1 /* 2 * Copyright (c) 1994, 2013, 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 // RE: Division by Invariant Integers using Multiplication 380 // T Gralund, P Montgomery 381 // ACM PLDI 1994 382 // 383 384 /** 385 * Returns a {@code String} object representing the 386 * specified integer. The argument is converted to signed decimal 387 * representation and returned as a string, exactly as if the 388 * argument and radix 10 were given as arguments to the {@link 389 * #toString(int, int)} method. 390 * 391 * @param i an integer to be converted. 392 * @return a string representation of the argument in base 10. 393 */ 394 public static String toString(int i) { 395 if (i == Integer.MIN_VALUE) 396 return "-2147483648"; 397 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); 398 char[] buf = new char[size]; 399 getChars(i, size, buf); 400 return new String(buf, true); 401 } 402 403 /** 404 * Returns a string representation of the argument as an unsigned 405 * decimal value. 406 * 407 * The argument is converted to unsigned decimal representation 408 * and returned as a string exactly as if the argument and radix 409 * 10 were given as arguments to the {@link #toUnsignedString(int, 410 * int)} method. 411 * 412 * @param i an integer to be converted to an unsigned string. 413 * @return an unsigned string representation of the argument. 414 * @see #toUnsignedString(int, int) 415 * @since 1.8 416 */ 417 public static String toUnsignedString(int i) { 418 return Long.toString(toUnsignedLong(i)); 419 } 420 421 /** 422 * Places characters representing the integer i into the 423 * character array buf. The characters are placed into 424 * the buffer backwards starting with the least significant 425 * digit at the specified index (exclusive), and working 426 * backwards from there. 427 * 428 * Will fail if i == Integer.MIN_VALUE 429 */ 430 static void getChars(int i, int index, char[] buf) { 431 int q, r; 432 int charPos = index; 433 char sign = 0; 434 435 if (i < 0) { 436 sign = '-'; 437 i = -i; 438 } 439 440 // Generate two digits per iteration 441 while (i >= 65536) { 442 q = i / 100; 443 // really: r = i - (q * 100); 444 r = i - ((q << 6) + (q << 5) + (q << 2)); 445 i = q; 446 buf [--charPos] = DigitOnes[r]; 447 buf [--charPos] = DigitTens[r]; 448 } 449 450 // Fall thru to fast mode for smaller numbers 451 // assert(i <= 65536, i); 452 for (;;) { 453 q = (i * 52429) >>> (16+3); 454 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ... 455 buf [--charPos] = digits [r]; 456 i = q; 457 if (i == 0) break; 458 } 459 if (sign != 0) { 460 buf [--charPos] = sign; 461 } 462 } 463 464 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 465 99999999, 999999999, Integer.MAX_VALUE }; 466 467 // Requires positive x 468 static int stringSize(int x) { 469 for (int i=0; ; i++) 470 if (x <= sizeTable[i]) 471 return i+1; 472 } 473 474 /** 475 * Parses the string argument as a signed integer in the radix 476 * specified by the second argument. The characters in the string 477 * must all be digits of the specified radix (as determined by 478 * whether {@link java.lang.Character#digit(char, int)} returns a 479 * nonnegative value), except that the first character may be an 480 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to 481 * indicate a negative value or an ASCII plus sign {@code '+'} 482 * ({@code '\u005Cu002B'}) to indicate a positive value. The 483 * resulting integer value is returned. 484 * 485 * <p>An exception of type {@code NumberFormatException} is 486 * thrown if any of the following situations occurs: 487 * <ul> 488 * <li>The first argument is {@code null} or is a string of 489 * length zero. 490 * 491 * <li>The radix is either smaller than 492 * {@link java.lang.Character#MIN_RADIX} or 493 * larger than {@link java.lang.Character#MAX_RADIX}. 494 * 495 * <li>Any character of the string is not a digit of the specified 496 * radix, except that the first character may be a minus sign 497 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign 498 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 499 * string is longer than length 1. 500 * 501 * <li>The value represented by the string is not a value of type 502 * {@code int}. 503 * </ul> 504 * 505 * <p>Examples: 506 * <blockquote><pre> 507 * parseInt("0", 10) returns 0 508 * parseInt("473", 10) returns 473 509 * parseInt("+42", 10) returns 42 510 * parseInt("-0", 10) returns 0 511 * parseInt("-FF", 16) returns -255 512 * parseInt("1100110", 2) returns 102 513 * parseInt("2147483647", 10) returns 2147483647 514 * parseInt("-2147483648", 10) returns -2147483648 515 * parseInt("2147483648", 10) throws a NumberFormatException 516 * parseInt("99", 8) throws a NumberFormatException 517 * parseInt("Kona", 10) throws a NumberFormatException 518 * parseInt("Kona", 27) returns 411787 519 * </pre></blockquote> 520 * 521 * @param s the {@code String} containing the integer 522 * representation to be parsed 523 * @param radix the radix to be used while parsing {@code s}. 524 * @return the integer represented by the string argument in the 525 * specified radix. 526 * @exception NumberFormatException if the {@code String} 527 * does not contain a parsable {@code int}. 528 */ 529 public static int parseInt(String s, int radix) 530 throws NumberFormatException 531 { 532 /* 533 * WARNING: This method may be invoked early during VM initialization 534 * before IntegerCache is initialized. Care must be taken to not use 535 * the valueOf method. 