1 /*
2 * Copyright 1994-2008 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.lang;
27
28
29 /**
30 * A thread-safe, mutable sequence of characters.
31 * A string buffer is like a {@link String}, but can be modified. At any
32 * point in time it contains some particular sequence of characters, but
33 * the length and content of the sequence can be changed through certain
34 * method calls.
35 * <p>
36 * String buffers are safe for use by multiple threads. The methods
37 * are synchronized where necessary so that all the operations on any
38 * particular instance behave as if they occur in some serial order
39 * that is consistent with the order of the method calls made by each of
40 * the individual threads involved.
41 * <p>
42 * The principal operations on a <code>StringBuffer</code> are the
43 * <code>append</code> and <code>insert</code> methods, which are
44 * overloaded so as to accept data of any type. Each effectively
45 * converts a given datum to a string and then appends or inserts the
46 * characters of that string to the string buffer. The
47 * <code>append</code> method always adds these characters at the end
48 * of the buffer; the <code>insert</code> method adds the characters at
49 * a specified point.
50 * <p>
51 * For example, if <code>z</code> refers to a string buffer object
52 * whose current contents are "<code>start</code>", then
53 * the method call <code>z.append("le")</code> would cause the string
54 * buffer to contain "<code>startle</code>", whereas
55 * <code>z.insert(4, "le")</code> would alter the string buffer to
56 * contain "<code>starlet</code>".
57 * <p>
58 * In general, if sb refers to an instance of a <code>StringBuffer</code>,
59 * then <code>sb.append(x)</code> has the same effect as
60 * <code>sb.insert(sb.length(), x)</code>.
61 * <p>
62 * Whenever an operation occurs involving a source sequence (such as
63 * appending or inserting from a source sequence) this class synchronizes
64 * only on the string buffer performing the operation, not on the source.
65 * <p>
66 * Every string buffer has a capacity. As long as the length of the
67 * character sequence contained in the string buffer does not exceed
68 * the capacity, it is not necessary to allocate a new internal
69 * buffer array. If the internal buffer overflows, it is
70 * automatically made larger.
71 *
72 * As of release JDK 5, this class has been supplemented with an equivalent
73 * class designed for use by a single thread, {@link StringBuilder}. The
74 * <tt>StringBuilder</tt> class should generally be used in preference to
75 * this one, as it supports all of the same operations but it is faster, as
76 * it performs no synchronization.
77 *
78 * @author Arthur van Hoff
79 * @see java.lang.StringBuilder
80 * @see java.lang.String
81 * @since JDK1.0
82 */
83 public final class StringBuffer
84 extends AbstractStringBuilder
85 implements java.io.Serializable, CharSequence
86 {
87
88 /** use serialVersionUID from JDK 1.0.2 for interoperability */
89 static final long serialVersionUID = 3388685877147921107L;
90
91 /**
92 * Constructs a string buffer with no characters in it and an
93 * initial capacity of 16 characters.
94 */
95 public StringBuffer() {
96 super(16);
97 }
98
99 /**
100 * Constructs a string buffer with no characters in it and
101 * the specified initial capacity.
102 *
103 * @param capacity the initial capacity.
104 * @exception NegativeArraySizeException if the <code>capacity</code>
105 * argument is less than <code>0</code>.
106 */
107 public StringBuffer(int capacity) {
108 super(capacity);
109 }
110
111 /**
112 * Constructs a string buffer initialized to the contents of the
113 * specified string. The initial capacity of the string buffer is
114 * <code>16</code> plus the length of the string argument.
115 *
116 * @param str the initial contents of the buffer.
117 * @exception NullPointerException if <code>str</code> is <code>null</code>
118 */
119 public StringBuffer(String str) {
120 super(str.length() + 16);
121 append(str);
122 }
123
124 /**
125 * Constructs a string buffer that contains the same characters
126 * as the specified <code>CharSequence</code>. The initial capacity of
127 * the string buffer is <code>16</code> plus the length of the
128 * <code>CharSequence</code> argument.
129 * <p>
130 * If the length of the specified <code>CharSequence</code> is
131 * less than or equal to zero, then an empty buffer of capacity
132 * <code>16</code> is returned.
133 *
134 * @param seq the sequence to copy.
