1 /*
2 * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.lang.annotation.Native;
29
30 /**
31 * The {@code Integer} class wraps a value of the primitive type
32 * {@code int} in an object. An object of type {@code Integer}
33 * contains a single field whose type is {@code int}.
34 *
35 * <p>In addition, this class provides several methods for converting
36 * an {@code int} to a {@code String} and a {@code String} to an
37 * {@code int}, as well as other constants and methods useful when
38 * dealing with an {@code int}.
39 *
40 * <p>Implementation note: The implementations of the "bit twiddling"
41 * methods (such as {@link #highestOneBit(int) highestOneBit} and
42 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
43 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
44 * Delight</i>, (Addison Wesley, 2002).
45 *
46 * @author Lee Boynton
47 * @author Arthur van Hoff
48 * @author Josh Bloch
49 * @author Joseph D. Darcy
50 * @since JDK1.0
51 */
52 public final class Integer extends Number implements Comparable<Integer> {
53 /**
54 * A constant holding the minimum value an {@code int} can
55 * have, -2<sup>31</sup>.
56 */
57 @Native public static final int MIN_VALUE = 0x80000000;
58
59 /**
60 * A constant holding the maximum value an {@code int} can
61 * have, 2<sup>31</sup>-1.
62 */
63 @Native public static final int MAX_VALUE = 0x7fffffff;
64
65 /**
66 * The {@code Class} instance representing the primitive type
67 * {@code int}.
68 *
69 * @since JDK1.1
70 */
71 @SuppressWarnings("unchecked")
72 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
73
74 /**
75 * All possible chars for representing a number as a String
76 */
77 final static char[] digits = {
78 '0' , '1' , '2' , '3' , '4' , '5' ,
79 '6' , '7' , '8' , '9' , 'a' , 'b' ,
80 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
81 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
82 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
83 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
84 };
85
86 /**
87 * Returns a string representation of the first argument in the
88 * radix specified by the second argument.
89 *
90 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
91 * or larger than {@code Character.MAX_RADIX}, then the radix
92 * {@code 10} is used instead.
93 *
94 * <p>If the first argument is negative, the first element of the
95 * result is the ASCII minus character {@code '-'}
96 * ({@code '\u005Cu002D'}). If the first argument is not
97 * negative, no sign character appears in the result.
98 *
99 * <p>The remaining characters of the result represent the magnitude
100 * of the first argument. If the magnitude is zero, it is
101 * represented by a single zero character {@code '0'}
102 * ({@code '\u005Cu0030'}); otherwise, the first character of
103 * the representation of the magnitude will not be the zero
104 * character. The following ASCII characters are used as digits:
105 *
106 * <blockquote>
107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
108 * </blockquote>
109 *
110 * These are {@code '\u005Cu0030'} through
111 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
112 * {@code '\u005Cu007A'}. If {@code radix} is
113 * <var>N</var>, then the first <var>N</var> of these characters
114 * are used as radix-<var>N</var> digits in the order shown. Thus,
115 * the digits for hexadecimal (radix 16) are
116 * {@code 0123456789abcdef}. If uppercase letters are
117 * desired, the {@link java.lang.String#toUpperCase()} method may
118 * be called on the result:
119 *
120 * <blockquote>
121 * {@code Integer.toString(n, 16).toUpperCase()}
122 * </blockquote>
123 *
124 * @param i an integer to be converted to a string.
125 * @param radix the radix to use in the string representation.
126 * @return a string representation of the argument in the specified radix.
127 * @see java.lang.Character#MAX_RADIX
128 * @see java.lang.Character#MIN_RADIX
129 */
130 public static String toString(int i, int radix) {
131 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
132 radix = 10;
133
134 /* Use the faster version */
135 if (radix == 10) {
136 return toString(i);
137 }
138
139 char buf[] = new char[33];
140 boolean negative = (i < 0);
141 int charPos = 32;
142
143 if (!negative) {
144 i = -i;
145 }
146
147 while (i <= -radix) {
148 buf[charPos--] = digits[-(i % radix)];
149 i = i / radix;
150 }
151 buf[charPos] = digits[-i];
152
153 if (negative) {
154 buf[--charPos] = '-';
155 }
156
157 return new String(buf, charPos, (33 - charPos));
158 }
159
160 /**
161 * Returns a string representation of the first argument as an
162 * unsigned integer value in the radix specified by the second
163 * argument.
164 *
165 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
166 * or larger than {@code Character.MAX_RADIX}, then the radix
167 * {@code 10} is used instead.
168 *
169 * <p>Note that since the first argument is treated as an unsigned
170 * value, no leading sign character is printed.
171 *
172 * <p>If the magnitude is zero, it is represented by a single zero
173 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
174 * the first character of the representation of the magnitude will
175 * not be the zero character.
176 *
177 * <p>The behavior of radixes and the characters used as digits
178 * are the same as {@link #toString(int, int) toString}.
179 *
180 * @param i an integer to be converted to an unsigned string.
181 * @param radix the radix to use in the string representation.
182 * @return an unsigned string representation of the argument in the specified radix.
183 * @see #toString(int, int)
184 * @since 1.8
185 */
186 public static String toUnsignedString(int i, int radix) {
187 return Long.toUnsignedString(toUnsignedLong(i), radix);
188 }
189
190 /**
191 * Returns a string representation of the integer argument as an
192 * unsigned integer in base 16.
193 *
194 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
195 * if the argument is negative; otherwise, it is equal to the
196 * argument. This value is converted to a string of ASCII digits
197 * in hexadecimal (base 16) with no extra leading
198 * {@code 0}s.
199 *
200 * <p>The value of the argument can be recovered from the returned
201 * string {@code s} by calling {@link
202 * Integer#parseUnsignedInt(String, int)
203 * Integer.parseUnsignedInt(s, 16)}.
204 *
205 * <p>If the unsigned magnitude is zero, it is represented by a
206 * single zero character {@code '0'} ({@code '\u005Cu0030'});
207 * otherwise, the first character of the representation of the
208 * unsigned magnitude will not be the zero character. The
209 * following characters are used as hexadecimal digits:
210 *
211 * <blockquote>
212 * {@code 0123456789abcdef}
213 * </blockquote>
214 *
215 * These are the characters {@code '\u005Cu0030'} through
216 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
217 * {@code '\u005Cu0066'}. If uppercase letters are
218 * desired, the {@link java.lang.String#toUpperCase()} method may
219 * be called on the result:
220 *
221 * <blockquote>
222 * {@code Integer.toHexString(n).toUpperCase()}
223 * </blockquote>
224 *
225 * @param i an integer to be converted to a string.