536 */ 537 538 if (s == null) { 539 throw new NumberFormatException("null"); 540 } 541 542 if (radix < Character.MIN_RADIX) { 543 throw new NumberFormatException("radix " + radix + 544 " less than Character.MIN_RADIX"); 545 } 546 547 if (radix > Character.MAX_RADIX) { 548 throw new NumberFormatException("radix " + radix + 549 " greater than Character.MAX_RADIX"); 550 } 551 552 int result = 0; 553 boolean negative = false; 554 int i = 0, len = s.length(); 555 int limit = -Integer.MAX_VALUE; 556 int multmin; 557 int digit; 558 559 if (len > 0) { 560 char firstChar = s.charAt(0); 561 if (firstChar < '0') { // Possible leading "+" or "-" 562 if (firstChar == '-') { 563 negative = true; 564 limit = Integer.MIN_VALUE; 565 } else if (firstChar != '+') 566 throw NumberFormatException.forInputString(s); 567 568 if (len == 1) // Cannot have lone "+" or "-" 569 throw NumberFormatException.forInputString(s); 570 i++; 571 } 572 multmin = limit / radix; 573 while (i < len) { 574 // Accumulating negatively avoids surprises near MAX_VALUE 575 digit = Character.digit(s.charAt(i++),radix); 576 if (digit < 0) { 577 throw NumberFormatException.forInputString(s); 578 } 579 if (result < multmin) { 580 throw NumberFormatException.forInputString(s); 581 } 582 result *= radix; 583 if (result < limit + digit) { 584 throw NumberFormatException.forInputString(s); 585 } 586 result -= digit; 587 } 588 } else { 589 throw NumberFormatException.forInputString(s); 590 } 591 return negative ? result : -result; 592 } 593 594 /** 595 * Parses the string argument as a signed decimal integer. The 596 * characters in the string must all be decimal digits, except 597 * that the first character may be an ASCII minus sign {@code '-'} 598 * ({@code '\u005Cu002D'}) to indicate a negative value or an 599 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to 600 * indicate a positive value. The resulting integer value is 601 * returned, exactly as if the argument and the radix 10 were 602 * given as arguments to the {@link #parseInt(java.lang.String, 603 * int)} method. 604 * 605 * @param s a {@code String} containing the {@code int} 606 * representation to be parsed 607 * @return the integer value represented by the argument in decimal. 608 * @exception NumberFormatException if the string does not contain a 609 * parsable integer. 610 */ 611 public static int parseInt(String s) throws NumberFormatException { 612 return parseInt(s,10); 613 } 614 615 /** 616 * Parses the string argument as an unsigned integer in the radix 617 * specified by the second argument. An unsigned integer maps the 618 * values usually associated with negative numbers to positive 619 * numbers larger than {@code MAX_VALUE}. 620 * 621 * The characters in the string must all be digits of the 622 * specified radix (as determined by whether {@link 623 * java.lang.Character#digit(char, int)} returns a nonnegative 624 * value), except that the first character may be an ASCII plus 625 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting 626 * integer value is returned. 627 * 628 * <p>An exception of type {@code NumberFormatException} is 629 * thrown if any of the following situations occurs: 630 * <ul> 631 * <li>The first argument is {@code null} or is a string of 632 * length zero. 633 * 634 * <li>The radix is either smaller than 635 * {@link java.lang.Character#MIN_RADIX} or 636 * larger than {@link java.lang.Character#MAX_RADIX}. 637 * 638 * <li>Any character of the string is not a digit of the specified 639 * radix, except that the first character may be a plus sign 640 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 641 * string is longer than length 1. 642 * 643 * <li>The value represented by the string is larger than the 644 * largest unsigned {@code int}, 2<sup>32</sup>-1. 645 * 646 * </ul> 647 * 648 * 649 * @param s the {@code String} containing the unsigned integer 650 * representation to be parsed 651 * @param radix the radix to be used while parsing {@code s}. 652 * @return the integer represented by the string argument in the 653 * specified radix. 654 * @throws NumberFormatException if the {@code String} 655 * does not contain a parsable {@code int}. 656 * @since 1.8 657 */ 658 public static int parseUnsignedInt(String s, int radix) 659 throws NumberFormatException { 660 if (s == null) { 661 throw new NumberFormatException("null"); 662 } 663 664 int len = s.length(); 665 if (len > 0) { 666 char firstChar = s.charAt(0); 667 if (firstChar == '-') { 668 throw new 669 NumberFormatException(String.format("Illegal leading minus sign " + 670 "on unsigned string %s.", s)); 671 } else { 672 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits 673 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits 674 return parseInt(s, radix); 675 } else { 676 long ell = Long.parseLong(s, radix); 677 if ((ell & 0xffff_ffff_0000_0000L) == 0) { 678 return (int) ell; 679 } else { 680 throw new 681 NumberFormatException(String.format("String value %s exceeds " + 682 "range of unsigned int.", s)); 683 } 684 } 685 } 686 } else { 687 throw NumberFormatException.forInputString(s); 688 } 689 } 690 691 /** 692 * Parses the string argument as an unsigned decimal integer. The 693 * characters in the string must all be decimal digits, except 694 * that the first character may be an an ASCII plus sign {@code 695 * '+'} ({@code '\u005Cu002B'}). The resulting integer value 696 * is returned, exactly as if the argument and the radix 10 were 697 * given as arguments to the {@link 698 * #parseUnsignedInt(java.lang.String, int)} method. 