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.util.Properties;
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 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 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.toString(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 char[] buf = new char[32];
311 int charPos = 32;
312 int radix = 1 << shift;
313 int mask = radix - 1;
314 do {
315 buf[--charPos] = digits[i & mask];
316 i >>>= shift;
317 } while (i != 0);
318
319 return new String(buf, charPos, (32 - charPos));
320 }
321
322
323 final static char [] DigitTens = {
324 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
325 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
326 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
327 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
328 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
329 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
330 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
331 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
332 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
333 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
334 } ;
335
336 final static char [] DigitOnes = {
337 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
338 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
339 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
340 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
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 } ;
348
349 // I use the "invariant division by multiplication" trick to
350 // accelerate Integer.toString. In particular we want to
351 // avoid division by 10.
352 //
353 // The "trick" has roughly the same performance characteristics
354 // as the "classic" Integer.toString code on a non-JIT VM.
355 // The trick avoids .rem and .div calls but has a longer code
356 // path and is thus dominated by dispatch overhead. In the
357 // JIT case the dispatch overhead doesn't exist and the
358 // "trick" is considerably faster than the classic code.
359 //
360 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
361 // sequence.
362 //
363 // RE: Division by Invariant Integers using Multiplication
364 // T Gralund, P Montgomery
365 // ACM PLDI 1994
366 //
367
368 /**
369 * Returns a {@code String} object representing the
370 * specified integer. The argument is converted to signed decimal
371 * representation and returned as a string, exactly as if the
372 * argument and radix 10 were given as arguments to the {@link
373 * #toString(int, int)} method.
374 *
375 * @param i an integer to be converted.
376 * @return a string representation of the argument in base 10.
377 */
378 public static String toString(int i) {
379 if (i == Integer.MIN_VALUE)
380 return "-2147483648";
381 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
382 char[] buf = new char[size];
383 getChars(i, size, buf);
384 return new String(buf, true);
385 }
386
387 /**
388 * Returns a string representation of the argument as an unsigned
389 * decimal value.
390 *
391 * The argument is converted to unsigned decimal representation
392 * and returned as a string exactly as if the argument and radix
393 * 10 were given as arguments to the {@link #toUnsignedString(int,
394 * int)} method.
395 *
396 * @param i an integer to be converted to an unsigned string.
397 * @return an unsigned string representation of the argument.
398 * @see #toUnsignedString(int, int)
399 * @since 1.8
400 */
401 public static String toUnsignedString(int i) {
402 return Long.toString(toUnsignedLong(i));
403 }
404
405 /**
406 * Places characters representing the integer i into the
407 * character array buf. The characters are placed into
408 * the buffer backwards starting with the least significant
409 * digit at the specified index (exclusive), and working
410 * backwards from there.
411 *
412 * Will fail if i == Integer.MIN_VALUE
413 */
414 static void getChars(int i, int index, char[] buf) {
415 int q, r;
416 int charPos = index;
417 char sign = 0;
418
419 if (i < 0) {
420 sign = '-';
421 i = -i;
422 }
423
424 // Generate two digits per iteration
425 while (i >= 65536) {
426 q = i / 100;
427 // really: r = i - (q * 100);
428 r = i - ((q << 6) + (q << 5) + (q << 2));
429 i = q;
430 buf [--charPos] = DigitOnes[r];
431 buf [--charPos] = DigitTens[r];
432 }
433
434 // Fall thru to fast mode for smaller numbers
435 // assert(i <= 65536, i);
436 for (;;) {
437 q = (i * 52429) >>> (16+3);
438 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
439 buf [--charPos] = digits [r];
440 i = q;
441 if (i == 0) break;
442 }
443 if (sign != 0) {
444 buf [--charPos] = sign;
445 }
446 }
447
448 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
449 99999999, 999999999, Integer.MAX_VALUE };
450
451 // Requires positive x
452 static int stringSize(int x) {
453 for (int i=0; ; i++)
454 if (x <= sizeTable[i])
455 return i+1;
456 }
457
458 /**
459 * Parses the string argument as a signed integer in the radix
460 * specified by the second argument. The characters in the string
461 * must all be digits of the specified radix (as determined by
462 * whether {@link java.lang.Character#digit(char, int)} returns a
463 * nonnegative value), except that the first character may be an
464 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
465 * indicate a negative value or an ASCII plus sign {@code '+'}
466 * ({@code '\u005Cu002B'}) to indicate a positive value. The
467 * resulting integer value is returned.
