&#92;u0130</td>
2678      *   <td>small letter i -&gt; capital letter I with dot above</td>
2679      * </tr>
2680      * <tr>
2681      *   <td>tr (Turkish)</td>
2682      *   <td>&#92;u0131</td>
2683      *   <td>&#92;u0049</td>
2684      *   <td>small letter dotless i -&gt; capital letter I</td>
2685      * </tr>
2686      * <tr>
2687      *   <td>(all)</td>
2688      *   <td>&#92;u00df</td>
2689      *   <td>&#92;u0053 &#92;u0053</td>
2690      *   <td>small letter sharp s -&gt; two letters: SS</td>
2691      * </tr>
2692      * <tr>
2693      *   <td>(all)</td>
2694      *   <td>Fahrvergn&uuml;gen</td>
2695      *   <td>FAHRVERGN&Uuml;GEN</td>
2696      *   <td></td>
2697      * </tr>
2698      * </table>
2699      * @param locale use the case transformation rules for this locale
2700      * @return the {@code String}, converted to uppercase.
2701      * @see     java.lang.String#toUpperCase()
2702      * @see     java.lang.String#toLowerCase()
2703      * @see     java.lang.String#toLowerCase(Locale)
2704      * @since   1.1
2705      */
2706     public String toUpperCase(Locale locale) {
2707         if (locale == null) {
2708             throw new NullPointerException();
2709         }
2710 
2711         int firstLower;
2712         final int len = value.length;
2713 
2714         /* Now check if there are any characters that need to be changed. */
2715         scan: {
2716             for (firstLower = 0 ; firstLower < len; ) {
2717                 int c = (int)value[firstLower];
2718                 int srcCount;
2719                 if ((c >= Character.MIN_HIGH_SURROGATE)
2720                         && (c <= Character.MAX_HIGH_SURROGATE)) {
2721                     c = codePointAt(firstLower);
2722                     srcCount = Character.charCount(c);
2723                 } else {
2724                     srcCount = 1;
2725                 }
2726                 int upperCaseChar = Character.toUpperCaseEx(c);
2727                 if ((upperCaseChar == Character.ERROR)
2728                         || (c != upperCaseChar)) {
2729                     break scan;
2730                 }
2731                 firstLower += srcCount;
2732             }
2733             return this;
2734         }
2735 
2736         /* result may grow, so i+resultOffset is the write location in result */
2737         int resultOffset = 0;
2738         char[] result = new char[len]; /* may grow */
2739 
2740         /* Just copy the first few upperCase characters. */
2741         System.arraycopy(value, 0, result, 0, firstLower);
2742 
2743         String lang = locale.getLanguage();
2744         boolean localeDependent =
2745                 (lang == "tr" || lang == "az" || lang == "lt");
2746         char[] upperCharArray;
2747         int upperChar;
2748         int srcChar;
2749         int srcCount;
2750         for (int i = firstLower; i < len; i += srcCount) {
2751             srcChar = (int)value[i];
2752             if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
2753                 (char)srcChar <= Character.MAX_HIGH_SURROGATE) {
2754                 srcChar = codePointAt(i);
2755                 srcCount = Character.charCount(srcChar);
2756             } else {
2757                 srcCount = 1;
2758             }
2759             if (localeDependent) {
2760                 upperChar = ConditionalSpecialCasing.toUpperCaseEx(this, i, locale);
2761             } else {
2762                 upperChar = Character.toUpperCaseEx(srcChar);
2763             }
2764             if ((upperChar == Character.ERROR)
2765                     || (upperChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
2766                 if (upperChar == Character.ERROR) {
2767                     if (localeDependent) {
2768                         upperCharArray =
2769                                 ConditionalSpecialCasing.toUpperCaseCharArray(this, i, locale);
2770                     } else {
2771                         upperCharArray = Character.toUpperCaseCharArray(srcChar);
2772                     }
2773                 } else if (srcCount == 2) {
2774                     resultOffset += Character.toChars(upperChar, result, i + resultOffset) - srcCount;
2775                     continue;
2776                 } else {
2777                     upperCharArray = Character.toChars(upperChar);
2778                 }
2779 
2780                 /* Grow result if needed */
2781                 int mapLen = upperCharArray.length;
2782                 if (mapLen > srcCount) {
2783                     char[] result2 = new char[result.length + mapLen - srcCount];
2784                     System.arraycopy(result, 0, result2, 0, i + resultOffset);
2785                     result = result2;
2786                 }
2787                 for (int x = 0; x < mapLen; ++x) {
2788                     result[i + resultOffset + x] = upperCharArray[x];
2789                 }
2790                 resultOffset += (mapLen - srcCount);
2791             } else {
2792                 result[i + resultOffset] = (char)upperChar;
2793             }
2794         }
2795         return new String(result, 0, len + resultOffset);
2796     }
2797 
2798     /**
2799      * Converts all of the characters in this {@code String} to upper
2800      * case using the rules of the default locale. This method is equivalent to
2801      * {@code toUpperCase(Locale.getDefault())}.
