1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.lang; 28 29 import java.util.Properties; 30 31 /** 32 * The {@code Integer} class wraps a value of the primitive type 33 * {@code int} in an object. An object of type {@code Integer} 34 * contains a single field whose type is {@code int}. 35 * 36 * <p>In addition, this class provides several methods for converting 37 * an {@code int} to a {@code String} and a {@code String} to an 38 * {@code int}, as well as other constants and methods useful when 39 * dealing with an {@code int}. 40 * 41 * <p>Implementation note: The implementations of the "bit twiddling" 42 * methods (such as {@link #highestOneBit(int) highestOneBit} and 43 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are 44 * based on material from Henry S. Warren, Jr.'s <i>Hacker's 45 * Delight</i>, (Addison Wesley, 2002). 46 * 47 * @author Lee Boynton 48 * @author Arthur van Hoff 49 * @author Josh Bloch 50 * @author Joseph D. Darcy 51 * @since JDK1.0 52 */ 53 public final class Integer extends Number implements Comparable<Integer> { 54 /** 55 * A constant holding the minimum value an {@code int} can 56 * have, -2<sup>31</sup>. 57 */ 58 public static final int MIN_VALUE = 0x80000000; 59 60 /** 61 * A constant holding the maximum value an {@code int} can 62 * have, 2<sup>31</sup>-1. 63 */ 64 public static final int MAX_VALUE = 0x7fffffff; 65 66 /** 67 * The {@code Class} instance representing the primitive type 68 * {@code int}. 69 * 70 * @since JDK1.1 71 */ 72 public static final Class<Integer> TYPE = (Class<Integer>) int[].class.getComponentType(); 73 74 /** 75 * All possible chars for representing a number as a String 76 */ 77 final static char[] digits = { 78 '0' , '1' , '2' , '3' , '4' , '5' , 79 '6' , '7' , '8' , '9' , 'a' , 'b' , 80 'c' , 'd' , 'e' , 'f' , 'g' , 'h' , 81 'i' , 'j' , 'k' , 'l' , 'm' , 'n' , 82 'o' , 'p' , 'q' , 'r' , 's' , 't' , 83 'u' , 'v' , 'w' , 'x' , 'y' , 'z' 84 }; 85 86 /** 87 * Returns a string representation of the first argument in the 88 * radix specified by the second argument. 89 * 90 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 91 * or larger than {@code Character.MAX_RADIX}, then the radix 92 * {@code 10} is used instead. 93 * 94 * <p>If the first argument is negative, the first element of the 95 * result is the ASCII minus character {@code '-'} 96 * (<code>'\u002D'</code>). If the first argument is not 97 * negative, no sign character appears in the result. 98 * 99 * <p>The remaining characters of the result represent the magnitude 100 * of the first argument. If the magnitude is zero, it is 101 * represented by a single zero character {@code '0'} 102 * (<code>'\u0030'</code>); otherwise, the first character of 103 * the representation of the magnitude will not be the zero 104 * character. The following ASCII characters are used as digits: 105 * 106 * <blockquote> 107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz} 108 * </blockquote> 109 * 110 * These are <code>'\u0030'</code> through 111 * <code>'\u0039'</code> and <code>'\u0061'</code> through 112 * <code>'\u007A'</code>. If {@code radix} is 113 * <var>N</var>, then the first <var>N</var> of these characters 114 * are used as radix-<var>N</var> digits in the order shown. Thus, 115 * the digits for hexadecimal (radix 16) are 116 * {@code 0123456789abcdef}. If uppercase letters are 117 * desired, the {@link java.lang.String#toUpperCase()} method may 118 * be called on the result: 119 * 120 * <blockquote> 121 * {@code Integer.toString(n, 16).toUpperCase()} 122 * </blockquote> 123 * 124 * @param i an integer to be converted to a string. 125 * @param radix the radix to use in the string representation. 126 * @return a string representation of the argument in the specified radix. 127 * @see java.lang.Character#MAX_RADIX 128 * @see java.lang.Character#MIN_RADIX 129 */ toString(int i, int radix)130 public static String toString(int i, int radix) { 131 132 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) 133 radix = 10; 134 135 /* Use the faster version */ 136 if (radix == 10) { 137 return toString(i); 138 } 139 140 char buf[] = new char[33]; 141 boolean negative = (i < 0); 142 int charPos = 32; 143 144 if (!negative) { 145 i = -i; 146 } 147 148 while (i <= -radix) { 149 int q = i / radix; 150 buf[charPos--] = digits[radix * q - i]; 151 i = q; 152 } 153 buf[charPos] = digits[-i]; 154 155 if (negative) { 156 buf[--charPos] = '-'; 157 } 158 159 return new String(buf, charPos, (33 - charPos)); 160 } 161 162 /** 163 * Returns a string representation of the integer argument as an 164 * unsigned integer in base 16. 165 * 166 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 167 * if the argument is negative; otherwise, it is equal to the 168 * argument. This value is converted to a string of ASCII digits 169 * in hexadecimal (base 16) with no extra leading 170 * {@code 0}s. If the unsigned magnitude is zero, it is 171 * represented by a single zero character {@code '0'} 172 * (<code>'\u0030'</code>); otherwise, the first character of 173 * the representation of the unsigned magnitude will not be the 174 * zero character. The following characters are used as 175 * hexadecimal digits: 176 * 177 * <blockquote> 178 * {@code 0123456789abcdef} 179 * </blockquote> 180 * 181 * These are the characters <code>'\u0030'</code> through 182 * <code>'\u0039'</code> and <code>'\u0061'</code> through 183 * <code>'\u0066'</code>. If uppercase letters are 184 * desired, the {@link java.lang.String#toUpperCase()} method may 185 * be called on the result: 186 * 187 * <blockquote> 188 * {@code Integer.toHexString(n).toUpperCase()} 189 * </blockquote> 190 * 191 * @param i an integer to be converted to a string. 