1 /* 2 * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.lang.annotation.Native; 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 */ 52 public 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 @Native 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 @Native 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 @SuppressWarnings("unchecked") 72 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int"); 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 '\u005Cu002D'}). 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 '\u005Cu0030'}); 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 '\u005Cu0030'} through 111 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through 112 * {@code '\u005Cu007A'}. 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 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 first argument as an 162 * unsigned integer value in the radix specified by the second 163 * argument. 164 * 165 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 166 * or larger than {@code Character.MAX_RADIX}, then the radix 167 * {@code 10} is used instead. 168 * 169 * <p>Note that since the first argument is treated as an unsigned 170 * value, no leading sign character is printed. 171 * 172 * <p>If the magnitude is zero, it is represented by a single zero 173 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise, 174 * the first character of the representation of the magnitude will 175 * not be the zero character. 176 * 177 * <p>The behavior of radixes and the characters used as digits 178 * are the same as {@link #toString(int, int) toString}. 179 * 180 * @param i an integer to be converted to an unsigned string. 181 * @param radix the radix to use in the string representation. 182 * @return an unsigned string representation of the argument in the specified radix. 183 * @see #toString(int, int) 184 * @since 1.8 185 */ 186 public static String toUnsignedString(int i, int radix) { 187 return Long.toUnsignedString(toUnsignedLong(i), radix); 188 } 189 190 /** 191 * Returns a string representation of the integer argument as an 192 * unsigned integer in base 16. 193 * 194 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 195 * if the argument is negative; otherwise, it is equal to the 196 * argument. This value is converted to a string of ASCII digits 197 * in hexadecimal (base 16) with no extra leading 198 * {@code 0}s. 199 * 200 * <p>The value of the argument can be recovered from the returned 201 * string {@code s} by calling {@link 202 * Integer#parseUnsignedInt(String, int) 203 * Integer.parseUnsignedInt(s, 16)}. 204 * 205 * <p>If the unsigned magnitude is zero, it is represented by a 206 * single zero character {@code '0'} ({@code '\u005Cu0030'}); 207 * otherwise, the first character of the representation of the 208 * unsigned magnitude will not be the zero character. The 209 * following characters are used as hexadecimal digits: 210 * 211 * <blockquote> 212 * {@code 0123456789abcdef} 213 * </blockquote> 214 * 215 * These are the characters {@code '\u005Cu0030'} through 216 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through 217 * {@code '\u005Cu0066'}. If uppercase letters are 218 * desired, the {@link java.lang.String#toUpperCase()} method may 219 * be called on the result: 220 * 221 * <blockquote> 222 * {@code Integer.toHexString(n).toUpperCase()} 223 * </blockquote> 224 * 225 * @param i an integer to be converted to a string. 226 * @return the string representation of the unsigned integer value 227 * represented by the argument in hexadecimal (base 16). 228 * @see #parseUnsignedInt(String, int) 229 * @see #toUnsignedString(int, int) 230 * @since JDK1.0.2 231 */ 232 public static String toHexString(int i) { 233 return toUnsignedString0(i, 4); 234 } 235 236 /** 237 * Returns a string representation of the integer argument as an 238 * unsigned integer in base 8. 239 * 240 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 241 * if the argument is negative; otherwise, it is equal to the 242 * argument. This value is converted to a string of ASCII digits 243 * in octal (base 8) with no extra leading {@code 0}s. 244 * 245 * <p>The value of the argument can be recovered from the returned 246 * string {@code s} by calling {@link 247 * Integer#parseUnsignedInt(String, int) 248 * Integer.parseUnsignedInt(s, 8)}. 249 * 250 * <p>If the unsigned magnitude is zero, it is represented by a 251 * single zero character {@code '0'} ({@code '\u005Cu0030'}); 252 * otherwise, the first character of the representation of the 253 * unsigned magnitude will not be the zero character. The 254 * following characters are used as octal digits: 255 * 256 * <blockquote> 257 * {@code 01234567} 258 * </blockquote> 259 * 260 * These are the characters {@code '\u005Cu0030'} through 261 * {@code '\u005Cu0037'}. 262 * 263 * @param i an integer to be converted to a string. 264 * @return the string representation of the unsigned integer value 265 * represented by the argument in octal (base 8). 266 * @see #parseUnsignedInt(String, int) 267 * @see #toUnsignedString(int, int) 268 * @since JDK1.0.2 269 */ 270 public static String toOctalString(int i) { 271 return toUnsignedString0(i, 3); 272 } 273 274 /** 275 * Returns a string representation of the integer argument as an 276 * unsigned integer in base 2. 277 * 278 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 279 * if the argument is negative; otherwise it is equal to the 280 * argument. This value is converted to a string of ASCII digits 281 * in binary (base 2) with no extra leading {@code 0}s. 282 * 283 * <p>The value of the argument can be recovered from the returned 284 * string {@code s} by calling {@link 285 * Integer#parseUnsignedInt(String, int) 286 * Integer.parseUnsignedInt(s, 2)}. 287 * 288 * <p>If the unsigned magnitude is zero, it is represented by a 289 * single zero character {@code '0'} ({@code '\u005Cu0030'}); 290 * otherwise, the first character of the representation of the 291 * unsigned magnitude will not be the zero character. The 292 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code 293 * '1'} ({@code '\u005Cu0031'}) are used as binary digits. 294 * 295 * @param i an integer to be converted to a string. 296 * @return the string representation of the unsigned integer value 297 * represented by the argument in binary (base 2). 