Integer.java revision e2f147b9b14c7645f29e92758f811a18258feef4
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1994, 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 27package java.lang; 28 29import java.util.Properties; 30 31/** 32 * The {@code Integer} class wraps a value of the primitive type 33 * {@code int} in an object. An object of type {@code Integer} 34 * contains a single field whose type is {@code int}. 35 * 36 * <p>In addition, this class provides several methods for converting 37 * an {@code int} to a {@code String} and a {@code String} to an 38 * {@code int}, as well as other constants and methods useful when 39 * dealing with an {@code int}. 40 * 41 * <p>Implementation note: The implementations of the "bit twiddling" 42 * methods (such as {@link #highestOneBit(int) highestOneBit} and 43 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are 44 * based on material from Henry S. Warren, Jr.'s <i>Hacker's 45 * Delight</i>, (Addison Wesley, 2002). 46 * 47 * @author Lee Boynton 48 * @author Arthur van Hoff 49 * @author Josh Bloch 50 * @author Joseph D. Darcy 51 * @since JDK1.0 52 */ 53public final class Integer extends Number implements Comparable<Integer> { 54 /** 55 * A constant holding the minimum value an {@code int} can 56 * have, -2<sup>31</sup>. 57 */ 58 public static final int MIN_VALUE = 0x80000000; 59 60 /** 61 * A constant holding the maximum value an {@code int} can 62 * have, 2<sup>31</sup>-1. 63 */ 64 public static final int MAX_VALUE = 0x7fffffff; 65 66 /** 67 * The {@code Class} instance representing the primitive type 68 * {@code int}. 69 * 70 * @since JDK1.1 71 */ 72 public static final Class<Integer> TYPE = (Class<Integer>) int[].class.getComponentType(); 73 74 /** 75 * All possible chars for representing a number as a String 76 */ 77 final static char[] digits = { 78 '0' , '1' , '2' , '3' , '4' , '5' , 79 '6' , '7' , '8' , '9' , 'a' , 'b' , 80 'c' , 'd' , 'e' , 'f' , 'g' , 'h' , 81 'i' , 'j' , 'k' , 'l' , 'm' , 'n' , 82 'o' , 'p' , 'q' , 'r' , 's' , 't' , 83 'u' , 'v' , 'w' , 'x' , 'y' , 'z' 84 }; 85 86 /** 87 * Returns a string representation of the first argument in the 88 * radix specified by the second argument. 89 * 90 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 91 * or larger than {@code Character.MAX_RADIX}, then the radix 92 * {@code 10} is used instead. 93 * 94 * <p>If the first argument is negative, the first element of the 95 * result is the ASCII minus character {@code '-'} 96 * (<code>'\u002D'</code>). If the first argument is not 97 * negative, no sign character appears in the result. 98 * 99 * <p>The remaining characters of the result represent the magnitude 100 * of the first argument. If the magnitude is zero, it is 101 * represented by a single zero character {@code '0'} 102 * (<code>'\u0030'</code>); otherwise, the first character of 103 * the representation of the magnitude will not be the zero 104 * character. The following ASCII characters are used as digits: 105 * 106 * <blockquote> 107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz} 108 * </blockquote> 109 * 110 * These are <code>'\u0030'</code> through 111 * <code>'\u0039'</code> and <code>'\u0061'</code> through 112 * <code>'\u007A'</code>. If {@code radix} is 113 * <var>N</var>, then the first <var>N</var> of these characters 114 * are used as radix-<var>N</var> digits in the order shown. Thus, 115 * the digits for hexadecimal (radix 16) are 116 * {@code 0123456789abcdef}. If uppercase letters are 117 * desired, the {@link java.lang.String#toUpperCase()} method may 118 * be called on the result: 119 * 120 * <blockquote> 121 * {@code Integer.toString(n, 16).toUpperCase()} 122 * </blockquote> 123 * 124 * @param i an integer to be converted to a string. 125 * @param radix the radix to use in the string representation. 126 * @return a string representation of the argument in the specified radix. 127 * @see java.lang.Character#MAX_RADIX 128 * @see java.lang.Character#MIN_RADIX 129 */ 130 public static String toString(int i, int radix) { 131 132 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) 133 radix = 10; 134 135 /* Use the faster version */ 136 if (radix == 10) { 137 return toString(i); 138 } 139 140 char buf[] = new char[33]; 141 boolean negative = (i < 0); 142 int charPos = 32; 143 144 if (!negative) { 145 i = -i; 146 } 147 148 while (i <= -radix) { 149 int q = i / radix; 150 buf[charPos--] = digits[radix * q - i]; 151 i = q; 152 } 153 buf[charPos] = digits[-i]; 154 155 if (negative) { 156 buf[--charPos] = '-'; 157 } 158 159 return new String(buf, charPos, (33 - charPos)); 160 } 161 162 /** 163 * Returns a string representation of the first argument as an 164 * unsigned integer value in the radix specified by the second 165 * argument. 166 * 167 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 168 * or larger than {@code Character.MAX_RADIX}, then the radix 169 * {@code 10} is used instead. 170 * 171 * <p>Note that since the first argument is treated as an unsigned 172 * value, no leading sign character is printed. 173 * 174 * <p>If the magnitude is zero, it is represented by a single zero 175 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise, 176 * the first character of the representation of the magnitude will 177 * not be the zero character. 178 * 179 * <p>The behavior of radixes and the characters used as digits 180 * are the same as {@link #toString(int, int) toString}. 181 * 182 * @param i an integer to be converted to an unsigned string. 183 * @param radix the radix to use in the string representation. 184 * @return an unsigned string representation of the argument in the specified radix. 185 * @see #toString(int, int) 186 * @since 1.8 187 */ 188 public static String toUnsignedString(int i, int radix) { 189 return Long.toUnsignedString(toUnsignedLong(i), radix); 190 } 191 192 /** 193 * Returns a string representation of the integer argument as an 194 * unsigned integer in base 16. 195 * 196 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 197 * if the argument is negative; otherwise, it is equal to the 198 * argument. This value is converted to a string of ASCII digits 199 * in hexadecimal (base 16) with no extra leading 200 * {@code 0}s. If the unsigned magnitude is zero, it is 201 * represented by a single zero character {@code '0'} 202 * (<code>'\u0030'</code>); otherwise, the first character of 203 * the representation of the unsigned magnitude will not be the 204 * zero character. The following characters are used as 205 * hexadecimal digits: 206 * 207 * <blockquote> 208 * {@code 0123456789abcdef} 209 * </blockquote> 210 * 211 * These are the characters <code>'\u0030'</code> through 212 * <code>'\u0039'</code> and <code>'\u0061'</code> through 213 * <code>'\u0066'</code>. If uppercase letters are 214 * desired, the {@link java.lang.String#toUpperCase()} method may 215 * be called on the result: 216 * 217 * <blockquote> 218 * {@code Integer.toHexString(n).toUpperCase()} 219 * </blockquote> 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 hexadecimal (base 16). 