226 * @return the string representation of the unsigned integer value
227 * represented by the argument in hexadecimal (base 16).
228 * @see #parseUnsignedInt(String, int)
229 * @see #toUnsignedString(int, int)
230 * @since JDK1.0.2
231 */
232 public static String toHexString(int i) {
233 return toUnsignedString0(i, 4);
234 }
235
236 /**
237 * Returns a string representation of the integer argument as an
238 * unsigned integer in base 8.
239 *
240 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
241 * if the argument is negative; otherwise, it is equal to the
242 * argument. This value is converted to a string of ASCII digits
243 * in octal (base 8) with no extra leading {@code 0}s.
244 *
245 * <p>The value of the argument can be recovered from the returned
246 * string {@code s} by calling {@link
247 * Integer#parseUnsignedInt(String, int)
248 * Integer.parseUnsignedInt(s, 8)}.
249 *
250 * <p>If the unsigned magnitude is zero, it is represented by a
251 * single zero character {@code '0'} ({@code '\u005Cu0030'});
252 * otherwise, the first character of the representation of the
253 * unsigned magnitude will not be the zero character. The
254 * following characters are used as octal digits:
255 *
256 * <blockquote>
257 * {@code 01234567}
258 * </blockquote>
259 *
260 * These are the characters {@code '\u005Cu0030'} through
261 * {@code '\u005Cu0037'}.
262 *
263 * @param i an integer to be converted to a string.
264 * @return the string representation of the unsigned integer value
265 * represented by the argument in octal (base 8).
266 * @see #parseUnsignedInt(String, int)
267 * @see #toUnsignedString(int, int)
268 * @since JDK1.0.2
269 */
270 public static String toOctalString(int i) {
271 return toUnsignedString0(i, 3);
272 }
273
274 /**
275 * Returns a string representation of the integer argument as an
276 * unsigned integer in base 2.
277 *
278 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
279 * if the argument is negative; otherwise it is equal to the
280 * argument. This value is converted to a string of ASCII digits
281 * in binary (base 2) with no extra leading {@code 0}s.
282 *
283 * <p>The value of the argument can be recovered from the returned
284 * string {@code s} by calling {@link
285 * Integer#parseUnsignedInt(String, int)
286 * Integer.parseUnsignedInt(s, 2)}.
287 *
288 * <p>If the unsigned magnitude is zero, it is represented by a
289 * single zero character {@code '0'} ({@code '\u005Cu0030'});
290 * otherwise, the first character of the representation of the
291 * unsigned magnitude will not be the zero character. The
292 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
293 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
294 *
295 * @param i an integer to be converted to a string.
296 * @return the string representation of the unsigned integer value
297 * represented by the argument in binary (base 2).
298 * @see #parseUnsignedInt(String, int)
299 * @see #toUnsignedString(int, int)
300 * @since JDK1.0.2
301 */
302 public static String toBinaryString(int i) {
303 return toUnsignedString0(i, 1);
304 }
305
306 /**
307 * Convert the integer to an unsigned number.
308 */
309 private static String toUnsignedString0(int i, int shift) {
310 // assert shift > 0 && shift <=5 : "Illegal shift value";
311 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(i);
312 int chars = Math.max(((mag + (shift - 1)) / shift), 1);
313 char[] buf = new char[chars];
314 int charPos = chars;
315 int radix = 1 << shift;
316 int mask = radix - 1;
317 do {
318 buf[--charPos] = digits[i & mask];
319 i >>>= shift;
320 } while (i != 0);
321
322 // Use special constructor which takes over "buf".
323 return new String(buf, true);
324 }
325
326
327 final static char [] DigitTens = {
328 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
329 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
330 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
331 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
332 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
333 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
334 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
335 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
336 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
337 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
338 } ;
339
340 final static char [] DigitOnes = {
341 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
342 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
343 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
344 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
345 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
346 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
347 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
348 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
349 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
350 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
351 } ;
352
353 // I use the "invariant division by multiplication" trick to
354 // accelerate Integer.toString. In particular we want to
355 // avoid division by 10.
356 //
357 // The "trick" has roughly the same performance characteristics
358 // as the "classic" Integer.toString code on a non-JIT VM.
359 // The trick avoids .rem and .div calls but has a longer code
360 // path and is thus dominated by dispatch overhead. In the
361 // JIT case the dispatch overhead doesn't exist and the
362 // "trick" is considerably faster than the classic code.
363 //
364 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
365 // sequence.
366 //
367 // RE: Division by Invariant Integers using Multiplication
368 // T Gralund, P Montgomery
369 // ACM PLDI 1994
370 //
371
372 /**
373 * Returns a {@code String} object representing the
374 * specified integer. The argument is converted to signed decimal
375 * representation and returned as a string, exactly as if the
376 * argument and radix 10 were given as arguments to the {@link
377 * #toString(int, int)} method.
378 *
379 * @param i an integer to be converted.
380 * @return a string representation of the argument in base 10.
381 */
382 public static String toString(int i) {
383 if (i == Integer.MIN_VALUE)
384 return "-2147483648";
385 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
386 char[] buf = new char[size];
387 getChars(i, size, buf);
388 return new String(buf, true);
389 }
390
391 /**
392 * Returns a string representation of the argument as an unsigned
393 * decimal value.
394 *
395 * The argument is converted to unsigned decimal representation
396 * and returned as a string exactly as if the argument and radix
397 * 10 were given as arguments to the {@link #toUnsignedString(int,
398 * int)} method.
399 *
400 * @param i an integer to be converted to an unsigned string.
401 * @return an unsigned string representation of the argument.
402 * @see #toUnsignedString(int, int)
403 * @since 1.8
404 */
405 public static String toUnsignedString(int i) {
406 return Long.toString(toUnsignedLong(i));
407 }
408
409 /**
410 * Places characters representing the integer i into the
411 * character array buf. The characters are placed into
412 * the buffer backwards starting with the least significant
413 * digit at the specified index (exclusive), and working
414 * backwards from there.
