Integer.java revision b90c36f25b990336a456daad69ea9db9256b86ce
1/* 2 * Copyright (c) 1994, 2010, 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 26package java.lang; 27 28import java.util.Properties; 29 30/** 31 * The {@code Integer} class wraps a value of the primitive type 32 * {@code int} in an object. An object of type {@code Integer} 33 * contains a single field whose type is {@code int}. 34 * 35 * <p>In addition, this class provides several methods for converting 36 * an {@code int} to a {@code String} and a {@code String} to an 37 * {@code int}, as well as other constants and methods useful when 38 * dealing with an {@code int}. 39 * 40 * <p>Implementation note: The implementations of the "bit twiddling" 41 * methods (such as {@link #highestOneBit(int) highestOneBit} and 42 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are 43 * based on material from Henry S. Warren, Jr.'s <i>Hacker's 44 * Delight</i>, (Addison Wesley, 2002). 45 * 46 * @author Lee Boynton 47 * @author Arthur van Hoff 48 * @author Josh Bloch 49 * @author Joseph D. Darcy 50 * @since JDK1.0 51 */ 52public final class Integer extends Number implements Comparable<Integer> { 53 /** 54 * A constant holding the minimum value an {@code int} can 55 * have, -2<sup>31</sup>. 56 */ 57 public static final int MIN_VALUE = 0x80000000; 58 59 /** 60 * A constant holding the maximum value an {@code int} can 61 * have, 2<sup>31</sup>-1. 62 */ 63 public static final int MAX_VALUE = 0x7fffffff; 64 65 /** 66 * The {@code Class} instance representing the primitive type 67 * {@code int}. 68 * 69 * @since JDK1.1 70 */ 71 public static final Class<Integer> TYPE = (Class<Integer>) int[].class.getComponentType(); 72 73 /** 74 * All possible chars for representing a number as a String 75 */ 76 final static char[] digits = { 77 '0' , '1' , '2' , '3' , '4' , '5' , 78 '6' , '7' , '8' , '9' , 'a' , 'b' , 79 'c' , 'd' , 'e' , 'f' , 'g' , 'h' , 80 'i' , 'j' , 'k' , 'l' , 'm' , 'n' , 81 'o' , 'p' , 'q' , 'r' , 's' , 't' , 82 'u' , 'v' , 'w' , 'x' , 'y' , 'z' 83 }; 84 85 /** 86 * Returns a string representation of the first argument in the 87 * radix specified by the second argument. 88 * 89 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 90 * or larger than {@code Character.MAX_RADIX}, then the radix 91 * {@code 10} is used instead. 92 * 93 * <p>If the first argument is negative, the first element of the 94 * result is the ASCII minus character {@code '-'} 95 * (<code>'\u002D'</code>). If the first argument is not 96 * negative, no sign character appears in the result. 97 * 98 * <p>The remaining characters of the result represent the magnitude 99 * of the first argument. If the magnitude is zero, it is 100 * represented by a single zero character {@code '0'} 101 * (<code>'\u0030'</code>); otherwise, the first character of 102 * the representation of the magnitude will not be the zero 103 * character. The following ASCII characters are used as digits: 104 * 105 * <blockquote> 106 * {@code 0123456789abcdefghijklmnopqrstuvwxyz} 107 * </blockquote> 108 * 109 * These are <code>'\u0030'</code> through 110 * <code>'\u0039'</code> and <code>'\u0061'</code> through 111 * <code>'\u007A'</code>. If {@code radix} is 112 * <var>N</var>, then the first <var>N</var> of these characters 113 * are used as radix-<var>N</var> digits in the order shown. Thus, 114 * the digits for hexadecimal (radix 16) are 115 * {@code 0123456789abcdef}. If uppercase letters are 116 * desired, the {@link java.lang.String#toUpperCase()} method may 117 * be called on the result: 118 * 119 * <blockquote> 120 * {@code Integer.toString(n, 16).toUpperCase()} 121 * </blockquote> 122 * 123 * @param i an integer to be converted to a string. 124 * @param radix the radix to use in the string representation. 125 * @return a string representation of the argument in the specified radix. 126 * @see java.lang.Character#MAX_RADIX 127 * @see java.lang.Character#MIN_RADIX 128 */ 129 public static String toString(int i, int radix) { 130 131 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) 132 radix = 10; 133 134 /* Use the faster version */ 135 if (radix == 10) { 136 return toString(i); 137 } 138 139 char buf[] = new char[33]; 140 boolean negative = (i < 0); 141 int charPos = 32; 142 143 if (!negative) { 144 i = -i; 145 } 146 147 while (i <= -radix) { 148 buf[charPos--] = digits[-(i % radix)]; 149 i = i / radix; 150 } 151 buf[charPos] = digits[-i]; 152 153 if (negative) { 154 buf[--charPos] = '-'; 155 } 156 157 return new String(buf, charPos, (33 - charPos)); 158 } 159 160 /** 161 * Returns a string representation of the integer argument as an 162 * unsigned integer in base 16. 163 * 164 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 165 * if the argument is negative; otherwise, it is equal to the 166 * argument. This value is converted to a string of ASCII digits 167 * in hexadecimal (base 16) with no extra leading 168 * {@code 0}s. If the unsigned magnitude is zero, it is 169 * represented by a single zero character {@code '0'} 170 * (<code>'\u0030'</code>); otherwise, the first character of 171 * the representation of the unsigned magnitude will not be the 172 * zero character. The following characters are used as 173 * hexadecimal digits: 174 * 175 * <blockquote> 176 * {@code 0123456789abcdef} 177 * </blockquote> 178 * 179 * These are the characters <code>'\u0030'</code> through 180 * <code>'\u0039'</code> and <code>'\u0061'</code> through 181 * <code>'\u0066'</code>. If uppercase letters are 182 * desired, the {@link java.lang.String#toUpperCase()} method may 183 * be called on the result: 184 * 185 * <blockquote> 186 * {@code Integer.toHexString(n).toUpperCase()} 187 * </blockquote> 188 * 189 * @param i an integer to be converted to a string. 