1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.lang; 28 29 30 /** 31 * A mutable sequence of characters. This class provides an API compatible 32 * with {@code StringBuffer}, but with no guarantee of synchronization. 33 * This class is designed for use as a drop-in replacement for 34 * {@code StringBuffer} in places where the string buffer was being 35 * used by a single thread (as is generally the case). Where possible, 36 * it is recommended that this class be used in preference to 37 * {@code StringBuffer} as it will be faster under most implementations. 38 * 39 * <p>The principal operations on a {@code StringBuilder} are the 40 * {@code append} and {@code insert} methods, which are 41 * overloaded so as to accept data of any type. Each effectively 42 * converts a given datum to a string and then appends or inserts the 43 * characters of that string to the string builder. The 44 * {@code append} method always adds these characters at the end 45 * of the builder; the {@code insert} method adds the characters at 46 * a specified point. 47 * <p> 48 * For example, if {@code z} refers to a string builder object 49 * whose current contents are "{@code start}", then 50 * the method call {@code z.append("le")} would cause the string 51 * builder to contain "{@code startle}", whereas 52 * {@code z.insert(4, "le")} would alter the string builder to 53 * contain "{@code starlet}". 54 * <p> 55 * In general, if sb refers to an instance of a {@code StringBuilder}, 56 * then {@code sb.append(x)} has the same effect as 57 * {@code sb.insert(sb.length(), x)}. 58 * <p> 59 * Every string builder has a capacity. As long as the length of the 60 * character sequence contained in the string builder does not exceed 61 * the capacity, it is not necessary to allocate a new internal 62 * buffer. If the internal buffer overflows, it is automatically made larger. 63 * 64 * <p>Instances of {@code StringBuilder} are not safe for 65 * use by multiple threads. If such synchronization is required then it is 66 * recommended that {@link java.lang.StringBuffer} be used. 67 * 68 * <p>Unless otherwise noted, passing a {@code null} argument to a constructor 69 * or method in this class will cause a {@link NullPointerException} to be 70 * thrown. 71 * 72 * @author Michael McCloskey 73 * @see java.lang.StringBuffer 74 * @see java.lang.String 75 * @since 1.5 76 */ 77 public final class StringBuilder 78 extends AbstractStringBuilder 79 implements java.io.Serializable, CharSequence 80 { 81 82 /** use serialVersionUID for interoperability */ 83 static final long serialVersionUID = 4383685877147921099L; 84 85 /** 86 * Constructs a string builder with no characters in it and an 87 * initial capacity of 16 characters. 88 */ StringBuilder()89 public StringBuilder() { 90 super(16); 91 } 92 93 /** 94 * Constructs a string builder with no characters in it and an 95 * initial capacity specified by the {@code capacity} argument. 96 * 97 * @param capacity the initial capacity. 98 * @throws NegativeArraySizeException if the {@code capacity} 99 * argument is less than {@code 0}. 100 */ StringBuilder(int capacity)101 public StringBuilder(int capacity) { 102 super(capacity); 103 } 104 105 /** 106 * Constructs a string builder initialized to the contents of the 107 * specified string. The initial capacity of the string builder is 108 * {@code 16} plus the length of the string argument. 109 * 110 * @param str the initial contents of the buffer. 111 */ StringBuilder(String str)112 public StringBuilder(String str) { 113 super(str.length() + 16); 114 append(str); 115 } 116 117 /** 118 * Constructs a string builder that contains the same characters 119 * as the specified {@code CharSequence}. The initial capacity of 120 * the string builder is {@code 16} plus the length of the 121 * {@code CharSequence} argument. 122 * 123 * @param seq the sequence to copy. 124 */ StringBuilder(CharSequence seq)125 public StringBuilder(CharSequence seq) { 126 this(seq.length() + 16); 127 append(seq); 128 } 129 130 @Override append(Object obj)131 public StringBuilder append(Object obj) { 132 return append(String.valueOf(obj)); 133 } 134 135 @Override append(String str)136 public StringBuilder append(String str) { 137 super.append(str); 138 return this; 139 } 140 141 /** 142 * Appends the specified {@code StringBuffer} to this sequence. 