699 * 700 * @param s a {@code String} containing the unsigned {@code int} 701 * representation to be parsed 702 * @return the unsigned integer value represented by the argument in decimal. 703 * @throws NumberFormatException if the string does not contain a 704 * parsable unsigned integer. 705 * @since 1.8 706 */ 707 public static int parseUnsignedInt(String s) throws NumberFormatException { 708 return parseUnsignedInt(s, 10); 709 } 710 711 /** 712 * Returns an {@code Integer} object holding the value 713 * extracted from the specified {@code String} when parsed 714 * with the radix given by the second argument. The first argument 715 * is interpreted as representing a signed integer in the radix 716 * specified by the second argument, exactly as if the arguments 717 * were given to the {@link #parseInt(java.lang.String, int)} 718 * method. The result is an {@code Integer} object that 719 * represents the integer value specified by the string. 720 * 721 * <p>In other words, this method returns an {@code Integer} 722 * object equal to the value of: 723 * 724 * <blockquote> 725 * {@code new Integer(Integer.parseInt(s, radix))} 726 * </blockquote> 727 * 728 * @param s the string to be parsed. 729 * @param radix the radix to be used in interpreting {@code s} 730 * @return an {@code Integer} object holding the value 731 * represented by the string argument in the specified 732 * radix. 733 * @exception NumberFormatException if the {@code String} 734 * does not contain a parsable {@code int}. 735 */ 736 public static Integer valueOf(String s, int radix) throws NumberFormatException { 737 return Integer.valueOf(parseInt(s,radix)); 738 } 739 740 /** 741 * Returns an {@code Integer} object holding the 742 * value of the specified {@code String}. The argument is 743 * interpreted as representing a signed decimal integer, exactly 744 * as if the argument were given to the {@link 745 * #parseInt(java.lang.String)} method. The result is an 746 * {@code Integer} object that represents the integer value 747 * specified by the string. 748 * 749 * <p>In other words, this method returns an {@code Integer} 750 * object equal to the value of: 751 * 752 * <blockquote> 753 * {@code new Integer(Integer.parseInt(s))} 754 * </blockquote> 755 * 756 * @param s the string to be parsed. 757 * @return an {@code Integer} object holding the value 758 * represented by the string argument. 759 * @exception NumberFormatException if the string cannot be parsed 760 * as an integer. 761 */ 762 public static Integer valueOf(String s) throws NumberFormatException { 763 return Integer.valueOf(parseInt(s, 10)); 764 } 765 766 /** 767 * Cache to support the object identity semantics of autoboxing for values between 768 * -128 and 127 (inclusive) as required by JLS. 769 * 770 * The cache is initialized on first usage. The size of the cache 771 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option. 772 * During VM initialization, java.lang.Integer.IntegerCache.high property 773 * may be set and saved in the private system properties in the 774 * sun.misc.VM class. 775 */ 776 777 private static class IntegerCache { 778 static final int low = -128; 779 static final int high; 780 static final Integer cache[]; 781 782 static { 783 // high value may be configured by property 784 int h = 127; 785 String integerCacheHighPropValue = 786 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); 787 if (integerCacheHighPropValue != null) { 788 try { 789 int i = parseInt(integerCacheHighPropValue); 790 i = Math.max(i, 127); 791 // Maximum array size is Integer.MAX_VALUE 792 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 793 } catch( NumberFormatException nfe) { 794 // If the property cannot be parsed into an int, ignore it. 795 } 796 } 797 high = h; 798 799 cache = new Integer[(high - low) + 1]; 800 int j = low; 801 for(int k = 0; k < cache.length; k++) 802 cache[k] = new Integer(j++); 803 804 // range [-128, 127] must be interned (JLS7 5.1.7) 805 assert IntegerCache.high >= 127; 806 } 807 808 private IntegerCache() {} 809 } 810 811 /** 812 * Returns an {@code Integer} instance representing the specified 813 * {@code int} value. If a new {@code Integer} instance is not 814 * required, this method should generally be used in preference to 815 * the constructor {@link #Integer(int)}, as this method is likely 816 * to yield significantly better space and time performance by 817 * caching frequently requested values. 818 * 819 * This method will always cache values in the range -128 to 127, 820 * inclusive, and may cache other values outside of this range. 821 * 822 * @param i an {@code int} value. 823 * @return an {@code Integer} instance representing {@code i}. 824 * @since 1.5 825 */ 826 public static Integer valueOf(int i) { 827 if (i >= IntegerCache.low && i <= IntegerCache.high) 828 return IntegerCache.cache[i + (-IntegerCache.low)]; 829 return new Integer(i); 830 } 831 832 /** 833 * The value of the {@code Integer}. 834 * 835 * @serial 836 */ 837 private final int value; 838 839 /** 840 * Constructs a newly allocated {@code Integer} object that 841 * represents the specified {@code int} value. 842 * 843 * @param value the value to be represented by the 844 * {@code Integer} object. 