190 * @return the string representation of the unsigned integer value 191 * represented by the argument in hexadecimal (base 16). 192 * @since JDK1.0.2 193 */ 194 public static String toHexString(int i) { 195 return toUnsignedString(i, 4); 196 } 197 198 /** 199 * Returns a string representation of the integer argument as an 200 * unsigned integer in base 8. 201 * 202 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 203 * if the argument is negative; otherwise, it is equal to the 204 * argument. This value is converted to a string of ASCII digits 205 * in octal (base 8) with no extra leading {@code 0}s. 206 * 207 * <p>If the unsigned magnitude is zero, it is represented by a 208 * single zero character {@code '0'} 209 * (<code>'\u0030'</code>); otherwise, the first character of 210 * the representation of the unsigned magnitude will not be the 211 * zero character. The following characters are used as octal 212 * digits: 213 * 214 * <blockquote> 215 * {@code 01234567} 216 * </blockquote> 217 * 218 * These are the characters <code>'\u0030'</code> through 219 * <code>'\u0037'</code>. 220 * 221 * @param i an integer to be converted to a string. 222 * @return the string representation of the unsigned integer value 223 * represented by the argument in octal (base 8). 224 * @since JDK1.0.2 225 */ 226 public static String toOctalString(int i) { 227 return toUnsignedString(i, 3); 228 } 229 230 /** 231 * Returns a string representation of the integer argument as an 232 * unsigned integer in base 2. 233 * 234 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 235 * if the argument is negative; otherwise it is equal to the 236 * argument. This value is converted to a string of ASCII digits 237 * in binary (base 2) with no extra leading {@code 0}s. 238 * If the unsigned magnitude is zero, it is represented by a 239 * single zero character {@code '0'} 240 * (<code>'\u0030'</code>); otherwise, the first character of 241 * the representation of the unsigned magnitude will not be the 242 * zero character. The characters {@code '0'} 243 * (<code>'\u0030'</code>) and {@code '1'} 244 * (<code>'\u0031'</code>) are used as binary digits. 245 * 246 * @param i an integer to be converted to a string. 247 * @return the string representation of the unsigned integer value 248 * represented by the argument in binary (base 2). 249 * @since JDK1.0.2 250 */ 251 public static String toBinaryString(int i) { 252 return toUnsignedString(i, 1); 253 } 254 255 /** 256 * Convert the integer to an unsigned number. 257 */ 258 private static String toUnsignedString(int i, int shift) { 259 char[] buf = new char[32]; 260 int charPos = 32; 261 int radix = 1 << shift; 262 int mask = radix - 1; 263 do { 264 buf[--charPos] = digits[i & mask]; 265 i >>>= shift; 266 } while (i != 0); 267 268 return new String(buf, charPos, (32 - charPos)); 269 } 270 271 272 final static char [] DigitTens = { 273 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', 274 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', 275 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', 276 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 277 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', 278 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', 279 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', 280 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', 281 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', 282 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', 283 } ; 284 285 final static char [] DigitOnes = { 286 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 287 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 288 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 289 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 290 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 291 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 292 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 293 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 294 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 295 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 296 } ; 297 298 // I use the "invariant division by multiplication" trick to 299 // accelerate Integer.toString. In particular we want to 300 // avoid division by 10. 301 // 302 // The "trick" has roughly the same performance characteristics 303 // as the "classic" Integer.toString code on a non-JIT VM. 304 // The trick avoids .rem and .div calls but has a longer code 305 // path and is thus dominated by dispatch overhead. In the 306 // JIT case the dispatch overhead doesn't exist and the 307 // "trick" is considerably faster than the classic code. 308 // 309 // TODO-FIXME: convert (x * 52429) into the equiv shift-add 310 // sequence. 311 // 312 // RE: Division by Invariant Integers using Multiplication 313 // T Gralund, P Montgomery 314 // ACM PLDI 1994 315 // 316 317 /** 318 * Returns a {@code String} object representing the 319 * specified integer. The argument is converted to signed decimal 320 * representation and returned as a string, exactly as if the 321 * argument and radix 10 were given as arguments to the {@link 322 * #toString(int, int)} method. 