298 * @see #parseUnsignedInt(String, int) 299 * @see #toUnsignedString(int, int) 300 * @since JDK1.0.2 301 */ 302 public static String toBinaryString(int i) { 303 return toUnsignedString0(i, 1); 304 } 305 306 /** 307 * Convert the integer to an unsigned number. 308 */ 309 private static String toUnsignedString0(int val, int shift) { 310 // assert shift > 0 && shift <=5 : "Illegal shift value"; 311 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val); 312 int chars = Math.max(((mag + (shift - 1)) / shift), 1); 313 char[] buf = new char[chars]; 314 315 formatUnsignedInt(val, shift, buf, 0, chars); 316 317 // Use special constructor which takes over "buf". 318 return new String(buf, true); 319 } 320 321 /** 322 * Format a long (treated as unsigned) into a character buffer. 323 * @param val the unsigned int to format 324 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) 325 * @param buf the character buffer to write to 326 * @param offset the offset in the destination buffer to start at 327 * @param len the number of characters to write 328 * @return the lowest character location used 329 */ 330 static int formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) { 331 int charPos = len; 332 int radix = 1 << shift; 333 int mask = radix - 1; 334 do { 335 buf[offset + --charPos] = Integer.digits[val & mask]; 336 val >>>= shift; 337 } while (val != 0 && charPos > 0); 338 339 return charPos; 340 } 341 342 final static char [] DigitTens = { 343 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', 344 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', 345 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', 346 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 347 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', 348 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', 349 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', 350 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', 351 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', 352 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', 353 } ; 354 355 final static char [] DigitOnes = { 356 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 357 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 358 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 359 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 360 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 361 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 362 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 363 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 364 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 365 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 366 } ; 367 368 // I use the "invariant division by multiplication" trick to 369 // accelerate Integer.toString. In particular we want to 370 // avoid division by 10. 371 // 372 // The "trick" has roughly the same performance characteristics 373 // as the "classic" Integer.toString code on a non-JIT VM. 374 // The trick avoids .rem and .div calls but has a longer code 375 // path and is thus dominated by dispatch overhead. In the 376 // JIT case the dispatch overhead doesn't exist and the 377 // "trick" is considerably faster than the classic code. 378 // 379 // TODO-FIXME: convert (x * 52429) into the equiv shift-add 380 // sequence. 381 // 382 // RE: Division by Invariant Integers using Multiplication 383 // T Gralund, P Montgomery 384 // ACM PLDI 1994 385 // 386 387 /** 388 * Returns a {@code String} object representing the 389 * specified integer. The argument is converted to signed decimal 390 * representation and returned as a string, exactly as if the 391 * argument and radix 10 were given as arguments to the {@link 392 * #toString(int, int)} method. 393 * 394 * @param i an integer to be converted. 395 * @return a string representation of the argument in base 10. 396 */ 397 public static String toString(int i) { 398 if (i == Integer.MIN_VALUE) 399 return "-2147483648"; 400 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); 401 char[] buf = new char[size]; 402 getChars(i, size, buf); 403 return new String(buf, true); 404 } 405 406 /** 407 * Returns a string representation of the argument as an unsigned 408 * decimal value. 409 * 410 * The argument is converted to unsigned decimal representation 411 * and returned as a string exactly as if the argument and radix 412 * 10 were given as arguments to the {@link #toUnsignedString(int, 413 * int)} method. 414 * 415 * @param i an integer to be converted to an unsigned string. 416 * @return an unsigned string representation of the argument. 417 * @see #toUnsignedString(int, int) 418 * @since 1.8 419 */ 420 public static String toUnsignedString(int i) { 421 return Long.toString(toUnsignedLong(i)); 422 } 423 424 /** 425 * Places characters representing the integer i into the 426 * character array buf. The characters are placed into 427 * the buffer backwards starting with the least significant 428 * digit at the specified index (exclusive), and working 429 * backwards from there. 430 * 431 * Will fail if i == Integer.MIN_VALUE 432 */ 433 static void getChars(int i, int index, char[] buf) { 434 int q, r; 435 int charPos = index; 436 char sign = 0; 437 438 if (i < 0) { 439 sign = '-'; 440 i = -i; 441 } 442 443 // Generate two digits per iteration 444 while (i >= 65536) { 445 q = i / 100; 446 // really: r = i - (q * 100); 447 r = i - ((q << 6) + (q << 5) + (q << 2)); 448 i = q; 449 buf [--charPos] = DigitOnes[r]; 450 buf [--charPos] = DigitTens[r]; 451 } 452 453 // Fall thru to fast mode for smaller numbers 454 // assert(i <= 65536, i); 455 for (;;) { 456 q = (i * 52429) >>> (16+3); 457 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ... 458 buf [--charPos] = digits [r]; 459 i = q; 460 if (i == 0) break; 461 } 462 if (sign != 0) { 463 buf [--charPos] = sign; 464 } 465 } 466 467 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 468 99999999, 999999999, Integer.MAX_VALUE }; 469 470 // Requires positive x 471 static int stringSize(int x) { 472 for (int i=0; ; i++) 473 if (x <= sizeTable[i]) 474 return i+1; 475 } 476 477 /** 478 * Parses the string argument as a signed integer in the radix 479 * specified by the second argument. The characters in the string 480 * must all be digits of the specified radix (as determined by 481 * whether {@link java.lang.Character#digit(char, int)} returns a 482 * nonnegative value), except that the first character may be an 483 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to 484 * indicate a negative value or an ASCII plus sign {@code '+'} 485 * ({@code '\u005Cu002B'}) to indicate a positive value. The 486 * resulting integer value is returned. 