415 *
416 * Will fail if i == Integer.MIN_VALUE
417 */
418 static void getChars(int i, int index, char[] buf) {
419 int q, r;
420 int charPos = index;
421 char sign = 0;
422
423 if (i < 0) {
424 sign = '-';
425 i = -i;
426 }
427
428 // Generate two digits per iteration
429 while (i >= 65536) {
430 q = i / 100;
431 // really: r = i - (q * 100);
432 r = i - ((q << 6) + (q << 5) + (q << 2));
433 i = q;
434 buf [--charPos] = DigitOnes[r];
435 buf [--charPos] = DigitTens[r];
436 }
437
438 // Fall thru to fast mode for smaller numbers
439 // assert(i <= 65536, i);
440 for (;;) {
441 q = (i * 52429) >>> (16+3);
442 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
443 buf [--charPos] = digits [r];
444 i = q;
445 if (i == 0) break;
446 }
447 if (sign != 0) {
448 buf [--charPos] = sign;
449 }
450 }
451
452 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
453 99999999, 999999999, Integer.MAX_VALUE };
454
455 // Requires positive x
456 static int stringSize(int x) {
457 for (int i=0; ; i++)
458 if (x <= sizeTable[i])
459 return i+1;
460 }
461
462 /**
463 * Parses the string argument as a signed integer in the radix
464 * specified by the second argument. The characters in the string
465 * must all be digits of the specified radix (as determined by
466 * whether {@link java.lang.Character#digit(char, int)} returns a
467 * nonnegative value), except that the first character may be an
468 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
469 * indicate a negative value or an ASCII plus sign {@code '+'}
470 * ({@code '\u005Cu002B'}) to indicate a positive value. The
471 * resulting integer value is returned.
472 *
473 * <p>An exception of type {@code NumberFormatException} is
474 * thrown if any of the following situations occurs:
475 * <ul>
476 * <li>The first argument is {@code null} or is a string of
477 * length zero.
478 *
479 * <li>The radix is either smaller than
480 * {@link java.lang.Character#MIN_RADIX} or
481 * larger than {@link java.lang.Character#MAX_RADIX}.
482 *
483 * <li>Any character of the string is not a digit of the specified
484 * radix, except that the first character may be a minus sign
485 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
486 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
487 * string is longer than length 1.
488 *
489 * <li>The value represented by the string is not a value of type
490 * {@code int}.
491 * </ul>
492 *
493 * <p>Examples:
494 * <blockquote><pre>
495 * parseInt("0", 10) returns 0
496 * parseInt("473", 10) returns 473
497 * parseInt("+42", 10) returns 42
498 * parseInt("-0", 10) returns 0
499 * parseInt("-FF", 16) returns -255
500 * parseInt("1100110", 2) returns 102
501 * parseInt("2147483647", 10) returns 2147483647
502 * parseInt("-2147483648", 10) returns -2147483648
503 * parseInt("2147483648", 10) throws a NumberFormatException
504 * parseInt("99", 8) throws a NumberFormatException
505 * parseInt("Kona", 10) throws a NumberFormatException
506 * parseInt("Kona", 27) returns 411787
507 * </pre></blockquote>
508 *
509 * @param s the {@code String} containing the integer
510 * representation to be parsed
511 * @param radix the radix to be used while parsing {@code s}.
512 * @return the integer represented by the string argument in the
513 * specified radix.
514 * @exception NumberFormatException if the {@code String}
515 * does not contain a parsable {@code int}.
516 */
517 public static int parseInt(String s, int radix)
518 throws NumberFormatException
519 {
520 /*
521 * WARNING: This method may be invoked early during VM initialization
522 * before IntegerCache is initialized. Care must be taken to not use
523 * the valueOf method.
524 */
525
526 if (s == null) {
527 throw new NumberFormatException("null");
528 }
529
530 if (radix < Character.MIN_RADIX) {
531 throw new NumberFormatException("radix " + radix +
532 " less than Character.MIN_RADIX");
533 }
534
535 if (radix > Character.MAX_RADIX) {
536 throw new NumberFormatException("radix " + radix +
537 " greater than Character.MAX_RADIX");
538 }
539
540 int result = 0;
541 boolean negative = false;
542 int i = 0, len = s.length();
543 int limit = -Integer.MAX_VALUE;
544 int multmin;
545 int digit;
546
547 if (len > 0) {
548 char firstChar = s.charAt(0);
549 if (firstChar < '0') { // Possible leading "+" or "-"
550 if (firstChar == '-') {
551 negative = true;
552 limit = Integer.MIN_VALUE;
553 } else if (firstChar != '+')
554 throw NumberFormatException.forInputString(s);
555
556 if (len == 1) // Cannot have lone "+" or "-"
557 throw NumberFormatException.forInputString(s);
558 i++;
559 }
560 multmin = limit / radix;
561 while (i < len) {
562 // Accumulating negatively avoids surprises near MAX_VALUE
563 digit = Character.digit(s.charAt(i++),radix);
564 if (digit < 0) {
565 throw NumberFormatException.forInputString(s);
566 }
567 if (result < multmin) {
568 throw NumberFormatException.forInputString(s);
569 }
570 result *= radix;
571 if (result < limit + digit) {
572 throw NumberFormatException.forInputString(s);
573 }
574 result -= digit;
575 }
576 } else {
577 throw NumberFormatException.forInputString(s);
578 }
579 return negative ? result : -result;
580 }
581
582 /**
583 * Parses the string argument as a signed decimal integer. The
584 * characters in the string must all be decimal digits, except
585 * that the first character may be an ASCII minus sign {@code '-'}
586 * ({@code '\u005Cu002D'}) to indicate a negative value or an
587 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
588 * indicate a positive value. The resulting integer value is
589 * returned, exactly as if the argument and the radix 10 were
590 * given as arguments to the {@link #parseInt(java.lang.String,
591 * int)} method.
592 *
593 * @param s a {@code String} containing the {@code int}
594 * representation to be parsed
595 * @return the integer value represented by the argument in decimal.
596 * @exception NumberFormatException if the string does not contain a
597 * parsable integer.
598 */
599 public static int parseInt(String s) throws NumberFormatException {
600 return parseInt(s,10);
601 }
602
603 /**
604 * Parses the string argument as an unsigned integer in the radix
605 * specified by the second argument. An unsigned integer maps the
606 * values usually associated with negative numbers to positive
607 * numbers larger than {@code MAX_VALUE}.
608 *
609 * The characters in the string must all be digits of the
610 * specified radix (as determined by whether {@link
611 * java.lang.Character#digit(char, int)} returns a nonnegative
612 * value), except that the first character may be an ASCII plus
613 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
614 * integer value is returned.