323 * 324 * @param i an integer to be converted. 325 * @return a string representation of the argument in base 10. 326 */ 327 public static String toString(int i) { 328 if (i == Integer.MIN_VALUE) 329 return "-2147483648"; 330 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); 331 char[] buf = new char[size]; 332 getChars(i, size, buf); 333 // Android-changed: change string constructor. 334 return new String(buf); 335 } 336 337 /** 338 * Places characters representing the integer i into the 339 * character array buf. The characters are placed into 340 * the buffer backwards starting with the least significant 341 * digit at the specified index (exclusive), and working 342 * backwards from there. 343 * 344 * Will fail if i == Integer.MIN_VALUE 345 */ 346 static void getChars(int i, int index, char[] buf) { 347 int q, r; 348 int charPos = index; 349 char sign = 0; 350 351 if (i < 0) { 352 sign = '-'; 353 i = -i; 354 } 355 356 // Generate two digits per iteration 357 while (i >= 65536) { 358 q = i / 100; 359 // really: r = i - (q * 100); 360 r = i - ((q << 6) + (q << 5) + (q << 2)); 361 i = q; 362 buf [--charPos] = DigitOnes[r]; 363 buf [--charPos] = DigitTens[r]; 364 } 365 366 // Fall thru to fast mode for smaller numbers 367 // assert(i <= 65536, i); 368 for (;;) { 369 q = (i * 52429) >>> (16+3); 370 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ... 371 buf [--charPos] = digits [r]; 372 i = q; 373 if (i == 0) break; 374 } 375 if (sign != 0) { 376 buf [--charPos] = sign; 377 } 378 } 379 380 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 381 99999999, 999999999, Integer.MAX_VALUE }; 382 383 // Requires positive x 384 static int stringSize(int x) { 385 for (int i=0; ; i++) 386 if (x <= sizeTable[i]) 387 return i+1; 388 } 389 390 /** 391 * Parses the string argument as a signed integer in the radix 392 * specified by the second argument. The characters in the string 393 * must all be digits of the specified radix (as determined by 394 * whether {@link java.lang.Character#digit(char, int)} returns a 395 * nonnegative value), except that the first character may be an 396 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to 397 * indicate a negative value or an ASCII plus sign {@code '+'} 398 * (<code>'\u002B'</code>) to indicate a positive value. The 399 * resulting integer value is returned. 400 * 401 * <p>An exception of type {@code NumberFormatException} is 402 * thrown if any of the following situations occurs: 403 * <ul> 404 * <li>The first argument is {@code null} or is a string of 405 * length zero. 406 * 407 * <li>The radix is either smaller than 408 * {@link java.lang.Character#MIN_RADIX} or 409 * larger than {@link java.lang.Character#MAX_RADIX}. 410 * 411 * <li>Any character of the string is not a digit of the specified 412 * radix, except that the first character may be a minus sign 413 * {@code '-'} (<code>'\u002D'</code>) or plus sign 414 * {@code '+'} (<code>'\u002B'</code>) provided that the 415 * string is longer than length 1. 416 * 417 * <li>The value represented by the string is not a value of type 418 * {@code int}. 419 * </ul> 420 * 421 * <p>Examples: 422 * <blockquote><pre> 423 * parseInt("0", 10) returns 0 424 * parseInt("473", 10) returns 473 425 * parseInt("+42", 10) returns 42 426 * parseInt("-0", 10) returns 0 427 * parseInt("-FF", 16) returns -255 428 * parseInt("1100110", 2) returns 102 429 * parseInt("2147483647", 10) returns 2147483647 430 * parseInt("-2147483648", 10) returns -2147483648 431 * parseInt("2147483648", 10) throws a NumberFormatException 432 * parseInt("99", 8) throws a NumberFormatException 433 * parseInt("Kona", 10) throws a NumberFormatException 434 * parseInt("Kona", 27) returns 411787 435 * </pre></blockquote> 436 * 437 * @param s the {@code String} containing the integer 438 * representation to be parsed 439 * @param radix the radix to be used while parsing {@code s}. 440 * @return the integer represented by the string argument in the 441 * specified radix. 442 * @exception NumberFormatException if the {@code String} 443 * does not contain a parsable {@code int}. 444 */ 445 public static int parseInt(String s, int radix) 446 throws NumberFormatException 447 { 448 /* 449 * WARNING: This method may be invoked early during VM initialization 450 * before IntegerCache is initialized. Care must be taken to not use 451 * the valueOf method. 452 */ 453 454 if (s == null) { 455 throw new NumberFormatException("null"); 456 } 457 458 if (radix < Character.MIN_RADIX) { 459 throw new NumberFormatException("radix " + radix + 460 " less than Character.MIN_RADIX"); 461 } 462 463 if (radix > Character.MAX_RADIX) { 464 throw new NumberFormatException("radix " + radix + 465 " greater than Character.MAX_RADIX"); 466 } 467 468 int result = 0; 469 boolean negative = false; 470 int i = 0, len = s.length(); 471 int limit = -Integer.MAX_VALUE; 472 int multmin; 473 int digit; 474 475 if (len > 0) { 476 char firstChar = s.charAt(0); 477 if (firstChar < '0') { // Possible leading "+" or "-" 478 if (firstChar == '-') { 479 negative = true; 480 limit = Integer.MIN_VALUE; 481 } else if (firstChar != '+') 482 throw NumberFormatException.forInputString(s); 483 484 if (len == 1) // Cannot have lone "+" or "-" 485 throw NumberFormatException.forInputString(s); 