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 1.0 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 1.1 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 1.0.2 231 */ 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 1.0.2 269 */ 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 1.0.2 301 */ 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 an {@code int} (treated as unsigned) into a character buffer. If 323 * {@code len} exceeds the formatted ASCII representation of {@code val}, 324 * {@code buf} will be padded with leading zeroes. 325 * 326 * @param val the unsigned int to format 327 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) 328 * @param buf the character buffer to write to 329 * @param offset the offset in the destination buffer to start at 330 * @param len the number of characters to write 331 */ 332 static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) { 333 // assert shift > 0 && shift <=5 : "Illegal shift value"; 334 // assert offset >= 0 && offset < buf.length : "illegal offset"; 335 // assert len > 0 && (offset + len) <= buf.length : "illegal length"; 336 int charPos = offset + len; 337 int radix = 1 << shift; 338 int mask = radix - 1; 339 while (charPos > offset) { 340 buf[--charPos] = Integer.digits[val & mask]; 341 val >>>= shift; 342 } 343 } 344 345 final static char [] DigitTens = { 346 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', 347 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', 348 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', 349 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 350 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', 351 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', 352 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', 353 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', 354 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', 355 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', 356 } ; 357 358 final static char [] DigitOnes = { 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 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 367 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 368 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 369 } ; 370 371 // I use the "invariant division by multiplication" trick to 372 // accelerate Integer.toString. In particular we want to 373 // avoid division by 10. 374 // 375 // The "trick" has roughly the same performance characteristics 376 // as the "classic" Integer.toString code on a non-JIT VM. 377 // The trick avoids .rem and .div calls but has a longer code 378 // path and is thus dominated by dispatch overhead. In the 379 // JIT case the dispatch overhead doesn't exist and the 380 // "trick" is considerably faster than the classic code. 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 try { 792 int i = parseInt(integerCacheHighPropValue); 793 i = Math.max(i, 127); 794 // Maximum array size is Integer.MAX_VALUE 795 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 796 } catch( NumberFormatException nfe) { 797 // If the property cannot be parsed into an int, ignore it. 798 } 799 } 800 high = h; 801 802 cache = new Integer[(high - low) + 1]; 803 int j = low; 804 for(int k = 0; k < cache.length; k++) 805 cache[k] = new Integer(j++); 806 807 // range [-128, 127] must be interned (JLS7 5.1.7) 808 assert IntegerCache.high >= 127; 809 } 810 811 private IntegerCache() {} 812 } 813 814 /** 815 * Returns an {@code Integer} instance representing the specified 816 * {@code int} value. If a new {@code Integer} instance is not 817 * required, this method should generally be used in preference to 818 * the constructor {@link #Integer(int)}, as this method is likely 819 * to yield significantly better space and time performance by 820 * caching frequently requested values. 821 * 822 * This method will always cache values in the range -128 to 127, 823 * inclusive, and may cache other values outside of this range. 824 * 825 * @param i an {@code int} value. 826 * @return an {@code Integer} instance representing {@code i}. 827 * @since 1.5 828 */ 829 public static Integer valueOf(int i) { 830 if (i >= IntegerCache.low && i <= IntegerCache.high) 831 return IntegerCache.cache[i + (-IntegerCache.low)]; 832 return new Integer(i); 833 } 834 835 /** 836 * The value of the {@code Integer}. 837 * 838 * @serial 839 */ 840 private final int value; 841 842 /** 843 * Constructs a newly allocated {@code Integer} object that 844 * represents the specified {@code int} value. 