845 */ 846 public Integer(int value) { 847 this.value = value; 848 } 849 850 /** 851 * Constructs a newly allocated {@code Integer} object that 852 * represents the {@code int} value indicated by the 853 * {@code String} parameter. The string is converted to an 854 * {@code int} value in exactly the manner used by the 855 * {@code parseInt} method for radix 10. 856 * 857 * @param s the {@code String} to be converted to an 858 * {@code Integer}. 859 * @exception NumberFormatException if the {@code String} does not 860 * contain a parsable integer. 861 * @see java.lang.Integer#parseInt(java.lang.String, int) 862 */ 863 public Integer(String s) throws NumberFormatException { 864 this.value = parseInt(s, 10); 865 } 866 867 /** 868 * Returns the value of this {@code Integer} as a {@code byte} 869 * after a narrowing primitive conversion. 870 * @jls 5.1.3 Narrowing Primitive Conversions 871 */ 872 public byte byteValue() { 873 return (byte)value; 874 } 875 876 /** 877 * Returns the value of this {@code Integer} as a {@code short} 878 * after a narrowing primitive conversion. 879 * @jls 5.1.3 Narrowing Primitive Conversions 880 */ 881 public short shortValue() { 882 return (short)value; 883 } 884 885 /** 886 * Returns the value of this {@code Integer} as an 887 * {@code int}. 888 */ 889 public int intValue() { 890 return value; 891 } 892 893 /** 894 * Returns the value of this {@code Integer} as a {@code long} 895 * after a widening primitive conversion. 896 * @jls 5.1.2 Widening Primitive Conversions 897 * @see Integer#toUnsignedLong(int) 898 */ 899 public long longValue() { 900 return (long)value; 901 } 902 903 /** 904 * Returns the value of this {@code Integer} as a {@code float} 905 * after a widening primitive conversion. 906 * @jls 5.1.2 Widening Primitive Conversions 907 */ 908 public float floatValue() { 909 return (float)value; 910 } 911 912 /** 913 * Returns the value of this {@code Integer} as a {@code double} 914 * after a widening primitive conversion. 915 * @jls 5.1.2 Widening Primitive Conversions 916 */ 917 public double doubleValue() { 918 return (double)value; 919 } 920 921 /** 922 * Returns a {@code String} object representing this 923 * {@code Integer}'s value. The value is converted to signed 924 * decimal representation and returned as a string, exactly as if 925 * the integer value were given as an argument to the {@link 926 * java.lang.Integer#toString(int)} method. 927 * 928 * @return a string representation of the value of this object in 929 * base 10. 930 */ 931 public String toString() { 932 return toString(value); 933 } 934 935 /** 936 * Returns a hash code for this {@code Integer}. 937 * 938 * @return a hash code value for this object, equal to the 939 * primitive {@code int} value represented by this 940 * {@code Integer} object. 941 */ 942 @Override 943 public int hashCode() { 944 return Integer.hashCode(value); 945 } 946 947 /** 948 * Returns a hash code for a {@code int} value; compatible with 949 * {@code Integer.hashCode()}. 950 * 951 * @param value the value to hash 952 * @since 1.8 953 * 954 * @return a hash code value for a {@code int} value. 955 */ 956 public static int hashCode(int value) { 957 return value; 958 } 959 960 /** 961 * Compares this object to the specified object. The result is 962 * {@code true} if and only if the argument is not 963 * {@code null} and is an {@code Integer} object that 964 * contains the same {@code int} value as this object. 965 * 966 * @param obj the object to compare with. 967 * @return {@code true} if the objects are the same; 968 * {@code false} otherwise. 969 */ 970 public boolean equals(Object obj) { 971 if (obj instanceof Integer) { 972 return value == ((Integer)obj).intValue(); 973 } 974 return false; 975 } 976 977 /** 978 * Determines the integer value of the system property with the 979 * specified name. 980 * 981 * <p>The first argument is treated as the name of a system 982 * property. System properties are accessible through the {@link 983 * java.lang.System#getProperty(java.lang.String)} method. The 984 * string value of this property is then interpreted as an integer 985 * value using the grammar supported by {@link Integer#decode decode} and 986 * an {@code Integer} object representing this value is returned. 987 * 988 * <p>If there is no property with the specified name, if the 989 * specified name is empty or {@code null}, or if the property 990 * does not have the correct numeric format, then {@code null} is 991 * returned. 992 * 993 * <p>In other words, this method returns an {@code Integer} 994 * object equal to the value of: 995 * 996 * <blockquote> 997 * {@code getInteger(nm, null)} 998 * </blockquote> 999 * 1000 * @param nm property name. 1001 * @return the {@code Integer} value of the property. 1002 * @throws SecurityException for the same reasons as 1003 * {@link System#getProperty(String) System.getProperty} 1004 * @see java.lang.System#getProperty(java.lang.String) 1005 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1006 */ 1007 public static Integer getInteger(String nm) { 1008 return getInteger(nm, null); 1009 } 1010 1011 /** 1012 * Determines the integer value of the system property with the 1013 * specified name. 1014 * 1015 * <p>The first argument is treated as the name of a system 1016 * property. System properties are accessible through the {@link 1017 * java.lang.System#getProperty(java.lang.String)} method. The 1018 * string value of this property is then interpreted as an integer 1019 * value using the grammar supported by {@link Integer#decode decode} and 1020 * an {@code Integer} object representing this value is returned. 