224 * @since JDK1.0.2 225 */ 226 public static String toHexString(int i) { 227 return toUnsignedString0(i, 4); 228 } 229 230 /** 231 * Returns a string representation of the integer argument as an 232 * unsigned integer in base 8. 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 octal (base 8) with no extra leading {@code 0}s. 238 * 239 * <p>If the unsigned magnitude is zero, it is represented by a 240 * single zero character {@code '0'} 241 * (<code>'\u0030'</code>); otherwise, the first character of 242 * the representation of the unsigned magnitude will not be the 243 * zero character. The following characters are used as octal 244 * digits: 245 * 246 * <blockquote> 247 * {@code 01234567} 248 * </blockquote> 249 * 250 * These are the characters <code>'\u0030'</code> through 251 * <code>'\u0037'</code>. 252 * 253 * @param i an integer to be converted to a string. 254 * @return the string representation of the unsigned integer value 255 * represented by the argument in octal (base 8). 256 * @since JDK1.0.2 257 */ 258 public static String toOctalString(int i) { 259 return toUnsignedString0(i, 3); 260 } 261 262 /** 263 * Returns a string representation of the integer argument as an 264 * unsigned integer in base 2. 265 * 266 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 267 * if the argument is negative; otherwise it is equal to the 268 * argument. This value is converted to a string of ASCII digits 269 * in binary (base 2) with no extra leading {@code 0}s. 270 * If the unsigned magnitude is zero, it is represented by a 271 * single zero character {@code '0'} 272 * (<code>'\u0030'</code>); otherwise, the first character of 273 * the representation of the unsigned magnitude will not be the 274 * zero character. The characters {@code '0'} 275 * (<code>'\u0030'</code>) and {@code '1'} 276 * (<code>'\u0031'</code>) are used as binary digits. 277 * 278 * @param i an integer to be converted to a string. 279 * @return the string representation of the unsigned integer value 280 * represented by the argument in binary (base 2). 281 * @since JDK1.0.2 282 */ 283 public static String toBinaryString(int i) { 284 return toUnsignedString0(i, 1); 285 } 286 287 /** 288 * Convert the integer to an unsigned number. 289 */ 290 private static String toUnsignedString0(int i, int shift) { 291 char[] buf = new char[32]; 292 int charPos = 32; 293 int radix = 1 << shift; 294 int mask = radix - 1; 295 do { 296 buf[--charPos] = digits[i & mask]; 297 i >>>= shift; 298 } while (i != 0); 299 300 return new String(buf, charPos, (32 - charPos)); 301 } 302 303 private static final String[] SMALL_NEG_VALUES = new String[100]; 304 private static final String[] SMALL_NONNEG_VALUES = new String[100]; 305 306 final static char [] DigitTens = { 307 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', 308 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', 309 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', 310 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 311 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', 312 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', 313 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', 314 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', 315 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', 316 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', 317 } ; 318 319 final static char [] DigitOnes = { 320 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 321 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 322 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 323 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 324 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 325 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 326 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 327 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 328 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 329 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 330 } ; 331 332 // I use the "invariant division by multiplication" trick to 333 // accelerate Integer.toString. In particular we want to 334 // avoid division by 10. 335 // 336 // The "trick" has roughly the same performance characteristics 337 // as the "classic" Integer.toString code on a non-JIT VM. 338 // The trick avoids .rem and .div calls but has a longer code 339 // path and is thus dominated by dispatch overhead. In the 340 // JIT case the dispatch overhead doesn't exist and the 341 // "trick" is considerably faster than the classic code. 342 // 343 // TODO-FIXME: convert (x * 52429) into the equiv shift-add 344 // sequence. 345 // 346 // RE: Division by Invariant Integers using Multiplication 347 // T Gralund, P Montgomery 348 // ACM PLDI 1994 349 // 350 351 /** 352 * Returns a {@code String} object representing the 353 * specified integer. The argument is converted to signed decimal 354 * representation and returned as a string, exactly as if the 355 * argument and radix 10 were given as arguments to the {@link 356 * #toString(int, int)} method. 357 * 358 * @param i an integer to be converted. 359 * @return a string representation of the argument in base 10. 360 */ 361 public static String toString(int i) { 362 if (i == Integer.MIN_VALUE) 363 return "-2147483648"; 364 365 // Android-changed: cache the string literal for small values. 366 boolean negative = i < 0; 367 boolean small = negative ? i > -100 : i < 100; 368 if (small) { 369 final String[] smallValues = negative ? SMALL_NEG_VALUES : SMALL_NONNEG_VALUES; 370 371 if (negative) { 372 i = -i; 373 if (smallValues[i] == null) { 374 smallValues[i] = 375 i < 10 ? new String(new char[]{'-', DigitOnes[i]}) 376 : new String(new char[]{'-', DigitTens[i], DigitOnes[i]}); 377 } 378 } else { 379 if (smallValues[i] == null) { 380 smallValues[i] = 381 i < 10 ? new String(new char[]{DigitOnes[i]}) 382 : new String(new char[]{DigitTens[i], DigitOnes[i]}); 383 } 384 } 385 return smallValues[i]; 386 } 387 388 int size = negative ? stringSize(-i) + 1 : stringSize(i); 389 char[] buf = new char[size]; 390 getChars(i, size, buf); 391 return new String(buf); 392 } 393 394 /** 395 * Returns a string representation of the argument as an unsigned 396 * decimal value. 397 * 398 * The argument is converted to unsigned decimal representation 399 * and returned as a string exactly as if the argument and radix 400 * 10 were given as arguments to the {@link #toUnsignedString(int, 401 * int)} method. 