1 /*
2 * Copyright (c) 2003, 2008, 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
29 /**
30 * A mutable sequence of characters. This class provides an API compatible
31 * with <code>StringBuffer</code>, but with no guarantee of synchronization.
32 * This class is designed for use as a drop-in replacement for
33 * <code>StringBuffer</code> in places where the string buffer was being
34 * used by a single thread (as is generally the case). Where possible,
35 * it is recommended that this class be used in preference to
36 * <code>StringBuffer</code> as it will be faster under most implementations.
37 *
38 * <p>The principal operations on a <code>StringBuilder</code> are the
39 * <code>append</code> and <code>insert</code> methods, which are
40 * overloaded so as to accept data of any type. Each effectively
41 * converts a given datum to a string and then appends or inserts the
42 * characters of that string to the string builder. The
43 * <code>append</code> method always adds these characters at the end
44 * of the builder; the <code>insert</code> method adds the characters at
45 * a specified point.
46 * <p>
47 * For example, if <code>z</code> refers to a string builder object
48 * whose current contents are "<code>start</code>", then
49 * the method call <code>z.append("le")</code> would cause the string
50 * builder to contain "<code>startle</code>", whereas
51 * <code>z.insert(4, "le")</code> would alter the string builder to
52 * contain "<code>starlet</code>".
53 * <p>
54 * In general, if sb refers to an instance of a <code>StringBuilder</code>,
55 * then <code>sb.append(x)</code> has the same effect as
56 * <code>sb.insert(sb.length(), x)</code>.
57 *
58 * Every string builder has a capacity. As long as the length of the
59 * character sequence contained in the string builder does not exceed
60 * the capacity, it is not necessary to allocate a new internal
61 * buffer. If the internal buffer overflows, it is automatically made larger.
62 *
63 * <p>Instances of <code>StringBuilder</code> are not safe for
64 * use by multiple threads. If such synchronization is required then it is
65 * recommended that {@link java.lang.StringBuffer} be used.
66 *
67 * @author Michael McCloskey
68 * @see java.lang.StringBuffer
69 * @see java.lang.String
70 * @since 1.5
71 */
72 public final class StringBuilder
73 extends AbstractStringBuilder
74 implements java.io.Serializable, CharSequence
75 {
76
77 /** use serialVersionUID for interoperability */
78 static final long serialVersionUID = 4383685877147921099L;
79
80 /**
81 * Constructs a string builder with no characters in it and an
82 * initial capacity of 16 characters.
83 */
84 public StringBuilder() {
85 super(16);
86 }
87
88 /**
89 * Constructs a string builder with no characters in it and an
90 * initial capacity specified by the <code>capacity</code> argument.
91 *
92 * @param capacity the initial capacity.
93 * @throws NegativeArraySizeException if the <code>capacity</code>
94 * argument is less than <code>0</code>.
95 */
96 public StringBuilder(int capacity) {
97 super(capacity);
98 }
99
100 /**
101 * Constructs a string builder initialized to the contents of the
102 * specified string. The initial capacity of the string builder is
103 * <code>16</code> plus the length of the string argument.
104 *
105 * @param str the initial contents of the buffer.
106 * @throws NullPointerException if <code>str</code> is <code>null</code>
107 */
108 public StringBuilder(String str) {
109 super(str.length() + 16);
110 append(str);
111 }
112
113 /**
114 * Constructs a string builder that contains the same characters
115 * as the specified <code>CharSequence</code>. The initial capacity of
116 * the string builder is <code>16</code> plus the length of the
117 * <code>CharSequence</code> argument.
118 *
119 * @param seq the sequence to copy.
120 * @throws NullPointerException if <code>seq</code> is <code>null</code>
121 */
122 public StringBuilder(CharSequence seq) {
123 this(seq.length() + 16);
124 append(seq);
125 }
126
127 @Override
128 public StringBuilder append(Object obj) {
129 return append(String.valueOf(obj));
130 }
131
132 @Override
133 public StringBuilder append(String str) {
134 super.append(str);
135 return this;
136 }
137
138 /**
139 * Appends the specified <tt>StringBuffer</tt> to this sequence.