1021 * 1022 * <p>The second argument is the default value. An {@code Integer} object 1023 * that represents the value of the second argument is returned if there 1024 * is no property of the specified name, if the property does not have 1025 * the correct numeric format, or if the specified name is empty or 1026 * {@code null}. 1027 * 1028 * <p>In other words, this method returns an {@code Integer} object 1029 * equal to the value of: 1030 * 1031 * <blockquote> 1032 * {@code getInteger(nm, new Integer(val))} 1033 * </blockquote> 1034 * 1035 * but in practice it may be implemented in a manner such as: 1036 * 1037 * <blockquote><pre> 1038 * Integer result = getInteger(nm, null); 1039 * return (result == null) ? new Integer(val) : result; 1040 * </pre></blockquote> 1041 * 1042 * to avoid the unnecessary allocation of an {@code Integer} 1043 * object when the default value is not needed. 1044 * 1045 * @param nm property name. 1046 * @param val default value. 1047 * @return the {@code Integer} value of the property. 1048 * @throws SecurityException for the same reasons as 1049 * {@link System#getProperty(String) System.getProperty} 1050 * @see java.lang.System#getProperty(java.lang.String) 1051 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1052 */ 1053 public static Integer getInteger(String nm, int val) { 1054 Integer result = getInteger(nm, null); 1055 return (result == null) ? Integer.valueOf(val) : result; 1056 } 1057 1058 /** 1059 * Returns the integer value of the system property with the 1060 * specified name. The first argument is treated as the name of a 1061 * system property. System properties are accessible through the 1062 * {@link java.lang.System#getProperty(java.lang.String)} method. 1063 * The string value of this property is then interpreted as an 1064 * integer value, as per the {@link Integer#decode decode} method, 1065 * and an {@code Integer} object representing this value is 1066 * returned; in summary: 1067 * 1068 * <ul><li>If the property value begins with the two ASCII characters 1069 * {@code 0x} or the ASCII character {@code #}, not 1070 * followed by a minus sign, then the rest of it is parsed as a 1071 * hexadecimal integer exactly as by the method 1072 * {@link #valueOf(java.lang.String, int)} with radix 16. 1073 * <li>If the property value begins with the ASCII character 1074 * {@code 0} followed by another character, it is parsed as an 1075 * octal integer exactly as by the method 1076 * {@link #valueOf(java.lang.String, int)} with radix 8. 1077 * <li>Otherwise, the property value is parsed as a decimal integer 1078 * exactly as by the method {@link #valueOf(java.lang.String, int)} 1079 * with radix 10. 1080 * </ul> 1081 * 1082 * <p>The second argument is the default value. The default value is 1083 * returned if there is no property of the specified name, if the 1084 * property does not have the correct numeric format, or if the 1085 * specified name is empty or {@code null}. 1086 * 1087 * @param nm property name. 1088 * @param val default value. 1089 * @return the {@code Integer} value of the property. 1090 * @throws SecurityException for the same reasons as 1091 * {@link System#getProperty(String) System.getProperty} 1092 * @see System#getProperty(java.lang.String) 1093 * @see System#getProperty(java.lang.String, java.lang.String) 1094 */ 1095 public static Integer getInteger(String nm, Integer val) { 1096 String v = null; 1097 try { 1098 v = System.getProperty(nm); 1099 } catch (IllegalArgumentException | NullPointerException e) { 1100 } 1101 if (v != null) { 1102 try { 1103 return Integer.decode(v); 1104 } catch (NumberFormatException e) { 1105 } 1106 } 1107 return val; 1108 } 1109 1110 /** 1111 * Decodes a {@code String} into an {@code Integer}. 1112 * Accepts decimal, hexadecimal, and octal numbers given 1113 * by the following grammar: 1114 * 1115 * <blockquote> 1116 * <dl> 1117 * <dt><i>DecodableString:</i> 1118 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 1119 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 1120 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 1121 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 1122 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 1123 * 1124 * <dt><i>Sign:</i> 1125 * <dd>{@code -} 1126 * <dd>{@code +} 1127 * </dl> 1128 * </blockquote> 1129 * 1130 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 1131 * are as defined in section 3.10.1 of 1132 * <cite>The Java™ Language Specification</cite>, 1133 * except that underscores are not accepted between digits. 1134 * 1135 * <p>The sequence of characters following an optional 1136 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 1137 * "{@code #}", or leading zero) is parsed as by the {@code 1138 * Integer.parseInt} method with the indicated radix (10, 16, or 1139 * 8). This sequence of characters must represent a positive 1140 * value or a {@link NumberFormatException} will be thrown. The 1141 * result is negated if first character of the specified {@code 1142 * String} is the minus sign. No whitespace characters are 1143 * permitted in the {@code String}. 1144 * 1145 * @param nm the {@code String} to decode. 1146 * @return an {@code Integer} object holding the {@code int} 1147 * value represented by {@code nm} 1148 * @exception NumberFormatException if the {@code String} does not 1149 * contain a parsable integer. 