487 * 488 * <p>An exception of type {@code NumberFormatException} is 489 * thrown if any of the following situations occurs: 490 * <ul> 491 * <li>The first argument is {@code null} or is a string of 492 * length zero. 493 * 494 * <li>The radix is either smaller than 495 * {@link java.lang.Character#MIN_RADIX} or 496 * larger than {@link java.lang.Character#MAX_RADIX}. 497 * 498 * <li>Any character of the string is not a digit of the specified 499 * radix, except that the first character may be a minus sign 500 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign 501 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 502 * string is longer than length 1. 503 * 504 * <li>The value represented by the string is not a value of type 505 * {@code int}. 506 * </ul> 507 * 508 * <p>Examples: 509 * <blockquote><pre> 510 * parseInt("0", 10) returns 0 511 * parseInt("473", 10) returns 473 512 * parseInt("+42", 10) returns 42 513 * parseInt("-0", 10) returns 0 514 * parseInt("-FF", 16) returns -255 515 * parseInt("1100110", 2) returns 102 516 * parseInt("2147483647", 10) returns 2147483647 517 * parseInt("-2147483648", 10) returns -2147483648 518 * parseInt("2147483648", 10) throws a NumberFormatException 519 * parseInt("99", 8) throws a NumberFormatException 520 * parseInt("Kona", 10) throws a NumberFormatException 521 * parseInt("Kona", 27) returns 411787 522 * </pre></blockquote> 523 * 524 * @param s the {@code String} containing the integer 525 * representation to be parsed 526 * @param radix the radix to be used while parsing {@code s}. 527 * @return the integer represented by the string argument in the 528 * specified radix. 529 * @exception NumberFormatException if the {@code String} 530 * does not contain a parsable {@code int}. 531 */ 532 public static int parseInt(String s, int radix) 533 throws NumberFormatException 534 { 535 /* 536 * WARNING: This method may be invoked early during VM initialization 537 * before IntegerCache is initialized. Care must be taken to not use 538 * the valueOf method. 539 */ 540 541 if (s == null) { 542 throw new NumberFormatException("null"); 543 } 544 545 if (radix < Character.MIN_RADIX) { 546 throw new NumberFormatException("radix " + radix + 547 " less than Character.MIN_RADIX"); 548 } 549 550 if (radix > Character.MAX_RADIX) { 551 throw new NumberFormatException("radix " + radix + 552 " greater than Character.MAX_RADIX"); 553 } 554 555 int result = 0; 556 boolean negative = false; 557 int i = 0, len = s.length(); 558 int limit = -Integer.MAX_VALUE; 559 int multmin; 560 int digit; 561 562 if (len > 0) { 563 char firstChar = s.charAt(0); 564 if (firstChar < '0') { // Possible leading "+" or "-" 565 if (firstChar == '-') { 566 negative = true; 567 limit = Integer.MIN_VALUE; 568 } else if (firstChar != '+') 569 throw NumberFormatException.forInputString(s); 570 571 if (len == 1) // Cannot have lone "+" or "-" 572 throw NumberFormatException.forInputString(s); 573 i++; 574 } 575 multmin = limit / radix; 576 while (i < len) { 577 // Accumulating negatively avoids surprises near MAX_VALUE 578 digit = Character.digit(s.charAt(i++),radix); 579 if (digit < 0) { 580 throw NumberFormatException.forInputString(s); 581 } 582 if (result < multmin) { 583 throw NumberFormatException.forInputString(s); 584 } 585 result *= radix; 586 if (result < limit + digit) { 587 throw NumberFormatException.forInputString(s); 588 } 589 result -= digit; 590 } 591 } else { 592 throw NumberFormatException.forInputString(s); 593 } 594 return negative ? result : -result; 595 } 596 597 /** 598 * Parses the string argument as a signed decimal integer. The 599 * characters in the string must all be decimal digits, except 600 * that the first character may be an ASCII minus sign {@code '-'} 601 * ({@code '\u005Cu002D'}) to indicate a negative value or an 602 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to 603 * indicate a positive value. The resulting integer value is 604 * returned, exactly as if the argument and the radix 10 were 605 * given as arguments to the {@link #parseInt(java.lang.String, 606 * int)} method. 607 * 608 * @param s a {@code String} containing the {@code int} 609 * representation to be parsed 610 * @return the integer value represented by the argument in decimal. 611 * @exception NumberFormatException if the string does not contain a 612 * parsable integer. 613 */ 614 public static int parseInt(String s) throws NumberFormatException { 615 return parseInt(s,10); 616 } 617 618 /** 619 * Parses the string argument as an unsigned integer in the radix 620 * specified by the second argument. An unsigned integer maps the 621 * values usually associated with negative numbers to positive 622 * numbers larger than {@code MAX_VALUE}. 623 * 624 * The characters in the string must all be digits of the 625 * specified radix (as determined by whether {@link 626 * java.lang.Character#digit(char, int)} returns a nonnegative 627 * value), except that the first character may be an ASCII plus 628 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting 629 * integer value is returned. 630 * 631 * <p>An exception of type {@code NumberFormatException} is 632 * thrown if any of the following situations occurs: 633 * <ul> 634 * <li>The first argument is {@code null} or is a string of 635 * length zero. 636 * 637 * <li>The radix is either smaller than 638 * {@link java.lang.Character#MIN_RADIX} or 639 * larger than {@link java.lang.Character#MAX_RADIX}. 640 * 641 * <li>Any character of the string is not a digit of the specified 642 * radix, except that the first character may be a plus sign 643 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 644 * string is longer than length 1. 645 * 646 * <li>The value represented by the string is larger than the 647 * largest unsigned {@code int}, 2<sup>32</sup>-1. 648 * 649 * </ul> 650 * 651 * 652 * @param s the {@code String} containing the unsigned integer 653 * representation to be parsed 654 * @param radix the radix to be used while parsing {@code s}. 655 * @return the integer represented by the string argument in the 656 * specified radix. 657 * @throws NumberFormatException if the {@code String} 658 * does not contain a parsable {@code int}. 