468 *
469 * <p>An exception of type {@code NumberFormatException} is
470 * thrown if any of the following situations occurs:
471 * <ul>
472 * <li>The first argument is {@code null} or is a string of
473 * length zero.
474 *
475 * <li>The radix is either smaller than
476 * {@link java.lang.Character#MIN_RADIX} or
477 * larger than {@link java.lang.Character#MAX_RADIX}.
478 *
479 * <li>Any character of the string is not a digit of the specified
480 * radix, except that the first character may be a minus sign
481 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
482 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
483 * string is longer than length 1.
484 *
485 * <li>The value represented by the string is not a value of type
486 * {@code int}.
487 * </ul>
488 *
489 * <p>Examples:
490 * <blockquote><pre>
491 * parseInt("0", 10) returns 0
492 * parseInt("473", 10) returns 473
493 * parseInt("+42", 10) returns 42
494 * parseInt("-0", 10) returns 0
495 * parseInt("-FF", 16) returns -255
496 * parseInt("1100110", 2) returns 102
497 * parseInt("2147483647", 10) returns 2147483647
498 * parseInt("-2147483648", 10) returns -2147483648
499 * parseInt("2147483648", 10) throws a NumberFormatException
500 * parseInt("99", 8) throws a NumberFormatException
501 * parseInt("Kona", 10) throws a NumberFormatException
502 * parseInt("Kona", 27) returns 411787
503 * </pre></blockquote>
504 *
505 * @param s the {@code String} containing the integer
506 * representation to be parsed
507 * @param radix the radix to be used while parsing {@code s}.
508 * @return the integer represented by the string argument in the
509 * specified radix.
510 * @exception NumberFormatException if the {@code String}
511 * does not contain a parsable {@code int}.
512 */
513 public static int parseInt(String s, int radix)
514 throws NumberFormatException
515 {
516 /*
517 * WARNING: This method may be invoked early during VM initialization
518 * before IntegerCache is initialized. Care must be taken to not use
519 * the valueOf method.
520 */
521
522 if (s == null) {
523 throw new NumberFormatException("null");
524 }
525
526 if (radix < Character.MIN_RADIX) {
527 throw new NumberFormatException("radix " + radix +
528 " less than Character.MIN_RADIX");
529 }
530
531 if (radix > Character.MAX_RADIX) {
532 throw new NumberFormatException("radix " + radix +
533 " greater than Character.MAX_RADIX");
534 }
535
536 int result = 0;
537 boolean negative = false;
538 int i = 0, len = s.length();
539 int limit = -Integer.MAX_VALUE;
540 int multmin;
541 int digit;
542
543 if (len > 0) {
544 char firstChar = s.charAt(0);
545 if (firstChar < '0') { // Possible leading "+" or "-"
546 if (firstChar == '-') {
547 negative = true;
548 limit = Integer.MIN_VALUE;
549 } else if (firstChar != '+')
550 throw NumberFormatException.forInputString(s);
551
552 if (len == 1) // Cannot have lone "+" or "-"
553 throw NumberFormatException.forInputString(s);
554 i++;
555 }
556 multmin = limit / radix;
557 while (i < len) {
558 // Accumulating negatively avoids surprises near MAX_VALUE
559 digit = Character.digit(s.charAt(i++),radix);
560 if (digit < 0) {
561 throw NumberFormatException.forInputString(s);
562 }
563 if (result < multmin) {
564 throw NumberFormatException.forInputString(s);
565 }
566 result *= radix;
567 if (result < limit + digit) {
568 throw NumberFormatException.forInputString(s);
569 }
570 result -= digit;
571 }
572 } else {
573 throw NumberFormatException.forInputString(s);
574 }
575 return negative ? result : -result;
576 }
577
578 /**
579 * Parses the string argument as a signed decimal integer. The
580 * characters in the string must all be decimal digits, except
581 * that the first character may be an ASCII minus sign {@code '-'}
582 * ({@code '\u005Cu002D'}) to indicate a negative value or an
583 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
584 * indicate a positive value. The resulting integer value is
585 * returned, exactly as if the argument and the radix 10 were
586 * given as arguments to the {@link #parseInt(java.lang.String,
587 * int)} method.