192 * @return the string representation of the unsigned integer value 193 * represented by the argument in hexadecimal (base 16). 194 * @since JDK1.0.2 195 */ toHexString(int i)196 public static String toHexString(int i) { 197 return toUnsignedString(i, 4); 198 } 199 200 /** 201 * Returns a string representation of the integer argument as an 202 * unsigned integer in base 8. 203 * 204 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 205 * if the argument is negative; otherwise, it is equal to the 206 * argument. This value is converted to a string of ASCII digits 207 * in octal (base 8) with no extra leading {@code 0}s. 208 * 209 * <p>If the unsigned magnitude is zero, it is represented by a 210 * single zero character {@code '0'} 211 * (<code>'\u0030'</code>); otherwise, the first character of 212 * the representation of the unsigned magnitude will not be the 213 * zero character. The following characters are used as octal 214 * digits: 215 * 216 * <blockquote> 217 * {@code 01234567} 218 * </blockquote> 219 * 220 * These are the characters <code>'\u0030'</code> through 221 * <code>'\u0037'</code>. 222 * 223 * @param i an integer to be converted to a string. 224 * @return the string representation of the unsigned integer value 225 * represented by the argument in octal (base 8). 226 * @since JDK1.0.2 227 */ toOctalString(int i)228 public static String toOctalString(int i) { 229 return toUnsignedString(i, 3); 230 } 231 232 /** 233 * Returns a string representation of the integer argument as an 234 * unsigned integer in base 2. 235 * 236 * <p>The unsigned integer value is the argument plus 2<sup>32</sup> 237 * if the argument is negative; otherwise it is equal to the 238 * argument. This value is converted to a string of ASCII digits 239 * in binary (base 2) with no extra leading {@code 0}s. 240 * If the unsigned magnitude is zero, it is represented by a 241 * single zero character {@code '0'} 242 * (<code>'\u0030'</code>); otherwise, the first character of 243 * the representation of the unsigned magnitude will not be the 244 * zero character. The characters {@code '0'} 245 * (<code>'\u0030'</code>) and {@code '1'} 246 * (<code>'\u0031'</code>) are used as binary digits. 247 * 248 * @param i an integer to be converted to a string. 249 * @return the string representation of the unsigned integer value 250 * represented by the argument in binary (base 2). 251 * @since JDK1.0.2 252 */ toBinaryString(int i)253 public static String toBinaryString(int i) { 254 return toUnsignedString(i, 1); 255 } 256 257 /** 258 * Convert the integer to an unsigned number. 259 */ toUnsignedString(int i, int shift)260 private static String toUnsignedString(int i, int shift) { 261 char[] buf = new char[32]; 262 int charPos = 32; 263 int radix = 1 << shift; 264 int mask = radix - 1; 265 do { 266 buf[--charPos] = digits[i & mask]; 267 i >>>= shift; 268 } while (i != 0); 269 270 return new String(buf, charPos, (32 - charPos)); 271 } 272 273 private static final String[] SMALL_NEG_VALUES = new String[100]; 274 private static final String[] SMALL_NONNEG_VALUES = new String[100]; 275 276 final static char [] DigitTens = { 277 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', 278 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', 279 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', 280 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 281 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', 282 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', 283 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', 284 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', 285 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', 286 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', 287 } ; 288 289 final static char [] DigitOnes = { 290 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 291 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 292 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 293 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 294 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 295 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 296 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 297 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 298 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 299 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 300 } ; 301 302 // I use the "invariant division by multiplication" trick to 303 // accelerate Integer.toString. In particular we want to 304 // avoid division by 10. 305 // 306 // The "trick" has roughly the same performance characteristics 307 // as the "classic" Integer.toString code on a non-JIT VM. 308 // The trick avoids .rem and .div calls but has a longer code 309 // path and is thus dominated by dispatch overhead. In the 310 // JIT case the dispatch overhead doesn't exist and the 311 // "trick" is considerably faster than the classic code. 312 // 313 // TODO-FIXME: convert (x * 52429) into the equiv shift-add 314 // sequence. 315 // 316 // RE: Division by Invariant Integers using Multiplication 317 // T Gralund, P Montgomery 318 // ACM PLDI 1994 319 // 320 321 /** 322 * Returns a {@code String} object representing the 323 * specified integer. The argument is converted to signed decimal 324 * representation and returned as a string, exactly as if the 325 * argument and radix 10 were given as arguments to the {@link 326 * #toString(int, int)} method. 327 * 328 * @param i an integer to be converted. 329 * @return a string representation of the argument in base 10. 330 */ toString(int i)331 public static String toString(int i) { 332 if (i == Integer.MIN_VALUE) 333 return "-2147483648"; 334 335 // Android-changed: cache the string literal for small values. 