615 *
616 * <p>An exception of type {@code NumberFormatException} is
617 * thrown if any of the following situations occurs:
618 * <ul>
619 * <li>The first argument is {@code null} or is a string of
620 * length zero.
621 *
622 * <li>The radix is either smaller than
623 * {@link java.lang.Character#MIN_RADIX} or
624 * larger than {@link java.lang.Character#MAX_RADIX}.
625 *
626 * <li>Any character of the string is not a digit of the specified
627 * radix, except that the first character may be a plus sign
628 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
629 * string is longer than length 1.
630 *
631 * <li>The value represented by the string is larger than the
632 * largest unsigned {@code int}, 2<sup>32</sup>-1.
633 *
634 * </ul>
635 *
636 *
637 * @param s the {@code String} containing the unsigned integer
638 * representation to be parsed
639 * @param radix the radix to be used while parsing {@code s}.
640 * @return the integer represented by the string argument in the
641 * specified radix.
642 * @throws NumberFormatException if the {@code String}
643 * does not contain a parsable {@code int}.
644 * @since 1.8
645 */
646 public static int parseUnsignedInt(String s, int radix)
647 throws NumberFormatException {
648 if (s == null) {
649 throw new NumberFormatException("null");
650 }
651
652 int len = s.length();
653 if (len > 0) {
654 char firstChar = s.charAt(0);
655 if (firstChar == '-') {
656 throw new
657 NumberFormatException(String.format("Illegal leading minus sign " +
658 "on unsigned string %s.", s));
659 } else {
660 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
661 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
662 return parseInt(s, radix);
663 } else {
664 long ell = Long.parseLong(s, radix);
665 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
666 return (int) ell;
667 } else {
668 throw new
669 NumberFormatException(String.format("String value %s exceeds " +
670 "range of unsigned int.", s));
671 }
672 }
673 }
674 } else {
675 throw NumberFormatException.forInputString(s);
676 }
677 }
678
679 /**
680 * Parses the string argument as an unsigned decimal integer. The
681 * characters in the string must all be decimal digits, except
682 * that the first character may be an an ASCII plus sign {@code
683 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
684 * is returned, exactly as if the argument and the radix 10 were
685 * given as arguments to the {@link
686 * #parseUnsignedInt(java.lang.String, int)} method.
687 *
688 * @param s a {@code String} containing the unsigned {@code int}
689 * representation to be parsed
690 * @return the unsigned integer value represented by the argument in decimal.
691 * @throws NumberFormatException if the string does not contain a
692 * parsable unsigned integer.
693 * @since 1.8
694 */
695 public static int parseUnsignedInt(String s) throws NumberFormatException {
696 return parseUnsignedInt(s, 10);
697 }
698
699 /**
700 * Returns an {@code Integer} object holding the value
701 * extracted from the specified {@code String} when parsed
702 * with the radix given by the second argument. The first argument
703 * is interpreted as representing a signed integer in the radix
704 * specified by the second argument, exactly as if the arguments
705 * were given to the {@link #parseInt(java.lang.String, int)}
706 * method. The result is an {@code Integer} object that
707 * represents the integer value specified by the string.
708 *
709 * <p>In other words, this method returns an {@code Integer}
710 * object equal to the value of:
711 *
712 * <blockquote>
713 * {@code new Integer(Integer.parseInt(s, radix))}
714 * </blockquote>
715 *
716 * @param s the string to be parsed.
717 * @param radix the radix to be used in interpreting {@code s}
718 * @return an {@code Integer} object holding the value
719 * represented by the string argument in the specified
720 * radix.
721 * @exception NumberFormatException if the {@code String}
722 * does not contain a parsable {@code int}.
723 */
724 public static Integer valueOf(String s, int radix) throws NumberFormatException {
725 return Integer.valueOf(parseInt(s,radix));
726 }
727
728 /**
729 * Returns an {@code Integer} object holding the
730 * value of the specified {@code String}. The argument is
731 * interpreted as representing a signed decimal integer, exactly
732 * as if the argument were given to the {@link
733 * #parseInt(java.lang.String)} method. The result is an
734 * {@code Integer} object that represents the integer value
735 * specified by the string.
736 *
737 * <p>In other words, this method returns an {@code Integer}
738 * object equal to the value of:
739 *
740 * <blockquote>
741 * {@code new Integer(Integer.parseInt(s))}
742 * </blockquote>
743 *
744 * @param s the string to be parsed.
745 * @return an {@code Integer} object holding the value
746 * represented by the string argument.
747 * @exception NumberFormatException if the string cannot be parsed
748 * as an integer.
749 */
750 public static Integer valueOf(String s) throws NumberFormatException {
751 return Integer.valueOf(parseInt(s, 10));
752 }
753
754 /**
755 * Cache to support the object identity semantics of autoboxing for values between
756 * -128 and 127 (inclusive) as required by JLS.
757 *
758 * The cache is initialized on first usage. The size of the cache
759 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
760 * During VM initialization, java.lang.Integer.IntegerCache.high property
761 * may be set and saved in the private system properties in the
762 * sun.misc.VM class.
763 */
764
765 private static class IntegerCache {
766 static final int low = -128;
767 static final int high;
768 static final Integer cache[];
769
770 static {
771 // high value may be configured by property
772 int h = 127;
773 String integerCacheHighPropValue =
774 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
775 if (integerCacheHighPropValue != null) {
776 int i = parseInt(integerCacheHighPropValue);
777 i = Math.max(i, 127);
778 // Maximum array size is Integer.MAX_VALUE
779 h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
780 }
781 high = h;
782
783 cache = new Integer[(high - low) + 1];
784 int j = low;
785 for(int k = 0; k < cache.length; k++)
786 cache[k] = new Integer(j++);
787
788 // range [-128, 127] must be interned (JLS7 5.1.7)
789 assert IntegerCache.high >= 127;
790 }
791
792 private IntegerCache() {}
793 }
794
795 /**
796 * Returns an {@code Integer} instance representing the specified
797 * {@code int} value. If a new {@code Integer} instance is not
798 * required, this method should generally be used in preference to
799 * the constructor {@link #Integer(int)}, as this method is likely
800 * to yield significantly better space and time performance by
801 * caching frequently requested values.
802 *
803 * This method will always cache values in the range -128 to 127,
804 * inclusive, and may cache other values outside of this range.
805 *
806 * @param i an {@code int} value.