402 * 403 * @param i an integer to be converted to an unsigned string. 404 * @return an unsigned string representation of the argument. 405 * @see #toUnsignedString(int, int) 406 * @since 1.8 407 */ 408 public static String toUnsignedString(int i) { 409 return Long.toString(toUnsignedLong(i)); 410 } 411 412 /** 413 * Places characters representing the integer i into the 414 * character array buf. The characters are placed into 415 * the buffer backwards starting with the least significant 416 * digit at the specified index (exclusive), and working 417 * backwards from there. 418 * 419 * Will fail if i == Integer.MIN_VALUE 420 */ 421 static void getChars(int i, int index, char[] buf) { 422 int q, r; 423 int charPos = index; 424 char sign = 0; 425 426 if (i < 0) { 427 sign = '-'; 428 i = -i; 429 } 430 431 // Generate two digits per iteration 432 while (i >= 65536) { 433 q = i / 100; 434 // really: r = i - (q * 100); 435 r = i - ((q << 6) + (q << 5) + (q << 2)); 436 i = q; 437 buf [--charPos] = DigitOnes[r]; 438 buf [--charPos] = DigitTens[r]; 439 } 440 441 // Fall thru to fast mode for smaller numbers 442 // assert(i <= 65536, i); 443 for (;;) { 444 q = (i * 52429) >>> (16+3); 445 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ... 446 buf [--charPos] = digits [r]; 447 i = q; 448 if (i == 0) break; 449 } 450 if (sign != 0) { 451 buf [--charPos] = sign; 452 } 453 } 454 455 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 456 99999999, 999999999, Integer.MAX_VALUE }; 457 458 // Requires positive x 459 static int stringSize(int x) { 460 for (int i=0; ; i++) 461 if (x <= sizeTable[i]) 462 return i+1; 463 } 464 465 /** 466 * Parses the string argument as a signed integer in the radix 467 * specified by the second argument. The characters in the string 468 * must all be digits of the specified radix (as determined by 469 * whether {@link java.lang.Character#digit(char, int)} returns a 470 * nonnegative value), except that the first character may be an 471 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to 472 * indicate a negative value or an ASCII plus sign {@code '+'} 473 * (<code>'\u002B'</code>) to indicate a positive value. The 474 * resulting integer value is returned. 475 * 476 * <p>An exception of type {@code NumberFormatException} is 477 * thrown if any of the following situations occurs: 478 * <ul> 479 * <li>The first argument is {@code null} or is a string of 480 * length zero. 481 * 482 * <li>The radix is either smaller than 483 * {@link java.lang.Character#MIN_RADIX} or 484 * larger than {@link java.lang.Character#MAX_RADIX}. 485 * 486 * <li>Any character of the string is not a digit of the specified 487 * radix, except that the first character may be a minus sign 488 * {@code '-'} (<code>'\u002D'</code>) or plus sign 489 * {@code '+'} (<code>'\u002B'</code>) provided that the 490 * string is longer than length 1. 491 * 492 * <li>The value represented by the string is not a value of type 493 * {@code int}. 494 * </ul> 495 * 496 * <p>Examples: 497 * <blockquote><pre> 498 * parseInt("0", 10) returns 0 499 * parseInt("473", 10) returns 473 500 * parseInt("+42", 10) returns 42 501 * parseInt("-0", 10) returns 0 502 * parseInt("-FF", 16) returns -255 503 * parseInt("1100110", 2) returns 102 504 * parseInt("2147483647", 10) returns 2147483647 505 * parseInt("-2147483648", 10) returns -2147483648 506 * parseInt("2147483648", 10) throws a NumberFormatException 507 * parseInt("99", 8) throws a NumberFormatException 508 * parseInt("Kona", 10) throws a NumberFormatException 509 * parseInt("Kona", 27) returns 411787 510 * </pre></blockquote> 511 * 512 * @param s the {@code String} containing the integer 513 * representation to be parsed 514 * @param radix the radix to be used while parsing {@code s}. 515 * @return the integer represented by the string argument in the 516 * specified radix. 517 * @exception NumberFormatException if the {@code String} 518 * does not contain a parsable {@code int}. 519 */ 520 public static int parseInt(String s, int radix) 521 throws NumberFormatException 522 { 523 /* 524 * WARNING: This method may be invoked early during VM initialization 525 * before IntegerCache is initialized. Care must be taken to not use 526 * the valueOf method. 527 */ 528 529 if (s == null) { 530 throw new NumberFormatException("s == null"); 531 } 532 533 if (radix < Character.MIN_RADIX) { 534 throw new NumberFormatException("radix " + radix + 535 " less than Character.MIN_RADIX"); 536 } 537 538 if (radix > Character.MAX_RADIX) { 539 throw new NumberFormatException("radix " + radix + 540 " greater than Character.MAX_RADIX"); 541 } 542 543 int result = 0; 544 boolean negative = false; 545 int i = 0, len = s.length(); 546 int limit = -Integer.MAX_VALUE; 547 int multmin; 548 int digit; 549 550 if (len > 0) { 551 char firstChar = s.charAt(0); 552 if (firstChar < '0') { // Possible leading "+" or "-" 553 if (firstChar == '-') { 554 negative = true; 555 limit = Integer.MIN_VALUE; 556 } else if (firstChar != '+') 557 throw NumberFormatException.forInputString(s); 558 559 if (len == 1) // Cannot have lone "+" or "-" 560 throw NumberFormatException.forInputString(s); 561 i++; 562 } 563 multmin = limit / radix; 564 while (i < len) { 565 // Accumulating negatively avoids surprises near MAX_VALUE 566 digit = Character.digit(s.charAt(i++),radix); 567 if (digit < 0) { 568 throw NumberFormatException.forInputString(s); 569 } 570 if (result < multmin) { 571 throw NumberFormatException.forInputString(s); 572 } 573 result *= radix; 574 if (result < limit + digit) { 575 throw NumberFormatException.forInputString(s); 576 } 577 result -= digit; 578 } 579 } else { 580 throw NumberFormatException.forInputString(s); 581 } 582 return negative ? result : -result; 583 } 584 585 /** 586 * Parses the string argument as a signed decimal integer. The 587 * characters in the string must all be decimal digits, except 588 * that the first character may be an ASCII minus sign {@code '-'} 589 * (<code>'\u002D'</code>) to indicate a negative value or an 590 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to 591 * indicate a positive value. The resulting integer value is 592 * returned, exactly as if the argument and the radix 10 were 593 * given as arguments to the {@link #parseInt(java.lang.String, 594 * int)} method. 595 * 596 * @param s a {@code String} containing the {@code int} 597 * representation to be parsed 598 * @return the integer value represented by the argument in decimal. 599 * @exception NumberFormatException if the string does not contain a 600 * parsable integer. 601 */ 602 public static int parseInt(String s) throws NumberFormatException { 603 return parseInt(s,10); 604 } 605 606 /** 607 * Parses the string argument as an unsigned integer in the radix 608 * specified by the second argument. An unsigned integer maps the 609 * values usually associated with negative numbers to positive 610 * numbers larger than {@code MAX_VALUE}. 