135 * @exception NullPointerException if <code>seq</code> is <code>null</code>
136 * @since 1.5
137 */
138 public StringBuffer(CharSequence seq) {
139 this(seq.length() + 16);
140 append(seq);
141 }
142
143 public synchronized int length() {
144 return count;
145 }
146
147 public synchronized int capacity() {
148 return value.length;
149 }
150
151
152 public synchronized void ensureCapacity(int minimumCapacity) {
153 if (minimumCapacity > value.length) {
154 expandCapacity(minimumCapacity);
155 }
156 }
157
158 /**
159 * @since 1.5
160 */
161 public synchronized void trimToSize() {
162 super.trimToSize();
163 }
164
165 /**
166 * @throws IndexOutOfBoundsException {@inheritDoc}
167 * @see #length()
168 */
169 public synchronized void setLength(int newLength) {
170 super.setLength(newLength);
171 }
172
173 /**
174 * @throws IndexOutOfBoundsException {@inheritDoc}
175 * @see #length()
176 */
177 public synchronized char charAt(int index) {
178 if ((index < 0) || (index >= count))
179 throw new StringIndexOutOfBoundsException(index);
180 return value[index];
181 }
182
183 /**
184 * @since 1.5
185 */
186 public synchronized int codePointAt(int index) {
187 return super.codePointAt(index);
188 }
189
190 /**
191 * @since 1.5
192 */
193 public synchronized int codePointBefore(int index) {
194 return super.codePointBefore(index);
195 }
196
197 /**
198 * @since 1.5
199 */
200 public synchronized int codePointCount(int beginIndex, int endIndex) {
201 return super.codePointCount(beginIndex, endIndex);
202 }
203
204 /**
205 * @since 1.5
206 */
207 public synchronized int offsetByCodePoints(int index, int codePointOffset) {
208 return super.offsetByCodePoints(index, codePointOffset);
209 }
210
211 /**
212 * @throws NullPointerException {@inheritDoc}
213 * @throws IndexOutOfBoundsException {@inheritDoc}
214 */
215 public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
216 int dstBegin)
217 {
218 super.getChars(srcBegin, srcEnd, dst, dstBegin);
219 }
220
221 /**
222 * @throws IndexOutOfBoundsException {@inheritDoc}
223 * @see #length()
224 */
225 public synchronized void setCharAt(int index, char ch) {
226 if ((index < 0) || (index >= count))
227 throw new StringIndexOutOfBoundsException(index);
228 value[index] = ch;
229 }
230
231 public synchronized StringBuffer append(Object obj) {
232 super.append(String.valueOf(obj));
233 return this;
234 }
235
236 public synchronized StringBuffer append(String str) {
237 super.append(str);
238 return this;
239 }
240
241 /**
242 * Appends the specified <tt>StringBuffer</tt> to this sequence.
243 * <p>
244 * The characters of the <tt>StringBuffer</tt> argument are appended,
245 * in order, to the contents of this <tt>StringBuffer</tt>, increasing the
246 * length of this <tt>StringBuffer</tt> by the length of the argument.
247 * If <tt>sb</tt> is <tt>null</tt>, then the four characters
248 * <tt>"null"</tt> are appended to this <tt>StringBuffer</tt>.
249 * <p>
250 * Let <i>n</i> be the length of the old character sequence, the one
251 * contained in the <tt>StringBuffer</tt> just prior to execution of the
252 * <tt>append</tt> method. Then the character at index <i>k</i> in
253 * the new character sequence is equal to the character at index <i>k</i>
254 * in the old character sequence, if <i>k</i> is less than <i>n</i>;
255 * otherwise, it is equal to the character at index <i>k-n</i> in the
256 * argument <code>sb</code>.
257 * <p>
258 * This method synchronizes on <code>this</code> (the destination)
259 * object but does not synchronize on the source (<code>sb</code>).
260 *
261 * @param sb the <tt>StringBuffer</tt> to append.
262 * @return a reference to this object.
263 * @since 1.4
264 */
265 public synchronized StringBuffer append(StringBuffer sb) {
266 super.append(sb);
267 return this;
268 }
269
270
271 /**
272 * Appends the specified <code>CharSequence</code> to this
273 * sequence.
274 * <p>
275 * The characters of the <code>CharSequence</code> argument are appended,
276 * in order, increasing the length of this sequence by the length of the
277 * argument.
278 *
279 * <p>The result of this method is exactly the same as if it were an
280 * invocation of this.append(s, 0, s.length());
281 *
282 * <p>This method synchronizes on this (the destination)
283 * object but does not synchronize on the source (<code>s</code>).
284 *
285 * <p>If <code>s</code> is <code>null</code>, then the four characters
286 * <code>"null"</code> are appended.
287 *
288 * @param s the <code>CharSequence</code> to append.
289 * @return a reference to this object.