486 i++; 487 } 488 multmin = limit / radix; 489 while (i < len) { 490 // Accumulating negatively avoids surprises near MAX_VALUE 491 digit = Character.digit(s.charAt(i++),radix); 492 if (digit < 0) { 493 throw NumberFormatException.forInputString(s); 494 } 495 if (result < multmin) { 496 throw NumberFormatException.forInputString(s); 497 } 498 result *= radix; 499 if (result < limit + digit) { 500 throw NumberFormatException.forInputString(s); 501 } 502 result -= digit; 503 } 504 } else { 505 throw NumberFormatException.forInputString(s); 506 } 507 return negative ? result : -result; 508 } 509 510 /** 511 * Parses the string argument as a signed decimal integer. The 512 * characters in the string must all be decimal digits, except 513 * that the first character may be an ASCII minus sign {@code '-'} 514 * (<code>'\u002D'</code>) to indicate a negative value or an 515 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to 516 * indicate a positive value. The resulting integer value is 517 * returned, exactly as if the argument and the radix 10 were 518 * given as arguments to the {@link #parseInt(java.lang.String, 519 * int)} method. 520 * 521 * @param s a {@code String} containing the {@code int} 522 * representation to be parsed 523 * @return the integer value represented by the argument in decimal. 524 * @exception NumberFormatException if the string does not contain a 525 * parsable integer. 526 */ 527 public static int parseInt(String s) throws NumberFormatException { 528 return parseInt(s,10); 529 } 530 531 /** 532 * Returns an {@code Integer} object holding the value 533 * extracted from the specified {@code String} when parsed 534 * with the radix given by the second argument. The first argument 535 * is interpreted as representing a signed integer in the radix 536 * specified by the second argument, exactly as if the arguments 537 * were given to the {@link #parseInt(java.lang.String, int)} 538 * method. The result is an {@code Integer} object that 539 * represents the integer value specified by the string. 540 * 541 * <p>In other words, this method returns an {@code Integer} 542 * object equal to the value of: 543 * 544 * <blockquote> 545 * {@code new Integer(Integer.parseInt(s, radix))} 546 * </blockquote> 547 * 548 * @param s the string to be parsed. 549 * @param radix the radix to be used in interpreting {@code s} 550 * @return an {@code Integer} object holding the value 551 * represented by the string argument in the specified 552 * radix. 553 * @exception NumberFormatException if the {@code String} 554 * does not contain a parsable {@code int}. 555 */ 556 public static Integer valueOf(String s, int radix) throws NumberFormatException { 557 return Integer.valueOf(parseInt(s,radix)); 558 } 559 560 /** 561 * Returns an {@code Integer} object holding the 562 * value of the specified {@code String}. The argument is 563 * interpreted as representing a signed decimal integer, exactly 564 * as if the argument were given to the {@link 565 * #parseInt(java.lang.String)} method. The result is an 566 * {@code Integer} object that represents the integer value 567 * specified by the string. 568 * 569 * <p>In other words, this method returns an {@code Integer} 570 * object equal to the value of: 571 * 572 * <blockquote> 573 * {@code new Integer(Integer.parseInt(s))} 574 * </blockquote> 575 * 576 * @param s the string to be parsed. 577 * @return an {@code Integer} object holding the value 578 * represented by the string argument. 579 * @exception NumberFormatException if the string cannot be parsed 580 * as an integer. 581 */ 582 public static Integer valueOf(String s) throws NumberFormatException { 583 return Integer.valueOf(parseInt(s, 10)); 584 } 585 586 /** 587 * Cache to support the object identity semantics of autoboxing for values between 588 * -128 and 127 (inclusive) as required by JLS. 589 * 590 * The cache is initialized on first usage. The size of the cache 591 * may be controlled by the -XX:AutoBoxCacheMax=<size> option. 592 * During VM initialization, java.lang.Integer.IntegerCache.high property 593 * may be set and saved in the private system properties in the 594 * sun.misc.VM class. 595 */ 596 597 private static class IntegerCache { 598 static final int low = -128; 599 static final int high; 600 static final Integer cache[]; 601 602 static { 603 // high value may be configured by property 604 int h = 127; 605 String integerCacheHighPropValue = 606 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); 607 if (integerCacheHighPropValue != null) { 608 int i = parseInt(integerCacheHighPropValue); 609 i = Math.max(i, 127); 610 // Maximum array size is Integer.MAX_VALUE 611 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 612 } 613 high = h; 614 615 cache = new Integer[(high - low) + 1]; 616 int j = low; 617 for(int k = 0; k < cache.length; k++) 618 cache[k] = new Integer(j++); 619 } 620 621 private IntegerCache() {} 622 } 623 624 /** 625 * Returns an {@code Integer} instance representing the specified 626 * {@code int} value. If a new {@code Integer} instance is not 627 * required, this method should generally be used in preference to 628 * the constructor {@link #Integer(int)}, as this method is likely 629 * to yield significantly better space and time performance by 630 * caching frequently requested values. 631 * 632 * This method will always cache values in the range -128 to 127, 633 * inclusive, and may cache other values outside of this range. 