611 * 612 * The characters in the string must all be digits of the 613 * specified radix (as determined by whether {@link 614 * java.lang.Character#digit(char, int)} returns a nonnegative 615 * value), except that the first character may be an ASCII plus 616 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting 617 * integer value is returned. 618 * 619 * <p>An exception of type {@code NumberFormatException} is 620 * thrown if any of the following situations occurs: 621 * <ul> 622 * <li>The first argument is {@code null} or is a string of 623 * length zero. 624 * 625 * <li>The radix is either smaller than 626 * {@link java.lang.Character#MIN_RADIX} or 627 * larger than {@link java.lang.Character#MAX_RADIX}. 628 * 629 * <li>Any character of the string is not a digit of the specified 630 * radix, except that the first character may be a plus sign 631 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 632 * string is longer than length 1. 633 * 634 * <li>The value represented by the string is larger than the 635 * largest unsigned {@code int}, 2<sup>32</sup>-1. 636 * 637 * </ul> 638 * 639 * 640 * @param s the {@code String} containing the unsigned integer 641 * representation to be parsed 642 * @param radix the radix to be used while parsing {@code s}. 643 * @return the integer represented by the string argument in the 644 * specified radix. 645 * @throws NumberFormatException if the {@code String} 646 * does not contain a parsable {@code int}. 647 * @since 1.8 648 */ 649 public static int parseUnsignedInt(String s, int radix) 650 throws NumberFormatException { 651 if (s == null) { 652 throw new NumberFormatException("null"); 653 } 654 655 int len = s.length(); 656 if (len > 0) { 657 char firstChar = s.charAt(0); 658 if (firstChar == '-') { 659 throw new 660 NumberFormatException(String.format("Illegal leading minus sign " + 661 "on unsigned string %s.", s)); 662 } else { 663 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits 664 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits 665 return parseInt(s, radix); 666 } else { 667 long ell = Long.parseLong(s, radix); 668 if ((ell & 0xffff_ffff_0000_0000L) == 0) { 669 return (int) ell; 670 } else { 671 throw new 672 NumberFormatException(String.format("String value %s exceeds " + 673 "range of unsigned int.", s)); 674 } 675 } 676 } 677 } else { 678 throw NumberFormatException.forInputString(s); 679 } 680 } 681 682 /** 683 * Parses the string argument as an unsigned decimal integer. The 684 * characters in the string must all be decimal digits, except 685 * that the first character may be an an ASCII plus sign {@code 686 * '+'} ({@code '\u005Cu002B'}). The resulting integer value 687 * is returned, exactly as if the argument and the radix 10 were 688 * given as arguments to the {@link 689 * #parseUnsignedInt(java.lang.String, int)} method. 690 * 691 * @param s a {@code String} containing the unsigned {@code int} 692 * representation to be parsed 693 * @return the unsigned integer value represented by the argument in decimal. 694 * @throws NumberFormatException if the string does not contain a 695 * parsable unsigned integer. 696 * @since 1.8 697 */ 698 public static int parseUnsignedInt(String s) throws NumberFormatException { 699 return parseUnsignedInt(s, 10); 700 } 701 702 /** 703 * Returns an {@code Integer} object holding the value 704 * extracted from the specified {@code String} when parsed 705 * with the radix given by the second argument. The first argument 706 * is interpreted as representing a signed integer in the radix 707 * specified by the second argument, exactly as if the arguments 708 * were given to the {@link #parseInt(java.lang.String, int)} 709 * method. The result is an {@code Integer} object that 710 * represents the integer value specified by the string. 711 * 712 * <p>In other words, this method returns an {@code Integer} 713 * object equal to the value of: 714 * 715 * <blockquote> 716 * {@code new Integer(Integer.parseInt(s, radix))} 717 * </blockquote> 718 * 719 * @param s the string to be parsed. 720 * @param radix the radix to be used in interpreting {@code s} 721 * @return an {@code Integer} object holding the value 722 * represented by the string argument in the specified 723 * radix. 724 * @exception NumberFormatException if the {@code String} 725 * does not contain a parsable {@code int}. 726 */ 727 public static Integer valueOf(String s, int radix) throws NumberFormatException { 728 return Integer.valueOf(parseInt(s,radix)); 729 } 730 731 /** 732 * Returns an {@code Integer} object holding the 733 * value of the specified {@code String}. The argument is 734 * interpreted as representing a signed decimal integer, exactly 735 * as if the argument were given to the {@link 736 * #parseInt(java.lang.String)} method. The result is an 737 * {@code Integer} object that represents the integer value 738 * specified by the string. 739 * 740 * <p>In other words, this method returns an {@code Integer} 741 * object equal to the value of: 742 * 743 * <blockquote> 744 * {@code new Integer(Integer.parseInt(s))} 745 * </blockquote> 746 * 747 * @param s the string to be parsed. 748 * @return an {@code Integer} object holding the value 749 * represented by the string argument. 750 * @exception NumberFormatException if the string cannot be parsed 751 * as an integer. 752 */ 753 public static Integer valueOf(String s) throws NumberFormatException { 754 return Integer.valueOf(parseInt(s, 10)); 755 } 756 757 /** 758 * Cache to support the object identity semantics of autoboxing for values between 759 * -128 and 127 (inclusive) as required by JLS. 760 * 761 * The cache is initialized on first usage. The size of the cache 762 * may be controlled by the -XX:AutoBoxCacheMax=<size> option. 763 * During VM initialization, java.lang.Integer.IntegerCache.high property 764 * may be set and saved in the private system properties in the 765 * sun.misc.VM class. 766 */ 767 768 private static class IntegerCache { 769 static final int low = -128; 770 static final int high; 771 static final Integer cache[]; 772 773 static { 774 // high value may be configured by property 775 int h = 127; 776 String integerCacheHighPropValue = 777 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); 778 if (integerCacheHighPropValue != null) { 779 int i = parseInt(integerCacheHighPropValue); 780 i = Math.max(i, 127); 781 // Maximum array size is Integer.MAX_VALUE 782 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 783 } 784 high = h; 785 786 cache = new Integer[(high - low) + 1]; 787 int j = low; 788 for(int k = 0; k < cache.length; k++) 789 cache[k] = new Integer(j++); 790 } 791 792 private IntegerCache() {} 793 } 794 795 /** 796 * Returns an {@code Integer} instance representing the specified 797 * {@code int} value. If a new {@code Integer} instance is not 798 * required, this method should generally be used in preference to 799 * the constructor {@link #Integer(int)}, as this method is likely 800 * to yield significantly better space and time performance by 801 * caching frequently requested values. 