659 * @since 1.8 660 */ 661 public static int parseUnsignedInt(String s, int radix) 662 throws NumberFormatException { 663 if (s == null) { 664 throw new NumberFormatException("null"); 665 } 666 667 int len = s.length(); 668 if (len > 0) { 669 char firstChar = s.charAt(0); 670 if (firstChar == '-') { 671 throw new 672 NumberFormatException(String.format("Illegal leading minus sign " + 673 "on unsigned string %s.", s)); 674 } else { 675 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits 676 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits 677 return parseInt(s, radix); 678 } else { 679 long ell = Long.parseLong(s, radix); 680 if ((ell & 0xffff_ffff_0000_0000L) == 0) { 681 return (int) ell; 682 } else { 683 throw new 684 NumberFormatException(String.format("String value %s exceeds " + 685 "range of unsigned int.", s)); 686 } 687 } 688 } 689 } else { 690 throw NumberFormatException.forInputString(s); 691 } 692 } 693 694 /** 695 * Parses the string argument as an unsigned decimal integer. The 696 * characters in the string must all be decimal digits, except 697 * that the first character may be an an ASCII plus sign {@code 698 * '+'} ({@code '\u005Cu002B'}). The resulting integer value 699 * is returned, exactly as if the argument and the radix 10 were 700 * given as arguments to the {@link 701 * #parseUnsignedInt(java.lang.String, int)} method. 702 * 703 * @param s a {@code String} containing the unsigned {@code int} 704 * representation to be parsed 705 * @return the unsigned integer value represented by the argument in decimal. 706 * @throws NumberFormatException if the string does not contain a 707 * parsable unsigned integer. 708 * @since 1.8 709 */ 710 public static int parseUnsignedInt(String s) throws NumberFormatException { 711 return parseUnsignedInt(s, 10); 712 } 713 714 /** 715 * Returns an {@code Integer} object holding the value 716 * extracted from the specified {@code String} when parsed 717 * with the radix given by the second argument. The first argument 718 * is interpreted as representing a signed integer in the radix 719 * specified by the second argument, exactly as if the arguments 720 * were given to the {@link #parseInt(java.lang.String, int)} 721 * method. The result is an {@code Integer} object that 722 * represents the integer value specified by the string. 723 * 724 * <p>In other words, this method returns an {@code Integer} 725 * object equal to the value of: 726 * 727 * <blockquote> 728 * {@code new Integer(Integer.parseInt(s, radix))} 729 * </blockquote> 730 * 731 * @param s the string to be parsed. 732 * @param radix the radix to be used in interpreting {@code s} 733 * @return an {@code Integer} object holding the value 734 * represented by the string argument in the specified 735 * radix. 736 * @exception NumberFormatException if the {@code String} 737 * does not contain a parsable {@code int}. 738 */ 739 public static Integer valueOf(String s, int radix) throws NumberFormatException { 740 return Integer.valueOf(parseInt(s,radix)); 741 } 742 743 /** 744 * Returns an {@code Integer} object holding the 745 * value of the specified {@code String}. The argument is 746 * interpreted as representing a signed decimal integer, exactly 747 * as if the argument were given to the {@link 748 * #parseInt(java.lang.String)} method. The result is an 749 * {@code Integer} object that represents the integer value 750 * specified by the string. 751 * 752 * <p>In other words, this method returns an {@code Integer} 753 * object equal to the value of: 754 * 755 * <blockquote> 756 * {@code new Integer(Integer.parseInt(s))} 757 * </blockquote> 758 * 759 * @param s the string to be parsed. 760 * @return an {@code Integer} object holding the value 761 * represented by the string argument. 762 * @exception NumberFormatException if the string cannot be parsed 763 * as an integer. 764 */ 765 public static Integer valueOf(String s) throws NumberFormatException { 766 return Integer.valueOf(parseInt(s, 10)); 767 } 768 769 /** 770 * Cache to support the object identity semantics of autoboxing for values between 771 * -128 and 127 (inclusive) as required by JLS. 772 * 773 * The cache is initialized on first usage. The size of the cache 774 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option. 775 * During VM initialization, java.lang.Integer.IntegerCache.high property 776 * may be set and saved in the private system properties in the 777 * sun.misc.VM class. 778 */ 779 780 private static class IntegerCache { 781 static final int low = -128; 782 static final int high; 783 static final Integer cache[]; 784 785 static { 786 // high value may be configured by property 787 int h = 127; 788 String integerCacheHighPropValue = 789 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); 790 if (integerCacheHighPropValue != null) { 791 int i = parseInt(integerCacheHighPropValue); 792 i = Math.max(i, 127); 793 // Maximum array size is Integer.MAX_VALUE 794 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 795 } 796 high = h; 797 798 cache = new Integer[(high - low) + 1]; 799 int j = low; 800 for(int k = 0; k < cache.length; k++) 801 cache[k] = new Integer(j++); 802 803 // range [-128, 127] must be interned (JLS7 5.1.7) 804 assert IntegerCache.high >= 127; 805 } 806 807 private IntegerCache() {} 808 } 809 810 /** 811 * Returns an {@code Integer} instance representing the specified 812 * {@code int} value. If a new {@code Integer} instance is not 813 * required, this method should generally be used in preference to 814 * the constructor {@link #Integer(int)}, as this method is likely 815 * to yield significantly better space and time performance by 816 * caching frequently requested values. 817 * 818 * This method will always cache values in the range -128 to 127, 819 * inclusive, and may cache other values outside of this range. 820 * 821 * @param i an {@code int} value. 822 * @return an {@code Integer} instance representing {@code i}. 823 * @since 1.5 824 */ 825 public static Integer valueOf(int i) { 826 if (i >= IntegerCache.low && i <= IntegerCache.high) 827 return IntegerCache.cache[i + (-IntegerCache.low)]; 828 return new Integer(i); 829 } 830 831 /** 832 * The value of the {@code Integer}. 833 * 834 * @serial 835 */ 836 private final int value; 837 838 /** 839 * Constructs a newly allocated {@code Integer} object that 840 * represents the specified {@code int} value. 841 * 842 * @param value the value to be represented by the 843 * {@code Integer} object. 