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
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.util.Arrays;
29 import jdk.internal.HotSpotIntrinsicCandidate;
30
31 /**
32 * A thread-safe, mutable sequence of characters.
33 * A string buffer is like a {@link String}, but can be modified. At any
34 * point in time it contains some particular sequence of characters, but
35 * the length and content of the sequence can be changed through certain
36 * method calls.
37 * <p>
38 * String buffers are safe for use by multiple threads. The methods
39 * are synchronized where necessary so that all the operations on any
40 * particular instance behave as if they occur in some serial order
41 * that is consistent with the order of the method calls made by each of
42 * the individual threads involved.
43 * <p>
44 * The principal operations on a {@code StringBuffer} are the
45 * {@code append} and {@code insert} methods, which are
46 * overloaded so as to accept data of any type. Each effectively
47 * converts a given datum to a string and then appends or inserts the
48 * characters of that string to the string buffer. The
49 * {@code append} method always adds these characters at the end
50 * of the buffer; the {@code insert} method adds the characters at
51 * a specified point.
52 * <p>
53 * For example, if {@code z} refers to a string buffer object
54 * whose current contents are {@code "start"}, then
55 * the method call {@code z.append("le")} would cause the string
56 * buffer to contain {@code "startle"}, whereas
57 * {@code z.insert(4, "le")} would alter the string buffer to
58 * contain {@code "starlet"}.
59 * <p>
60 * In general, if sb refers to an instance of a {@code StringBuffer},
61 * then {@code sb.append(x)} has the same effect as
62 * {@code sb.insert(sb.length(), x)}.
63 * <p>
64 * Whenever an operation occurs involving a source sequence (such as
65 * appending or inserting from a source sequence), this class synchronizes
66 * only on the string buffer performing the operation, not on the source.
67 * Note that while {@code StringBuffer} is designed to be safe to use
68 * concurrently from multiple threads, if the constructor or the
69 * {@code append} or {@code insert} operation is passed a source sequence
70 * that is shared across threads, the calling code must ensure
71 * that the operation has a consistent and unchanging view of the source
72 * sequence for the duration of the operation.
73 * This could be satisfied by the caller holding a lock during the
74 * operation's call, by using an immutable source sequence, or by not
75 * sharing the source sequence across threads.
76 * <p>
77 * Every string buffer has a capacity. As long as the length of the
78 * character sequence contained in the string buffer does not exceed
79 * the capacity, it is not necessary to allocate a new internal
80 * buffer array. If the internal buffer overflows, it is
81 * automatically made larger.
82 * <p>
83 * Unless otherwise noted, passing a {@code null} argument to a constructor
84 * or method in this class will cause a {@link NullPointerException} to be
85 * thrown.
86 * <p>
87 * As of release JDK 5, this class has been supplemented with an equivalent
88 * class designed for use by a single thread, {@link StringBuilder}. The
89 * {@code StringBuilder} class should generally be used in preference to
90 * this one, as it supports all of the same operations but it is faster, as
91 * it performs no synchronization.
92 *
93 * @author Arthur van Hoff
94 * @see java.lang.StringBuilder
95 * @see java.lang.String
96 * @since 1.0
97 */
98 public final class StringBuffer
99 extends AbstractStringBuilder
100 implements java.io.Serializable, CharSequence
101 {
102
103 /**
104 * A cache of the last value returned by toString. Cleared
105 * whenever the StringBuffer is modified.
106 */
107 private transient String toStringCache;
108
109 /** use serialVersionUID from JDK 1.0.2 for interoperability */
110 static final long serialVersionUID = 3388685877147921107L;
111
112 /**
113 * Constructs a string buffer with no characters in it and an
114 * initial capacity of 16 characters.
115 */
116 @HotSpotIntrinsicCandidate
117 public StringBuffer() {
118 super(16);
119 }
120
121 /**
122 * Constructs a string buffer with no characters in it and
123 * the specified initial capacity.
124 *
125 * @param capacity the initial capacity.
126 * @exception NegativeArraySizeException if the {@code capacity}
127 * argument is less than {@code 0}.
128 */
129 @HotSpotIntrinsicCandidate
130 public StringBuffer(int capacity) {
131 super(capacity);
132 }
133
134 /**
135 * Constructs a string buffer initialized to the contents of the
136 * specified string. The initial capacity of the string buffer is
137 * {@code 16} plus the length of the string argument.