807 * @return an {@code Integer} instance representing {@code i}.
808 * @since 1.5
809 */
810 public static Integer valueOf(int i) {
811 if (i >= IntegerCache.low && i <= IntegerCache.high)
812 return IntegerCache.cache[i + (-IntegerCache.low)];
813 return new Integer(i);
814 }
815
816 /**
817 * The value of the {@code Integer}.
818 *
819 * @serial
820 */
821 private final int value;
822
823 /**
824 * Constructs a newly allocated {@code Integer} object that
825 * represents the specified {@code int} value.
826 *
827 * @param value the value to be represented by the
828 * {@code Integer} object.
829 */
830 public Integer(int value) {
831 this.value = value;
832 }
833
834 /**
835 * Constructs a newly allocated {@code Integer} object that
836 * represents the {@code int} value indicated by the
837 * {@code String} parameter. The string is converted to an
838 * {@code int} value in exactly the manner used by the
839 * {@code parseInt} method for radix 10.
840 *
841 * @param s the {@code String} to be converted to an
842 * {@code Integer}.
843 * @exception NumberFormatException if the {@code String} does not
844 * contain a parsable integer.
845 * @see java.lang.Integer#parseInt(java.lang.String, int)
846 */
847 public Integer(String s) throws NumberFormatException {
848 this.value = parseInt(s, 10);
849 }
850
851 /**
852 * Returns the value of this {@code Integer} as a {@code byte}
853 * after a narrowing primitive conversion.
854 * @jls 5.1.3 Narrowing Primitive Conversions
855 */
856 public byte byteValue() {
857 return (byte)value;
858 }
859
860 /**
861 * Returns the value of this {@code Integer} as a {@code short}
862 * after a narrowing primitive conversion.
863 * @jls 5.1.3 Narrowing Primitive Conversions
864 */
865 public short shortValue() {
866 return (short)value;
867 }
868
869 /**
870 * Returns the value of this {@code Integer} as an
871 * {@code int}.
872 */
873 public int intValue() {
874 return value;
875 }
876
877 /**
878 * Returns the value of this {@code Integer} as a {@code long}
879 * after a widening primitive conversion.
880 * @jls 5.1.2 Widening Primitive Conversions
881 * @see Integer#toUnsignedLong(int)
882 */
883 public long longValue() {
884 return (long)value;
885 }
886
887 /**
888 * Returns the value of this {@code Integer} as a {@code float}
889 * after a widening primitive conversion.
890 * @jls 5.1.2 Widening Primitive Conversions
891 */
892 public float floatValue() {
893 return (float)value;
894 }
895
896 /**
897 * Returns the value of this {@code Integer} as a {@code double}
898 * after a widening primitive conversion.
899 * @jls 5.1.2 Widening Primitive Conversions
900 */
901 public double doubleValue() {
902 return (double)value;
903 }
904
905 /**
906 * Returns a {@code String} object representing this
907 * {@code Integer}'s value. The value is converted to signed
908 * decimal representation and returned as a string, exactly as if
909 * the integer value were given as an argument to the {@link
910 * java.lang.Integer#toString(int)} method.
911 *
912 * @return a string representation of the value of this object in
913 * base 10.
914 */
915 public String toString() {
916 return toString(value);
917 }
918
919 /**
920 * Returns a hash code for this {@code Integer}.
921 *
922 * @return a hash code value for this object, equal to the
923 * primitive {@code int} value represented by this
924 * {@code Integer} object.
925 */
926 @Override
927 public int hashCode() {
928 return Integer.hashCode(value);
929 }
930
931 /**
932 * Returns a hash code for a {@code int} value; compatible with
933 * {@code Integer.hashCode()}.
934 *
935 * @since 1.8
936 *
937 * @return a hash code value for a {@code int} value.
938 */
939 public static int hashCode(int value) {
940 return value;
941 }
942
943 /**
944 * Compares this object to the specified object. The result is
945 * {@code true} if and only if the argument is not
946 * {@code null} and is an {@code Integer} object that
947 * contains the same {@code int} value as this object.
948 *
949 * @param obj the object to compare with.
950 * @return {@code true} if the objects are the same;
951 * {@code false} otherwise.
952 */
953 public boolean equals(Object obj) {
954 if (obj instanceof Integer) {
955 return value == ((Integer)obj).intValue();
956 }
957 return false;
958 }
959
960 /**
961 * Determines the integer value of the system property with the
962 * specified name.
963 *
964 * <p>The first argument is treated as the name of a system
965 * property. System properties are accessible through the {@link
966 * java.lang.System#getProperty(java.lang.String)} method. The
967 * string value of this property is then interpreted as an integer
968 * value using the grammar supported by {@link Integer#decode decode} and
969 * an {@code Integer} object representing this value is returned.
970 *
971 * <p>If there is no property with the specified name, if the
972 * specified name is empty or {@code null}, or if the property
973 * does not have the correct numeric format, then {@code null} is
974 * returned.
975 *
976 * <p>In other words, this method returns an {@code Integer}
977 * object equal to the value of:
978 *
979 * <blockquote>
980 * {@code getInteger(nm, null)}
981 * </blockquote>
982 *
983 * @param nm property name.
984 * @return the {@code Integer} value of the property.
985 * @throws SecurityException for the same reasons as
986 * {@link System#getProperty(String) System.getProperty}
987 * @see java.lang.System#getProperty(java.lang.String)
988 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
989 */
990 public static Integer getInteger(String nm) {
991 return getInteger(nm, null);
992 }
993
994 /**
995 * Determines the integer value of the system property with the
996 * specified name.
997 *
998 * <p>The first argument is treated as the name of a system
999 * property. System properties are accessible through the {@link
1000 * java.lang.System#getProperty(java.lang.String)} method. The
1001 * string value of this property is then interpreted as an integer
1002 * value using the grammar supported by {@link Integer#decode decode} and
1003 * an {@code Integer} object representing this value is returned.
1004 *
1005 * <p>The second argument is the default value. An {@code Integer} object
1006 * that represents the value of the second argument is returned if there
1007 * is no property of the specified name, if the property does not have
1008 * the correct numeric format, or if the specified name is empty or
1009 * {@code null}.