845 * 846 * @param value the value to be represented by the 847 * {@code Integer} object. 848 */ 849 public Integer(int value) { 850 this.value = value; 851 } 852 853 /** 854 * Constructs a newly allocated {@code Integer} object that 855 * represents the {@code int} value indicated by the 856 * {@code String} parameter. The string is converted to an 857 * {@code int} value in exactly the manner used by the 858 * {@code parseInt} method for radix 10. 859 * 860 * @param s the {@code String} to be converted to an 861 * {@code Integer}. 862 * @exception NumberFormatException if the {@code String} does not 863 * contain a parsable integer. 864 * @see java.lang.Integer#parseInt(java.lang.String, int) 865 */ 866 public Integer(String s) throws NumberFormatException { 867 this.value = parseInt(s, 10); 868 } 869 870 /** 871 * Returns the value of this {@code Integer} as a {@code byte} 872 * after a narrowing primitive conversion. 873 * @jls 5.1.3 Narrowing Primitive Conversions 874 */ 875 public byte byteValue() { 876 return (byte)value; 877 } 878 879 /** 880 * Returns the value of this {@code Integer} as a {@code short} 881 * after a narrowing primitive conversion. 882 * @jls 5.1.3 Narrowing Primitive Conversions 883 */ 884 public short shortValue() { 885 return (short)value; 886 } 887 888 /** 889 * Returns the value of this {@code Integer} as an 890 * {@code int}. 891 */ 892 public int intValue() { 893 return value; 894 } 895 896 /** 897 * Returns the value of this {@code Integer} as a {@code long} 898 * after a widening primitive conversion. 899 * @jls 5.1.2 Widening Primitive Conversions 900 * @see Integer#toUnsignedLong(int) 901 */ 902 public long longValue() { 903 return (long)value; 904 } 905 906 /** 907 * Returns the value of this {@code Integer} as a {@code float} 908 * after a widening primitive conversion. 909 * @jls 5.1.2 Widening Primitive Conversions 910 */ 911 public float floatValue() { 912 return (float)value; 913 } 914 915 /** 916 * Returns the value of this {@code Integer} as a {@code double} 917 * after a widening primitive conversion. 918 * @jls 5.1.2 Widening Primitive Conversions 919 */ 920 public double doubleValue() { 921 return (double)value; 922 } 923 924 /** 925 * Returns a {@code String} object representing this 926 * {@code Integer}'s value. The value is converted to signed 927 * decimal representation and returned as a string, exactly as if 928 * the integer value were given as an argument to the {@link 929 * java.lang.Integer#toString(int)} method. 930 * 931 * @return a string representation of the value of this object in 932 * base 10. 933 */ 934 public String toString() { 935 return toString(value); 936 } 937 938 /** 939 * Returns a hash code for this {@code Integer}. 940 * 941 * @return a hash code value for this object, equal to the 942 * primitive {@code int} value represented by this 943 * {@code Integer} object. 944 */ 945 @Override 946 public int hashCode() { 947 return Integer.hashCode(value); 948 } 949 950 /** 951 * Returns a hash code for a {@code int} value; compatible with 952 * {@code Integer.hashCode()}. 953 * 954 * @param value the value to hash 955 * @since 1.8 956 * 957 * @return a hash code value for a {@code int} value. 958 */ 959 public static int hashCode(int value) { 960 return value; 961 } 962 963 /** 964 * Compares this object to the specified object. The result is 965 * {@code true} if and only if the argument is not 966 * {@code null} and is an {@code Integer} object that 967 * contains the same {@code int} value as this object. 968 * 969 * @param obj the object to compare with. 970 * @return {@code true} if the objects are the same; 971 * {@code false} otherwise. 972 */ 973 public boolean equals(Object obj) { 974 if (obj instanceof Integer) { 975 return value == ((Integer)obj).intValue(); 976 } 977 return false; 978 } 979 980 /** 981 * Determines the integer value of the system property with the 982 * specified name. 983 * 984 * <p>The first argument is treated as the name of a system 985 * property. System properties are accessible through the {@link 986 * java.lang.System#getProperty(java.lang.String)} method. The 987 * string value of this property is then interpreted as an integer 988 * value using the grammar supported by {@link Integer#decode decode} and 989 * an {@code Integer} object representing this value is returned. 990 * 991 * <p>If there is no property with the specified name, if the 992 * specified name is empty or {@code null}, or if the property 993 * does not have the correct numeric format, then {@code null} is 994 * returned. 