138 *
139 * @param str the initial contents of the buffer.
140 */
141 @HotSpotIntrinsicCandidate
142 public StringBuffer(String str) {
143 super(str.length() + 16);
144 append(str);
145 }
146
147 /**
148 * Constructs a string buffer that contains the same characters
149 * as the specified {@code CharSequence}. The initial capacity of
150 * the string buffer is {@code 16} plus the length of the
151 * {@code CharSequence} argument.
152 * <p>
153 * If the length of the specified {@code CharSequence} is
154 * less than or equal to zero, then an empty buffer of capacity
155 * {@code 16} is returned.
156 *
157 * @param seq the sequence to copy.
158 * @since 1.5
159 */
160 public StringBuffer(CharSequence seq) {
161 this(seq.length() + 16);
162 append(seq);
163 }
164
165 @Override
166 public synchronized int length() {
167 return count;
168 }
169
170 @Override
171 public synchronized int capacity() {
172 return super.capacity();
173 }
174
175
176 @Override
177 public synchronized void ensureCapacity(int minimumCapacity) {
178 super.ensureCapacity(minimumCapacity);
179 }
180
181 /**
182 * @since 1.5
183 */
184 @Override
185 public synchronized void trimToSize() {
186 super.trimToSize();
187 }
188
189 /**
190 * @throws IndexOutOfBoundsException {@inheritDoc}
191 * @see #length()
192 */
193 @Override
194 public synchronized void setLength(int newLength) {
195 toStringCache = null;
196 super.setLength(newLength);
197 }
198
199 /**
200 * @throws IndexOutOfBoundsException {@inheritDoc}
201 * @see #length()
202 */
203 @Override
204 public synchronized char charAt(int index) {
205 return super.charAt(index);
206 }
207
208 /**
209 * @throws IndexOutOfBoundsException {@inheritDoc}
210 * @since 1.5
211 */
212 @Override
213 public synchronized int codePointAt(int index) {
214 return super.codePointAt(index);
215 }
216
217 /**
218 * @throws IndexOutOfBoundsException {@inheritDoc}
219 * @since 1.5
220 */
221 @Override
222 public synchronized int codePointBefore(int index) {
223 return super.codePointBefore(index);
224 }
225
226 /**
227 * @throws IndexOutOfBoundsException {@inheritDoc}
228 * @since 1.5
229 */
230 @Override
231 public synchronized int codePointCount(int beginIndex, int endIndex) {
232 return super.codePointCount(beginIndex, endIndex);
233 }
234
235 /**
236 * @throws IndexOutOfBoundsException {@inheritDoc}
237 * @since 1.5
238 */
239 @Override
240 public synchronized int offsetByCodePoints(int index, int codePointOffset) {
241 return super.offsetByCodePoints(index, codePointOffset);
242 }
243
244 /**
245 * @throws IndexOutOfBoundsException {@inheritDoc}
246 */
247 @Override
248 public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
249 int dstBegin)
250 {
251 super.getChars(srcBegin, srcEnd, dst, dstBegin);
252 }
253
254 /**
255 * @throws IndexOutOfBoundsException {@inheritDoc}
256 * @see #length()
257 */
258 @Override
259 public synchronized void setCharAt(int index, char ch) {
260 toStringCache = null;
261 super.setCharAt(index, ch);
262 }
263
264 @Override
265 public synchronized StringBuffer append(Object obj) {
266 toStringCache = null;
267 super.append(String.valueOf(obj));
268 return this;
269 }
270
271 @Override
272 @HotSpotIntrinsicCandidate
273 public synchronized StringBuffer append(String str) {
274 toStringCache = null;
275 super.append(str);
276 return this;
277 }
278
279 /**
280 * Appends the specified {@code StringBuffer} to this sequence.
281 * <p>
282 * The characters of the {@code StringBuffer} argument are appended,
283 * in order, to the contents of this {@code StringBuffer}, increasing the
284 * length of this {@code StringBuffer} by the length of the argument.
285 * If {@code sb} is {@code null}, then the four characters
286 * {@code "null"} are appended to this {@code StringBuffer}.