588 *
589 * @param s a {@code String} containing the {@code int}
590 * representation to be parsed
591 * @return the integer value represented by the argument in decimal.
592 * @exception NumberFormatException if the string does not contain a
593 * parsable integer.
594 */
595 public static int parseInt(String s) throws NumberFormatException {
596 return parseInt(s,10);
597 }
598
599 /**
600 * Parses the string argument as an unsigned integer in the radix
601 * specified by the second argument. An unsigned integer maps the
602 * values usually associated with negative numbers to positive
603 * numbers larger than {@code MAX_VALUE}.
604 *
605 * The characters in the string must all be digits of the
606 * specified radix (as determined by whether {@link
607 * java.lang.Character#digit(char, int)} returns a nonnegative
608 * value), except that the first character may be an ASCII plus
609 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
610 * integer value is returned.
611 *
612 * <p>An exception of type {@code NumberFormatException} is
613 * thrown if any of the following situations occurs:
614 * <ul>
615 * <li>The first argument is {@code null} or is a string of
616 * length zero.
617 *
618 * <li>The radix is either smaller than
619 * {@link java.lang.Character#MIN_RADIX} or
620 * larger than {@link java.lang.Character#MAX_RADIX}.
621 *
622 * <li>Any character of the string is not a digit of the specified
623 * radix, except that the first character may be a plus sign
624 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
625 * string is longer than length 1.
626 *
627 * <li>The value represented by the string is larger than the
628 * largest unsigned {@code int}, 2<sup>32</sup>-1.
629 *
630 * </ul>
631 *
632 *
633 * @param s the {@code String} containing the unsigned integer
634 * representation to be parsed
635 * @param radix the radix to be used while parsing {@code s}.
636 * @return the integer represented by the string argument in the
637 * specified radix.
638 * @throws NumberFormatException if the {@code String}
639 * does not contain a parsable {@code int}.
640 * @since 1.8
641 */
642 public static int parseUnsignedInt(String s, int radix)
643 throws NumberFormatException {
644 if (s == null) {
645 throw new NumberFormatException("null");
646 }
647
648 int len = s.length();
649 if (len > 0) {
650 char firstChar = s.charAt(0);
651 if (firstChar == '-') {
652 throw new
653 NumberFormatException(String.format("Illegal leading minus sign " +
654 "on unsigned string %s.", s));
655 } else {
656 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
657 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
658 return parseInt(s, radix);
659 } else {
660 long ell = Long.parseLong(s, radix);
661 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
662 return (int) ell;
663 } else {
664 throw new
665 NumberFormatException(String.format("String value %s exceeds " +
666 "range of unsigned int.", s));
667 }
668 }
669 }
670 } else {
671 throw NumberFormatException.forInputString(s);
672 }
673 }
674
675 /**
676 * Parses the string argument as an unsigned decimal integer. The
677 * characters in the string must all be decimal digits, except
678 * that the first character may be an an ASCII plus sign {@code
679 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
680 * is returned, exactly as if the argument and the radix 10 were
681 * given as arguments to the {@link
682 * #parseUnsignedInt(java.lang.String, int)} method.
683 *
684 * @param s a {@code String} containing the unsigned {@code int}
685 * representation to be parsed
686 * @return the unsigned integer value represented by the argument in decimal.
687 * @throws NumberFormatException if the string does not contain a
688 * parsable unsigned integer.