336 boolean negative = i < 0; 337 boolean small = negative ? i > -100 : i < 100; 338 if (small) { 339 final String[] smallValues = negative ? SMALL_NEG_VALUES : SMALL_NONNEG_VALUES; 340 341 if (negative) { 342 i = -i; 343 if (smallValues[i] == null) { 344 smallValues[i] = 345 i < 10 ? new String(new char[]{'-', DigitOnes[i]}) 346 : new String(new char[]{'-', DigitTens[i], DigitOnes[i]}); 347 } 348 } else { 349 if (smallValues[i] == null) { 350 smallValues[i] = 351 i < 10 ? new String(new char[]{DigitOnes[i]}) 352 : new String(new char[]{DigitTens[i], DigitOnes[i]}); 353 } 354 } 355 return smallValues[i]; 356 } 357 358 int size = negative ? stringSize(-i) + 1 : stringSize(i); 359 char[] buf = new char[size]; 360 getChars(i, size, buf); 361 // Android-changed: change string constructor. 362 return new String(buf); 363 } 364 365 /** 366 * Places characters representing the integer i into the 367 * character array buf. The characters are placed into 368 * the buffer backwards starting with the least significant 369 * digit at the specified index (exclusive), and working 370 * backwards from there. 371 * 372 * Will fail if i == Integer.MIN_VALUE 373 */ 374 static void getChars(int i, int index, char[] buf) { 375 int q, r; 376 int charPos = index; 377 char sign = 0; 378 379 if (i < 0) { 380 sign = '-'; 381 i = -i; 382 } 383 384 // Generate two digits per iteration 385 while (i >= 65536) { 386 q = i / 100; 387 // really: r = i - (q * 100); 388 r = i - ((q << 6) + (q << 5) + (q << 2)); 389 i = q; 390 buf [--charPos] = DigitOnes[r]; 391 buf [--charPos] = DigitTens[r]; 392 } 393 394 // Fall thru to fast mode for smaller numbers 395 // assert(i <= 65536, i); 396 for (;;) { 397 q = (i * 52429) >>> (16+3); 398 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ... 399 buf [--charPos] = digits [r]; 400 i = q; 401 if (i == 0) break; 402 } 403 if (sign != 0) { 404 buf [--charPos] = sign; 405 } 406 } 407 408 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 409 99999999, 999999999, Integer.MAX_VALUE }; 410 411 // Requires positive x 412 static int stringSize(int x) { 413 for (int i=0; ; i++) 414 if (x <= sizeTable[i]) 415 return i+1; 416 } 417 418 /** 419 * Parses the string argument as a signed integer in the radix 420 * specified by the second argument. The characters in the string 421 * must all be digits of the specified radix (as determined by 422 * whether {@link java.lang.Character#digit(char, int)} returns a 423 * nonnegative value), except that the first character may be an 424 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to 425 * indicate a negative value or an ASCII plus sign {@code '+'} 426 * (<code>'\u002B'</code>) to indicate a positive value. The 427 * resulting integer value is returned. 428 * 429 * <p>An exception of type {@code NumberFormatException} is 430 * thrown if any of the following situations occurs: 431 * <ul> 432 * <li>The first argument is {@code null} or is a string of 433 * length zero. 434 * 435 * <li>The radix is either smaller than 436 * {@link java.lang.Character#MIN_RADIX} or 437 * larger than {@link java.lang.Character#MAX_RADIX}. 438 * 439 * <li>Any character of the string is not a digit of the specified 440 * radix, except that the first character may be a minus sign 441 * {@code '-'} (<code>'\u002D'</code>) or plus sign 442 * {@code '+'} (<code>'\u002B'</code>) provided that the 443 * string is longer than length 1. 444 * 445 * <li>The value represented by the string is not a value of type 446 * {@code int}. 447 * </ul> 448 * 449 * <p>Examples: 450 * <blockquote><pre> 451 * parseInt("0", 10) returns 0 452 * parseInt("473", 10) returns 473 453 * parseInt("+42", 10) returns 42 454 * parseInt("-0", 10) returns 0 455 * parseInt("-FF", 16) returns -255 456 * parseInt("1100110", 2) returns 102 457 * parseInt("2147483647", 10) returns 2147483647 458 * parseInt("-2147483648", 10) returns -2147483648 459 * parseInt("2147483648", 10) throws a NumberFormatException 460 * parseInt("99", 8) throws a NumberFormatException 461 * parseInt("Kona", 10) throws a NumberFormatException 462 * parseInt("Kona", 27) returns 411787 463 * </pre></blockquote> 464 * 465 * @param s the {@code String} containing the integer 466 * representation to be parsed 467 * @param radix the radix to be used while parsing {@code s}. 468 * @return the integer represented by the string argument in the 469 * specified radix. 470 * @exception NumberFormatException if the {@code String} 471 * does not contain a parsable {@code int}. 472 */ 473 public static int parseInt(String s, int radix) 474 throws NumberFormatException 475 { 476 /* 477 * WARNING: This method may be invoked early during VM initialization 478 * before IntegerCache is initialized. Care must be taken to not use 479 * the valueOf method. 480 */ 481 482 if (s == null) { 483 throw new NumberFormatException("null"); 484 } 485 486 if (radix < Character.MIN_RADIX) { 487 throw new NumberFormatException("radix " + radix + 488 " less than Character.MIN_RADIX"); 489 } 490 491 if (radix > Character.MAX_RADIX) { 492 throw new NumberFormatException("radix " + radix + 493 " greater than Character.MAX_RADIX"); 494 } 495 496 int result = 0; 497 boolean negative = false; 498 int i = 0, len = s.length(); 499 int limit = -Integer.MAX_VALUE; 500 int multmin; 501 int digit; 502 503 if (len > 0) { 504 char firstChar = s.charAt(0); 505 if (firstChar < '0') { // Possible leading "+" or "-" 506 if (firstChar == '-') { 507 negative = true; 508 limit = Integer.MIN_VALUE; 509 } else if (firstChar != '+') 510 throw NumberFormatException.forInputString(s); 511 512 if (len == 1) // Cannot have lone "+" or "-" 513 throw NumberFormatException.forInputString(s); 514 i++; 515 } 516 multmin = limit / radix; 517 while (i < len) { 518 // Accumulating negatively avoids surprises