844 */ 845 public Integer(int value) { 846 this.value = value; 847 } 848 849 /** 850 * Constructs a newly allocated {@code Integer} object that 851 * represents the {@code int} value indicated by the 852 * {@code String} parameter. The string is converted to an 853 * {@code int} value in exactly the manner used by the 854 * {@code parseInt} method for radix 10. 855 * 856 * @param s the {@code String} to be converted to an 857 * {@code Integer}. 858 * @exception NumberFormatException if the {@code String} does not 859 * contain a parsable integer. 860 * @see java.lang.Integer#parseInt(java.lang.String, int) 861 */ 862 public Integer(String s) throws NumberFormatException { 863 this.value = parseInt(s, 10); 864 } 865 866 /** 867 * Returns the value of this {@code Integer} as a {@code byte} 868 * after a narrowing primitive conversion. 869 * @jls 5.1.3 Narrowing Primitive Conversions 870 */ 871 public byte byteValue() { 872 return (byte)value; 873 } 874 875 /** 876 * Returns the value of this {@code Integer} as a {@code short} 877 * after a narrowing primitive conversion. 878 * @jls 5.1.3 Narrowing Primitive Conversions 879 */ 880 public short shortValue() { 881 return (short)value; 882 } 883 884 /** 885 * Returns the value of this {@code Integer} as an 886 * {@code int}. 887 */ 888 public int intValue() { 889 return value; 890 } 891 892 /** 893 * Returns the value of this {@code Integer} as a {@code long} 894 * after a widening primitive conversion. 895 * @jls 5.1.2 Widening Primitive Conversions 896 * @see Integer#toUnsignedLong(int) 897 */ 898 public long longValue() { 899 return (long)value; 900 } 901 902 /** 903 * Returns the value of this {@code Integer} as a {@code float} 904 * after a widening primitive conversion. 905 * @jls 5.1.2 Widening Primitive Conversions 906 */ 907 public float floatValue() { 908 return (float)value; 909 } 910 911 /** 912 * Returns the value of this {@code Integer} as a {@code double} 913 * after a widening primitive conversion. 914 * @jls 5.1.2 Widening Primitive Conversions 915 */ 916 public double doubleValue() { 917 return (double)value; 918 } 919 920 /** 921 * Returns a {@code String} object representing this 922 * {@code Integer}'s value. The value is converted to signed 923 * decimal representation and returned as a string, exactly as if 924 * the integer value were given as an argument to the {@link 925 * java.lang.Integer#toString(int)} method. 926 * 927 * @return a string representation of the value of this object in 928 * base 10. 929 */ 930 public String toString() { 931 return toString(value); 932 } 933 934 /** 935 * Returns a hash code for this {@code Integer}. 936 * 937 * @return a hash code value for this object, equal to the 938 * primitive {@code int} value represented by this 939 * {@code Integer} object. 940 */ 941 @Override 942 public int hashCode() { 943 return Integer.hashCode(value); 944 } 945 946 /** 947 * Returns a hash code for a {@code int} value; compatible with 948 * {@code Integer.hashCode()}. 949 * 950 * @since 1.8 951 * 952 * @return a hash code value for a {@code int} value. 953 */ 954 public static int hashCode(int value) { 955 return value; 956 } 957 958 /** 959 * Compares this object to the specified object. The result is 960 * {@code true} if and only if the argument is not 961 * {@code null} and is an {@code Integer} object that 962 * contains the same {@code int} value as this object. 963 * 964 * @param obj the object to compare with. 965 * @return {@code true} if the objects are the same; 966 * {@code false} otherwise. 967 */ 968 public boolean equals(Object obj) { 969 if (obj instanceof Integer) { 970 return value == ((Integer)obj).intValue(); 971 } 972 return false; 973 } 974 975 /** 976 * Determines the integer value of the system property with the 977 * specified name. 978 * 979 * <p>The first argument is treated as the name of a system 980 * property. System properties are accessible through the {@link 981 * java.lang.System#getProperty(java.lang.String)} method. The 982 * string value of this property is then interpreted as an integer 983 * value using the grammar supported by {@link Integer#decode decode} and 984 * an {@code Integer} object representing this value is returned. 985 * 986 * <p>If there is no property with the specified name, if the 987 * specified name is empty or {@code null}, or if the property 988 * does not have the correct numeric format, then {@code null} is 989 * returned. 990 * 991 * <p>In other words, this method returns an {@code Integer} 992 * object equal to the value of: 993 * 994 * <blockquote> 995 * {@code getInteger(nm, null)} 996 * </blockquote> 997 * 998 * @param nm property name. 999 * @return the {@code Integer} value of the property. 1000 * @throws SecurityException for the same reasons as 1001 * {@link System#getProperty(String) System.getProperty} 1002 * @see java.lang.System#getProperty(java.lang.String) 1003 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1004 */ 1005 public static Integer getInteger(String nm) { 1006 return getInteger(nm, null); 1007 } 1008 1009 /** 1010 * Determines the integer value of the system property with the 1011 * specified name. 1012 * 1013 * <p>The first argument is treated as the name of a system 1014 * property. System properties are accessible through the {@link 1015 * java.lang.System#getProperty(java.lang.String)} method. The 1016 * string value of this property is then interpreted as an integer 1017 * value using the grammar supported by {@link Integer#decode decode} and 1018 * an {@code Integer} object representing this value is returned. 1019 * 1020 * <p>The second argument is the default value. An {@code Integer} object 1021 * that represents the value of the second argument is returned if there 1022 * is no property of the specified name, if the property does not have 1023 * the correct numeric format, or if the specified name is empty or 1024 * {@code null}. 1025 * 1026 * <p>In other words, this method returns an {@code Integer} object 1027 * equal to the value of: 1028 * 1029 * <blockquote> 1030 * {@code getInteger(nm, new Integer(val))} 1031 * </blockquote> 1032 * 1033 * but in practice it may be implemented in a manner such as: 1034 * 1035 * <blockquote><pre> 1036 * Integer result = getInteger(nm, null); 1037 * return (result == null) ? new Integer(val) : result; 1038 * </pre></blockquote> 1039 * 1040 * to avoid the unnecessary allocation of an {@code Integer} 1041 * object when the default value is not needed. 1042 * 1043 * @param nm property name. 1044 * @param val default value. 1045 * @return the {@code Integer} value of the property. 