1010 *
1011 * <p>In other words, this method returns an {@code Integer} object
1012 * equal to the value of:
1013 *
1014 * <blockquote>
1015 * {@code getInteger(nm, new Integer(val))}
1016 * </blockquote>
1017 *
1018 * but in practice it may be implemented in a manner such as:
1019 *
1020 * <blockquote><pre>
1021 * Integer result = getInteger(nm, null);
1022 * return (result == null) ? new Integer(val) : result;
1023 * </pre></blockquote>
1024 *
1025 * to avoid the unnecessary allocation of an {@code Integer}
1026 * object when the default value is not needed.
1027 *
1028 * @param nm property name.
1029 * @param val default value.
1030 * @return the {@code Integer} value of the property.
1031 * @throws SecurityException for the same reasons as
1032 * {@link System#getProperty(String) System.getProperty}
1033 * @see java.lang.System#getProperty(java.lang.String)
1034 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1035 */
1036 public static Integer getInteger(String nm, int val) {
1037 Integer result = getInteger(nm, null);
1038 return (result == null) ? Integer.valueOf(val) : result;
1039 }
1040
1041 /**
1042 * Returns the integer value of the system property with the
1043 * specified name. The first argument is treated as the name of a
1044 * system property. System properties are accessible through the
1045 * {@link java.lang.System#getProperty(java.lang.String)} method.
1046 * The string value of this property is then interpreted as an
1047 * integer value, as per the {@link Integer#decode decode} method,
1048 * and an {@code Integer} object representing this value is
1049 * returned; in summary:
1050 *
1051 * <ul><li>If the property value begins with the two ASCII characters
1052 * {@code 0x} or the ASCII character {@code #}, not
1053 * followed by a minus sign, then the rest of it is parsed as a
1054 * hexadecimal integer exactly as by the method
1055 * {@link #valueOf(java.lang.String, int)} with radix 16.
1056 * <li>If the property value begins with the ASCII character
1057 * {@code 0} followed by another character, it is parsed as an
1058 * octal integer exactly as by the method
1059 * {@link #valueOf(java.lang.String, int)} with radix 8.
1060 * <li>Otherwise, the property value is parsed as a decimal integer
1061 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1062 * with radix 10.
1063 * </ul>
1064 *
1065 * <p>The second argument is the default value. The default value is
1066 * returned if there is no property of the specified name, if the
1067 * property does not have the correct numeric format, or if the
1068 * specified name is empty or {@code null}.
1069 *
1070 * @param nm property name.
1071 * @param val default value.
1072 * @return the {@code Integer} value of the property.
1073 * @throws SecurityException for the same reasons as
1074 * {@link System#getProperty(String) System.getProperty}
1075 * @see System#getProperty(java.lang.String)
1076 * @see System#getProperty(java.lang.String, java.lang.String)
1077 */
1078 public static Integer getInteger(String nm, Integer val) {
1079 String v = null;
1080 try {
1081 v = System.getProperty(nm);
1082 } catch (IllegalArgumentException | NullPointerException e) {
1083 }
1084 if (v != null) {
1085 try {
1086 return Integer.decode(v);
1087 } catch (NumberFormatException e) {
1088 }
1089 }
1090 return val;
1091 }
1092
1093 /**
1094 * Decodes a {@code String} into an {@code Integer}.
1095 * Accepts decimal, hexadecimal, and octal numbers given
1096 * by the following grammar:
1097 *
1098 * <blockquote>
1099 * <dl>
1100 * <dt><i>DecodableString:</i>
1101 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1102 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1103 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1104 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1105 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1106 * <p>
1107 * <dt><i>Sign:</i>
1108 * <dd>{@code -}
1109 * <dd>{@code +}
1110 * </dl>
1111 * </blockquote>
1112 *
1113 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1114 * are as defined in section 3.10.1 of
1115 * <cite>The Java™ Language Specification</cite>,
1116 * except that underscores are not accepted between digits.
1117 *
1118 * <p>The sequence of characters following an optional
1119 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1120 * "{@code #}", or leading zero) is parsed as by the {@code
1121 * Integer.parseInt} method with the indicated radix (10, 16, or
1122 * 8). This sequence of characters must represent a positive
1123 * value or a {@link NumberFormatException} will be thrown. The
1124 * result is negated if first character of the specified {@code
1125 * String} is the minus sign. No whitespace characters are
1126 * permitted in the {@code String}.
1127 *
1128 * @param nm the {@code String} to decode.
1129 * @return an {@code Integer} object holding the {@code int}
1130 * value represented by {@code nm}
1131 * @exception NumberFormatException if the {@code String} does not
1132 * contain a parsable integer.
1133 * @see java.lang.Integer#parseInt(java.lang.String, int)
1134 */
1135 public static Integer decode(String nm) throws NumberFormatException {
1136 int radix = 10;
1137 int index = 0;
1138 boolean negative = false;
1139 Integer result;
1140
1141 if (nm.length() == 0)
1142 throw new NumberFormatException("Zero length string");
1143 char firstChar = nm.charAt(0);
1144 // Handle sign, if present
1145 if (firstChar == '-') {
1146 negative = true;
1147 index++;
1148 } else if (firstChar == '+')
1149 index++;
1150
1151 // Handle radix specifier, if present
1152 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1153 index += 2;
1154 radix = 16;
1155 }
1156 else if (nm.startsWith("#", index)) {
1157 index ++;
1158 radix = 16;
1159 }
1160 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1161 index ++;
1162 radix = 8;
1163 }
1164
1165 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1166 throw new NumberFormatException("Sign character in wrong position");
1167
1168 try {
1169 result = Integer.valueOf(nm.substring(index), radix);
1170 result = negative ? Integer.valueOf(-result.intValue()) : result;
1171 } catch (NumberFormatException e) {
1172 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1173 // handles this case, and causes any genuine format error to be
1174 // rethrown.
1175 String constant = negative ? ("-" + nm.substring(index))
1176 : nm.substring(index);
1177 result = Integer.valueOf(constant, radix);
1178 }
1179 return result;
1180 }
1181
1182 /**
1183 * Compares two {@code Integer} objects numerically.
1184 *
1185 * @param anotherInteger the {@code Integer} to be compared.
1186 * @return the value {@code 0} if this {@code Integer} is
1187 * equal to the argument {@code Integer}; a value less than
1188 * {@code 0} if this {@code Integer} is numerically less
1189 * than the argument {@code Integer}; and a value greater
1190 * than {@code 0} if this {@code Integer} is numerically
1191 * greater than the argument {@code Integer} (signed
1192 * comparison).
1193 * @since 1.2
1194 */
1195 public int compareTo(Integer anotherInteger) {
1196 return compare(this.value, anotherInteger.value);
1197 }
1198
1199 /**
1200 * Compares two {@code int} values numerically.