689 * @since 1.8
690 */
691 public static int parseUnsignedInt(String s) throws NumberFormatException {
692 return parseUnsignedInt(s, 10);
693 }
694
695 /**
696 * Returns an {@code Integer} object holding the value
697 * extracted from the specified {@code String} when parsed
698 * with the radix given by the second argument. The first argument
699 * is interpreted as representing a signed integer in the radix
700 * specified by the second argument, exactly as if the arguments
701 * were given to the {@link #parseInt(java.lang.String, int)}
702 * method. The result is an {@code Integer} object that
703 * represents the integer value specified by the string.
704 *
705 * <p>In other words, this method returns an {@code Integer}
706 * object equal to the value of:
707 *
708 * <blockquote>
709 * {@code new Integer(Integer.parseInt(s, radix))}
710 * </blockquote>
711 *
712 * @param s the string to be parsed.
713 * @param radix the radix to be used in interpreting {@code s}
714 * @return an {@code Integer} object holding the value
715 * represented by the string argument in the specified
716 * radix.
717 * @exception NumberFormatException if the {@code String}
718 * does not contain a parsable {@code int}.
719 */
720 public static Integer valueOf(String s, int radix) throws NumberFormatException {
721 return Integer.valueOf(parseInt(s,radix));
722 }
723
724 /**
725 * Returns an {@code Integer} object holding the
726 * value of the specified {@code String}. The argument is
727 * interpreted as representing a signed decimal integer, exactly
728 * as if the argument were given to the {@link
729 * #parseInt(java.lang.String)} method. The result is an
730 * {@code Integer} object that represents the integer value
731 * specified by the string.
732 *
733 * <p>In other words, this method returns an {@code Integer}
734 * object equal to the value of:
735 *
736 * <blockquote>
737 * {@code new Integer(Integer.parseInt(s))}
738 * </blockquote>
739 *
740 * @param s the string to be parsed.
741 * @return an {@code Integer} object holding the value
742 * represented by the string argument.
743 * @exception NumberFormatException if the string cannot be parsed
744 * as an integer.
745 */
746 public static Integer valueOf(String s) throws NumberFormatException {
747 return Integer.valueOf(parseInt(s, 10));
748 }
749
750 /**
751 * Cache to support the object identity semantics of autoboxing for values between
752 * -128 and 127 (inclusive) as required by JLS.
753 *
754 * The cache is initialized on first usage. The size of the cache
755 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
756 * During VM initialization, java.lang.Integer.IntegerCache.high property
757 * may be set and saved in the private system properties in the
758 * sun.misc.VM class.
759 */
760
761 private static class IntegerCache {
762 static final int low = -128;
763 static final int high;
764 static final Integer cache[];
765
766 static {
767 // high value may be configured by property
768 int h = 127;
769 String integerCacheHighPropValue =
770 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
771 if (integerCacheHighPropValue != null) {
772 int i = parseInt(integerCacheHighPropValue);
773 i = Math.max(i, 127);
774 // Maximum array size is Integer.MAX_VALUE
775 h = Math.min(i, Integer.MAX_VALUE - (-low));
776 }
777 high = h;
778
779 cache = new Integer[(high - low) + 1];
780 int j = low;
781 for(int k = 0; k < cache.length; k++)
782 cache[k] = new Integer(j++);
783
784 // range [-128, 127] must be interned (JLS7 5.1.7)
785 assert IntegerCache.high >= 127;
786 }
787
788 private IntegerCache() {}
789 }
790
791 /**
792 * Returns an {@code Integer} instance representing the specified
793 * {@code int} value. If a new {@code Integer} instance is not
794 * required, this method should generally be used in preference to
795 * the constructor {@link #Integer(int)}, as this method is likely
796 * to yield significantly better space and time performance by
797 * caching frequently requested values.
798 *
799 * This method will always cache values in the range -128 to 127,
800 * inclusive, and may cache other values outside of this range.
801 *
802 * @param i an {@code int} value.
803 * @return an {@code Integer} instance representing {@code i}.