995 * 996 * <p>In other words, this method returns an {@code Integer} 997 * object equal to the value of: 998 * 999 * <blockquote> 1000 * {@code getInteger(nm, null)} 1001 * </blockquote> 1002 * 1003 * @param nm property name. 1004 * @return the {@code Integer} value of the property. 1005 * @throws SecurityException for the same reasons as 1006 * {@link System#getProperty(String) System.getProperty} 1007 * @see java.lang.System#getProperty(java.lang.String) 1008 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1009 */ 1010 public static Integer getInteger(String nm) { 1011 return getInteger(nm, null); 1012 } 1013 1014 /** 1015 * Determines the integer value of the system property with the 1016 * specified name. 1017 * 1018 * <p>The first argument is treated as the name of a system 1019 * property. System properties are accessible through the {@link 1020 * java.lang.System#getProperty(java.lang.String)} method. The 1021 * string value of this property is then interpreted as an integer 1022 * value using the grammar supported by {@link Integer#decode decode} and 1023 * an {@code Integer} object representing this value is returned. 1024 * 1025 * <p>The second argument is the default value. An {@code Integer} object 1026 * that represents the value of the second argument is returned if there 1027 * is no property of the specified name, if the property does not have 1028 * the correct numeric format, or if the specified name is empty or 1029 * {@code null}. 1030 * 1031 * <p>In other words, this method returns an {@code Integer} object 1032 * equal to the value of: 1033 * 1034 * <blockquote> 1035 * {@code getInteger(nm, new Integer(val))} 1036 * </blockquote> 1037 * 1038 * but in practice it may be implemented in a manner such as: 1039 * 1040 * <blockquote><pre> 1041 * Integer result = getInteger(nm, null); 1042 * return (result == null) ? new Integer(val) : result; 1043 * </pre></blockquote> 1044 * 1045 * to avoid the unnecessary allocation of an {@code Integer} 1046 * object when the default value is not needed. 1047 * 1048 * @param nm property name. 1049 * @param val default value. 1050 * @return the {@code Integer} value of the property. 1051 * @throws SecurityException for the same reasons as 1052 * {@link System#getProperty(String) System.getProperty} 1053 * @see java.lang.System#getProperty(java.lang.String) 1054 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1055 */ 1056 public static Integer getInteger(String nm, int val) { 1057 Integer result = getInteger(nm, null); 1058 return (result == null) ? Integer.valueOf(val) : result; 1059 } 1060 1061 /** 1062 * Returns the integer value of the system property with the 1063 * specified name. The first argument is treated as the name of a 1064 * system property. System properties are accessible through the 1065 * {@link java.lang.System#getProperty(java.lang.String)} method. 1066 * The string value of this property is then interpreted as an 1067 * integer value, as per the {@link Integer#decode decode} method, 1068 * and an {@code Integer} object representing this value is 1069 * returned; in summary: 1070 * 1071 * <ul><li>If the property value begins with the two ASCII characters 1072 * {@code 0x} or the ASCII character {@code #}, not 1073 * followed by a minus sign, then the rest of it is parsed as a 1074 * hexadecimal integer exactly as by the method 1075 * {@link #valueOf(java.lang.String, int)} with radix 16. 1076 * <li>If the property value begins with the ASCII character 1077 * {@code 0} followed by another character, it is parsed as an 1078 * octal integer exactly as by the method 1079 * {@link #valueOf(java.lang.String, int)} with radix 8. 1080 * <li>Otherwise, the property value is parsed as a decimal integer 1081 * exactly as by the method {@link #valueOf(java.lang.String, int)} 1082 * with radix 10. 1083 * </ul> 1084 * 1085 * <p>The second argument is the default value. The default value is 1086 * returned if there is no property of the specified name, if the 1087 * property does not have the correct numeric format, or if the 1088 * specified name is empty or {@code null}. 1089 * 1090 * @param nm property name. 1091 * @param val default value. 1092 * @return the {@code Integer} value of the property. 