290 * @since 1.5
291 */
292 public StringBuffer append(CharSequence s) {
293 // Note, synchronization achieved via other invocations
294 if (s == null)
295 s = "null";
296 if (s instanceof String)
297 return this.append((String)s);
298 if (s instanceof StringBuffer)
299 return this.append((StringBuffer)s);
300 return this.append(s, 0, s.length());
301 }
302
303 /**
304 * @throws IndexOutOfBoundsException {@inheritDoc}
305 * @since 1.5
306 */
307 public synchronized StringBuffer append(CharSequence s, int start, int end)
308 {
309 super.append(s, start, end);
310 return this;
311 }
312
313 public synchronized StringBuffer append(char[] str) {
314 super.append(str);
315 return this;
316 }
317
318 /**
319 * @throws IndexOutOfBoundsException {@inheritDoc}
320 */
321 public synchronized StringBuffer append(char[] str, int offset, int len) {
322 super.append(str, offset, len);
323 return this;
324 }
325
326 public synchronized StringBuffer append(boolean b) {
327 super.append(b);
328 return this;
329 }
330
331 public synchronized StringBuffer append(char c) {
332 super.append(c);
333 return this;
334 }
335
336 public synchronized StringBuffer append(int i) {
337 super.append(i);
338 return this;
339 }
340
341 /**
342 * @since 1.5
343 */
344 public synchronized StringBuffer appendCodePoint(int codePoint) {
345 super.appendCodePoint(codePoint);
346 return this;
347 }
348
349 public synchronized StringBuffer append(long lng) {
350 super.append(lng);
351 return this;
352 }
353
354 public synchronized StringBuffer append(float f) {
355 super.append(f);
356 return this;
357 }
358
359 public synchronized StringBuffer append(double d) {
360 super.append(d);
361 return this;
362 }
363
364 /**
365 * @throws StringIndexOutOfBoundsException {@inheritDoc}
366 * @since 1.2
367 */
368 public synchronized StringBuffer delete(int start, int end) {
369 super.delete(start, end);
370 return this;
371 }
372
373 /**
374 * @throws StringIndexOutOfBoundsException {@inheritDoc}
375 * @since 1.2
376 */
377 public synchronized StringBuffer deleteCharAt(int index) {
378 super.deleteCharAt(index);
379 return this;
380 }
381
382 /**
383 * @throws StringIndexOutOfBoundsException {@inheritDoc}
384 * @since 1.2
385 */
386 public synchronized StringBuffer replace(int start, int end, String str) {
387 super.replace(start, end, str);
388 return this;
389 }
390
391 /**
392 * @throws StringIndexOutOfBoundsException {@inheritDoc}
393 * @since 1.2
394 */
395 public synchronized String substring(int start) {
396 return substring(start, count);
397 }
398
399 /**
400 * @throws IndexOutOfBoundsException {@inheritDoc}
401 * @since 1.4
402 */
403 public synchronized CharSequence subSequence(int start, int end) {
404 return super.substring(start, end);
405 }
406
407 /**
408 * @throws StringIndexOutOfBoundsException {@inheritDoc}
409 * @since 1.2
410 */
411 public synchronized String substring(int start, int end) {
412 return super.substring(start, end);
413 }
414
415 /**
416 * @throws StringIndexOutOfBoundsException {@inheritDoc}
417 * @since 1.2
418 */
419 public synchronized StringBuffer insert(int index, char[] str, int offset,
420 int len)
421 {
422 super.insert(index, str, offset, len);
423 return this;
424 }
425
426 /**
427 * @throws StringIndexOutOfBoundsException {@inheritDoc}
428 */
429 public synchronized StringBuffer insert(int offset, Object obj) {
430 super.insert(offset, String.valueOf(obj));
431 return this;
432 }
433
434 /**
435 * @throws StringIndexOutOfBoundsException {@inheritDoc}
436 */
437 public synchronized StringBuffer insert(int offset, String str) {
438 super.insert(offset, str);
439 return this;
440 }
441
442 /**
443 * @throws StringIndexOutOfBoundsException {@inheritDoc}
444 */
445 public synchronized StringBuffer insert(int offset, char[] str) {
446 super.insert(offset, str);
447 return this;
448 }
449
450 /**
451 * @throws IndexOutOfBoundsException {@inheritDoc}
452 * @since 1.5
453 */
454 public StringBuffer insert(int dstOffset, CharSequence s) {
455 // Note, synchronization achieved via other invocations
456 if (s == null)
457 s = "null";
458 if (s instanceof String)
459 return this.insert(dstOffset, (String)s);
460 return this.insert(dstOffset, s, 0, s.length());
461 }
462
463 /**
464 * @throws IndexOutOfBoundsException {@inheritDoc}
465 * @since 1.5
466 */
467 public synchronized StringBuffer insert(int dstOffset, CharSequence s,
468 int start, int end)
469 {
470 super.insert(dstOffset, s, start, end);