near MAX_VALUE 519 digit = Character.digit(s.charAt(i++),radix); 520 if (digit < 0) { 521 throw NumberFormatException.forInputString(s); 522 } 523 if (result < multmin) { 524 throw NumberFormatException.forInputString(s); 525 } 526 result *= radix; 527 if (result < limit + digit) { 528 throw NumberFormatException.forInputString(s); 529 } 530 result -= digit; 531 } 532 } else { 533 throw NumberFormatException.forInputString(s); 534 } 535 return negative ? result : -result; 536 } 537 538 /** 539 * Parses the string argument as a signed decimal integer. The 540 * characters in the string must all be decimal digits, except 541 * that the first character may be an ASCII minus sign {@code '-'} 542 * (<code>'\u002D'</code>) to indicate a negative value or an 543 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to 544 * indicate a positive value. The resulting integer value is 545 * returned, exactly as if the argument and the radix 10 were 546 * given as arguments to the {@link #parseInt(java.lang.String, 547 * int)} method. 548 * 549 * @param s a {@code String} containing the {@code int} 550 * representation to be parsed 551 * @return the integer value represented by the argument in decimal. 552 * @exception NumberFormatException if the string does not contain a 553 * parsable integer. 554 */ 555 public static int parseInt(String s) throws NumberFormatException { 556 return parseInt(s,10); 557 } 558 559 /** 560 * Returns an {@code Integer} object holding the value 561 * extracted from the specified {@code String} when parsed 562 * with the radix given by the second argument. The first argument 563 * is interpreted as representing a signed integer in the radix 564 * specified by the second argument, exactly as if the arguments 565 * were given to the {@link #parseInt(java.lang.String, int)} 566 * method. The result is an {@code Integer} object that 567 * represents the integer value specified by the string. 568 * 569 * <p>In other words, this method returns an {@code Integer} 570 * object equal to the value of: 571 * 572 * <blockquote> 573 * {@code new Integer(Integer.parseInt(s, radix))} 574 * </blockquote> 575 * 576 * @param s the string to be parsed. 577 * @param radix the radix to be used in interpreting {@code s} 578 * @return an {@code Integer} object holding the value 579 * represented by the string argument in the specified 580 * radix. 581 * @exception NumberFormatException if the {@code String} 582 * does not contain a parsable {@code int}. 583 */ 584 public static Integer valueOf(String s, int radix) throws NumberFormatException { 585 return Integer.valueOf(parseInt(s,radix)); 586 } 587 588 /** 589 * Returns an {@code Integer} object holding the 590 * value of the specified {@code String}. The argument is 591 * interpreted as representing a signed decimal integer, exactly 592 * as if the argument were given to the {@link 593 * #parseInt(java.lang.String)} method. The result is an 594 * {@code Integer} object that represents the integer value 595 * specified by the string. 596 * 597 * <p>In other words, this method returns an {@code Integer} 598 * object equal to the value of: 599 * 600 * <blockquote> 601 * {@code new Integer(Integer.parseInt(s))} 602 * </blockquote> 603 * 604 * @param s the string to be parsed. 605 * @return an {@code Integer} object holding the value 606 * represented by the string argument. 607 * @exception NumberFormatException if the string cannot be parsed 608 * as an integer. 609 */ 610 public static Integer valueOf(String s) throws NumberFormatException { 611 return Integer.valueOf(parseInt(s, 10)); 612 } 613 614 /** 615 * Cache to support the object identity semantics of autoboxing for values between 616 * -128 and 127 (inclusive) as required by JLS. 617 * 618 * The cache is initialized on first usage. The size of the cache 619 * may be controlled by the -XX:AutoBoxCacheMax=<size> option. 620 * During VM initialization, java.lang.Integer.IntegerCache.high property 621 * may be set and saved in the private system properties in the 622 * sun.misc.VM class. 623 */ 624 625 private static class IntegerCache { 626 static final int low = -128; 627 static final int high; 628 static final Integer cache[]; 629 630 static { 631 // high value may be configured by property 632 int h = 127; 633 String integerCacheHighPropValue = 634 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); 635 if (integerCacheHighPropValue != null) { 636 int i = parseInt(integerCacheHighPropValue); 637 i = Math.max(i, 127); 638 // Maximum array size is Integer.MAX_VALUE 639 h = Math.min(i, Integer.MAX_VALUE - (-low) -1); 640 } 641 high = h; 642 643 cache = new Integer[(high - low) + 1]; 644 int j = low; 645 for(int k = 0; k < cache.length; k++) 646 cache[k] = new Integer(j++); 647 } 648 649 private IntegerCache() {} 650 } 651 652 /** 653 * Returns an {@code Integer} instance representing the specified 654 * {@code int} value. If a new {@code Integer} instance is not 655 * required, this method should generally be used in preference to 656 * the constructor {@link #Integer(int)}, as this method is likely 657 * to yield significantly better space and time performance by 658 * caching frequently requested values. 659 * 660 * This method will always cache values in the range -128 to 127, 661 * inclusive, and may cache other values outside of this range. 662 * 663 * @param i an {@code int} value. 664 * @return an {@code Integer} instance representing {@code i}. 665 * @since 1.5 666 */ 667 public static Integer valueOf(int i) { 668 assert IntegerCache.high >= 127; 669 if (i >= IntegerCache.low && i <= IntegerCache.high) 670 return IntegerCache.cache[i + (-IntegerCache.low)]; 671 return new Integer(i); 672 } 673 674 /** 675 * The value of the {@code Integer}. 