1093 * @throws SecurityException for the same reasons as 1094 * {@link System#getProperty(String) System.getProperty} 1095 * @see System#getProperty(java.lang.String) 1096 * @see System#getProperty(java.lang.String, java.lang.String) 1097 */ 1098 public static Integer getInteger(String nm, Integer val) { 1099 String v = null; 1100 try { 1101 v = System.getProperty(nm); 1102 } catch (IllegalArgumentException | NullPointerException e) { 1103 } 1104 if (v != null) { 1105 try { 1106 return Integer.decode(v); 1107 } catch (NumberFormatException e) { 1108 } 1109 } 1110 return val; 1111 } 1112 1113 /** 1114 * Decodes a {@code String} into an {@code Integer}. 1115 * Accepts decimal, hexadecimal, and octal numbers given 1116 * by the following grammar: 1117 * 1118 * <blockquote> 1119 * <dl> 1120 * <dt><i>DecodableString:</i> 1121 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 1122 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 1123 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 1124 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 1125 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 1126 * 1127 * <dt><i>Sign:</i> 1128 * <dd>{@code -} 1129 * <dd>{@code +} 1130 * </dl> 1131 * </blockquote> 1132 * 1133 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 1134 * are as defined in section 3.10.1 of 1135 * <cite>The Java™ Language Specification</cite>, 1136 * except that underscores are not accepted between digits. 1137 * 1138 * <p>The sequence of characters following an optional 1139 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 1140 * "{@code #}", or leading zero) is parsed as by the {@code 1141 * Integer.parseInt} method with the indicated radix (10, 16, or 1142 * 8). This sequence of characters must represent a positive 1143 * value or a {@link NumberFormatException} will be thrown. The 1144 * result is negated if first character of the specified {@code 1145 * String} is the minus sign. No whitespace characters are 1146 * permitted in the {@code String}. 1147 * 1148 * @param nm the {@code String} to decode. 1149 * @return an {@code Integer} object holding the {@code int} 1150 * value represented by {@code nm} 1151 * @exception NumberFormatException if the {@code String} does not 1152 * contain a parsable integer. 1153 * @see java.lang.Integer#parseInt(java.lang.String, int) 1154 */ 1155 public static Integer decode(String nm) throws NumberFormatException { 1156 int radix = 10; 1157 int index = 0; 1158 boolean negative = false; 1159 Integer result; 1160 1161 if (nm.length() == 0) 1162 throw new NumberFormatException("Zero length string"); 1163 char firstChar = nm.charAt(0); 1164 // Handle sign, if present 1165 if (firstChar == '-') { 1166 negative = true; 1167 index++; 1168 } else if (firstChar == '+') 1169 index++; 1170 1171 // Handle radix specifier, if present 1172 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 1173 index += 2; 1174 radix = 16; 1175 } 1176 else if (nm.startsWith("#", index)) { 1177 index ++; 1178 radix = 16; 1179 } 1180 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 1181 index ++; 1182 radix = 8; 1183 } 1184 1185 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 1186 throw new NumberFormatException("Sign character in wrong position"); 1187 1188 try { 1189 result = Integer.valueOf(nm.substring(index), radix); 1190 result = negative ? Integer.valueOf(-result.intValue()) : result; 1191 } catch (NumberFormatException e) { 1192 // If number is Integer.MIN_VALUE, we'll end up here. The next line 1193 // handles this case, and causes any genuine format error to be 1194 // rethrown. 1195 String constant = negative ? ("-" + nm.substring(index)) 1196 : nm.substring(index); 1197 result = Integer.valueOf(constant, radix); 1198 } 1199 return result; 1200 } 1201 1202 /** 1203 * Compares two {@code Integer} objects numerically. 1204 * 1205 * @param anotherInteger the {@code Integer} to be compared. 1206 * @return the value {@code 0} if this {@code Integer} is 1207 * equal to the argument {@code Integer}; a value less than 1208 * {@code 0} if this {@code Integer} is numerically less 1209 * than the argument {@code Integer}; and a value greater 1210 * than {@code 0} if this {@code Integer} is numerically 1211 * greater than the argument {@code Integer} (signed 1212 * comparison). 1213 * @since 1.2 1214 */ 1215 public int compareTo(Integer anotherInteger) { 1216 return compare(this.value, anotherInteger.value); 1217 } 1218 1219 /** 1220 * Compares two {@code int} values numerically. 