634 * 635 * @param i an {@code int} value. 636 * @return an {@code Integer} instance representing {@code i}. 637 * @since 1.5 638 */ 639 public static Integer valueOf(int i) { 640 assert IntegerCache.high >= 127; 641 if (i >= IntegerCache.low && i <= IntegerCache.high) 642 return IntegerCache.cache[i + (-IntegerCache.low)]; 643 return new Integer(i); 644 } 645 646 /** 647 * The value of the {@code Integer}. 648 * 649 * @serial 650 */ 651 private final int value; 652 653 /** 654 * Constructs a newly allocated {@code Integer} object that 655 * represents the specified {@code int} value. 656 * 657 * @param value the value to be represented by the 658 * {@code Integer} object. 659 */ 660 public Integer(int value) { 661 this.value = value; 662 } 663 664 /** 665 * Constructs a newly allocated {@code Integer} object that 666 * represents the {@code int} value indicated by the 667 * {@code String} parameter. The string is converted to an 668 * {@code int} value in exactly the manner used by the 669 * {@code parseInt} method for radix 10. 670 * 671 * @param s the {@code String} to be converted to an 672 * {@code Integer}. 673 * @exception NumberFormatException if the {@code String} does not 674 * contain a parsable integer. 675 * @see java.lang.Integer#parseInt(java.lang.String, int) 676 */ 677 public Integer(String s) throws NumberFormatException { 678 this.value = parseInt(s, 10); 679 } 680 681 /** 682 * Returns the value of this {@code Integer} as a 683 * {@code byte}. 684 */ 685 public byte byteValue() { 686 return (byte)value; 687 } 688 689 /** 690 * Returns the value of this {@code Integer} as a 691 * {@code short}. 692 */ 693 public short shortValue() { 694 return (short)value; 695 } 696 697 /** 698 * Returns the value of this {@code Integer} as an 699 * {@code int}. 700 */ 701 public int intValue() { 702 return value; 703 } 704 705 /** 706 * Returns the value of this {@code Integer} as a 707 * {@code long}. 708 */ 709 public long longValue() { 710 return (long)value; 711 } 712 713 /** 714 * Returns the value of this {@code Integer} as a 715 * {@code float}. 716 */ 717 public float floatValue() { 718 return (float)value; 719 } 720 721 /** 722 * Returns the value of this {@code Integer} as a 723 * {@code double}. 724 */ 725 public double doubleValue() { 726 return (double)value; 727 } 728 729 /** 730 * Returns a {@code String} object representing this 731 * {@code Integer}'s value. The value is converted to signed 732 * decimal representation and returned as a string, exactly as if 733 * the integer value were given as an argument to the {@link 734 * java.lang.Integer#toString(int)} method. 735 * 736 * @return a string representation of the value of this object in 737 * base 10. 738 */ 739 public String toString() { 740 return toString(value); 741 } 742 743 /** 744 * Returns a hash code for this {@code Integer}. 745 * 746 * @return a hash code value for this object, equal to the 747 * primitive {@code int} value represented by this 748 * {@code Integer} object. 749 */ 750 public int hashCode() { 751 return value; 752 } 753 754 /** 755 * Compares this object to the specified object. The result is 756 * {@code true} if and only if the argument is not 757 * {@code null} and is an {@code Integer} object that 758 * contains the same {@code int} value as this object. 759 * 760 * @param obj the object to compare with. 761 * @return {@code true} if the objects are the same; 762 * {@code false} otherwise. 763 */ 764 public boolean equals(Object obj) { 765 if (obj instanceof Integer) { 766 return value == ((Integer)obj).intValue(); 767 } 768 return false; 769 } 770 771 /** 772 * Determines the integer value of the system property with the 773 * specified name. 774 * 775 * <p>The first argument is treated as the name of a system property. 776 * System properties are accessible through the 777 * {@link java.lang.System#getProperty(java.lang.String)} method. The 778 * string value of this property is then interpreted as an integer 779 * value and an {@code Integer} object representing this value is 780 * returned. Details of possible numeric formats can be found with 781 * the definition of {@code getProperty}. 782 * 783 * <p>If there is no property with the specified name, if the specified name 784 * is empty or {@code null}, or if the property does not have 785 * the correct numeric format, then {@code null} is returned. 786 * 787 * <p>In other words, this method returns an {@code Integer} 788 * object equal to the value of: 789 * 790 * <blockquote> 791 * {@code getInteger(nm, null)} 792 * </blockquote> 793 * 794 * @param nm property name. 795 * @return the {@code Integer} value of the property. 796 * @see java.lang.System#getProperty(java.lang.String) 797 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 798 */ 799 public static Integer getInteger(String nm) { 800 return getInteger(nm, null); 801 } 802 803 /** 804 * Determines the integer value of the system property with the 805 * specified name. 806 * 807 * <p>The first argument is treated as the name of a system property. 808 * System properties are accessible through the {@link 809 * java.lang.System#getProperty(java.lang.String)} method. The 810 * string value of this property is then interpreted as an integer 811 * value and an {@code Integer} object representing this value is 812 * returned. Details of possible numeric formats can be found with 813 * the definition of {@code getProperty}. 