1201 * The value returned is identical to what would be returned by:
1202 * <pre>
1203 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1204 * </pre>
1205 *
1206 * @param x the first {@code int} to compare
1207 * @param y the second {@code int} to compare
1208 * @return the value {@code 0} if {@code x == y};
1209 * a value less than {@code 0} if {@code x < y}; and
1210 * a value greater than {@code 0} if {@code x > y}
1211 * @since 1.7
1212 */
1213 public static int compare(int x, int y) {
1214 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1215 }
1216
1217 /**
1218 * Compares two {@code int} values numerically treating the values
1219 * as unsigned.
1220 *
1221 * @param x the first {@code int} to compare
1222 * @param y the second {@code int} to compare
1223 * @return the value {@code 0} if {@code x == y}; a value less
1224 * than {@code 0} if {@code x < y} as unsigned values; and
1225 * a value greater than {@code 0} if {@code x > y} as
1226 * unsigned values
1227 * @since 1.8
1228 */
1229 public static int compareUnsigned(int x, int y) {
1230 return compare(x + MIN_VALUE, y + MIN_VALUE);
1231 }
1232
1233 /**
1234 * Converts the argument to a {@code long} by an unsigned
1235 * conversion. In an unsigned conversion to a {@code long}, the
1236 * high-order 32 bits of the {@code long} are zero and the
1237 * low-order 32 bits are equal to the bits of the integer
1238 * argument.
1239 *
1240 * Consequently, zero and positive {@code int} values are mapped
1241 * to a numerically equal {@code long} value and negative {@code
1242 * int} values are mapped to a {@code long} value equal to the
1243 * input plus 2<sup>32</sup>.
1244 *
1245 * @param x the value to convert to an unsigned {@code long}
1246 * @return the argument converted to {@code long} by an unsigned
1247 * conversion
1248 * @since 1.8
1249 */
1250 public static long toUnsignedLong(int x) {
1251 return ((long) x) & 0xffffffffL;
1252 }
1253
1254 /**
1255 * Returns the unsigned quotient of dividing the first argument by
1256 * the second where each argument and the result is interpreted as
1257 * an unsigned value.
1258 *
1259 * <p>Note that in two's complement arithmetic, the three other
1260 * basic arithmetic operations of add, subtract, and multiply are
1261 * bit-wise identical if the two operands are regarded as both
1262 * being signed or both being unsigned. Therefore separate {@code
1263 * addUnsigned}, etc. methods are not provided.
1264 *
1265 * @param dividend the value to be divided
1266 * @param divisor the value doing the dividing
1267 * @return the unsigned quotient of the first argument divided by
1268 * the second argument
1269 * @see #remainderUnsigned
1270 * @since 1.8
1271 */
1272 public static int divideUnsigned(int dividend, int divisor) {
1273 // In lieu of tricky code, for now just use long arithmetic.
1274 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1275 }
1276
1277 /**
1278 * Returns the unsigned remainder from dividing the first argument
1279 * by the second where each argument and the result is interpreted
1280 * as an unsigned value.
1281 *
1282 * @param dividend the value to be divided
1283 * @param divisor the value doing the dividing
1284 * @return the unsigned remainder of the first argument divided by
1285 * the second argument
1286 * @see #divideUnsigned
1287 * @since 1.8
1288 */
1289 public static int remainderUnsigned(int dividend, int divisor) {
1290 // In lieu of tricky code, for now just use long arithmetic.
1291 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1292 }
1293
1294
1295 // Bit twiddling
1296
1297 /**
1298 * The number of bits used to represent an {@code int} value in two's
1299 * complement binary form.
1300 *
1301 * @since 1.5
1302 */
1303 @Native public static final int SIZE = 32;
1304
1305 /**
1306 * The number of bytes used to represent a {@code int} value in two's
1307 * complement binary form.
1308 *
1309 * @since 1.8
1310 */
1311 public static final int BYTES = SIZE / Byte.SIZE;
1312
1313 /**
1314 * Returns an {@code int} value with at most a single one-bit, in the
1315 * position of the highest-order ("leftmost") one-bit in the specified
1316 * {@code int} value. Returns zero if the specified value has no
1317 * one-bits in its two's complement binary representation, that is, if it
1318 * is equal to zero.
1319 *
1320 * @return an {@code int} value with a single one-bit, in the position
1321 * of the highest-order one-bit in the specified value, or zero if
1322 * the specified value is itself equal to zero.
1323 * @since 1.5
1324 */
1325 public static int highestOneBit(int i) {
1326 // HD, Figure 3-1
1327 i |= (i >> 1);
1328 i |= (i >> 2);
1329 i |= (i >> 4);
1330 i |= (i >> 8);
1331 i |= (i >> 16);
1332 return i - (i >>> 1);
1333 }
1334
1335 /**
1336 * Returns an {@code int} value with at most a single one-bit, in the
1337 * position of the lowest-order ("rightmost") one-bit in the specified
1338 * {@code int} value. Returns zero if the specified value has no
1339 * one-bits in its two's complement binary representation, that is, if it
1340 * is equal to zero.
1341 *
1342 * @return an {@code int} value with a single one-bit, in the position
1343 * of the lowest-order one-bit in the specified value, or zero if
1344 * the specified value is itself equal to zero.
1345 * @since 1.5
1346 */
1347 public static int lowestOneBit(int i) {
1348 // HD, Section 2-1
1349 return i & -i;
1350 }
1351
1352 /**
1353 * Returns the number of zero bits preceding the highest-order
1354 * ("leftmost") one-bit in the two's complement binary representation
1355 * of the specified {@code int} value. Returns 32 if the
1356 * specified value has no one-bits in its two's complement representation,
1357 * in other words if it is equal to zero.
1358 *
1359 * <p>Note that this method is closely related to the logarithm base 2.
1360 * For all positive {@code int} values x:
1361 * <ul>
1362 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1363 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1364 * </ul>
1365 *
1366 * @return the number of zero bits preceding the highest-order
1367 * ("leftmost") one-bit in the two's complement binary representation
1368 * of the specified {@code int} value, or 32 if the value
1369 * is equal to zero.