802 * 803 * This method will always cache values in the range -128 to 127, 804 * inclusive, and may cache other values outside of this range. 805 * 806 * @param i an {@code int} value. 807 * @return an {@code Integer} instance representing {@code i}. 808 * @since 1.5 809 */ 810 public static Integer valueOf(int i) { 811 assert IntegerCache.high >= 127; 812 if (i >= IntegerCache.low && i <= IntegerCache.high) 813 return IntegerCache.cache[i + (-IntegerCache.low)]; 814 return new Integer(i); 815 } 816 817 /** 818 * The value of the {@code Integer}. 819 * 820 * @serial 821 */ 822 private final int value; 823 824 /** 825 * Constructs a newly allocated {@code Integer} object that 826 * represents the specified {@code int} value. 827 * 828 * @param value the value to be represented by the 829 * {@code Integer} object. 830 */ 831 public Integer(int value) { 832 this.value = value; 833 } 834 835 /** 836 * Constructs a newly allocated {@code Integer} object that 837 * represents the {@code int} value indicated by the 838 * {@code String} parameter. The string is converted to an 839 * {@code int} value in exactly the manner used by the 840 * {@code parseInt} method for radix 10. 841 * 842 * @param s the {@code String} to be converted to an 843 * {@code Integer}. 844 * @exception NumberFormatException if the {@code String} does not 845 * contain a parsable integer. 846 * @see java.lang.Integer#parseInt(java.lang.String, int) 847 */ 848 public Integer(String s) throws NumberFormatException { 849 this.value = parseInt(s, 10); 850 } 851 852 /** 853 * Returns the value of this {@code Integer} as a 854 * {@code byte}. 855 */ 856 public byte byteValue() { 857 return (byte)value; 858 } 859 860 /** 861 * Returns the value of this {@code Integer} as a 862 * {@code short}. 863 */ 864 public short shortValue() { 865 return (short)value; 866 } 867 868 /** 869 * Returns the value of this {@code Integer} as an 870 * {@code int}. 871 */ 872 public int intValue() { 873 return value; 874 } 875 876 /** 877 * Returns the value of this {@code Integer} as a 878 * {@code long}. 879 */ 880 public long longValue() { 881 return (long)value; 882 } 883 884 /** 885 * Returns the value of this {@code Integer} as a 886 * {@code float}. 887 */ 888 public float floatValue() { 889 return (float)value; 890 } 891 892 /** 893 * Returns the value of this {@code Integer} as a 894 * {@code double}. 895 */ 896 public double doubleValue() { 897 return (double)value; 898 } 899 900 /** 901 * Returns a {@code String} object representing this 902 * {@code Integer}'s value. The value is converted to signed 903 * decimal representation and returned as a string, exactly as if 904 * the integer value were given as an argument to the {@link 905 * java.lang.Integer#toString(int)} method. 906 * 907 * @return a string representation of the value of this object in 908 * base 10. 909 */ 910 public String toString() { 911 return toString(value); 912 } 913 914 /** 915 * Returns a hash code for this {@code Integer}. 916 * 917 * @return a hash code value for this object, equal to the 918 * primitive {@code int} value represented by this 919 * {@code Integer} object. 920 */ 921 public int hashCode() { 922 return value; 923 } 924 925 /** 926 * Returns a hash code for a {@code int} value; compatible with 927 * {@code Integer.hashCode()}. 928 * 929 * @param value the value to hash 930 * @since 1.8 931 * 932 * @return a hash code value for a {@code int} value. 933 */ 934 public static int hashCode(int value) { 935 return value; 936 } 937 938 /** 939 * Compares this object to the specified object. The result is 940 * {@code true} if and only if the argument is not 941 * {@code null} and is an {@code Integer} object that 942 * contains the same {@code int} value as this object. 943 * 944 * @param obj the object to compare with. 945 * @return {@code true} if the objects are the same; 946 * {@code false} otherwise. 947 */ 948 public boolean equals(Object obj) { 949 if (obj instanceof Integer) { 950 return value == ((Integer)obj).intValue(); 951 } 952 return false; 953 } 954 955 /** 956 * Determines the integer value of the system property with the 957 * specified name. 958 * 959 * <p>The first argument is treated as the name of a system property. 960 * System properties are accessible through the 961 * {@link java.lang.System#getProperty(java.lang.String)} method. The 962 * string value of this property is then interpreted as an integer 963 * value and an {@code Integer} object representing this value is 964 * returned. Details of possible numeric formats can be found with 965 * the definition of {@code getProperty}. 966 * 967 * <p>If there is no property with the specified name, if the specified name 968 * is empty or {@code null}, or if the property does not have 969 * the correct numeric format, then {@code null} is returned. 970 * 971 * <p>In other words, this method returns an {@code Integer} 972 * object equal to the value of: 973 * 974 * <blockquote> 975 * {@code getInteger(nm, null)} 976 * </blockquote> 977 * 978 * @param nm property name. 979 * @return the {@code Integer} value of the property. 980 * @see java.lang.System#getProperty(java.lang.String) 981 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 982 */ 983 public static Integer getInteger(String nm) { 984 return getInteger(nm, null); 985 } 986 987 /** 988 * Determines the integer value of the system property with the 989 * specified name. 990 * 991 * <p>The first argument is treated as the name of a system property. 992 * System properties are accessible through the {@link 993 * java.lang.System#getProperty(java.lang.String)} method. The 994 * string value of this property is then interpreted as an integer 995 * value and an {@code Integer} object representing this value is 996 * returned. Details of possible numeric formats can be found with 997 * the definition of {@code getProperty}. 998 * 999 * <p>The second argument is the default value. An {@code Integer} object 1000 * that represents the value of the second argument is returned if there 1001 * is no property of the specified name, if the property does not have 1002 * the correct numeric format, or if the specified name is empty or 1003 * {@code null}. 