287 * <p>
288 * Let <i>n</i> be the length of the old character sequence, the one
289 * contained in the {@code StringBuffer} just prior to execution of the
290 * {@code append} method. Then the character at index <i>k</i> in
291 * the new character sequence is equal to the character at index <i>k</i>
292 * in the old character sequence, if <i>k</i> is less than <i>n</i>;
293 * otherwise, it is equal to the character at index <i>k-n</i> in the
294 * argument {@code sb}.
295 * <p>
296 * This method synchronizes on {@code this}, the destination
297 * object, but does not synchronize on the source ({@code sb}).
298 *
299 * @param sb the {@code StringBuffer} to append.
300 * @return a reference to this object.
301 * @since 1.4
302 */
303 public synchronized StringBuffer append(StringBuffer sb) {
304 toStringCache = null;
305 super.append(sb);
306 return this;
307 }
308
309 /**
310 * @since 1.8
311 */
312 @Override
313 synchronized StringBuffer append(AbstractStringBuilder asb) {
314 toStringCache = null;
315 super.append(asb);
316 return this;
317 }
318
319 /**
320 * Appends the specified {@code CharSequence} to this
321 * sequence.
322 * <p>
323 * The characters of the {@code CharSequence} argument are appended,
324 * in order, increasing the length of this sequence by the length of the
325 * argument.
326 *
327 * <p>The result of this method is exactly the same as if it were an
328 * invocation of this.append(s, 0, s.length());
329 *
330 * <p>This method synchronizes on {@code this}, the destination
331 * object, but does not synchronize on the source ({@code s}).
332 *
333 * <p>If {@code s} is {@code null}, then the four characters
334 * {@code "null"} are appended.
335 *
336 * @param s the {@code CharSequence} to append.
337 * @return a reference to this object.
338 * @since 1.5
339 */
340 @Override
341 public synchronized StringBuffer append(CharSequence s) {
342 toStringCache = null;
343 super.append(s);
344 return this;
345 }
346
347 /**
348 * @throws IndexOutOfBoundsException {@inheritDoc}
349 * @since 1.5
350 */
351 @Override
352 public synchronized StringBuffer append(CharSequence s, int start, int end)
353 {
354 toStringCache = null;
355 super.append(s, start, end);
356 return this;
357 }
358
359 @Override
360 public synchronized StringBuffer append(char[] str) {
361 toStringCache = null;
362 super.append(str);
363 return this;
364 }
365
366 /**
367 * @throws IndexOutOfBoundsException {@inheritDoc}
368 */
369 @Override
370 public synchronized StringBuffer append(char[] str, int offset, int len) {
371 toStringCache = null;
372 super.append(str, offset, len);
373 return this;
374 }
375
376 @Override
377 public synchronized StringBuffer append(boolean b) {
378 toStringCache = null;
379 super.append(b);
380 return this;
381 }
382
383 @Override
384 @HotSpotIntrinsicCandidate
385 public synchronized StringBuffer append(char c) {
386 toStringCache = null;
387 super.append(c);
388 return this;
389 }
390
391 @Override
392 @HotSpotIntrinsicCandidate
393 public synchronized StringBuffer append(int i) {
394 toStringCache = null;
395 super.append(i);
396 return this;
397 }
398
399 /**
400 * @since 1.5
401 */
402 @Override
403 public synchronized StringBuffer appendCodePoint(int codePoint) {
404 toStringCache = null;
405 super.appendCodePoint(codePoint);
406 return this;
407 }
408
409 @Override
410 public synchronized StringBuffer append(long lng) {
411 toStringCache = null;
412 super.append(lng);
413 return this;
414 }
415
416 @Override
417 public synchronized StringBuffer append(float f) {
418 toStringCache = null;
419 super.append(f);
420 return this;
421 }
422
423 @Override
424 public synchronized StringBuffer append(double d) {
425 toStringCache = null;
426 super.append(d);
427 return this;
428 }
429
430 /**
431 * @throws StringIndexOutOfBoundsException {@inheritDoc}
432 * @since 1.2
433 */
434 @Override
435 public synchronized StringBuffer delete(int start, int end) {
436 toStringCache = null;
437 super.delete(start, end);
438 return this;
439 }
440
441 /**