1221 * The value returned is identical to what would be returned by: 1222 * <pre> 1223 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1224 * </pre> 1225 * 1226 * @param x the first {@code int} to compare 1227 * @param y the second {@code int} to compare 1228 * @return the value {@code 0} if {@code x == y}; 1229 * a value less than {@code 0} if {@code x < y}; and 1230 * a value greater than {@code 0} if {@code x > y} 1231 * @since 1.7 1232 */ 1233 public static int compare(int x, int y) { 1234 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1235 } 1236 1237 /** 1238 * Compares two {@code int} values numerically treating the values 1239 * as unsigned. 1240 * 1241 * @param x the first {@code int} to compare 1242 * @param y the second {@code int} to compare 1243 * @return the value {@code 0} if {@code x == y}; a value less 1244 * than {@code 0} if {@code x < y} as unsigned values; and 1245 * a value greater than {@code 0} if {@code x > y} as 1246 * unsigned values 1247 * @since 1.8 1248 */ 1249 public static int compareUnsigned(int x, int y) { 1250 return compare(x + MIN_VALUE, y + MIN_VALUE); 1251 } 1252 1253 /** 1254 * Converts the argument to a {@code long} by an unsigned 1255 * conversion. In an unsigned conversion to a {@code long}, the 1256 * high-order 32 bits of the {@code long} are zero and the 1257 * low-order 32 bits are equal to the bits of the integer 1258 * argument. 1259 * 1260 * Consequently, zero and positive {@code int} values are mapped 1261 * to a numerically equal {@code long} value and negative {@code 1262 * int} values are mapped to a {@code long} value equal to the 1263 * input plus 2<sup>32</sup>. 1264 * 1265 * @param x the value to convert to an unsigned {@code long} 1266 * @return the argument converted to {@code long} by an unsigned 1267 * conversion 1268 * @since 1.8 1269 */ 1270 public static long toUnsignedLong(int x) { 1271 return ((long) x) & 0xffffffffL; 1272 } 1273 1274 /** 1275 * Returns the unsigned quotient of dividing the first argument by 1276 * the second where each argument and the result is interpreted as 1277 * an unsigned value. 1278 * 1279 * <p>Note that in two's complement arithmetic, the three other 1280 * basic arithmetic operations of add, subtract, and multiply are 1281 * bit-wise identical if the two operands are regarded as both 1282 * being signed or both being unsigned. Therefore separate {@code 1283 * addUnsigned}, etc. methods are not provided. 1284 * 1285 * @param dividend the value to be divided 1286 * @param divisor the value doing the dividing 1287 * @return the unsigned quotient of the first argument divided by 1288 * the second argument 1289 * @see #remainderUnsigned 1290 * @since 1.8 1291 */ 1292 public static int divideUnsigned(int dividend, int divisor) { 1293 // In lieu of tricky code, for now just use long arithmetic. 1294 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor)); 1295 } 1296 1297 /** 1298 * Returns the unsigned remainder from dividing the first argument 1299 * by the second where each argument and the result is interpreted 1300 * as an unsigned value. 1301 * 1302 * @param dividend the value to be divided 1303 * @param divisor the value doing the dividing 1304 * @return the unsigned remainder of the first argument divided by 1305 * the second argument 1306 * @see #divideUnsigned 1307 * @since 1.8 1308 */ 1309 public static int remainderUnsigned(int dividend, int divisor) { 1310 // In lieu of tricky code, for now just use long arithmetic. 1311 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor)); 1312 } 1313 1314 1315 // Bit twiddling 1316 1317 /** 1318 * The number of bits used to represent an {@code int} value in two's 1319 * complement binary form. 1320 * 1321 * @since 1.5 1322 */ 1323 @Native public static final int SIZE = 32; 1324 1325 /** 1326 * The number of bytes used to represent a {@code int} value in two's 1327 * complement binary form. 1328 * 1329 * @since 1.8 1330 */ 1331 public static final int BYTES = SIZE / Byte.SIZE; 1332 1333 /** 1334 * Returns an {@code int} value with at most a single one-bit, in the 1335 * position of the highest-order ("leftmost") one-bit in the specified 1336 * {@code int} value. Returns zero if the specified value has no 1337 * one-bits in its two's complement binary representation, that is, if it 1338 * is equal to zero. 1339 * 1340 * @param i the value whose highest one bit is to be computed 1341 * @return an {@code int} value with a single one-bit, in the position 1342 * of the highest-order one-bit in the specified value, or zero if 1343 * the specified value is itself equal to zero. 1344 * @since 1.5 1345 */ 1346 public static int highestOneBit(int i) { 1347 // HD, Figure 3-1 1348 i |= (i >> 1); 1349 i |= (i >> 2); 1350 i |= (i >> 4); 1351 i |= (i >> 8); 1352 i |= (i >> 16); 1353 return i - (i >>> 1); 1354 } 1355 1356 /** 