1004 * 1005 * <p>In other words, this method returns an {@code Integer} object 1006 * equal to the value of: 1007 * 1008 * <blockquote> 1009 * {@code getInteger(nm, new Integer(val))} 1010 * </blockquote> 1011 * 1012 * but in practice it may be implemented in a manner such as: 1013 * 1014 * <blockquote><pre> 1015 * Integer result = getInteger(nm, null); 1016 * return (result == null) ? new Integer(val) : result; 1017 * </pre></blockquote> 1018 * 1019 * to avoid the unnecessary allocation of an {@code Integer} 1020 * object when the default value is not needed. 1021 * 1022 * @param nm property name. 1023 * @param val default value. 1024 * @return the {@code Integer} value of the property. 1025 * @see java.lang.System#getProperty(java.lang.String) 1026 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1027 */ 1028 public static Integer getInteger(String nm, int val) { 1029 Integer result = getInteger(nm, null); 1030 return (result == null) ? Integer.valueOf(val) : result; 1031 } 1032 1033 /** 1034 * Returns the integer value of the system property with the 1035 * specified name. The first argument is treated as the name of a 1036 * system property. System properties are accessible through the 1037 * {@link java.lang.System#getProperty(java.lang.String)} method. 1038 * The string value of this property is then interpreted as an 1039 * integer value, as per the {@code Integer.decode} method, 1040 * and an {@code Integer} object representing this value is 1041 * returned. 1042 * 1043 * <ul><li>If the property value begins with the two ASCII characters 1044 * {@code 0x} or the ASCII character {@code #}, not 1045 * followed by a minus sign, then the rest of it is parsed as a 1046 * hexadecimal integer exactly as by the method 1047 * {@link #valueOf(java.lang.String, int)} with radix 16. 1048 * <li>If the property value begins with the ASCII character 1049 * {@code 0} followed by another character, it is parsed as an 1050 * octal integer exactly as by the method 1051 * {@link #valueOf(java.lang.String, int)} with radix 8. 1052 * <li>Otherwise, the property value is parsed as a decimal integer 1053 * exactly as by the method {@link #valueOf(java.lang.String, int)} 1054 * with radix 10. 1055 * </ul> 1056 * 1057 * <p>The second argument is the default value. The default value is 1058 * returned if there is no property of the specified name, if the 1059 * property does not have the correct numeric format, or if the 1060 * specified name is empty or {@code null}. 1061 * 1062 * @param nm property name. 1063 * @param val default value. 1064 * @return the {@code Integer} value of the property. 1065 * @see java.lang.System#getProperty(java.lang.String) 1066 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1067 * @see java.lang.Integer#decode 1068 */ 1069 public static Integer getInteger(String nm, Integer val) { 1070 String v = null; 1071 try { 1072 v = System.getProperty(nm); 1073 } catch (IllegalArgumentException e) { 1074 } catch (NullPointerException e) { 1075 } 1076 if (v != null) { 1077 try { 1078 return Integer.decode(v); 1079 } catch (NumberFormatException e) { 1080 } 1081 } 1082 return val; 1083 } 1084 1085 /** 1086 * Decodes a {@code String} into an {@code Integer}. 1087 * Accepts decimal, hexadecimal, and octal numbers given 1088 * by the following grammar: 1089 * 1090 * <blockquote> 1091 * <dl> 1092 * <dt><i>DecodableString:</i> 1093 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 1094 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 1095 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 1096 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 1097 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 1098 * <p> 1099 * <dt><i>Sign:</i> 1100 * <dd>{@code -} 1101 * <dd>{@code +} 1102 * </dl> 1103 * </blockquote> 1104 * 1105 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 1106 * are as defined in section 3.10.1 of 1107 * <cite>The Java™ Language Specification</cite>, 1108 * except that underscores are not accepted between digits. 1109 * 1110 * <p>The sequence of characters following an optional 1111 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 1112 * "{@code #}", or leading zero) is parsed as by the {@code 1113 * Integer.parseInt} method with the indicated radix (10, 16, or 1114 * 8). This sequence of characters must represent a positive 1115 * value or a {@link NumberFormatException} will be thrown. The 1116 * result is negated if first character of the specified {@code 1117 * String} is the minus sign. No whitespace characters are 1118 * permitted in the {@code String}. 1119 * 1120 * @param nm the {@code String} to decode. 1121 * @return an {@code Integer} object holding the {@code int} 1122 * value represented by {@code nm} 1123 * @exception NumberFormatException if the {@code String} does not 1124 * contain a parsable integer. 1125 * @see java.lang.Integer#parseInt(java.lang.String, int) 1126 */ 1127 public static Integer decode(String nm) throws NumberFormatException { 1128 int radix = 10; 1129 int index = 0; 1130 boolean negative = false; 1131 Integer result; 1132 1133 if (nm.length() == 0) 1134 throw new NumberFormatException("Zero length string"); 1135 char firstChar = nm.charAt(0); 1136 // Handle sign, if present 1137 if (firstChar == '-') { 1138 negative = true; 1139 index++; 1140 } else if (firstChar == '+') 1141 index++; 1142 1143 // Handle radix specifier, if present 1144 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 1145 index += 2; 1146 radix = 16; 1147 } 1148 else if (nm.startsWith("#", index)) { 1149 index ++; 1150 radix = 16; 1151 } 1152 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 1153 index ++; 1154 radix = 8; 1155 } 1156 1157 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 1158 throw new NumberFormatException("Sign character in wrong position"); 1159 1160 try { 1161 result = Integer.valueOf(nm.substring(index), radix); 1162 result = negative ? Integer.valueOf(-result.intValue()) : result; 1163 } catch (NumberFormatException e) { 1164 // If number is Integer.MIN_VALUE, we'll end up here. The next line 1165 // handles this case, and causes any genuine format error to be 1166 // rethrown. 1167 String constant = negative ? ("-" + nm.substring(index)) 1168 : nm.substring(index); 1169 result = Integer.valueOf(constant, radix); 1170 } 1171 return result; 1172 } 1173 1174 /** 1175 * Compares two {@code Integer} objects numerically. 1176 * 1177 * @param anotherInteger the {@code Integer} to be compared. 1178 * @return the value {@code 0} if this {@code Integer} is 1179 * equal to the argument {@code Integer}; a value less than 1180 * {@code 0} if this {@code Integer} is numerically less 1181 * than the argument {@code Integer}; and a value greater 1182 * than {@code 0} if this {@code Integer} is numerically 1183 * greater than the argument {@code Integer} (signed 1184 * comparison). 