814 * 815 * <p>The second argument is the default value. An {@code Integer} object 816 * that represents the value of the second argument is returned if there 817 * is no property of the specified name, if the property does not have 818 * the correct numeric format, or if the specified name is empty or 819 * {@code null}. 820 * 821 * <p>In other words, this method returns an {@code Integer} object 822 * equal to the value of: 823 * 824 * <blockquote> 825 * {@code getInteger(nm, new Integer(val))} 826 * </blockquote> 827 * 828 * but in practice it may be implemented in a manner such as: 829 * 830 * <blockquote><pre> 831 * Integer result = getInteger(nm, null); 832 * return (result == null) ? new Integer(val) : result; 833 * </pre></blockquote> 834 * 835 * to avoid the unnecessary allocation of an {@code Integer} 836 * object when the default value is not needed. 837 * 838 * @param nm property name. 839 * @param val default value. 840 * @return the {@code Integer} value of the property. 841 * @see java.lang.System#getProperty(java.lang.String) 842 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 843 */ 844 public static Integer getInteger(String nm, int val) { 845 Integer result = getInteger(nm, null); 846 return (result == null) ? Integer.valueOf(val) : result; 847 } 848 849 /** 850 * Returns the integer value of the system property with the 851 * specified name. The first argument is treated as the name of a 852 * system property. System properties are accessible through the 853 * {@link java.lang.System#getProperty(java.lang.String)} method. 854 * The string value of this property is then interpreted as an 855 * integer value, as per the {@code Integer.decode} method, 856 * and an {@code Integer} object representing this value is 857 * returned. 858 * 859 * <ul><li>If the property value begins with the two ASCII characters 860 * {@code 0x} or the ASCII character {@code #}, not 861 * followed by a minus sign, then the rest of it is parsed as a 862 * hexadecimal integer exactly as by the method 863 * {@link #valueOf(java.lang.String, int)} with radix 16. 864 * <li>If the property value begins with the ASCII character 865 * {@code 0} followed by another character, it is parsed as an 866 * octal integer exactly as by the method 867 * {@link #valueOf(java.lang.String, int)} with radix 8. 868 * <li>Otherwise, the property value is parsed as a decimal integer 869 * exactly as by the method {@link #valueOf(java.lang.String, int)} 870 * with radix 10. 871 * </ul> 872 * 873 * <p>The second argument is the default value. The default value is 874 * returned if there is no property of the specified name, if the 875 * property does not have the correct numeric format, or if the 876 * specified name is empty or {@code null}. 877 * 878 * @param nm property name. 879 * @param val default value. 880 * @return the {@code Integer} value of the property. 881 * @see java.lang.System#getProperty(java.lang.String) 882 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 883 * @see java.lang.Integer#decode 884 */ 885 public static Integer getInteger(String nm, Integer val) { 886 String v = null; 887 try { 888 v = System.getProperty(nm); 889 } catch (IllegalArgumentException e) { 890 } catch (NullPointerException e) { 891 } 892 if (v != null) { 893 try { 894 return Integer.decode(v); 895 } catch (NumberFormatException e) { 896 } 897 } 898 return val; 899 } 900 901 /** 902 * Decodes a {@code String} into an {@code Integer}. 903 * Accepts decimal, hexadecimal, and octal numbers given 904 * by the following grammar: 905 * 906 * <blockquote> 907 * <dl> 908 * <dt><i>DecodableString:</i> 909 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 910 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 911 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 912 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 913 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 914 * <p> 915 * <dt><i>Sign:</i> 916 * <dd>{@code -} 917 * <dd>{@code +} 918 * </dl> 919 * </blockquote> 920 * 921 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 922 * are as defined in section 3.10.1 of 923 * <cite>The Java™ Language Specification</cite>, 924 * except that underscores are not accepted between digits. 925 * 926 * <p>The sequence of characters following an optional 927 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 928 * "{@code #}", or leading zero) is parsed as by the {@code 929 * Integer.parseInt} method with the indicated radix (10, 16, or 930 * 8). This sequence of characters must represent a positive 931 * value or a {@link NumberFormatException} will be thrown. The 932 * result is negated if first character of the specified {@code 933 * String} is the minus sign. No whitespace characters are 934 * permitted in the {@code String}. 935 * 936 * @param nm the {@code String} to decode. 937 * @return an {@code Integer} object holding the {@code int} 938 * value represented by {@code nm} 939 * @exception NumberFormatException if the {@code String} does not 940 * contain a parsable integer. 