442 * @throws StringIndexOutOfBoundsException {@inheritDoc}
443 * @since 1.2
444 */
445 @Override
446 public synchronized StringBuffer deleteCharAt(int index) {
447 toStringCache = null;
448 super.deleteCharAt(index);
449 return this;
450 }
451
452 /**
453 * @throws StringIndexOutOfBoundsException {@inheritDoc}
454 * @since 1.2
455 */
456 @Override
457 public synchronized StringBuffer replace(int start, int end, String str) {
458 toStringCache = null;
459 super.replace(start, end, str);
460 return this;
461 }
462
463 /**
464 * @throws StringIndexOutOfBoundsException {@inheritDoc}
465 * @since 1.2
466 */
467 @Override
468 public synchronized String substring(int start) {
469 return substring(start, count);
470 }
471
472 /**
473 * @throws IndexOutOfBoundsException {@inheritDoc}
474 * @since 1.4
475 */
476 @Override
477 public synchronized CharSequence subSequence(int start, int end) {
478 return super.substring(start, end);
479 }
480
481 /**
482 * @throws StringIndexOutOfBoundsException {@inheritDoc}
483 * @since 1.2
484 */
485 @Override
486 public synchronized String substring(int start, int end) {
487 return super.substring(start, end);
488 }
489
490 /**
491 * @throws StringIndexOutOfBoundsException {@inheritDoc}
492 * @since 1.2
493 */
494 @Override
495 public synchronized StringBuffer insert(int index, char[] str, int offset,
496 int len)
497 {
498 toStringCache = null;
499 super.insert(index, str, offset, len);
500 return this;
501 }
502
503 /**
504 * @throws StringIndexOutOfBoundsException {@inheritDoc}
505 */
506 @Override
507 public synchronized StringBuffer insert(int offset, Object obj) {
508 toStringCache = null;
509 super.insert(offset, String.valueOf(obj));
510 return this;
511 }
512
513 /**
514 * @throws StringIndexOutOfBoundsException {@inheritDoc}
515 */
516 @Override
517 public synchronized StringBuffer insert(int offset, String str) {
518 toStringCache = null;
519 super.insert(offset, str);
520 return this;
521 }
522
523 /**
524 * @throws StringIndexOutOfBoundsException {@inheritDoc}
525 */
526 @Override
527 public synchronized StringBuffer insert(int offset, char[] str) {
528 toStringCache = null;
529 super.insert(offset, str);
530 return this;
531 }
532
533 /**
534 * @throws IndexOutOfBoundsException {@inheritDoc}
535 * @since 1.5
536 */
537 @Override
538 public StringBuffer insert(int dstOffset, CharSequence s) {
539 // Note, synchronization achieved via invocations of other StringBuffer methods
540 // after narrowing of s to specific type
541 // Ditto for toStringCache clearing
542 super.insert(dstOffset, s);
543 return this;
544 }
545
546 /**
547 * @throws IndexOutOfBoundsException {@inheritDoc}
548 * @since 1.5
549 */
550 @Override
551 public synchronized StringBuffer insert(int dstOffset, CharSequence s,
552 int start, int end)
553 {
554 toStringCache = null;
555 super.insert(dstOffset, s, start, end);
556 return this;
557 }
558
559 /**
560 * @throws StringIndexOutOfBoundsException {@inheritDoc}
561 */
562 @Override
563 public StringBuffer insert(int offset, boolean b) {
564 // Note, synchronization achieved via invocation of StringBuffer insert(int, String)
565 // after conversion of b to String by super class method
566 // Ditto for toStringCache clearing
567 super.insert(offset, b);
568 return this;
569 }
570
571 /**
572 * @throws IndexOutOfBoundsException {@inheritDoc}
573 */
574 @Override
575 public synchronized StringBuffer insert(int offset, char c) {
576 toStringCache = null;
577 super.insert(offset, c);
578 return this;
579 }
580
581 /**
582 * @throws StringIndexOutOfBoundsException {@inheritDoc}
583 */
584 @Override
585 public StringBuffer insert(int offset, int i) {
586 // Note, synchronization achieved via invocation of StringBuffer insert(int, String)
587 // after conversion of i to String by super class method
588 // Ditto for toStringCache clearing
589 super.insert(offset, i);
590 return this;
591 }
592
593 /**
594 * @throws StringIndexOutOfBoundsException {@inheritDoc}
595 */
596 @Override
597 public StringBuffer insert(int offset, long l) {