1185 * @since 1.2 1186 */ 1187 public int compareTo(Integer anotherInteger) { 1188 return compare(this.value, anotherInteger.value); 1189 } 1190 1191 /** 1192 * Compares two {@code int} values numerically. 1193 * The value returned is identical to what would be returned by: 1194 * <pre> 1195 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1196 * </pre> 1197 * 1198 * @param x the first {@code int} to compare 1199 * @param y the second {@code int} to compare 1200 * @return the value {@code 0} if {@code x == y}; 1201 * a value less than {@code 0} if {@code x < y}; and 1202 * a value greater than {@code 0} if {@code x > y} 1203 * @since 1.7 1204 */ 1205 public static int compare(int x, int y) { 1206 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1207 } 1208 1209 /** 1210 * Compares two {@code int} values numerically treating the values 1211 * as unsigned. 1212 * 1213 * @param x the first {@code int} to compare 1214 * @param y the second {@code int} to compare 1215 * @return the value {@code 0} if {@code x == y}; a value less 1216 * than {@code 0} if {@code x < y} as unsigned values; and 1217 * a value greater than {@code 0} if {@code x > y} as 1218 * unsigned values 1219 * @since 1.8 1220 */ 1221 public static int compareUnsigned(int x, int y) { 1222 return compare(x + MIN_VALUE, y + MIN_VALUE); 1223 } 1224 1225 /** 1226 * Converts the argument to a {@code long} by an unsigned 1227 * conversion. In an unsigned conversion to a {@code long}, the 1228 * high-order 32 bits of the {@code long} are zero and the 1229 * low-order 32 bits are equal to the bits of the integer 1230 * argument. 1231 * 1232 * Consequently, zero and positive {@code int} values are mapped 1233 * to a numerically equal {@code long} value and negative {@code 1234 * int} values are mapped to a {@code long} value equal to the 1235 * input plus 2<sup>32</sup>. 1236 * 1237 * @param x the value to convert to an unsigned {@code long} 1238 * @return the argument converted to {@code long} by an unsigned 1239 * conversion 1240 * @since 1.8 1241 */ 1242 public static long toUnsignedLong(int x) { 1243 return ((long) x) & 0xffffffffL; 1244 } 1245 1246 /** 1247 * Returns the unsigned quotient of dividing the first argument by 1248 * the second where each argument and the result is interpreted as 1249 * an unsigned value. 1250 * 1251 * <p>Note that in two's complement arithmetic, the three other 1252 * basic arithmetic operations of add, subtract, and multiply are 1253 * bit-wise identical if the two operands are regarded as both 1254 * being signed or both being unsigned. Therefore separate {@code 1255 * addUnsigned}, etc. methods are not provided. 1256 * 1257 * @param dividend the value to be divided 1258 * @param divisor the value doing the dividing 1259 * @return the unsigned quotient of the first argument divided by 1260 * the second argument 1261 * @see #remainderUnsigned 1262 * @since 1.8 1263 */ 1264 public static int divideUnsigned(int dividend, int divisor) { 1265 // In lieu of tricky code, for now just use long arithmetic. 1266 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor)); 1267 } 1268 1269 /** 1270 * Returns the unsigned remainder from dividing the first argument 1271 * by the second where each argument and the result is interpreted 1272 * as an unsigned value. 1273 * 1274 * @param dividend the value to be divided 1275 * @param divisor the value doing the dividing 1276 * @return the unsigned remainder of the first argument divided by 1277 * the second argument 1278 * @see #divideUnsigned 1279 * @since 1.8 1280 */ 1281 public static int remainderUnsigned(int dividend, int divisor) { 1282 // In lieu of tricky code, for now just use long arithmetic. 1283 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor)); 1284 } 1285 1286 1287 // Bit twiddling 1288 1289 /** 1290 * The number of bits used to represent an {@code int} value in two's 1291 * complement binary form. 1292 * 1293 * @since 1.5 1294 */ 1295 public static final int SIZE = 32; 1296 1297 1298 /** 1299 * The number of bytes used to represent a {@code int} value in two's 1300 * complement binary form. 1301 * 1302 * @since 1.8 1303 */ 1304 public static final int BYTES = SIZE / Byte.SIZE; 1305 1306 /** 1307 * Returns an {@code int} value with at most a single one-bit, in the 1308 * position of the highest-order ("leftmost") one-bit in the specified 1309 * {@code int} value. Returns zero if the specified value has no 1310 * one-bits in its two's complement binary representation, that is, if it 1311 * is equal to zero. 1312 * 1313 * @return an {@code int} value with a single one-bit, in the position 1314 * of the highest-order one-bit in the specified value, or zero if 1315 * the specified value is itself equal to zero. 1316 * @since 1.5 1317 */ 1318 public static int highestOneBit(int i) { 1319 // HD, Figure 3-1 1320 i |= (i >> 1); 1321 i |= (i >> 2); 1322 i |= (i >> 4); 1323 i |= (i >> 8); 1324 i |= (i >> 16); 1325 return i - (i >>> 1); 1326 } 1327 1328 /** 1329 * Returns an {@code int} value with at most a single one-bit, in the 1330 * position of the lowest-order ("rightmost") one-bit in the specified 1331 * {@code int} value. Returns zero if the specified value has no 1332 * one-bits in its two's complement binary representation, that is, if it 1333 * is equal to zero. 1334 * 1335 * @return an {@code int} value with a single one-bit, in the position 1336 * of the lowest-order one-bit in the specified value, or zero if 1337 * the specified value is itself equal to zero. 1338 * @since 1.5 1339 */ 1340 public static int lowestOneBit(int i) { 1341 // HD, Section 2-1 1342 return i & -i; 1343 } 1344 1345 /** 1346 * Returns the number of zero bits preceding the highest-order 1347 * ("leftmost") one-bit in the two's complement binary representation 1348 * of the specified {@code int} value. Returns 32 if the 1349 * specified value has no one-bits in its two's complement representation, 1350 * in other words if it is equal to zero. 1351 * 1352 * <p>Note that this method is closely related to the logarithm base 2. 