941 * @see java.lang.Integer#parseInt(java.lang.String, int) 942 */ 943 public static Integer decode(String nm) throws NumberFormatException { 944 int radix = 10; 945 int index = 0; 946 boolean negative = false; 947 Integer result; 948 949 if (nm.length() == 0) 950 throw new NumberFormatException("Zero length string"); 951 char firstChar = nm.charAt(0); 952 // Handle sign, if present 953 if (firstChar == '-') { 954 negative = true; 955 index++; 956 } else if (firstChar == '+') 957 index++; 958 959 // Handle radix specifier, if present 960 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 961 index += 2; 962 radix = 16; 963 } 964 else if (nm.startsWith("#", index)) { 965 index ++; 966 radix = 16; 967 } 968 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 969 index ++; 970 radix = 8; 971 } 972 973 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 974 throw new NumberFormatException("Sign character in wrong position"); 975 976 try { 977 result = Integer.valueOf(nm.substring(index), radix); 978 result = negative ? Integer.valueOf(-result.intValue()) : result; 979 } catch (NumberFormatException e) { 980 // If number is Integer.MIN_VALUE, we'll end up here. The next line 981 // handles this case, and causes any genuine format error to be 982 // rethrown. 983 String constant = negative ? ("-" + nm.substring(index)) 984 : nm.substring(index); 985 result = Integer.valueOf(constant, radix); 986 } 987 return result; 988 } 989 990 /** 991 * Compares two {@code Integer} objects numerically. 992 * 993 * @param anotherInteger the {@code Integer} to be compared. 994 * @return the value {@code 0} if this {@code Integer} is 995 * equal to the argument {@code Integer}; a value less than 996 * {@code 0} if this {@code Integer} is numerically less 997 * than the argument {@code Integer}; and a value greater 998 * than {@code 0} if this {@code Integer} is numerically 999 * greater than the argument {@code Integer} (signed 1000 * comparison). 1001 * @since 1.2 1002 */ 1003 public int compareTo(Integer anotherInteger) { 1004 return compare(this.value, anotherInteger.value); 1005 } 1006 1007 /** 1008 * Compares two {@code int} values numerically. 1009 * The value returned is identical to what would be returned by: 1010 * <pre> 1011 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1012 * </pre> 1013 * 1014 * @param x the first {@code int} to compare 1015 * @param y the second {@code int} to compare 1016 * @return the value {@code 0} if {@code x == y}; 1017 * a value less than {@code 0} if {@code x < y}; and 1018 * a value greater than {@code 0} if {@code x > y} 1019 * @since 1.7 1020 */ 1021 public static int compare(int x, int y) { 1022 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1023 } 1024 1025 1026 // Bit twiddling 1027 1028 /** 1029 * The number of bits used to represent an {@code int} value in two's 1030 * complement binary form. 1031 * 1032 * @since 1.5 1033 */ 1034 public static final int SIZE = 32; 1035 1036 /** 1037 * Returns an {@code int} value with at most a single one-bit, in the 1038 * position of the highest-order ("leftmost") one-bit in the specified 1039 * {@code int} value. Returns zero if the specified value has no 1040 * one-bits in its two's complement binary representation, that is, if it 1041 * is equal to zero. 1042 * 1043 * @return an {@code int} value with a single one-bit, in the position 1044 * of the highest-order one-bit in the specified value, or zero if 1045 * the specified value is itself equal to zero. 1046 * @since 1.5 1047 */ 1048 public static int highestOneBit(int i) { 1049 // HD, Figure 3-1 1050 i |= (i >> 1); 1051 i |= (i >> 2); 1052 i |= (i >> 4); 1053 i |= (i >> 8); 1054 i |= (i >> 16); 1055 return i - (i >>> 1); 1056 } 1057 1058 /** 1059 * Returns an {@code int} value with at most a single one-bit, in the 1060 * position of the lowest-order ("rightmost") one-bit in the specified 1061 * {@code int} value. Returns zero if the specified value has no 1062 * one-bits in its two's complement binary representation, that is, if it 1063 * is equal to zero. 1064 * 1065 * @return an {@code int} value with a single one-bit, in the position 1066 * of the lowest-order one-bit in the specified value, or zero if 1067 * the specified value is itself equal to zero. 1068 * @since 1.5 1069 */ 1070 public static int lowestOneBit(int i) { 1071 // HD, Section 2-1 1072 return i & -i; 1073 } 1074 1075 /** 1076 * Returns the number of zero bits preceding the highest-order 1077 * ("leftmost") one-bit in the two's complement binary representation 1078 * of the specified {@code int} value. Returns 32 if the 1079 * specified value has no one-bits in its two's complement representation, 1080 * in other words if it is equal to zero. 1081 * 1082 * <p>Note that this method is closely related to the logarithm base 2. 1083 * For all positive {@code int} values x: 1084 * <ul> 1085 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1086 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1087 * </ul> 1088 * 1089 * @return the number of zero bits preceding the highest-order 1090 * ("leftmost") one-bit in the two's complement binary representation 1091 * of the specified {@code int} value, or 32 if the value 1092 * is equal to zero. 1093 * @since 1.5 1094 */ 1095 public static int numberOfLeadingZeros(int i) { 1096 // HD, Figure 5-6 1097 if (i == 0) 1098 return 32; 1099 int n = 1; 1100 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1101 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1102 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1103 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1104 n -= i >>> 31; 1105 return n; 1106 } 1107 1108 /** 1109 * Returns