1046 * @throws SecurityException for the same reasons as 1047 * {@link System#getProperty(String) System.getProperty} 1048 * @see java.lang.System#getProperty(java.lang.String) 1049 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1050 */ 1051 public static Integer getInteger(String nm, int val) { 1052 Integer result = getInteger(nm, null); 1053 return (result == null) ? Integer.valueOf(val) : result; 1054 } 1055 1056 /** 1057 * Returns the integer value of the system property with the 1058 * specified name. The first argument is treated as the name of a 1059 * system property. System properties are accessible through the 1060 * {@link java.lang.System#getProperty(java.lang.String)} method. 1061 * The string value of this property is then interpreted as an 1062 * integer value, as per the {@link Integer#decode decode} method, 1063 * and an {@code Integer} object representing this value is 1064 * returned; in summary: 1065 * 1066 * <ul><li>If the property value begins with the two ASCII characters 1067 * {@code 0x} or the ASCII character {@code #}, not 1068 * followed by a minus sign, then the rest of it is parsed as a 1069 * hexadecimal integer exactly as by the method 1070 * {@link #valueOf(java.lang.String, int)} with radix 16. 1071 * <li>If the property value begins with the ASCII character 1072 * {@code 0} followed by another character, it is parsed as an 1073 * octal integer exactly as by the method 1074 * {@link #valueOf(java.lang.String, int)} with radix 8. 1075 * <li>Otherwise, the property value is parsed as a decimal integer 1076 * exactly as by the method {@link #valueOf(java.lang.String, int)} 1077 * with radix 10. 1078 * </ul> 1079 * 1080 * <p>The second argument is the default value. The default value is 1081 * returned if there is no property of the specified name, if the 1082 * property does not have the correct numeric format, or if the 1083 * specified name is empty or {@code null}. 1084 * 1085 * @param nm property name. 1086 * @param val default value. 1087 * @return the {@code Integer} value of the property. 1088 * @throws SecurityException for the same reasons as 1089 * {@link System#getProperty(String) System.getProperty} 1090 * @see System#getProperty(java.lang.String) 1091 * @see System#getProperty(java.lang.String, java.lang.String) 1092 */ 1093 public static Integer getInteger(String nm, Integer val) { 1094 String v = null; 1095 try { 1096 v = System.getProperty(nm); 1097 } catch (IllegalArgumentException | NullPointerException e) { 1098 } 1099 if (v != null) { 1100 try { 1101 return Integer.decode(v); 1102 } catch (NumberFormatException e) { 1103 } 1104 } 1105 return val; 1106 } 1107 1108 /** 1109 * Decodes a {@code String} into an {@code Integer}. 1110 * Accepts decimal, hexadecimal, and octal numbers given 1111 * by the following grammar: 1112 * 1113 * <blockquote> 1114 * <dl> 1115 * <dt><i>DecodableString:</i> 1116 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 1117 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 1118 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 1119 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 1120 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 1121 * <p> 1122 * <dt><i>Sign:</i> 1123 * <dd>{@code -} 1124 * <dd>{@code +} 1125 * </dl> 1126 * </blockquote> 1127 * 1128 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 1129 * are as defined in section 3.10.1 of 1130 * <cite>The Java™ Language Specification</cite>, 1131 * except that underscores are not accepted between digits. 1132 * 1133 * <p>The sequence of characters following an optional 1134 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 1135 * "{@code #}", or leading zero) is parsed as by the {@code 1136 * Integer.parseInt} method with the indicated radix (10, 16, or 1137 * 8). This sequence of characters must represent a positive 1138 * value or a {@link NumberFormatException} will be thrown. The 1139 * result is negated if first character of the specified {@code 1140 * String} is the minus sign. No whitespace characters are 1141 * permitted in the {@code String}. 1142 * 1143 * @param nm the {@code String} to decode. 1144 * @return an {@code Integer} object holding the {@code int} 1145 * value represented by {@code nm} 1146 * @exception NumberFormatException if the {@code String} does not 1147 * contain a parsable integer. 1148 * @see java.lang.Integer#parseInt(java.lang.String, int) 1149 */ 1150 public static Integer decode(String nm) throws NumberFormatException { 1151 int radix = 10; 1152 int index = 0; 1153 boolean negative = false; 1154 Integer result; 1155 1156 if (nm.length() == 0) 1157 throw new NumberFormatException("Zero length string"); 1158 char firstChar = nm.charAt(0); 1159 // Handle sign, if present 1160 if (firstChar == '-') { 1161 negative = true; 1162 index++; 1163 } else if (firstChar == '+') 1164 index++; 1165 1166 // Handle radix specifier, if present 1167 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 1168 index += 2; 1169 radix = 16; 1170 } 1171 else if (nm.startsWith("#", index)) { 1172 index ++; 1173 radix = 16; 1174 } 1175 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 1176 index ++; 1177 radix = 8; 1178 } 1179 1180 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 1181 throw new NumberFormatException("Sign character in wrong position"); 1182 1183 try { 1184 result = Integer.valueOf(nm.substring(index), radix); 1185 result = negative ? Integer.valueOf(-result.intValue()) : result; 1186 } catch (NumberFormatException e) { 1187 // If number is Integer.MIN_VALUE, we'll end up here. The next line 1188 // handles this case, and causes any genuine format error to be 1189 // rethrown. 1190 String constant = negative ? ("-" + nm.substring(index)) 1191 : nm.substring(index); 1192 result = Integer.valueOf(constant, radix); 1193 } 1194 return result; 1195 } 1196 1197 /** 1198 * Compares two {@code Integer} objects numerically. 1199 * 1200 * @param anotherInteger the {@code Integer} to be compared. 1201 * @return the value {@code 0} if this {@code Integer} is 1202 * equal to the argument {@code Integer}; a value less than 1203 * {@code 0} if this {@code Integer} is numerically less 1204 * than the argument {@code Integer}; and a value greater 1205 * than {@code 0} if this {@code Integer} is numerically 1206 * greater than the argument {@code Integer} (signed 1207 * comparison). 