1353 * For all positive {@code int} values x: 1354 * <ul> 1355 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1356 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1357 * </ul> 1358 * 1359 * @return the number of zero bits preceding the highest-order 1360 * ("leftmost") one-bit in the two's complement binary representation 1361 * of the specified {@code int} value, or 32 if the value 1362 * is equal to zero. 1363 * @since 1.5 1364 */ 1365 public static int numberOfLeadingZeros(int i) { 1366 // HD, Figure 5-6 1367 if (i == 0) 1368 return 32; 1369 int n = 1; 1370 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1371 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1372 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1373 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1374 n -= i >>> 31; 1375 return n; 1376 } 1377 1378 /** 1379 * Returns the number of zero bits following the lowest-order ("rightmost") 1380 * one-bit in the two's complement binary representation of the specified 1381 * {@code int} value. Returns 32 if the specified value has no 1382 * one-bits in its two's complement representation, in other words if it is 1383 * equal to zero. 1384 * 1385 * @return the number of zero bits following the lowest-order ("rightmost") 1386 * one-bit in the two's complement binary representation of the 1387 * specified {@code int} value, or 32 if the value is equal 1388 * to zero. 1389 * @since 1.5 1390 */ 1391 public static int numberOfTrailingZeros(int i) { 1392 // HD, Figure 5-14 1393 int y; 1394 if (i == 0) return 32; 1395 int n = 31; 1396 y = i <<16; if (y != 0) { n = n -16; i = y; } 1397 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1398 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1399 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1400 return n - ((i << 1) >>> 31); 1401 } 1402 1403 /** 1404 * Returns the number of one-bits in the two's complement binary 1405 * representation of the specified {@code int} value. This function is 1406 * sometimes referred to as the <i>population count</i>. 1407 * 1408 * @return the number of one-bits in the two's complement binary 1409 * representation of the specified {@code int} value. 1410 * @since 1.5 1411 */ 1412 public static int bitCount(int i) { 1413 // HD, Figure 5-2 1414 i = i - ((i >>> 1) & 0x55555555); 1415 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1416 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1417 i = i + (i >>> 8); 1418 i = i + (i >>> 16); 1419 return i & 0x3f; 1420 } 1421 1422 /** 1423 * Returns the value obtained by rotating the two's complement binary 1424 * representation of the specified {@code int} value left by the 1425 * specified number of bits. (Bits shifted out of the left hand, or 1426 * high-order, side reenter on the right, or low-order.) 1427 * 1428 * <p>Note that left rotation with a negative distance is equivalent to 1429 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1430 * distance)}. Note also that rotation by any multiple of 32 is a 1431 * no-op, so all but the last five bits of the rotation distance can be 1432 * ignored, even if the distance is negative: {@code rotateLeft(val, 1433 * distance) == rotateLeft(val, distance & 0x1F)}. 1434 * 1435 * @return the value obtained by rotating the two's complement binary 1436 * representation of the specified {@code int} value left by the 1437 * specified number of bits. 1438 * @since 1.5 1439 */ 1440 public static int rotateLeft(int i, int distance) { 1441 return (i << distance) | (i >>> -distance); 1442 } 1443 1444 /** 1445 * Returns the value obtained by rotating the two's complement binary 1446 * representation of the specified {@code int} value right by the 1447 * specified number of bits. (Bits shifted out of the right hand, or 1448 * low-order, side reenter on the left, or high-order.) 1449 * 1450 * <p>Note that right rotation with a negative distance is equivalent to 1451 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1452 * distance)}. Note also that rotation by any multiple of 32 is a 1453 * no-op, so all but the last five bits of the rotation distance can be 1454 * ignored, even if the distance is negative: {@code rotateRight(val, 1455 * distance) == rotateRight(val, distance & 0x1F)}. 1456 * 1457 * @return the value obtained by rotating the two's complement binary 1458 * representation of the specified {@code int} value right by the 1459 * specified number of bits. 1460 * @since 1.5 1461 */ 1462 public static int rotateRight(int i, int distance) { 1463 return (i >>> distance) | (i << -distance); 1464 } 1465 1466 /** 1467 * Returns the value obtained by reversing the order of the bits in the 1468 * two's complement binary representation of the specified {@code int} 1469 * value. 1470 * 1471 * @return the value obtained by reversing order of the bits in the 1472 * specified {@code int} value. 1473 * @since 1.5 1474 */ 1475 public static int reverse(int i) { 1476 // HD, Figure 7-1 1477 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1478 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1479 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1480 i = (i << 24) | ((i & 0xff00) << 8) | 1481 ((i >>> 8) & 0xff00) | (i >>> 24); 1482 return i; 1483 } 1484 1485 /** 1486 * Returns the signum function of the specified {@code int} value. (The 1487 * return value is -1 if the specified value is negative; 0 if the 1488 * specified value is zero; and 1 if the specified value is positive.) 1489 * 1490 * @return the signum function of the specified {@code int} value. 1491 * @since 1.5 1492 */ 1493 public static int signum(int i) { 1494 // HD, Section 2-7 1495 return (i >> 31) | (-i >>> 31); 1496 } 1497 1498 /** 1499 * Returns the value obtained by reversing the order of the bytes in the 1500 * two's complement representation of the specified {@code int} value. 1501 * 1502 * @return the value obtained by reversing the bytes in the specified 1503 * {@code int} value. 1504 * @since 1.5 1505 */ 1506 public static int reverseBytes(int i) { 1507 return ((i >>> 24) ) | 1508 ((i >> 8) & 0xFF00) | 1509 ((i << 8) & 0xFF0000) | 1510 ((i << 24)); 1511 } 1512 1513 /** 1514 * Adds two integers together as per the + operator. 1515 * 1516 * @param a the first operand 1517 * @param b the second operand 1518 * @return the sum of {@code a} and {@code b} 1519 * @see java.util.function.BinaryOperator 1520 * @since 1.8 1521 */ 1522 public static int sum(int a, int b) { 1523 return a + b; 1524 } 1525 1526 /** 1527 * Returns the greater of two {@code int} values 1528 * as if by calling {@link Math#max(int, int) Math.max}. 1529 * 1530 * @param a the first operand 1531 * @param b the second operand 1532 * @return the greater of {@code a} and {@code b} 1533 * @see java.util.function.BinaryOperator 1534 * @since 1.8 1535 */ 1536 public static int max(int a, int b) { 1537 return Math.max(a, b); 1538 } 1539 1540 /** 1541 * Returns the smaller of two {@code int} values 1542 * as if by calling {@link Math#min(int, int) Math.min}. 1543 * 1544 * @param a the first operand 1545 * @param b the second operand 1546 * @return the smaller of {@code a} and {@code b} 1547 * @see java.util.function.BinaryOperator 1548 * @since 1.8 1549 */ 1550 public static int min(int a, int b) { 1551 return Math.min(a, b); 1552 } 1553 1554 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1555 private static final long serialVersionUID = 1360826667806852920L; 1556} 1557