1357 * Returns an {@code int} value with at most a single one-bit, in the 1358 * position of the lowest-order ("rightmost") one-bit in the specified 1359 * {@code int} value. Returns zero if the specified value has no 1360 * one-bits in its two's complement binary representation, that is, if it 1361 * is equal to zero. 1362 * 1363 * @param i the value whose lowest one bit is to be computed 1364 * @return an {@code int} value with a single one-bit, in the position 1365 * of the lowest-order one-bit in the specified value, or zero if 1366 * the specified value is itself equal to zero. 1367 * @since 1.5 1368 */ 1369 public static int lowestOneBit(int i) { 1370 // HD, Section 2-1 1371 return i & -i; 1372 } 1373 1374 /** 1375 * Returns the number of zero bits preceding the highest-order 1376 * ("leftmost") one-bit in the two's complement binary representation 1377 * of the specified {@code int} value. Returns 32 if the 1378 * specified value has no one-bits in its two's complement representation, 1379 * in other words if it is equal to zero. 1380 * 1381 * <p>Note that this method is closely related to the logarithm base 2. 1382 * For all positive {@code int} values x: 1383 * <ul> 1384 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1385 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1386 * </ul> 1387 * 1388 * @param i the value whose number of leading zeros is to be computed 1389 * @return the number of zero bits preceding the highest-order 1390 * ("leftmost") one-bit in the two's complement binary representation 1391 * of the specified {@code int} value, or 32 if the value 1392 * is equal to zero. 1393 * @since 1.5 1394 */ 1395 public static int numberOfLeadingZeros(int i) { 1396 // HD, Figure 5-6 1397 if (i == 0) 1398 return 32; 1399 int n = 1; 1400 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1401 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1402 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1403 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1404 n -= i >>> 31; 1405 return n; 1406 } 1407 1408 /** 1409 * Returns the number of zero bits following the lowest-order ("rightmost") 1410 * one-bit in the two's complement binary representation of the specified 1411 * {@code int} value. Returns 32 if the specified value has no 1412 * one-bits in its two's complement representation, in other words if it is 1413 * equal to zero. 1414 * 1415 * @param i the value whose number of trailing zeros is to be computed 1416 * @return the number of zero bits following the lowest-order ("rightmost") 1417 * one-bit in the two's complement binary representation of the 1418 * specified {@code int} value, or 32 if the value is equal 1419 * to zero. 1420 * @since 1.5 1421 */ 1422 public static int numberOfTrailingZeros(int i) { 1423 // HD, Figure 5-14 1424 int y; 1425 if (i == 0) return 32; 1426 int n = 31; 1427 y = i <<16; if (y != 0) { n = n -16; i = y; } 1428 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1429 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1430 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1431 return n - ((i << 1) >>> 31); 1432 } 1433 1434 /** 1435 * Returns the number of one-bits in the two's complement binary 1436 * representation of the specified {@code int} value. This function is 1437 * sometimes referred to as the <i>population count</i>. 1438 * 1439 * @param i the value whose bits are to be counted 1440 * @return the number of one-bits in the two's complement binary 1441 * representation of the specified {@code int} value. 1442 * @since 1.5 1443 */ 1444 public static int bitCount(int i) { 1445 // HD, Figure 5-2 1446 i = i - ((i >>> 1) & 0x55555555); 1447 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1448 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1449 i = i + (i >>> 8); 1450 i = i + (i >>> 16); 1451 return i & 0x3f; 1452 } 1453 1454 /** 1455 * Returns the value obtained by rotating the two's complement binary 1456 * representation of the specified {@code int} value left by the 1457 * specified number of bits. (Bits shifted out of the left hand, or 1458 * high-order, side reenter on the right, or low-order.) 1459 * 1460 * <p>Note that left rotation with a negative distance is equivalent to 1461 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1462 * distance)}. Note also that rotation by any multiple of 32 is a 1463 * no-op, so all but the last five bits of the rotation distance can be 1464 * ignored, even if the distance is negative: {@code rotateLeft(val, 1465 * distance) == rotateLeft(val, distance & 0x1F)}. 