1208 * @since 1.2 1209 */ 1210 public int compareTo(Integer anotherInteger) { 1211 return compare(this.value, anotherInteger.value); 1212 } 1213 1214 /** 1215 * Compares two {@code int} values numerically. 1216 * The value returned is identical to what would be returned by: 1217 * <pre> 1218 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1219 * </pre> 1220 * 1221 * @param x the first {@code int} to compare 1222 * @param y the second {@code int} to compare 1223 * @return the value {@code 0} if {@code x == y}; 1224 * a value less than {@code 0} if {@code x < y}; and 1225 * a value greater than {@code 0} if {@code x > y} 1226 * @since 1.7 1227 */ 1228 public static int compare(int x, int y) { 1229 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1230 } 1231 1232 /** 1233 * Compares two {@code int} values numerically treating the values 1234 * as unsigned. 1235 * 1236 * @param x the first {@code int} to compare 1237 * @param y the second {@code int} to compare 1238 * @return the value {@code 0} if {@code x == y}; a value less 1239 * than {@code 0} if {@code x < y} as unsigned values; and 1240 * a value greater than {@code 0} if {@code x > y} as 1241 * unsigned values 1242 * @since 1.8 1243 */ 1244 public static int compareUnsigned(int x, int y) { 1245 return compare(x + MIN_VALUE, y + MIN_VALUE); 1246 } 1247 1248 /** 1249 * Converts the argument to a {@code long} by an unsigned 1250 * conversion. In an unsigned conversion to a {@code long}, the 1251 * high-order 32 bits of the {@code long} are zero and the 1252 * low-order 32 bits are equal to the bits of the integer 1253 * argument. 1254 * 1255 * Consequently, zero and positive {@code int} values are mapped 1256 * to a numerically equal {@code long} value and negative {@code 1257 * int} values are mapped to a {@code long} value equal to the 1258 * input plus 2<sup>32</sup>. 1259 * 1260 * @param x the value to convert to an unsigned {@code long} 1261 * @return the argument converted to {@code long} by an unsigned 1262 * conversion 1263 * @since 1.8 1264 */ 1265 public static long toUnsignedLong(int x) { 1266 return ((long) x) & 0xffffffffL; 1267 } 1268 1269 /** 1270 * Returns the unsigned quotient of dividing the first argument by 1271 * the second where each argument and the result is interpreted as 1272 * an unsigned value. 1273 * 1274 * <p>Note that in two's complement arithmetic, the three other 1275 * basic arithmetic operations of add, subtract, and multiply are 1276 * bit-wise identical if the two operands are regarded as both 1277 * being signed or both being unsigned. Therefore separate {@code 1278 * addUnsigned}, etc. methods are not provided. 1279 * 1280 * @param dividend the value to be divided 1281 * @param divisor the value doing the dividing 1282 * @return the unsigned quotient of the first argument divided by 1283 * the second argument 1284 * @see #remainderUnsigned 1285 * @since 1.8 1286 */ 1287 public static int divideUnsigned(int dividend, int divisor) { 1288 // In lieu of tricky code, for now just use long arithmetic. 1289 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor)); 1290 } 1291 1292 /** 1293 * Returns the unsigned remainder from dividing the first argument 1294 * by the second where each argument and the result is interpreted 1295 * as an unsigned value. 1296 * 1297 * @param dividend the value to be divided 1298 * @param divisor the value doing the dividing 1299 * @return the unsigned remainder of the first argument divided by 1300 * the second argument 1301 * @see #divideUnsigned 1302 * @since 1.8 1303 */ 1304 public static int remainderUnsigned(int dividend, int divisor) { 1305 // In lieu of tricky code, for now just use long arithmetic. 1306 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor)); 1307 } 1308 1309 1310 // Bit twiddling 1311 1312 /** 1313 * The number of bits used to represent an {@code int} value in two's 1314 * complement binary form. 1315 * 1316 * @since 1.5 1317 */ 1318 @Native public static final int SIZE = 32; 1319 1320 /** 1321 * The number of bytes used to represent a {@code int} value in two's 1322 * complement binary form. 1323 * 1324 * @since 1.8 1325 */ 1326 public static final int BYTES = SIZE / Byte.SIZE; 1327 1328 /** 1329 * Returns an {@code int} value with at most a single one-bit, in the 1330 * position of the highest-order ("leftmost") 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 highest-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 highestOneBit(int i) { 1341 // HD, Figure 3-1 1342 i |= (i >> 1); 1343 i |= (i >> 2); 1344 i |= (i >> 4); 1345 i |= (i >> 8); 1346 i |= (i >> 16); 1347 return i - (i >>> 1); 1348 } 1349 1350 /** 1351 * Returns an {@code int} value with at most a single one-bit, in the 1352 * position of the lowest-order ("rightmost") one-bit in the specified 1353 * {@code int} value. Returns zero if the specified value has no 1354 * one-bits in its two's complement binary representation, that is, if it 1355 * is equal to zero. 1356 * 1357 * @return an {@code int} value with a single one-bit, in the position 1358 * of the lowest-order one-bit in the specified value, or zero if 1359 * the specified value is itself equal to zero. 1360 * @since 1.5 1361 */ 1362 public static int lowestOneBit(int i) { 1363 // HD, Section 2-1 1364 return i & -i; 1365 } 1366 1367 /** 1368 * Returns the number of zero bits preceding the highest-order 1369 * ("leftmost") one-bit in the two's complement binary representation 1370 * of the specified {@code int} value. Returns 32 if the 1371 * specified value has no one-bits in its two's complement representation, 1372 * in other words if it is equal to zero. 1373 * 1374 * <p>Note that this method is closely related to the logarithm base 2. 