143 * <p> 144 * The characters of the {@code StringBuffer} argument are appended, 145 * in order, to this sequence, increasing the 146 * length of this sequence by the length of the argument. 147 * If {@code sb} is {@code null}, then the four characters 148 * {@code "null"} are appended to this sequence. 149 * <p> 150 * Let <i>n</i> be the length of this character sequence just prior to 151 * execution of the {@code append} method. Then the character at index 152 * <i>k</i> in the new character sequence is equal to the character at 153 * index <i>k</i> in the old character sequence, if <i>k</i> is less than 154 * <i>n</i>; otherwise, it is equal to the character at index <i>k-n</i> 155 * in the argument {@code sb}. 156 * 157 * @param sb the {@code StringBuffer} to append. 158 * @return a reference to this object. 159 */ append(StringBuffer sb)160 public StringBuilder append(StringBuffer sb) { 161 super.append(sb); 162 return this; 163 } 164 165 @Override append(CharSequence s)166 public StringBuilder append(CharSequence s) { 167 super.append(s); 168 return this; 169 } 170 171 /** 172 * @throws IndexOutOfBoundsException {@inheritDoc} 173 */ 174 @Override append(CharSequence s, int start, int end)175 public StringBuilder append(CharSequence s, int start, int end) { 176 super.append(s, start, end); 177 return this; 178 } 179 180 @Override append(char[] str)181 public StringBuilder append(char[] str) { 182 super.append(str); 183 return this; 184 } 185 186 /** 187 * @throws IndexOutOfBoundsException {@inheritDoc} 188 */ 189 @Override append(char[] str, int offset, int len)190 public StringBuilder append(char[] str, int offset, int len) { 191 super.append(str, offset, len); 192 return this; 193 } 194 195 @Override append(boolean b)196 public StringBuilder append(boolean b) { 197 super.append(b); 198 return this; 199 } 200 201 @Override append(char c)202 public StringBuilder append(char c) { 203 super.append(c); 204 return this; 205 } 206 207 @Override append(int i)208 public StringBuilder append(int i) { 209 super.append(i); 210 return this; 211 } 212 213 @Override append(long lng)214 public StringBuilder append(long lng) { 215 super.append(lng); 216 return this; 217 } 218 219 @Override append(float f)220 public StringBuilder append(float f) { 221 super.append(f); 222 return this; 223 } 224 225 @Override append(double d)226 public StringBuilder append(double d) { 227 super.append(d); 228 return this; 229 } 230 231 /** 232 * @since 1.5 233 */ 234 @Override appendCodePoint(int codePoint)235 public StringBuilder appendCodePoint(int codePoint) { 236 super.appendCodePoint(codePoint); 237 return this; 238 } 239 240 /** 241 * @throws StringIndexOutOfBoundsException {@inheritDoc} 242 */ 243 @Override delete(int start, int end)244 public StringBuilder delete(int start, int end) { 245 super.delete(start, end); 246 return this; 247 } 248 249 /** 250 * @throws StringIndexOutOfBoundsException {@inheritDoc} 251 */ 252 @Override deleteCharAt(int index)253 public StringBuilder deleteCharAt(int index) { 254 super.deleteCharAt(index); 255 return this; 256 } 257 258 /** 259 * @throws StringIndexOutOfBoundsException {@inheritDoc} 260 */ 261 @Override replace(int start, int end, String str)262 public StringBuilder replace(int start, int end, String str) { 263 super.replace(start, end, str); 264 return this; 265 } 266 267 /** 268 * @throws StringIndexOutOfBoundsException {@inheritDoc} 269 */ 270 @Override insert(int index, char[] str, int offset, int len)271 public StringBuilder insert(int index, char[] str, int offset, 272 int len) 273 { 274 super.insert(index, str, offset, len); 275 return this; 276 } 277 278 /** 279 * @throws StringIndexOutOfBoundsException {@inheritDoc} 280 */ 281 @Override insert(int offset, Object obj)282 public StringBuilder insert(int offset, Object obj) { 283 super.insert(offset, obj); 284 return this; 285 } 286 287 /** 288 * @throws StringIndexOutOfBoundsException {@inheritDoc} 289 */ 290 @Override insert(int offset, String str)291 public StringBuilder insert(int offset, String str) { 292 super.insert(offset, str); 293 return this; 294 } 295 296 /** 