676 * 677 * @serial 678 */ 679 private final int value; 680 681 /** 682 * Constructs a newly allocated {@code Integer} object that 683 * represents the specified {@code int} value. 684 * 685 * @param value the value to be represented by the 686 * {@code Integer} object. 687 */ 688 public Integer(int value) { 689 this.value = value; 690 } 691 692 /** 693 * Constructs a newly allocated {@code Integer} object that 694 * represents the {@code int} value indicated by the 695 * {@code String} parameter. The string is converted to an 696 * {@code int} value in exactly the manner used by the 697 * {@code parseInt} method for radix 10. 698 * 699 * @param s the {@code String} to be converted to an 700 * {@code Integer}. 701 * @exception NumberFormatException if the {@code String} does not 702 * contain a parsable integer. 703 * @see java.lang.Integer#parseInt(java.lang.String, int) 704 */ 705 public Integer(String s) throws NumberFormatException { 706 this.value = parseInt(s, 10); 707 } 708 709 /** 710 * Returns the value of this {@code Integer} as a 711 * {@code byte}. 712 */ 713 public byte byteValue() { 714 return (byte)value; 715 } 716 717 /** 718 * Returns the value of this {@code Integer} as a 719 * {@code short}. 720 */ 721 public short shortValue() { 722 return (short)value; 723 } 724 725 /** 726 * Returns the value of this {@code Integer} as an 727 * {@code int}. 728 */ 729 public int intValue() { 730 return value; 731 } 732 733 /** 734 * Returns the value of this {@code Integer} as a 735 * {@code long}. 736 */ 737 public long longValue() { 738 return (long)value; 739 } 740 741 /** 742 * Returns the value of this {@code Integer} as a 743 * {@code float}. 744 */ 745 public float floatValue() { 746 return (float)value; 747 } 748 749 /** 750 * Returns the value of this {@code Integer} as a 751 * {@code double}. 752 */ 753 public double doubleValue() { 754 return (double)value; 755 } 756 757 /** 758 * Returns a {@code String} object representing this 759 * {@code Integer}'s value. The value is converted to signed 760 * decimal representation and returned as a string, exactly as if 761 * the integer value were given as an argument to the {@link 762 * java.lang.Integer#toString(int)} method. 763 * 764 * @return a string representation of the value of this object in 765 * base 10. 766 */ 767 public String toString() { 768 return toString(value); 769 } 770 771 /** 772 * Returns a hash code for this {@code Integer}. 773 * 774 * @return a hash code value for this object, equal to the 775 * primitive {@code int} value represented by this 776 * {@code Integer} object. 777 */ 778 public int hashCode() { 779 return value; 780 } 781 782 /** 783 * Returns a hash code for a {@code int} value; compatible with 784 * {@code Integer.hashCode()}. 785 * 786 * @param value the value to hash 787 * @since 1.8 788 * 789 * @return a hash code value for a {@code int} value. 790 */ 791 public static int hashCode(int value) { 792 return value; 793 } 794 795 /** 796 * Compares this object to the specified object. The result is 797 * {@code true} if and only if the argument is not 798 * {@code null} and is an {@code Integer} object that 799 * contains the same {@code int} value as this object. 800 * 801 * @param obj the object to compare with. 802 * @return {@code true} if the objects are the same; 803 * {@code false} otherwise. 804 */ 805 public boolean equals(Object obj) { 806 if (obj instanceof Integer) { 807 return value == ((Integer)obj).intValue(); 808 } 809 return false; 810 } 811 812 /** 813 * Determines the integer value of the system property with the 814 * specified name. 815 * 816 * <p>The first argument is treated as the name of a system property. 817 * System properties are accessible through the 818 * {@link java.lang.System#getProperty(java.lang.String)} method. The 819 * string value of this property is then interpreted as an integer 820 * value and an {@code Integer} object representing this value is 821 * returned. Details of possible numeric formats can be found with 822 * the definition of {@code getProperty}. 823 * 824 * <p>If there is no property with the specified name, if the specified name 825 * is empty or {@code null}, or if the property does not have 826 * the correct numeric format, then {@code null} is returned. 827 * 828 * <p>In other words, this method returns an {@code Integer} 829 * object equal to the value of: 830 * 831 * <blockquote> 832 * {@code getInteger(nm, null)} 833 * </blockquote> 834 * 835 * @param nm property name. 836 * @return the {@code Integer} value of the property. 837 * @see java.lang.System#getProperty(java.lang.String) 838 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 839 */ 840 public static Integer getInteger(String nm) { 841 return getInteger(nm, null); 842 } 843 844 /** 845 * Determines the integer value of the system property with the 846 * specified name. 847 * 848 * <p>The first argument is treated as the name of a system property. 849 * System properties are accessible through the {@link 850 * java.lang.System#getProperty(java.lang.String)} method. The 851 * string value of this property is then interpreted as an integer 852 * value and an {@code Integer} object representing this value is 853 * returned. Details of possible numeric formats can be found with 854 * the definition of {@code getProperty}. 855 * 856 * <p>The second argument is the default value. An {@code Integer} object 857 * that represents the value of the second argument is returned if there 858 * is no property of the specified name, if the property does not have 859 * the correct numeric format, or if the specified name is empty or 860 * {@code null}. 