140 * <p>
141 * The characters of the <tt>StringBuffer</tt> argument are appended,
142 * in order, to this sequence, increasing the
143 * length of this sequence by the length of the argument.
144 * If <tt>sb</tt> is <tt>null</tt>, then the four characters
145 * <tt>"null"</tt> are appended to this sequence.
146 * <p>
147 * Let <i>n</i> be the length of this character sequence just prior to
148 * execution of the <tt>append</tt> method. Then the character at index
149 * <i>k</i> in the new character sequence is equal to the character at
150 * index <i>k</i> in the old character sequence, if <i>k</i> is less than
151 * <i>n</i>; otherwise, it is equal to the character at index <i>k-n</i>
152 * in the argument <code>sb</code>.
153 *
154 * @param sb the <tt>StringBuffer</tt> to append.
155 * @return a reference to this object.
156 */
157 public StringBuilder append(StringBuffer sb) {
158 super.append(sb);
159 return this;
160 }
161
162 @Override
163 public StringBuilder append(CharSequence s) {
164 super.append(s);
165 return this;
166 }
167
168 /**
169 * @throws IndexOutOfBoundsException {@inheritDoc}
170 */
171 @Override
172 public StringBuilder append(CharSequence s, int start, int end) {
173 super.append(s, start, end);
174 return this;
175 }
176
177 @Override
178 public StringBuilder append(char[] str) {
179 super.append(str);
180 return this;
181 }
182
183 /**
184 * @throws IndexOutOfBoundsException {@inheritDoc}
185 */
186 @Override
187 public StringBuilder append(char[] str, int offset, int len) {
188 super.append(str, offset, len);
189 return this;
190 }
191
192 @Override
193 public StringBuilder append(boolean b) {
194 super.append(b);
195 return this;
196 }
197
198 @Override
199 public StringBuilder append(char c) {
200 super.append(c);
201 return this;
202 }
203
204 @Override
205 public StringBuilder append(int i) {
206 super.append(i);
207 return this;
208 }
209
210 @Override
211 public StringBuilder append(long lng) {
212 super.append(lng);
213 return this;
214 }
215
216 @Override
217 public StringBuilder append(float f) {
218 super.append(f);
219 return this;
220 }
221
222 @Override
223 public StringBuilder append(double d) {
224 super.append(d);
225 return this;
226 }
227
228 /**
229 * @since 1.5
230 */
231 @Override
232 public StringBuilder appendCodePoint(int codePoint) {
233 super.appendCodePoint(codePoint);
234 return this;
235 }
236
237 /**
238 * @throws StringIndexOutOfBoundsException {@inheritDoc}
239 */
240 @Override
241 public StringBuilder delete(int start, int end) {
242 super.delete(start, end);
243 return this;
244 }
245
246 /**
247 * @throws StringIndexOutOfBoundsException {@inheritDoc}
248 */
249 @Override
250 public StringBuilder deleteCharAt(int index) {
251 super.deleteCharAt(index);
252 return this;
253 }
254
255 /**
256 * @throws StringIndexOutOfBoundsException {@inheritDoc}
257 */
258 @Override
259 public StringBuilder replace(int start, int end, String str) {
260 super.replace(start, end, str);
261 return this;
262 }
263
264 /**
265 * @throws StringIndexOutOfBoundsException {@inheritDoc}
266 */
267 @Override
268 public StringBuilder insert(int index, char[] str, int offset,
269 int len)
270 {
271 super.insert(index, str, offset, len);
272 return this;
273 }
274
275 /**
276 * @throws StringIndexOutOfBoundsException {@inheritDoc}
277 */
278 @Override
279 public StringBuilder insert(int offset, Object obj) {
280 super.insert(offset, obj);
281 return this;
282 }
283
284 /**
285 * @throws StringIndexOutOfBoundsException {@inheritDoc}
286 */
287 @Override
288 public StringBuilder insert(int offset, String str) {
289 super.insert(offset, str);
290 return this;
291 }
292
293 /**
294 * @throws StringIndexOutOfBoundsException {@inheritDoc}