2802      * <p>
2803      * <b>Note:</b> This method is locale sensitive, and may produce unexpected
2804      * results if used for strings that are intended to be interpreted locale
2805      * independently.
2806      * Examples are programming language identifiers, protocol keys, and HTML
2807      * tags.
2808      * For instance, {@code "title".toUpperCase()} in a Turkish locale
2809      * returns {@code "T\u005Cu0130TLE"}, where '\u005Cu0130' is the
2810      * LATIN CAPITAL LETTER I WITH DOT ABOVE character.
2811      * To obtain correct results for locale insensitive strings, use
2812      * {@code toUpperCase(Locale.ROOT)}.
2813      * <p>
2814      * @return  the {@code String}, converted to uppercase.
2815      * @see     java.lang.String#toUpperCase(Locale)
2816      */
2817     public String toUpperCase() {
2818         return toUpperCase(Locale.getDefault());
2819     }
2820 
2821     /**
2822      * Returns a string whose value is this string, with any leading and trailing
2823      * whitespace removed.
2824      * <p>
2825      * If this {@code String} object represents an empty character
2826      * sequence, or the first and last characters of character sequence
2827      * represented by this {@code String} object both have codes
2828      * greater than {@code '\u005Cu0020'} (the space character), then a
2829      * reference to this {@code String} object is returned.
2830      * <p>
2831      * Otherwise, if there is no character with a code greater than
2832      * {@code '\u005Cu0020'} in the string, then a
2833      * {@code String} object representing an empty string is
2834      * returned.
2835      * <p>
2836      * Otherwise, let <i>k</i> be the index of the first character in the
2837      * string whose code is greater than {@code '\u005Cu0020'}, and let
2838      * <i>m</i> be the index of the last character in the string whose code
2839      * is greater than {@code '\u005Cu0020'}. A {@code String}
2840      * object is returned, representing the substring of this string that
2841      * begins with the character at index <i>k</i> and ends with the
2842      * character at index <i>m</i>-that is, the result of
2843      * {@code this.substring(k, m + 1)}.
2844      * <p>
2845      * This method may be used to trim whitespace (as defined above) from
2846      * the beginning and end of a string.
2847      *
2848      * @return  A string whose value is this string, with any leading and trailing white
2849      *          space removed, or this string if it has no leading or
2850      *          trailing white space.
2851      */
2852     public String trim() {
2853         int len = value.length;
2854         int st = 0;
2855         char[] val = value;    /* avoid getfield opcode */
2856 
2857         while ((st < len) && (val[st] <= ' ')) {
2858             st++;
2859         }
2860         while ((st < len) && (val[len - 1] <= ' ')) {
2861             len--;
2862         }
2863         return ((st > 0) || (len < value.length)) ? substring(st, len) : this;
2864     }
2865 
2866     /**
2867      * This object (which is already a string!) is itself returned.
2868      *
2869      * @return  the string itself.
2870      */
2871     public String toString() {
2872         return this;
2873     }
2874 
2875     /**
2876      * Converts this string to a new character array.
2877      *
2878      * @return  a newly allocated character array whose length is the length
2879      *          of this string and whose contents are initialized to contain
2880      *          the character sequence represented by this string.
2881      */
2882     public char[] toCharArray() {
2883         // Cannot use Arrays.copyOf because of class initialization order issues
2884         char result[] = new char[value.length];
2885         System.arraycopy(value, 0, result, 0, value.length);
2886         return result;
2887     }
2888 
2889     /**
2890      * Returns a formatted string using the specified format string and
2891      * arguments.
2892      *
2893      * <p> The locale always used is the one returned by {@link
2894      * java.util.Locale#getDefault() Locale.getDefault()}.
2895      *
2896      * @param  format
2897      *         A <a href="../util/Formatter.html#syntax">format string</a>
2898      *
2899      * @param  args
2900      *         Arguments referenced by the format specifiers in the format
2901      *         string.  If there are more arguments than format specifiers, the
2902      *         extra arguments are ignored.  The number of arguments is
2903      *         variable and may be zero.  The maximum number of arguments is
2904      *         limited by the maximum dimension of a Java array as defined by
2905      *         <cite>The Java&trade; Virtual Machine Specification</cite>.