1150 * @see java.lang.Integer#parseInt(java.lang.String, int) 1151 */ 1152 public static Integer decode(String nm) throws NumberFormatException { 1153 int radix = 10; 1154 int index = 0; 1155 boolean negative = false; 1156 Integer result; 1157 1158 if (nm.length() == 0) 1159 throw new NumberFormatException("Zero length string"); 1160 char firstChar = nm.charAt(0); 1161 // Handle sign, if present 1162 if (firstChar == '-') { 1163 negative = true; 1164 index++; 1165 } else if (firstChar == '+') 1166 index++; 1167 1168 // Handle radix specifier, if present 1169 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 1170 index += 2; 1171 radix = 16; 1172 } 1173 else if (nm.startsWith("#", index)) { 1174 index ++; 1175 radix = 16; 1176 } 1177 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 1178 index ++; 1179 radix = 8; 1180 } 1181 1182 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 1183 throw new NumberFormatException("Sign character in wrong position"); 1184 1185 try { 1186 result = Integer.valueOf(nm.substring(index), radix); 1187 result = negative ? Integer.valueOf(-result.intValue()) : result; 1188 } catch (NumberFormatException e) { 1189 // If number is Integer.MIN_VALUE, we'll end up here. The next line 1190 // handles this case, and causes any genuine format error to be 1191 // rethrown. 1192 String constant = negative ? ("-" + nm.substring(index)) 1193 : nm.substring(index); 1194 result = Integer.valueOf(constant, radix); 1195 } 1196 return result; 1197 } 1198 1199 /** 1200 * Compares two {@code Integer} objects numerically. 1201 * 1202 * @param anotherInteger the {@code Integer} to be compared. 1203 * @return the value {@code 0} if this {@code Integer} is 1204 * equal to the argument {@code Integer}; a value less than 1205 * {@code 0} if this {@code Integer} is numerically less 1206 * than the argument {@code Integer}; and a value greater 1207 * than {@code 0} if this {@code Integer} is numerically 1208 * greater than the argument {@code Integer} (signed 1209 * comparison). 1210 * @since 1.2 1211 */ 1212 public int compareTo(Integer anotherInteger) { 1213 return compare(this.value, anotherInteger.value); 1214 } 1215 1216 /** 1217 * Compares two {@code int} values numerically. 1218 * The value returned is identical to what would be returned by: 1219 * <pre> 1220 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1221 * </pre> 1222 * 1223 * @param x the first {@code int} to compare 1224 * @param y the second {@code int} to compare 1225 * @return the value {@code 0} if {@code x == y}; 1226 * a value less than {@code 0} if {@code x < y}; and 1227 * a value greater than {@code 0} if {@code x > y} 1228 * @since 1.7 1229 */ 1230 public static int compare(int x, int y) { 1231 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1232 } 1233 1234 /** 1235 * Compares two {@code int} values numerically treating the values 1236 * as unsigned. 1237 * 1238 * @param x the first {@code int} to compare 1239 * @param y the second {@code int} to compare 1240 * @return the value {@code 0} if {@code x == y}; a value less 1241 * than {@code 0} if {@code x < y} as unsigned values; and 1242 * a value greater than {@code 0} if {@code x > y} as 1243 * unsigned values 1244 * @since 1.8 1245 */ 1246 public static int compareUnsigned(int x, int y) { 1247 return compare(x + MIN_VALUE, y + MIN_VALUE); 1248 } 1249 1250 /** 1251 * Converts the argument to a {@code long} by an unsigned 1252 * conversion. In an unsigned conversion to a {@code long}, the 1253 * high-order 32 bits of the {@code long} are zero and the 1254 * low-order 32 bits are equal to the bits of the integer 1255 * argument. 1256 * 1257 * Consequently, zero and positive {@code int} values are mapped 1258 * to a numerically equal {@code long} value and negative {@code 1259 * int} values are mapped to a {@code long} value equal to the 1260 * input plus 2<sup>32</sup>. 1261 * 1262 * @param x the value to convert to an unsigned {@code long} 1263 * @return the argument converted to {@code long} by an unsigned 1264 * conversion 1265 * @since 1.8 1266 */ 1267 public static long toUnsignedLong(int x) { 1268 return ((long) x) & 0xffffffffL; 1269 } 1270 1271 /** 1272 * Returns the unsigned quotient of dividing the first argument by 1273 * the second where each argument and the result is interpreted as 1274 * an unsigned value. 1275 * 1276 * <p>Note that in two's complement arithmetic, the three other 1277 * basic arithmetic operations of add, subtract, and multiply are 1278 * bit-wise identical if the two operands are regarded as both 1279 * being signed or both being unsigned. Therefore separate {@code 1280 * addUnsigned}, etc. methods are not provided. 1281 * 1282 * @param dividend the value to be divided 1283 * @param divisor the value doing the dividing 1284 * @return the unsigned quotient of the first argument divided by 1285 * the second argument 1286 * @see #remainderUnsigned 1287 * @since 1.8 1288 */ 1289 public static int divideUnsigned(int dividend, int divisor) { 1290 // In lieu of tricky code, for now just use long arithmetic. 1291 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor)); 1292 } 1293 1294 /** 1295 * Returns the unsigned remainder from dividing the first argument 1296 * by the second where each argument and the result is interpreted 1297 * as an unsigned value. 