1370 * @since 1.5
1371 */
1372 public static int numberOfLeadingZeros(int i) {
1373 // HD, Figure 5-6
1374 if (i == 0)
1375 return 32;
1376 int n = 1;
1377 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1378 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1379 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1380 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1381 n -= i >>> 31;
1382 return n;
1383 }
1384
1385 /**
1386 * Returns the number of zero bits following the lowest-order ("rightmost")
1387 * one-bit in the two's complement binary representation of the specified
1388 * {@code int} value. Returns 32 if the specified value has no
1389 * one-bits in its two's complement representation, in other words if it is
1390 * equal to zero.
1391 *
1392 * @return the number of zero bits following the lowest-order ("rightmost")
1393 * one-bit in the two's complement binary representation of the
1394 * specified {@code int} value, or 32 if the value is equal
1395 * to zero.
1396 * @since 1.5
1397 */
1398 public static int numberOfTrailingZeros(int i) {
1399 // HD, Figure 5-14
1400 int y;
1401 if (i == 0) return 32;
1402 int n = 31;
1403 y = i <<16; if (y != 0) { n = n -16; i = y; }
1404 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1405 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1406 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1407 return n - ((i << 1) >>> 31);
1408 }
1409
1410 /**
1411 * Returns the number of one-bits in the two's complement binary
1412 * representation of the specified {@code int} value. This function is
1413 * sometimes referred to as the <i>population count</i>.
1414 *
1415 * @return the number of one-bits in the two's complement binary
1416 * representation of the specified {@code int} value.
1417 * @since 1.5
1418 */
1419 public static int bitCount(int i) {
1420 // HD, Figure 5-2
1421 i = i - ((i >>> 1) & 0x55555555);
1422 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1423 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1424 i = i + (i >>> 8);
1425 i = i + (i >>> 16);
1426 return i & 0x3f;
1427 }
1428
1429 /**
1430 * Returns the value obtained by rotating the two's complement binary
1431 * representation of the specified {@code int} value left by the
1432 * specified number of bits. (Bits shifted out of the left hand, or
1433 * high-order, side reenter on the right, or low-order.)
1434 *
1435 * <p>Note that left rotation with a negative distance is equivalent to
1436 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1437 * distance)}. Note also that rotation by any multiple of 32 is a
1438 * no-op, so all but the last five bits of the rotation distance can be
1439 * ignored, even if the distance is negative: {@code rotateLeft(val,
1440 * distance) == rotateLeft(val, distance & 0x1F)}.
1441 *
1442 * @return the value obtained by rotating the two's complement binary
1443 * representation of the specified {@code int} value left by the
1444 * specified number of bits.
1445 * @since 1.5
1446 */
1447 public static int rotateLeft(int i, int distance) {
1448 return (i << distance) | (i >>> -distance);
1449 }
1450
1451 /**
1452 * Returns the value obtained by rotating the two's complement binary
1453 * representation of the specified {@code int} value right by the
1454 * specified number of bits. (Bits shifted out of the right hand, or
1455 * low-order, side reenter on the left, or high-order.)
1456 *
1457 * <p>Note that right rotation with a negative distance is equivalent to
1458 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1459 * distance)}. Note also that rotation by any multiple of 32 is a
1460 * no-op, so all but the last five bits of the rotation distance can be
1461 * ignored, even if the distance is negative: {@code rotateRight(val,
1462 * distance) == rotateRight(val, distance & 0x1F)}.
1463 *
1464 * @return the value obtained by rotating the two's complement binary
1465 * representation of the specified {@code int} value right by the
1466 * specified number of bits.
1467 * @since 1.5
1468 */
1469 public static int rotateRight(int i, int distance) {
1470 return (i >>> distance) | (i << -distance);
1471 }
1472
1473 /**
1474 * Returns the value obtained by reversing the order of the bits in the
1475 * two's complement binary representation of the specified {@code int}
1476 * value.
1477 *
1478 * @return the value obtained by reversing order of the bits in the
1479 * specified {@code int} value.
1480 * @since 1.5
1481 */
1482 public static int reverse(int i) {
1483 // HD, Figure 7-1
1484 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1485 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1486 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1487 i = (i << 24) | ((i & 0xff00) << 8) |
1488 ((i >>> 8) & 0xff00) | (i >>> 24);
1489 return i;
1490 }
1491
1492 /**
1493 * Returns the signum function of the specified {@code int} value. (The
1494 * return value is -1 if the specified value is negative; 0 if the
1495 * specified value is zero; and 1 if the specified value is positive.)
1496 *
1497 * @return the signum function of the specified {@code int} value.
1498 * @since 1.5
1499 */
1500 public static int signum(int i) {
1501 // HD, Section 2-7
1502 return (i >> 31) | (-i >>> 31);
1503 }
1504
1505 /**
1506 * Returns the value obtained by reversing the order of the bytes in the
1507 * two's complement representation of the specified {@code int} value.
1508 *
1509 * @return the value obtained by reversing the bytes in the specified
1510 * {@code int} value.
1511 * @since 1.5
1512 */
1513 public static int reverseBytes(int i) {
1514 return ((i >>> 24) ) |
1515 ((i >> 8) & 0xFF00) |
1516 ((i << 8) & 0xFF0000) |
1517 ((i << 24));
1518 }
1519
1520 /**
1521 * Adds two integers together as per the + operator.
1522 *
1523 * @param a the first operand
1524 * @param b the second operand
1525 * @return the sum of {@code a} and {@code b}
1526 * @see java.util.function.BinaryOperator
1527 * @since 1.8
1528 */
1529 public static int sum(int a, int b) {
1530 return a + b;
1531 }
1532
1533 /**
1534 * Returns the greater of two {@code int} values
1535 * as if by calling {@link Math#max(int, int) Math.max}.
1536 *
1537 * @param a the first operand
1538 * @param b the second operand
1539 * @return the greater of {@code a} and {@code b}
1540 * @see java.util.function.BinaryOperator
1541 * @since 1.8
1542 */
1543 public static int max(int a, int b) {
1544 return Math.max(a, b);
1545 }
1546
1547 /**
1548 * Returns the smaller of two {@code int} values
1549 * as if by calling {@link Math#min(int, int) Math.min}.
1550 *
1551 * @param a the first operand
1552 * @param b the second operand
1553 * @return the smaller of {@code a} and {@code b}
1554 * @see java.util.function.BinaryOperator
1555 * @since 1.8
1556 */
1557 public static int min(int a, int b) {
1558 return Math.min(a, b);
1559 }
1560
1561 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1562 @Native private static final long serialVersionUID = 1360826667806852920L;
1563 }