861 * 862 * <p>In other words, this method returns an {@code Integer} object 863 * equal to the value of: 864 * 865 * <blockquote> 866 * {@code getInteger(nm, new Integer(val))} 867 * </blockquote> 868 * 869 * but in practice it may be implemented in a manner such as: 870 * 871 * <blockquote><pre> 872 * Integer result = getInteger(nm, null); 873 * return (result == null) ? new Integer(val) : result; 874 * </pre></blockquote> 875 * 876 * to avoid the unnecessary allocation of an {@code Integer} 877 * object when the default value is not needed. 878 * 879 * @param nm property name. 880 * @param val default value. 881 * @return the {@code Integer} value of the property. 882 * @see java.lang.System#getProperty(java.lang.String) 883 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 884 */ 885 public static Integer getInteger(String nm, int val) { 886 Integer result = getInteger(nm, null); 887 return (result == null) ? Integer.valueOf(val) : result; 888 } 889 890 /** 891 * Returns the integer value of the system property with the 892 * specified name. The first argument is treated as the name of a 893 * system property. System properties are accessible through the 894 * {@link java.lang.System#getProperty(java.lang.String)} method. 895 * The string value of this property is then interpreted as an 896 * integer value, as per the {@code Integer.decode} method, 897 * and an {@code Integer} object representing this value is 898 * returned. 899 * 900 * <ul><li>If the property value begins with the two ASCII characters 901 * {@code 0x} or the ASCII character {@code #}, not 902 * followed by a minus sign, then the rest of it is parsed as a 903 * hexadecimal integer exactly as by the method 904 * {@link #valueOf(java.lang.String, int)} with radix 16. 905 * <li>If the property value begins with the ASCII character 906 * {@code 0} followed by another character, it is parsed as an 907 * octal integer exactly as by the method 908 * {@link #valueOf(java.lang.String, int)} with radix 8. 909 * <li>Otherwise, the property value is parsed as a decimal integer 910 * exactly as by the method {@link #valueOf(java.lang.String, int)} 911 * with radix 10. 912 * </ul> 913 * 914 * <p>The second argument is the default value. The default value is 915 * returned if there is no property of the specified name, if the 916 * property does not have the correct numeric format, or if the 917 * specified name is empty or {@code null}. 918 * 919 * @param nm property name. 920 * @param val default value. 921 * @return the {@code Integer} value of the property. 922 * @see java.lang.System#getProperty(java.lang.String) 923 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 924 * @see java.lang.Integer#decode 925 */ 926 public static Integer getInteger(String nm, Integer val) { 927 String v = null; 928 try { 929 v = System.getProperty(nm); 930 } catch (IllegalArgumentException e) { 931 } catch (NullPointerException e) { 932 } 933 if (v != null) { 934 try { 935 return Integer.decode(v); 936 } catch (NumberFormatException e) { 937 } 938 } 939 return val; 940 } 941 942 /** 943 * Decodes a {@code String} into an {@code Integer}. 944 * Accepts decimal, hexadecimal, and octal numbers given 945 * by the following grammar: 946 * 947 * <blockquote> 948 * <dl> 949 * <dt><i>DecodableString:</i> 950 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 951 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 952 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 953 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 954 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 955 * <p> 956 * <dt><i>Sign:</i> 957 * <dd>{@code -} 958 * <dd>{@code +} 959 * </dl> 960 * </blockquote> 961 * 962 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 963 * are as defined in section 3.10.1 of 964 * <cite>The Java™ Language Specification</cite>, 965 * except that underscores are not accepted between digits. 966 * 967 * <p>The sequence of characters following an optional 968 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 969 * "{@code #}", or leading zero) is parsed as by the {@code 970 * Integer.parseInt} method with the indicated radix (10, 16, or 971 * 8). This sequence of characters must represent a positive 972 * value or a {@link NumberFormatException} will be thrown. The 973 * result is negated if first character of the specified {@code 974 * String} is the minus sign. No whitespace characters are 975 * permitted in the {@code String}. 976 * 977 * @param nm the {@code String} to decode. 978 * @return an {@code Integer} object holding the {@code int} 979 * value represented by {@code nm} 980 * @exception NumberFormatException if the {@code String} does not 981 * contain a parsable integer. 982 * @see java.lang.Integer#parseInt(java.lang.String, int) 983 */ 984 public static Integer decode(String nm) throws NumberFormatException { 985 int radix = 10; 986 int index = 0; 987 boolean negative = false; 988 Integer result; 989 990 if (nm.length() == 0) 991 throw new NumberFormatException("Zero length string"); 992 char firstChar = nm.charAt(0); 993 // Handle sign, if present 994 if (firstChar == '-') { 995 negative = true; 996 index++; 997 } else if (firstChar == '+') 998 index++; 999 1000 // Handle radix specifier, if present 1001 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 1002 index += 2; 1003 radix = 16; 1004 } 1005 else if (nm.startsWith("#", index)) { 1006 index ++; 1007 radix = 16; 1008 } 1009 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 1010 index ++; 1011 radix = 8; 1012 } 1013 1014 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 1015 throw new NumberFormatException("Sign character in wrong position"); 1016 1017 try { 1018 result = Integer.valueOf(nm.substring(index), radix); 1019 result = negative ? Integer.valueOf(-result.intValue()) : result; 1020 } catch (NumberFormatException e) { 1021 // If number is Integer.MIN_VALUE, we'll end up here. The next line 1022 // handles this case, and causes any genuine format error to be 1023 // rethrown. 