598 // Note, synchronization achieved via invocation of StringBuffer insert(int, String)
599 // after conversion of l to String by super class method
600 // Ditto for toStringCache clearing
601 super.insert(offset, l);
602 return this;
603 }
604
605 /**
606 * @throws StringIndexOutOfBoundsException {@inheritDoc}
607 */
608 @Override
609 public StringBuffer insert(int offset, float f) {
610 // Note, synchronization achieved via invocation of StringBuffer insert(int, String)
611 // after conversion of f to String by super class method
612 // Ditto for toStringCache clearing
613 super.insert(offset, f);
614 return this;
615 }
616
617 /**
618 * @throws StringIndexOutOfBoundsException {@inheritDoc}
619 */
620 @Override
621 public StringBuffer insert(int offset, double d) {
622 // Note, synchronization achieved via invocation of StringBuffer insert(int, String)
623 // after conversion of d to String by super class method
624 // Ditto for toStringCache clearing
625 super.insert(offset, d);
626 return this;
627 }
628
629 /**
630 * @since 1.4
631 */
632 @Override
633 public int indexOf(String str) {
634 // Note, synchronization achieved via invocations of other StringBuffer methods
635 return super.indexOf(str);
636 }
637
638 /**
639 * @since 1.4
640 */
641 @Override
642 public synchronized int indexOf(String str, int fromIndex) {
643 return super.indexOf(str, fromIndex);
644 }
645
646 /**
647 * @since 1.4
648 */
649 @Override
650 public int lastIndexOf(String str) {
651 // Note, synchronization achieved via invocations of other StringBuffer methods
652 return lastIndexOf(str, count);
653 }
654
655 /**
656 * @since 1.4
657 */
658 @Override
659 public synchronized int lastIndexOf(String str, int fromIndex) {
660 return super.lastIndexOf(str, fromIndex);
661 }
662
663 /**
664 * @since 1.0.2
665 */
666 @Override
667 public synchronized StringBuffer reverse() {
668 toStringCache = null;
669 super.reverse();
670 return this;
671 }
672
673 @Override
674 @HotSpotIntrinsicCandidate
675 public synchronized String toString() {
676 if (toStringCache == null) {
677 return toStringCache =
678 isLatin1() ? StringLatin1.newString(value, 0, count)
679 : StringUTF16.newString(value, 0, count);
680 }
681 return new String(toStringCache);
682 }
683
684 /**
685 * Serializable fields for StringBuffer.
686 *
687 * @serialField value char[]
688 * The backing character array of this StringBuffer.
689 * @serialField count int
690 * The number of characters in this StringBuffer.
691 * @serialField shared boolean
692 * A flag indicating whether the backing array is shared.
693 * The value is ignored upon deserialization.
694 */
695 private static final java.io.ObjectStreamField[] serialPersistentFields =
696 {
697 new java.io.ObjectStreamField("value", char[].class),
698 new java.io.ObjectStreamField("count", Integer.TYPE),
699 new java.io.ObjectStreamField("shared", Boolean.TYPE),
700 };
701
702 /**
703 * readObject is called to restore the state of the StringBuffer from
704 * a stream.
705 */
706 private synchronized void writeObject(java.io.ObjectOutputStream s)
707 throws java.io.IOException {
708 java.io.ObjectOutputStream.PutField fields = s.putFields();
709 char[] val = new char[capacity()];
710 if (isLatin1()) {
711 StringLatin1.getChars(value, 0, count, val, 0);
712 } else {
713 StringUTF16.getChars(value, 0, count, val, 0);
714 }
715 fields.put("value", val);
716 fields.put("count", count);
717 fields.put("shared", false);
718 s.writeFields();
719 }
720
721 /**
722 * readObject is called to restore the state of the StringBuffer from
723 * a stream.
724 */
725 private void readObject(java.io.ObjectInputStream s)
726 throws java.io.IOException, ClassNotFoundException {
727 java.io.ObjectInputStream.GetField fields = s.readFields();
728 char[] val = (char[])fields.get("value", null);
729 initBytes(val, 0, val.length);
730 count = fields.get("count", 0);
731 }
732
733 synchronized void getBytes(byte dst[], int dstBegin, byte coder) {
734 super.getBytes(dst, dstBegin, coder);
735 }
736 }