295 */
296 @Override
297 public StringBuilder insert(int offset, char[] str) {
298 super.insert(offset, str);
299 return this;
300 }
301
302 /**
303 * @throws IndexOutOfBoundsException {@inheritDoc}
304 */
305 @Override
306 public StringBuilder insert(int dstOffset, CharSequence s) {
307 super.insert(dstOffset, s);
308 return this;
309 }
310
311 /**
312 * @throws IndexOutOfBoundsException {@inheritDoc}
313 */
314 @Override
315 public StringBuilder insert(int dstOffset, CharSequence s,
316 int start, int end)
317 {
318 super.insert(dstOffset, s, start, end);
319 return this;
320 }
321
322 /**
323 * @throws StringIndexOutOfBoundsException {@inheritDoc}
324 */
325 @Override
326 public StringBuilder insert(int offset, boolean b) {
327 super.insert(offset, b);
328 return this;
329 }
330
331 /**
332 * @throws IndexOutOfBoundsException {@inheritDoc}
333 */
334 @Override
335 public StringBuilder insert(int offset, char c) {
336 super.insert(offset, c);
337 return this;
338 }
339
340 /**
341 * @throws StringIndexOutOfBoundsException {@inheritDoc}
342 */
343 @Override
344 public StringBuilder insert(int offset, int i) {
345 super.insert(offset, i);
346 return this;
347 }
348
349 /**
350 * @throws StringIndexOutOfBoundsException {@inheritDoc}
351 */
352 @Override
353 public StringBuilder insert(int offset, long l) {
354 super.insert(offset, l);
355 return this;
356 }
357
358 /**
359 * @throws StringIndexOutOfBoundsException {@inheritDoc}
360 */
361 @Override
362 public StringBuilder insert(int offset, float f) {
363 super.insert(offset, f);
364 return this;
365 }
366
367 /**
368 * @throws StringIndexOutOfBoundsException {@inheritDoc}
369 */
370 @Override
371 public StringBuilder insert(int offset, double d) {
372 super.insert(offset, d);
373 return this;
374 }
375
376 /**
377 * @throws NullPointerException {@inheritDoc}
378 */
379 @Override
380 public int indexOf(String str) {
381 return super.indexOf(str);
382 }
383
384 /**
385 * @throws NullPointerException {@inheritDoc}
386 */
387 @Override
388 public int indexOf(String str, int fromIndex) {
389 return super.indexOf(str, fromIndex);
390 }
391
392 /**
393 * @throws NullPointerException {@inheritDoc}
394 */
395 @Override
396 public int lastIndexOf(String str) {
397 return super.lastIndexOf(str);
398 }
399
400 /**
401 * @throws NullPointerException {@inheritDoc}
402 */
403 @Override
404 public int lastIndexOf(String str, int fromIndex) {
405 return super.lastIndexOf(str, fromIndex);
406 }
407
408 @Override
409 public StringBuilder reverse() {
410 super.reverse();
411 return this;
412 }
413
414 @Override
415 public String toString() {
416 // Create a copy, don't share the array
417 return new String(value, 0, count);
418 }
419
420 /**
421 * Save the state of the <tt>StringBuilder</tt> instance to a stream
422 * (that is, serialize it).
423 *
424 * @serialData the number of characters currently stored in the string
425 * builder (<tt>int</tt>), followed by the characters in the
426 * string builder (<tt>char[]</tt>). The length of the
427 * <tt>char</tt> array may be greater than the number of
428 * characters currently stored in the string builder, in which
429 * case extra characters are ignored.
430 */
431 private void writeObject(java.io.ObjectOutputStream s)
432 throws java.io.IOException {
433 s.defaultWriteObject();
434 s.writeInt(count);
435 s.writeObject(value);
436 }
437
438 /**
439 * readObject is called to restore the state of the StringBuffer from
440 * a stream.
441 */
442 private void readObject(java.io.ObjectInputStream s)
443 throws java.io.IOException, ClassNotFoundException {
444 s.defaultReadObject();
445 count = s.readInt();
446 value = (char[]) s.readObject();
447 }
448
449 }