1298 * 1299 * @param dividend the value to be divided 1300 * @param divisor the value doing the dividing 1301 * @return the unsigned remainder of the first argument divided by 1302 * the second argument 1303 * @see #divideUnsigned 1304 * @since 1.8 1305 */ 1306 public static int remainderUnsigned(int dividend, int divisor) { 1307 // In lieu of tricky code, for now just use long arithmetic. 1308 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor)); 1309 } 1310 1311 1312 // Bit twiddling 1313 1314 /** 1315 * The number of bits used to represent an {@code int} value in two's 1316 * complement binary form. 1317 * 1318 * @since 1.5 1319 */ 1320 @Native public static final int SIZE = 32; 1321 1322 /** 1323 * The number of bytes used to represent a {@code int} value in two's 1324 * complement binary form. 1325 * 1326 * @since 1.8 1327 */ 1328 public static final int BYTES = SIZE / Byte.SIZE; 1329 1330 /** 1331 * Returns an {@code int} value with at most a single one-bit, in the 1332 * position of the highest-order ("leftmost") one-bit in the specified 1333 * {@code int} value. Returns zero if the specified value has no 1334 * one-bits in its two's complement binary representation, that is, if it 1335 * is equal to zero. 1336 * 1337 * @param i the value whose highest one bit is to be computed 1338 * @return an {@code int} value with a single one-bit, in the position 1339 * of the highest-order one-bit in the specified value, or zero if 1340 * the specified value is itself equal to zero. 1341 * @since 1.5 1342 */ 1343 public static int highestOneBit(int i) { 1344 // HD, Figure 3-1 1345 i |= (i >> 1); 1346 i |= (i >> 2); 1347 i |= (i >> 4); 1348 i |= (i >> 8); 1349 i |= (i >> 16); 1350 return i - (i >>> 1); 1351 } 1352 1353 /** 1354 * Returns an {@code int} value with at most a single one-bit, in the 1355 * position of the lowest-order ("rightmost") one-bit in the specified 1356 * {@code int} value. Returns zero if the specified value has no 1357 * one-bits in its two's complement binary representation, that is, if it 1358 * is equal to zero. 1359 * 1360 * @param i the value whose lowest one bit is to be computed 1361 * @return an {@code int} value with a single one-bit, in the position 1362 * of the lowest-order one-bit in the specified value, or zero if 1363 * the specified value is itself equal to zero. 1364 * @since 1.5 1365 */ 1366 public static int lowestOneBit(int i) { 1367 // HD, Section 2-1 1368 return i & -i; 1369 } 1370 1371 /** 1372 * Returns the number of zero bits preceding the highest-order 1373 * ("leftmost") one-bit in the two's complement binary representation 1374 * of the specified {@code int} value. Returns 32 if the 1375 * specified value has no one-bits in its two's complement representation, 1376 * in other words if it is equal to zero. 1377 * 1378 * <p>Note that this method is closely related to the logarithm base 2. 1379 * For all positive {@code int} values x: 1380 * <ul> 1381 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1382 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1383 * </ul> 1384 * 1385 * @param i the value whose number of leading zeros is to be computed 1386 * @return the number of zero bits preceding the highest-order 1387 * ("leftmost") one-bit in the two's complement binary representation 1388 * of the specified {@code int} value, or 32 if the value 1389 * is equal to zero. 1390 * @since 1.5 1391 */ 1392 public static int numberOfLeadingZeros(int i) { 1393 // HD, Figure 5-6 1394 if (i == 0) 1395 return 32; 1396 int n = 1; 1397 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1398 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1399 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1400 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1401 n -= i >>> 31; 1402 return n; 1403 } 1404 1405 /** 1406 * Returns the number of zero bits following the lowest-order ("rightmost") 1407 * one-bit in the two's complement binary representation of the specified 1408 * {@code int} value. Returns 32 if the specified value has no 1409 * one-bits in its two's complement representation, in other words if it is 1410 * equal to zero. 1411 * 1412 * @param i the value whose number of trailing zeros is to be computed 1413 * @return the number of zero bits following the lowest-order ("rightmost") 1414 * one-bit in the two's complement binary representation of the 1415 * specified {@code int} value, or 32 if the value is equal 1416 * to zero. 1417 * @since 1.5 1418 */ 1419 public static int numberOfTrailingZeros(int i) { 1420 // HD, Figure 5-14 1421 int y; 1422 if (i == 0) return 32; 1423 int n = 31; 1424 y = i <<16; if (y != 0) { n = n -16; i = y; } 1425 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1426 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1427 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1428 return n - ((i << 1) >>> 31); 1429 } 1430 1431 /** 1432 * Returns the number of one-bits in the two's complement binary 1433 * representation of the specified {@code int} value. This function is 1434 * sometimes referred to as the <i>population count</i>. 1435 * 1436 * @param i the value whose bits are to be counted 1437 * @return the number of one-bits in the two's complement binary 1438 * representation of the specified {@code int} value. 