1466 * 1467 * @param i the value whose bits are to be rotated left 1468 * @param distance the number of bit positions to rotate left 1469 * @return the value obtained by rotating the two's complement binary 1470 * representation of the specified {@code int} value left by the 1471 * specified number of bits. 1472 * @since 1.5 1473 */ 1474 public static int rotateLeft(int i, int distance) { 1475 return (i << distance) | (i >>> -distance); 1476 } 1477 1478 /** 1479 * Returns 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. (Bits shifted out of the right hand, or 1482 * low-order, side reenter on the left, or high-order.) 1483 * 1484 * <p>Note that right rotation with a negative distance is equivalent to 1485 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1486 * distance)}. Note also that rotation by any multiple of 32 is a 1487 * no-op, so all but the last five bits of the rotation distance can be 1488 * ignored, even if the distance is negative: {@code rotateRight(val, 1489 * distance) == rotateRight(val, distance & 0x1F)}. 1490 * 1491 * @param i the value whose bits are to be rotated right 1492 * @param distance the number of bit positions to rotate right 1493 * @return the value obtained by rotating the two's complement binary 1494 * representation of the specified {@code int} value right by the 1495 * specified number of bits. 1496 * @since 1.5 1497 */ 1498 public static int rotateRight(int i, int distance) { 1499 return (i >>> distance) | (i << -distance); 1500 } 1501 1502 /** 1503 * Returns the value obtained by reversing the order of the bits in the 1504 * two's complement binary representation of the specified {@code int} 1505 * value. 1506 * 1507 * @param i the value to be reversed 1508 * @return the value obtained by reversing order of the bits in the 1509 * specified {@code int} value. 1510 * @since 1.5 1511 */ 1512 public static int reverse(int i) { 1513 // HD, Figure 7-1 1514 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1515 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1516 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1517 i = (i << 24) | ((i & 0xff00) << 8) | 1518 ((i >>> 8) & 0xff00) | (i >>> 24); 1519 return i; 1520 } 1521 1522 /** 1523 * Returns the signum function of the specified {@code int} value. (The 1524 * return value is -1 if the specified value is negative; 0 if the 1525 * specified value is zero; and 1 if the specified value is positive.) 1526 * 1527 * @param i the value whose signum is to be computed 1528 * @return the signum function of the specified {@code int} value. 1529 * @since 1.5 1530 */ 1531 public static int signum(int i) { 1532 // HD, Section 2-7 1533 return (i >> 31) | (-i >>> 31); 1534 } 1535 1536 /** 1537 * Returns the value obtained by reversing the order of the bytes in the 1538 * two's complement representation of the specified {@code int} value. 1539 * 1540 * @param i the value whose bytes are to be reversed 1541 * @return the value obtained by reversing the bytes in the specified 1542 * {@code int} value. 1543 * @since 1.5 1544 */ 1545 public static int reverseBytes(int i) { 1546 return ((i >>> 24) ) | 1547 ((i >> 8) & 0xFF00) | 1548 ((i << 8) & 0xFF0000) | 1549 ((i << 24)); 1550 } 1551 1552 /** 1553 * Adds two integers together as per the + operator. 1554 * 1555 * @param a the first operand 1556 * @param b the second operand 1557 * @return the sum of {@code a} and {@code b} 1558 * @see java.util.function.BinaryOperator 1559 * @since 1.8 1560 */ 1561 public static int sum(int a, int b) { 1562 return a + b; 1563 } 1564 1565 /** 1566 * Returns the greater of two {@code int} values 1567 * as if by calling {@link Math#max(int, int) Math.max}. 1568 * 1569 * @param a the first operand 1570 * @param b the second operand 1571 * @return the greater of {@code a} and {@code b} 1572 * @see java.util.function.BinaryOperator 1573 * @since 1.8 1574 */ 1575 public static int max(int a, int b) { 1576 return Math.max(a, b); 1577 } 1578 1579 /** 1580 * Returns the smaller of two {@code int} values 1581 * as if by calling {@link Math#min(int, int) Math.min}. 1582 * 1583 * @param a the first operand 1584 * @param b the second operand 1585 * @return the smaller of {@code a} and {@code b} 1586 * @see java.util.function.BinaryOperator 1587 * @since 1.8 1588 */ 1589 public static int min(int a, int b) { 1590 return Math.min(a, b); 1591 } 1592 1593 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1594 @Native private static final long serialVersionUID = 1360826667806852920L; 1595 }