2906      *         The behaviour on a
2907      *         {@code null} argument depends on the <a
2908      *         href="../util/Formatter.html#syntax">conversion</a>.
2909      *
2910      * @throws  java.util.IllegalFormatException
2911      *          If a format string contains an illegal syntax, a format
2912      *          specifier that is incompatible with the given arguments,
2913      *          insufficient arguments given the format string, or other
2914      *          illegal conditions.  For specification of all possible
2915      *          formatting errors, see the <a
2916      *          href="../util/Formatter.html#detail">Details</a> section of the
2917      *          formatter class specification.
2918      *
2919      * @return  A formatted string
2920      *
2921      * @see  java.util.Formatter
2922      * @since  1.5
2923      */
2924     public static String format(String format, Object... args) {
2925         return new Formatter().format(format, args).toString();
2926     }
2927 
2928     /**
2929      * Returns a formatted string using the specified locale, format string,
2930      * and arguments.
2931      *
2932      * @param  l
2933      *         The {@linkplain java.util.Locale locale} to apply during
2934      *         formatting.  If {@code l} is {@code null} then no localization
2935      *         is applied.
2936      *
2937      * @param  format
2938      *         A <a href="../util/Formatter.html#syntax">format string</a>
2939      *
2940      * @param  args
2941      *         Arguments referenced by the format specifiers in the format
2942      *         string.  If there are more arguments than format specifiers, the
2943      *         extra arguments are ignored.  The number of arguments is
2944      *         variable and may be zero.  The maximum number of arguments is
2945      *         limited by the maximum dimension of a Java array as defined by
2946      *         <cite>The Java&trade; Virtual Machine Specification</cite>.
2947      *         The behaviour on a
2948      *         {@code null} argument depends on the
2949      *         <a href="../util/Formatter.html#syntax">conversion</a>.
2950      *
2951      * @throws  java.util.IllegalFormatException
2952      *          If a format string contains an illegal syntax, a format
2953      *          specifier that is incompatible with the given arguments,
2954      *          insufficient arguments given the format string, or other
2955      *          illegal conditions.  For specification of all possible
2956      *          formatting errors, see the <a
2957      *          href="../util/Formatter.html#detail">Details</a> section of the
2958      *          formatter class specification
2959      *
2960      * @return  A formatted string
2961      *
2962      * @see  java.util.Formatter
2963      * @since  1.5
2964      */
2965     public static String format(Locale l, String format, Object... args) {
2966         return new Formatter(l).format(format, args).toString();
2967     }
2968 
2969     /**
2970      * Returns the string representation of the {@code Object} argument.
2971      *
2972      * @param   obj   an {@code Object}.
2973      * @return  if the argument is {@code null}, then a string equal to
2974      *          {@code "null"}; otherwise, the value of
2975      *          {@code obj.toString()} is returned.
2976      * @see     java.lang.Object#toString()
2977      */
2978     public static String valueOf(Object obj) {
2979         return (obj == null) ? "null" : obj.toString();
2980     }
2981 
2982     /**
2983      * Returns the string representation of the {@code char} array
2984      * argument. The contents of the character array are copied; subsequent
2985      * modification of the character array does not affect the returned
2986      * string.
2987      *
2988      * @param   data     the character array.
2989      * @return  a {@code String} that contains the characters of the
2990      *          character array.
2991      */
2992     public static String valueOf(char data[]) {
2993         return new String(data);
2994     }
2995 
2996     /**
2997      * Returns the string representation of a specific subarray of the
2998      * {@code char} array argument.
2999      * <p>
3000      * The {@code offset} argument is the index of the first
3001      * character of the subarray. The {@code count} argument
3002      * specifies the length of the subarray. The contents of the subarray
3003      * are copied; subsequent modification of the character array does not
3004      * affect the returned string.
3005      *
3006      * @param   data     the character array.
3007      * @param   offset   initial offset of the subarray.
3008      * @param   count    length of the subarray.
3009      * @return  a {@code String} that contains the characters of the
3010      *          specified subarray of the character array.
3011      * @exception IndexOutOfBoundsException if {@code offset} is
3012      *          negative, or {@code count} is negative, or
3013      *          {@code offset+count} is larger than
3014      *          {@code data.length}.
3015      */
3016     public static String valueOf(char data[], int offset, int count) {
3017         return new String(data, offset, count);
3018     }
3019 
3020     /**
3021      * Equivalent to {@link #valueOf(char[], int, int)}.
3022      *
3023      * @param   data     the character array.