1024 String constant = negative ? ("-" + nm.substring(index)) 1025 : nm.substring(index); 1026 result = Integer.valueOf(constant, radix); 1027 } 1028 return result; 1029 } 1030 1031 /** 1032 * Compares two {@code Integer} objects numerically. 1033 * 1034 * @param anotherInteger the {@code Integer} to be compared. 1035 * @return the value {@code 0} if this {@code Integer} is 1036 * equal to the argument {@code Integer}; a value less than 1037 * {@code 0} if this {@code Integer} is numerically less 1038 * than the argument {@code Integer}; and a value greater 1039 * than {@code 0} if this {@code Integer} is numerically 1040 * greater than the argument {@code Integer} (signed 1041 * comparison). 1042 * @since 1.2 1043 */ 1044 public int compareTo(Integer anotherInteger) { 1045 return compare(this.value, anotherInteger.value); 1046 } 1047 1048 /** 1049 * Compares two {@code int} values numerically. 1050 * The value returned is identical to what would be returned by: 1051 * <pre> 1052 * Integer.valueOf(x).compareTo(Integer.valueOf(y)) 1053 * </pre> 1054 * 1055 * @param x the first {@code int} to compare 1056 * @param y the second {@code int} to compare 1057 * @return the value {@code 0} if {@code x == y}; 1058 * a value less than {@code 0} if {@code x < y}; and 1059 * a value greater than {@code 0} if {@code x > y} 1060 * @since 1.7 1061 */ 1062 public static int compare(int x, int y) { 1063 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1064 } 1065 1066 1067 // Bit twiddling 1068 1069 /** 1070 * The number of bits used to represent an {@code int} value in two's 1071 * complement binary form. 1072 * 1073 * @since 1.5 1074 */ 1075 public static final int SIZE = 32; 1076 1077 1078 /** 1079 * The number of bytes used to represent a {@code int} value in two's 1080 * complement binary form. 1081 * 1082 * @since 1.8 1083 */ 1084 public static final int BYTES = SIZE / Byte.SIZE; 1085 1086 /** 1087 * Returns an {@code int} value with at most a single one-bit, in the 1088 * position of the highest-order ("leftmost") one-bit in the specified 1089 * {@code int} value. Returns zero if the specified value has no 1090 * one-bits in its two's complement binary representation, that is, if it 1091 * is equal to zero. 1092 * 1093 * @return an {@code int} value with a single one-bit, in the position 1094 * of the highest-order one-bit in the specified value, or zero if 1095 * the specified value is itself equal to zero. 1096 * @since 1.5 1097 */ 1098 public static int highestOneBit(int i) { 1099 // HD, Figure 3-1 1100 i |= (i >> 1); 1101 i |= (i >> 2); 1102 i |= (i >> 4); 1103 i |= (i >> 8); 1104 i |= (i >> 16); 1105 return i - (i >>> 1); 1106 } 1107 1108 /** 1109 * Returns an {@code int} value with at most a single one-bit, in the 1110 * position of the lowest-order ("rightmost") one-bit in the specified 1111 * {@code int} value. Returns zero if the specified value has no 1112 * one-bits in its two's complement binary representation, that is, if it 1113 * is equal to zero. 1114 * 1115 * @return an {@code int} value with a single one-bit, in the position 1116 * of the lowest-order one-bit in the specified value, or zero if 1117 * the specified value is itself equal to zero. 1118 * @since 1.5 1119 */ 1120 public static int lowestOneBit(int i) { 1121 // HD, Section 2-1 1122 return i & -i; 1123 } 1124 1125 /** 1126 * Returns the number of zero bits preceding the highest-order 1127 * ("leftmost") one-bit in the two's complement binary representation 1128 * of the specified {@code int} value. Returns 32 if the 1129 * specified value has no one-bits in its two's complement representation, 1130 * in other words if it is equal to zero. 1131 * 1132 * <p>Note that this method is closely related to the logarithm base 2. 1133 * For all positive {@code int} values x: 1134 * <ul> 1135 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} 1136 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} 1137 * </ul> 1138 * 1139 * @return the number of zero bits preceding the highest-order 1140 * ("leftmost") one-bit in the two's complement binary representation 1141 * of the specified {@code int} value, or 32 if the value 1142 * is equal to zero. 1143 * @since 1.5 1144 */ 1145 public static int numberOfLeadingZeros(int i) { 1146 // HD, Figure 5-6 1147 if (i == 0) 1148 return 32; 1149 int n = 1; 1150 if (i >>> 16 == 0) { n += 16; i <<= 16; } 1151 if (i >>> 24 == 0) { n += 8; i <<= 8; } 1152 if (i >>> 28 == 0) { n += 4; i <<= 4; } 1153 if (i >>> 30 == 0) { n += 2; i <<= 2; } 1154 n -= i >>> 31; 1155 return n; 1156 } 1157 1158 /** 1159 * Returns the number of zero bits following the lowest-order ("rightmost") 1160 * one-bit in the two's complement binary representation of the specified 1161 * {@code int} value. Returns 32 if the specified value has no 1162 * one-bits in its two's complement representation, in other words if it is 1163 * equal to zero. 1164 * 1165 * @return the number of zero bits following the lowest-order ("rightmost") 1166 * one-bit in the two's complement binary representation of the 1167 * specified {@code int} value, or 32 if the value is equal 1168 * to zero. 1169 * @since 1.5 1170 */ numberOfTrailingZeros(int i)1171 public static int numberOfTrailingZeros(int i) { 1172 // HD, Figure 5-14 1173 int y; 1174 if (i == 0) return 32; 1175 int n = 31; 1176 y = i <<16; if (y != 0) { n = n -16; i = y; } 1177 y = i << 8; if (y != 0) { n = n - 8; i = y; } 1178 y = i << 4; if (y != 0) { n = n - 4; i = y; } 1179 y = i << 2; if (y != 0) { n = n - 2; i = y; } 1180 return n - ((i << 1) >>> 31); 1181 } 1182 1183 /** 1184 * Returns the number of one-bits in the two's complement binary 1185 * representation of the specified {@code int} value. This function is 1186 * sometimes referred to as the <i>population count</i>. 