471 return this;
472 }
473
474 /**
475 * @throws StringIndexOutOfBoundsException {@inheritDoc}
476 */
477 public StringBuffer insert(int offset, boolean b) {
478 return insert(offset, String.valueOf(b));
479 }
480
481 /**
482 * @throws IndexOutOfBoundsException {@inheritDoc}
483 */
484 public synchronized StringBuffer insert(int offset, char c) {
485 super.insert(offset, c);
486 return this;
487 }
488
489 /**
490 * @throws StringIndexOutOfBoundsException {@inheritDoc}
491 */
492 public StringBuffer insert(int offset, int i) {
493 return insert(offset, String.valueOf(i));
494 }
495
496 /**
497 * @throws StringIndexOutOfBoundsException {@inheritDoc}
498 */
499 public StringBuffer insert(int offset, long l) {
500 return insert(offset, String.valueOf(l));
501 }
502
503 /**
504 * @throws StringIndexOutOfBoundsException {@inheritDoc}
505 */
506 public StringBuffer insert(int offset, float f) {
507 return insert(offset, String.valueOf(f));
508 }
509
510 /**
511 * @throws StringIndexOutOfBoundsException {@inheritDoc}
512 */
513 public StringBuffer insert(int offset, double d) {
514 return insert(offset, String.valueOf(d));
515 }
516
517 /**
518 * @throws NullPointerException {@inheritDoc}
519 * @since 1.4
520 */
521 public int indexOf(String str) {
522 return indexOf(str, 0);
523 }
524
525 /**
526 * @throws NullPointerException {@inheritDoc}
527 * @since 1.4
528 */
529 public synchronized int indexOf(String str, int fromIndex) {
530 return String.indexOf(value, 0, count,
531 str.toCharArray(), 0, str.length(), fromIndex);
532 }
533
534 /**
535 * @throws NullPointerException {@inheritDoc}
536 * @since 1.4
537 */
538 public int lastIndexOf(String str) {
539 // Note, synchronization achieved via other invocations
540 return lastIndexOf(str, count);
541 }
542
543 /**
544 * @throws NullPointerException {@inheritDoc}
545 * @since 1.4
546 */
547 public synchronized int lastIndexOf(String str, int fromIndex) {
548 return String.lastIndexOf(value, 0, count,
549 str.toCharArray(), 0, str.length(), fromIndex);
550 }
551
552 /**
553 * @since JDK1.0.2
554 */
555 public synchronized StringBuffer reverse() {
556 super.reverse();
557 return this;
558 }
559
560 /**
561 * @throws NullPointerException {@inheritDoc}
562 * @since 1.7
563 */
564 @Override
565 public synchronized StringBuffer join(String delimiter, Object first, Object... elements) {
566 super.join(delimiter, first, elements);
567 return this;
568 }
569
570 /**
571 * @throws NullPointerException {@inheritDoc}
572 * @since 1.7
573 */
574 @Override
575 public synchronized StringBuffer join(String delimiter, Object[] elements) {
576 super.join(delimiter, elements);
577 return this;
578 }
579
580 /**
581 * @throws NullPointerException {@inheritDoc}
582 * @since 1.7
583 */
584 @Override
585 public synchronized StringBuffer join(String delimiter, Iterable<?> elements) {
586 super.join(delimiter, elements);
587 return this;
588 }
589
590 public synchronized String toString() {
591 return new String(value, 0, count);
592 }
593
594 /**
595 * Serializable fields for StringBuffer.
596 *
597 * @serialField value char[]
598 * The backing character array of this StringBuffer.
599 * @serialField count int
600 * The number of characters in this StringBuffer.
601 * @serialField shared boolean
602 * A flag indicating whether the backing array is shared.
603 * The value is ignored upon deserialization.
604 */
605 private static final java.io.ObjectStreamField[] serialPersistentFields =
606 {
607 new java.io.ObjectStreamField("value", char[].class),
608 new java.io.ObjectStreamField("count", Integer.TYPE),
609 new java.io.ObjectStreamField("shared", Boolean.TYPE),
610 };
611
612 /**
613 * readObject is called to restore the state of the StringBuffer from
614 * a stream.
615 */
616 private synchronized void writeObject(java.io.ObjectOutputStream s)
617 throws java.io.IOException {
618 java.io.ObjectOutputStream.PutField fields = s.putFields();
619 fields.put("value", value);
620 fields.put("count", count);
621 fields.put("shared", false);
622 s.writeFields();
623 }
624
625 /**
626 * readObject is called to restore the state of the StringBuffer from
627 * a stream.
628 */
629 private void readObject(java.io.ObjectInputStream s)
630 throws java.io.IOException, ClassNotFoundException {
631 java.io.ObjectInputStream.GetField fields = s.readFields();
632 value = (char[])fields.get("value", null);
633 count = fields.get("count", 0);
634 }
635 }