297 * @throws StringIndexOutOfBoundsException {@inheritDoc} 298 */ 299 @Override insert(int offset, char[] str)300 public StringBuilder insert(int offset, char[] str) { 301 super.insert(offset, str); 302 return this; 303 } 304 305 /** 306 * @throws IndexOutOfBoundsException {@inheritDoc} 307 */ 308 @Override insert(int dstOffset, CharSequence s)309 public StringBuilder insert(int dstOffset, CharSequence s) { 310 super.insert(dstOffset, s); 311 return this; 312 } 313 314 /** 315 * @throws IndexOutOfBoundsException {@inheritDoc} 316 */ 317 @Override insert(int dstOffset, CharSequence s, int start, int end)318 public StringBuilder insert(int dstOffset, CharSequence s, 319 int start, int end) 320 { 321 super.insert(dstOffset, s, start, end); 322 return this; 323 } 324 325 /** 326 * @throws StringIndexOutOfBoundsException {@inheritDoc} 327 */ 328 @Override insert(int offset, boolean b)329 public StringBuilder insert(int offset, boolean b) { 330 super.insert(offset, b); 331 return this; 332 } 333 334 /** 335 * @throws IndexOutOfBoundsException {@inheritDoc} 336 */ 337 @Override insert(int offset, char c)338 public StringBuilder insert(int offset, char c) { 339 super.insert(offset, c); 340 return this; 341 } 342 343 /** 344 * @throws StringIndexOutOfBoundsException {@inheritDoc} 345 */ 346 @Override insert(int offset, int i)347 public StringBuilder insert(int offset, int i) { 348 super.insert(offset, i); 349 return this; 350 } 351 352 /** 353 * @throws StringIndexOutOfBoundsException {@inheritDoc} 354 */ 355 @Override insert(int offset, long l)356 public StringBuilder insert(int offset, long l) { 357 super.insert(offset, l); 358 return this; 359 } 360 361 /** 362 * @throws StringIndexOutOfBoundsException {@inheritDoc} 363 */ 364 @Override insert(int offset, float f)365 public StringBuilder insert(int offset, float f) { 366 super.insert(offset, f); 367 return this; 368 } 369 370 /** 371 * @throws StringIndexOutOfBoundsException {@inheritDoc} 372 */ 373 @Override insert(int offset, double d)374 public StringBuilder insert(int offset, double d) { 375 super.insert(offset, d); 376 return this; 377 } 378 379 @Override indexOf(String str)380 public int indexOf(String str) { 381 return super.indexOf(str); 382 } 383 384 @Override indexOf(String str, int fromIndex)385 public int indexOf(String str, int fromIndex) { 386 return super.indexOf(str, fromIndex); 387 } 388 389 @Override lastIndexOf(String str)390 public int lastIndexOf(String str) { 391 return super.lastIndexOf(str); 392 } 393 394 @Override lastIndexOf(String str, int fromIndex)395 public int lastIndexOf(String str, int fromIndex) { 396 return super.lastIndexOf(str, fromIndex); 397 } 398 399 @Override reverse()400 public StringBuilder reverse() { 401 super.reverse(); 402 return this; 403 } 404 405 @Override toString()406 public String toString() { 407 // BEGIN Android-added: Return a constant "" for an empty buffer to keep historic behavior. 408 if (count == 0) { 409 return ""; 410 } 411 // END Android-added: Return a constant "" for an empty buffer to keep historic behavior. 412 // Create a copy, don't share the array 413 return new String(value, 0, count); 414 } 415 416 /** 417 * Save the state of the {@code StringBuilder} instance to a stream 418 * (that is, serialize it). 419 * 420 * @serialData the number of characters currently stored in the string 421 * builder ({@code int}), followed by the characters in the 422 * string builder ({@code char[]}). The length of the 423 * {@code char} array may be greater than the number of 424 * characters currently stored in the string builder, in which 425 * case extra characters are ignored. 426 */ writeObject(java.io.ObjectOutputStream s)427 private void writeObject(java.io.ObjectOutputStream s) 428 throws java.io.IOException { 429 s.defaultWriteObject(); 430 s.writeInt(count); 431 s.writeObject(value); 432 } 433 434 /** 435 * readObject is called to restore the state of the StringBuffer from 436 * a stream. 437 */ readObject(java.io.ObjectInputStream s)438 private void readObject(java.io.ObjectInputStream s) 439 throws java.io.IOException, ClassNotFoundException { 440 s.defaultReadObject(); 441 count = s.readInt(); 442 value = (char[]) s.readObject(); 443 } 444 445 } 446