1187 * 1188 * @return the number of one-bits in the two's complement binary 1189 * representation of the specified {@code int} value. 1190 * @since 1.5 1191 */ bitCount(int i)1192 public static int bitCount(int i) { 1193 // HD, Figure 5-2 1194 i = i - ((i >>> 1) & 0x55555555); 1195 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); 1196 i = (i + (i >>> 4)) & 0x0f0f0f0f; 1197 i = i + (i >>> 8); 1198 i = i + (i >>> 16); 1199 return i & 0x3f; 1200 } 1201 1202 /** 1203 * Returns the value obtained by rotating the two's complement binary 1204 * representation of the specified {@code int} value left by the 1205 * specified number of bits. (Bits shifted out of the left hand, or 1206 * high-order, side reenter on the right, or low-order.) 1207 * 1208 * <p>Note that left rotation with a negative distance is equivalent to 1209 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1210 * distance)}. Note also that rotation by any multiple of 32 is a 1211 * no-op, so all but the last five bits of the rotation distance can be 1212 * ignored, even if the distance is negative: {@code rotateLeft(val, 1213 * distance) == rotateLeft(val, distance & 0x1F)}. 1214 * 1215 * @return the value obtained by rotating the two's complement binary 1216 * representation of the specified {@code int} value left by the 1217 * specified number of bits. 1218 * @since 1.5 1219 */ rotateLeft(int i, int distance)1220 public static int rotateLeft(int i, int distance) { 1221 return (i << distance) | (i >>> -distance); 1222 } 1223 1224 /** 1225 * Returns the value obtained by rotating the two's complement binary 1226 * representation of the specified {@code int} value right by the 1227 * specified number of bits. (Bits shifted out of the right hand, or 1228 * low-order, side reenter on the left, or high-order.) 1229 * 1230 * <p>Note that right rotation with a negative distance is equivalent to 1231 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1232 * distance)}. Note also that rotation by any multiple of 32 is a 1233 * no-op, so all but the last five bits of the rotation distance can be 1234 * ignored, even if the distance is negative: {@code rotateRight(val, 1235 * distance) == rotateRight(val, distance & 0x1F)}. 1236 * 1237 * @return the value obtained by rotating the two's complement binary 1238 * representation of the specified {@code int} value right by the 1239 * specified number of bits. 1240 * @since 1.5 1241 */ rotateRight(int i, int distance)1242 public static int rotateRight(int i, int distance) { 1243 return (i >>> distance) | (i << -distance); 1244 } 1245 1246 /** 1247 * Returns the value obtained by reversing the order of the bits in the 1248 * two's complement binary representation of the specified {@code int} 1249 * value. 1250 * 1251 * @return the value obtained by reversing order of the bits in the 1252 * specified {@code int} value. 1253 * @since 1.5 1254 */ reverse(int i)1255 public static int reverse(int i) { 1256 // HD, Figure 7-1 1257 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 1258 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; 1259 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 1260 i = (i << 24) | ((i & 0xff00) << 8) | 1261 ((i >>> 8) & 0xff00) | (i >>> 24); 1262 return i; 1263 } 1264 1265 /** 1266 * Returns the signum function of the specified {@code int} value. (The 1267 * return value is -1 if the specified value is negative; 0 if the 1268 * specified value is zero; and 1 if the specified value is positive.) 1269 * 1270 * @return the signum function of the specified {@code int} value. 1271 * @since 1.5 1272 */ signum(int i)1273 public static int signum(int i) { 1274 // HD, Section 2-7 1275 return (i >> 31) | (-i >>> 31); 1276 } 1277 1278 /** 1279 * Returns the value obtained by reversing the order of the bytes in the 1280 * two's complement representation of the specified {@code int} value. 1281 * 1282 * @return the value obtained by reversing the bytes in the specified 1283 * {@code int} value. 1284 * @since 1.5 1285 */ reverseBytes(int i)1286 public static int reverseBytes(int i) { 1287 return ((i >>> 24) ) | 1288 ((i >> 8) & 0xFF00) | 1289 ((i << 8) & 0xFF0000) | 1290 ((i << 24)); 1291 } 1292 1293 /** 1294 * Adds two integers together as per the + operator. 1295 * 1296 * @param a the first operand 1297 * @param b the second operand 1298 * @return the sum of {@code a} and {@code b} 1299 * @see java.util.function.BinaryOperator 1300 * @since 1.8 1301 */ sum(int a, int b)1302 public static int sum(int a, int b) { 1303 return a + b; 1304 } 1305 1306 /** 1307 * Returns the greater of two {@code int} values 1308 * as if by calling {@link Math#max(int, int) Math.max}. 1309 * 1310 * @param a the first operand 1311 * @param b the second operand 1312 * @return the greater of {@code a} and {@code b} 1313 * @see java.util.function.BinaryOperator 1314 * @since 1.8 1315 */ max(int a, int b)1316 public static int max(int a, int b) { 1317 return Math.max(a, b); 1318 } 1319 1320 /** 1321 * Returns the smaller of two {@code int} values 1322 * as if by calling {@link Math#min(int, int) Math.min}. 1323 * 1324 * @param a the first operand 1325 * @param b the second operand 1326 * @return the smaller of {@code a} and {@code b} 1327 * @see java.util.function.BinaryOperator 1328 * @since 1.8 1329 */ min(int a, int b)1330 public static int min(int a, int b) { 1331 return Math.min(a, b); 1332 } 1333 1334 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1335 private static final long serialVersionUID = 1360826667806852920L; 1336 } 1337