3024      * @param   offset   initial offset of the subarray.
3025      * @param   count    length of the subarray.
3026      * @return  a {@code String} that contains the characters of the
3027      *          specified subarray of the character array.
3028      * @exception IndexOutOfBoundsException if {@code offset} is
3029      *          negative, or {@code count} is negative, or
3030      *          {@code offset+count} is larger than
3031      *          {@code data.length}.
3032      */
3033     public static String copyValueOf(char data[], int offset, int count) {
3034         return new String(data, offset, count);
3035     }
3036 
3037     /**
3038      * Equivalent to {@link #valueOf(char[])}.
3039      *
3040      * @param   data   the character array.
3041      * @return  a {@code String} that contains the characters of the
3042      *          character array.
3043      */
3044     public static String copyValueOf(char data[]) {
3045         return new String(data);
3046     }
3047 
3048     /**
3049      * Returns the string representation of the {@code boolean} argument.
3050      *
3051      * @param   b   a {@code boolean}.
3052      * @return  if the argument is {@code true}, a string equal to
3053      *          {@code "true"} is returned; otherwise, a string equal to
3054      *          {@code "false"} is returned.
3055      */
3056     public static String valueOf(boolean b) {
3057         return b ? "true" : "false";
3058     }
3059 
3060     /**
3061      * Returns the string representation of the {@code char}
3062      * argument.
3063      *
3064      * @param   c   a {@code char}.
3065      * @return  a string of length {@code 1} containing
3066      *          as its single character the argument {@code c}.
3067      */
3068     public static String valueOf(char c) {
3069         char data[] = {c};
3070         return new String(data, true);
3071     }
3072 
3073     /**
3074      * Returns the string representation of the {@code int} argument.
3075      * <p>
3076      * The representation is exactly the one returned by the
3077      * {@code Integer.toString} method of one argument.
3078      *
3079      * @param   i   an {@code int}.
3080      * @return  a string representation of the {@code int} argument.
3081      * @see     java.lang.Integer#toString(int, int)
3082      */
3083     public static String valueOf(int i) {
3084         return Integer.toString(i);
3085     }
3086 
3087     /**
3088      * Returns the string representation of the {@code long} argument.
3089      * <p>
3090      * The representation is exactly the one returned by the
3091      * {@code Long.toString} method of one argument.
3092      *
3093      * @param   l   a {@code long}.
3094      * @return  a string representation of the {@code long} argument.
3095      * @see     java.lang.Long#toString(long)
3096      */
3097     public static String valueOf(long l) {
3098         return Long.toString(l);
3099     }
3100 
3101     /**
3102      * Returns the string representation of the {@code float} argument.
3103      * <p>
3104      * The representation is exactly the one returned by the
3105      * {@code Float.toString} method of one argument.
3106      *
3107      * @param   f   a {@code float}.
3108      * @return  a string representation of the {@code float} argument.
3109      * @see     java.lang.Float#toString(float)
3110      */
3111     public static String valueOf(float f) {
3112         return Float.toString(f);
3113     }
3114 
3115     /**
3116      * Returns the string representation of the {@code double} argument.
3117      * <p>
3118      * The representation is exactly the one returned by the
3119      * {@code Double.toString} method of one argument.
3120      *
3121      * @param   d   a {@code double}.
3122      * @return  a  string representation of the {@code double} argument.
3123      * @see     java.lang.Double#toString(double)
3124      */
3125     public static String valueOf(double d) {
3126         return Double.toString(d);
3127     }
3128 
3129     /**
3130      * Returns a canonical representation for the string object.
3131      * <p>
3132      * A pool of strings, initially empty, is maintained privately by the
3133      * class {@code String}.
3134      * <p>
3135      * When the intern method is invoked, if the pool already contains a
3136      * string equal to this {@code String} object as determined by
3137      * the {@link #equals(Object)} method, then the string from the pool is
3138      * returned. Otherwise, this {@code String} object is added to the
3139      * pool and a reference to this {@code String} object is returned.
3140      * <p>
3141      * It follows that for any two strings {@code s} and {@code t},
3142      * {@code s.intern() == t.intern()} is {@code true}
3143      * if and only if {@code s.equals(t)} is {@code true}.
3144      * <p>
3145      * All literal strings and string-valued constant expressions are
3146      * interned. String literals are defined in section 3.10.5 of the
3147      * <cite>The Java&trade; Language Specification</cite>.
3148      *
3149      * @return  a string that has the same contents as this string, but is
3150      *          guaranteed to be from a pool of unique strings.
3151      */
3152     public native String intern();
3153 }