the number of zero bits following the lowest-order ("rightmost") 1110 * one-bit in the two's complement binary representation of the specified 1111 * {@code int} value. Returns 32 if the specified value has no 1112 * one-bits in its two's complement representation, in other words if it is 1113 * equal to zero. 1114 * 1115 * @return the number of zero bits following the lowest-order ("rightmost") 1116 * one-bit in the two's complement binary representation of the 1117 * specified {@code int} value, or 32 if the value is equal 1118 * to zero. 1119 * @since 1.5 1120 */ 1121 public static int numberOfTrailingZeros(int i) { 1122 // HD, Figure 5-14 1123 int y; 1124 if (i == 0) return 32; 1125 int n = 31; 1126 y = i <<16; if (y != 0) { n = n -16; i = y; } 1127 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1128 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1129 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1130 return n - ((i << 1) >>> 31); 1131 } 1132 1133 /** 1134 * Returns the number of one-bits in the two's complement binary 1135 * representation of the specified {@code int} value. This function is 1136 * sometimes referred to as the <i>population count</i>. 1137 * 1138 * @return the number of one-bits in the two's complement binary 1139 * representation of the specified {@code int} value. 1140 * @since 1.5 1141 */ 1142 public static int bitCount(int i) { 1143 // HD, Figure 5-2 1144 i = i - ((i >>> 1) & 0x55555555); 1145 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1146 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1147 i = i + (i >>> 8); 1148 i = i + (i >>> 16); 1149 return i & 0x3f; 1150 } 1151 1152 /** 1153 * Returns the value obtained by rotating the two's complement binary 1154 * representation of the specified {@code int} value left by the 1155 * specified number of bits. (Bits shifted out of the left hand, or 1156 * high-order, side reenter on the right, or low-order.) 1157 * 1158 * <p>Note that left rotation with a negative distance is equivalent to 1159 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1160 * distance)}. Note also that rotation by any multiple of 32 is a 1161 * no-op, so all but the last five bits of the rotation distance can be 1162 * ignored, even if the distance is negative: {@code rotateLeft(val, 1163 * distance) == rotateLeft(val, distance & 0x1F)}. 1164 * 1165 * @return the value obtained by rotating the two's complement binary 1166 * representation of the specified {@code int} value left by the 1167 * specified number of bits. 1168 * @since 1.5 1169 */ 1170 public static int rotateLeft(int i, int distance) { 1171 return (i << distance) | (i >>> -distance); 1172 } 1173 1174 /** 1175 * Returns the value obtained by rotating the two's complement binary 1176 * representation of the specified {@code int} value right by the 1177 * specified number of bits. (Bits shifted out of the right hand, or 1178 * low-order, side reenter on the left, or high-order.) 1179 * 1180 * <p>Note that right rotation with a negative distance is equivalent to 1181 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1182 * distance)}. Note also that rotation by any multiple of 32 is a 1183 * no-op, so all but the last five bits of the rotation distance can be 1184 * ignored, even if the distance is negative: {@code rotateRight(val, 1185 * distance) == rotateRight(val, distance & 0x1F)}. 1186 * 1187 * @return the value obtained by rotating the two's complement binary 1188 * representation of the specified {@code int} value right by the 1189 * specified number of bits. 1190 * @since 1.5 1191 */ 1192 public static int rotateRight(int i, int distance) { 1193 return (i >>> distance) | (i << -distance); 1194 } 1195 1196 /** 1197 * Returns the value obtained by reversing the order of the bits in the 1198 * two's complement binary representation of the specified {@code int} 1199 * value. 1200 * 1201 * @return the value obtained by reversing order of the bits in the 1202 * specified {@code int} value. 1203 * @since 1.5 1204 */ 1205 public static int reverse(int i) { 1206 // HD, Figure 7-1 1207 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1208 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1209 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1210 i = (i << 24) | ((i & 0xff00) << 8) | 1211 ((i >>> 8) & 0xff00) | (i >>> 24); 1212 return i; 1213 } 1214 1215 /** 1216 * Returns the signum function of the specified {@code int} value. (The 1217 * return value is -1 if the specified value is negative; 0 if the 1218 * specified value is zero; and 1 if the specified value is positive.) 1219 * 1220 * @return the signum function of the specified {@code int} value. 1221 * @since 1.5 1222 */ 1223 public static int signum(int i) { 1224 // HD, Section 2-7 1225 return (i >> 31) | (-i >>> 31); 1226 } 1227 1228 /** 1229 * Returns the value obtained by reversing the order of the bytes in the 1230 * two's complement representation of the specified {@code int} value. 1231 * 1232 * @return the value obtained by reversing the bytes in the specified 1233 * {@code int} value. 1234 * @since 1.5 1235 */ 1236 public static int reverseBytes(int i) { 1237 return ((i >>> 24) ) | 1238 ((i >> 8) & 0xFF00) | 1239 ((i << 8) & 0xFF0000) | 1240 ((i << 24)); 1241 } 1242 1243 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1244 private static final long serialVersionUID = 1360826667806852920L; 1245} 1246