1439 * @since 1.5 1440 */ 1441 public static int bitCount(int i) { 1442 // HD, Figure 5-2 1443 i = i - ((i >>> 1) & 0x55555555); 1444 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1445 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1446 i = i + (i >>> 8); 1447 i = i + (i >>> 16); 1448 return i & 0x3f; 1449 } 1450 1451 /** 1452 * Returns the value obtained by rotating the two's complement binary 1453 * representation of the specified {@code int} value left by the 1454 * specified number of bits. (Bits shifted out of the left hand, or 1455 * high-order, side reenter on the right, or low-order.) 1456 * 1457 * <p>Note that left rotation with a negative distance is equivalent to 1458 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1459 * distance)}. Note also that rotation by any multiple of 32 is a 1460 * no-op, so all but the last five bits of the rotation distance can be 1461 * ignored, even if the distance is negative: {@code rotateLeft(val, 1462 * distance) == rotateLeft(val, distance & 0x1F)}. 1463 * 1464 * @param i the value whose bits are to be rotated left 1465 * @param distance the number of bit positions to rotate left 1466 * @return the value obtained by rotating the two's complement binary 1467 * representation of the specified {@code int} value left by the 1468 * specified number of bits. 1469 * @since 1.5 1470 */ 1471 public static int rotateLeft(int i, int distance) { 1472 return (i << distance) | (i >>> -distance); 1473 } 1474 1475 /** 1476 * Returns the value obtained by rotating the two's complement binary 1477 * representation of the specified {@code int} value right by the 1478 * specified number of bits. (Bits shifted out of the right hand, or 1479 * low-order, side reenter on the left, or high-order.) 1480 * 1481 * <p>Note that right rotation with a negative distance is equivalent to 1482 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1483 * distance)}. Note also that rotation by any multiple of 32 is a 1484 * no-op, so all but the last five bits of the rotation distance can be 1485 * ignored, even if the distance is negative: {@code rotateRight(val, 1486 * distance) == rotateRight(val, distance & 0x1F)}. 1487 * 1488 * @param i the value whose bits are to be rotated right 1489 * @param distance the number of bit positions to rotate right 1490 * @return the value obtained by rotating the two's complement binary 1491 * representation of the specified {@code int} value right by the 1492 * specified number of bits. 1493 * @since 1.5 1494 */ 1495 public static int rotateRight(int i, int distance) { 1496 return (i >>> distance) | (i << -distance); 1497 } 1498 1499 /** 1500 * Returns the value obtained by reversing the order of the bits in the 1501 * two's complement binary representation of the specified {@code int} 1502 * value. 1503 * 1504 * @param i the value to be reversed 1505 * @return the value obtained by reversing order of the bits in the 1506 * specified {@code int} value. 1507 * @since 1.5 1508 */ 1509 public static int reverse(int i) { 1510 // HD, Figure 7-1 1511 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1512 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1513 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1514 i = (i << 24) | ((i & 0xff00) << 8) | 1515 ((i >>> 8) & 0xff00) | (i >>> 24); 1516 return i; 1517 } 1518 1519 /** 1520 * Returns the signum function of the specified {@code int} value. (The 1521 * return value is -1 if the specified value is negative; 0 if the 1522 * specified value is zero; and 1 if the specified value is positive.) 1523 * 1524 * @param i the value whose signum is to be computed 1525 * @return the signum function of the specified {@code int} value. 1526 * @since 1.5 1527 */ 1528 public static int signum(int i) { 1529 // HD, Section 2-7 1530 return (i >> 31) | (-i >>> 31); 1531 } 1532 1533 /** 1534 * Returns the value obtained by reversing the order of the bytes in the 1535 * two's complement representation of the specified {@code int} value. 1536 * 1537 * @param i the value whose bytes are to be reversed 1538 * @return the value obtained by reversing the bytes in the specified 1539 * {@code int} value. 1540 * @since 1.5 1541 */ 1542 public static int reverseBytes(int i) { 1543 return ((i >>> 24) ) | 1544 ((i >> 8) & 0xFF00) | 1545 ((i << 8) & 0xFF0000) | 1546 ((i << 24)); 1547 } 1548 1549 /** 1550 * Adds two integers together as per the + operator. 1551 * 1552 * @param a the first operand 1553 * @param b the second operand 1554 * @return the sum of {@code a} and {@code b} 1555 * @see java.util.function.BinaryOperator 1556 * @since 1.8 1557 */ 1558 public static int sum(int a, int b) { 1559 return a + b; 1560 } 1561 1562 /** 1563 * Returns the greater of two {@code int} values 1564 * as if by calling {@link Math#max(int, int) Math.max}. 1565 * 1566 * @param a the first operand 1567 * @param b the second operand 1568 * @return the greater of {@code a} and {@code b} 1569 * @see java.util.function.BinaryOperator 1570 * @since 1.8 1571 */ 1572 public static int max(int a, int b) { 1573 return Math.max(a, b); 1574 } 1575 1576 /** 1577 * Returns the smaller of two {@code int} values 1578 * as if by calling {@link Math#min(int, int) Math.min}. 1579 * 1580 * @param a the first operand 1581 * @param b the second operand 1582 * @return the smaller of {@code a} and {@code b} 1583 * @see java.util.function.BinaryOperator 1584 * @since 1.8 1585 */ 1586 public static int min(int a, int b) { 1587 return Math.min(a, b); 1588 } 1589 1590 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1591 @Native private static final long serialVersionUID = 1360826667806852920L; 1592 }