1375 * For all positive {@code int} values x: 1376 * <ul> 1377 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1378 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1379 * </ul> 1380 * 1381 * @return the number of zero bits preceding the highest-order 1382 * ("leftmost") one-bit in the two's complement binary representation 1383 * of the specified {@code int} value, or 32 if the value 1384 * is equal to zero. 1385 * @since 1.5 1386 */ 1387 public static int numberOfLeadingZeros(int i) { 1388 // HD, Figure 5-6 1389 if (i == 0) 1390 return 32; 1391 int n = 1; 1392 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1393 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1394 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1395 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1396 n -= i >>> 31; 1397 return n; 1398 } 1399 1400 /** 1401 * Returns the number of zero bits following the lowest-order ("rightmost") 1402 * one-bit in the two's complement binary representation of the specified 1403 * {@code int} value. Returns 32 if the specified value has no 1404 * one-bits in its two's complement representation, in other words if it is 1405 * equal to zero. 1406 * 1407 * @return the number of zero bits following the lowest-order ("rightmost") 1408 * one-bit in the two's complement binary representation of the 1409 * specified {@code int} value, or 32 if the value is equal 1410 * to zero. 1411 * @since 1.5 1412 */ 1413 public static int numberOfTrailingZeros(int i) { 1414 // HD, Figure 5-14 1415 int y; 1416 if (i == 0) return 32; 1417 int n = 31; 1418 y = i <<16; if (y != 0) { n = n -16; i = y; } 1419 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1420 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1421 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1422 return n - ((i << 1) >>> 31); 1423 } 1424 1425 /** 1426 * Returns the number of one-bits in the two's complement binary 1427 * representation of the specified {@code int} value. This function is 1428 * sometimes referred to as the <i>population count</i>. 1429 * 1430 * @return the number of one-bits in the two's complement binary 1431 * representation of the specified {@code int} value. 1432 * @since 1.5 1433 */ 1434 public static int bitCount(int i) { 1435 // HD, Figure 5-2 1436 i = i - ((i >>> 1) & 0x55555555); 1437 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1438 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1439 i = i + (i >>> 8); 1440 i = i + (i >>> 16); 1441 return i & 0x3f; 1442 } 1443 1444 /** 1445 * Returns the value obtained by rotating the two's complement binary 1446 * representation of the specified {@code int} value left by the 1447 * specified number of bits. (Bits shifted out of the left hand, or 1448 * high-order, side reenter on the right, or low-order.) 1449 * 1450 * <p>Note that left rotation with a negative distance is equivalent to 1451 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(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 rotateLeft(val, 1455 * distance) == rotateLeft(val, distance & 0x1F)}. 1456 * 1457 * @return the value obtained by rotating the two's complement binary 1458 * representation of the specified {@code int} value left by the 1459 * specified number of bits. 1460 * @since 1.5 1461 */ 1462 public static int rotateLeft(int i, int distance) { 1463 return (i << distance) | (i >>> -distance); 1464 } 1465 1466 /** 1467 * Returns the value obtained by rotating the two's complement binary 1468 * representation of the specified {@code int} value right by the 1469 * specified number of bits. (Bits shifted out of the right hand, or 1470 * low-order, side reenter on the left, or high-order.) 1471 * 1472 * <p>Note that right rotation with a negative distance is equivalent to 1473 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1474 * distance)}. Note also that rotation by any multiple of 32 is a 1475 * no-op, so all but the last five bits of the rotation distance can be 1476 * ignored, even if the distance is negative: {@code rotateRight(val, 1477 * distance) == rotateRight(val, distance & 0x1F)}. 1478 * 1479 * @return the value obtained by rotating the two's complement binary 1480 * representation of the specified {@code int} value right by the 1481 * specified number of bits. 1482 * @since 1.5 1483 */ 1484 public static int rotateRight(int i, int distance) { 1485 return (i >>> distance) | (i << -distance); 1486 } 1487 1488 /** 1489 * Returns the value obtained by reversing the order of the bits in the 1490 * two's complement binary representation of the specified {@code int} 1491 * value. 1492 * 1493 * @return the value obtained by reversing order of the bits in the 1494 * specified {@code int} value. 1495 * @since 1.5 1496 */ 1497 public static int reverse(int i) { 1498 // HD, Figure 7-1 1499 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1500 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1501 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1502 i = (i << 24) | ((i & 0xff00) << 8) | 1503 ((i >>> 8) & 0xff00) | (i >>> 24); 1504 return i; 1505 } 1506 1507 /** 1508 * Returns the signum function of the specified {@code int} value. (The 1509 * return value is -1 if the specified value is negative; 0 if the 1510 * specified value is zero; and 1 if the specified value is positive.) 1511 * 1512 * @return the signum function of the specified {@code int} value. 1513 * @since 1.5 1514 */ 1515 public static int signum(int i) { 1516 // HD, Section 2-7 1517 return (i >> 31) | (-i >>> 31); 1518 } 1519 1520 /** 1521 * Returns the value obtained by reversing the order of the bytes in the 1522 * two's complement representation of the specified {@code int} value. 1523 * 1524 * @return the value obtained by reversing the bytes in the specified 1525 * {@code int} value. 1526 * @since 1.5 1527 */ 1528 public static int reverseBytes(int i) { 1529 return ((i >>> 24) ) | 1530 ((i >> 8) & 0xFF00) | 1531 ((i << 8) & 0xFF0000) | 1532 ((i << 24)); 1533 } 1534 1535 /** 1536 * Adds two integers together as per the + operator. 1537 * 1538 * @param a the first operand 1539 * @param b the second operand 1540 * @return the sum of {@code a} and {@code b} 1541 * @see java.util.function.BinaryOperator 1542 * @since 1.8 1543 */ 1544 public static int sum(int a, int b) { 1545 return a + b; 1546 } 1547 1548 /** 1549 * Returns the greater of two {@code int} values 1550 * as if by calling {@link Math#max(int, int) Math.max}. 1551 * 1552 * @param a the first operand 1553 * @param b the second operand 1554 * @return the greater of {@code a} and {@code b} 1555 * @see java.util.function.BinaryOperator 1556 * @since 1.8 1557 */ 1558 public static int max(int a, int b) { 1559 return Math.max(a, b); 1560 } 1561 1562 /** 1563 * Returns the smaller of two {@code int} values 1564 * as if by calling {@link Math#min(int, int) Math.min}. 1565 * 1566 * @param a the first operand 1567 * @param b the second operand 1568 * @return the smaller of {@code a} and {@code b} 1569 * @see java.util.function.BinaryOperator 1570 * @since 1.8 1571 */ 1572 public static int min(int a, int b) { 1573 return Math.min(a, b); 1574 } 1575 1576 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1577 @Native private static final long serialVersionUID = 1360826667806852920L; 1578 }