804 * @since 1.5
805 */
806 public static Integer valueOf(int i) {
807 if (i >= IntegerCache.low && i <= IntegerCache.high)
808 return IntegerCache.cache[i + (-IntegerCache.low)];
809 return new Integer(i);
810 }
811
812 /**
813 * The value of the {@code Integer}.
814 *
815 * @serial
816 */
817 private final int value;
818
819 /**
820 * Constructs a newly allocated {@code Integer} object that
821 * represents the specified {@code int} value.
822 *
823 * @param value the value to be represented by the
824 * {@code Integer} object.
825 */
826 public Integer(int value) {
827 this.value = value;
828 }
829
830 /**
831 * Constructs a newly allocated {@code Integer} object that
832 * represents the {@code int} value indicated by the
833 * {@code String} parameter. The string is converted to an
834 * {@code int} value in exactly the manner used by the
835 * {@code parseInt} method for radix 10.
836 *
837 * @param s the {@code String} to be converted to an
838 * {@code Integer}.
839 * @exception NumberFormatException if the {@code String} does not
840 * contain a parsable integer.
841 * @see java.lang.Integer#parseInt(java.lang.String, int)
842 */
843 public Integer(String s) throws NumberFormatException {
844 this.value = parseInt(s, 10);
845 }
846
847 /**
848 * Returns the value of this {@code Integer} as a {@code byte}
849 * after a narrowing primitive conversion.
850 * @jls 5.1.3 Narrowing Primitive Conversions
851 */
852 public byte byteValue() {
853 return (byte)value;
854 }
855
856 /**
857 * Returns the value of this {@code Integer} as a {@code short}
858 * after a narrowing primitive conversion.
859 * @jls 5.1.3 Narrowing Primitive Conversions
860 */
861 public short shortValue() {
862 return (short)value;
863 }
864
865 /**
866 * Returns the value of this {@code Integer} as an
867 * {@code int}.
868 */
869 public int intValue() {
870 return value;
871 }
872
873 /**
874 * Returns the value of this {@code Integer} as a {@code long}
875 * after a widening primitive conversion.
876 * @jls 5.1.2 Widening Primitive Conversions
877 */
878 public long longValue() {
879 return (long)value;
880 }
881
882 /**
883 * Returns the value of this {@code Integer} as a {@code float}
884 * after a widening primitive conversion.
885 * @jls 5.1.2 Widening Primitive Conversions
886 */
887 public float floatValue() {
888 return (float)value;
889 }
890
891 /**
892 * Returns the value of this {@code Integer} as a {@code double}
893 * after a widening primitive conversion.
894 * @jls 5.1.2 Widening Primitive Conversions
895 */
896 public double doubleValue() {
897 return (double)value;
898 }
899
900 /**
901 * Returns a {@code String} object representing this
902 * {@code Integer}'s value. The value is converted to signed
903 * decimal representation and returned as a string, exactly as if
904 * the integer value were given as an argument to the {@link
905 * java.lang.Integer#toString(int)} method.
906 *
907 * @return a string representation of the value of this object in
908 * base 10.
909 */
910 public String toString() {
911 return toString(value);
912 }
913
914 /**
915 * Returns a hash code for this {@code Integer}.
916 *
917 * @return a hash code value for this object, equal to the
918 * primitive {@code int} value represented by this
919 * {@code Integer} object.
920 */
921 public int hashCode() {
922 return value;
923 }
924
925 /**
926 * Compares this object to the specified object. The result is
927 * {@code true} if and only if the argument is not
928 * {@code null} and is an {@code Integer} object that
929 * contains the same {@code int} value as this object.
930 *
931 * @param obj the object to compare with.
932 * @return {@code true} if the objects are the same;
933 * {@code false} otherwise.
934 */
935 public boolean equals(Object obj) {
936 if (obj instanceof Integer) {
937 return value == ((Integer)obj).intValue();
938 }
939 return false;
940 }
941
942 /**
943 * Determines the integer value of the system property with the
944 * specified name.
945 *
946 * <p>The first argument is treated as the name of a system
947 * property. System properties are accessible through the {@link
948 * java.lang.System#getProperty(java.lang.String)} method. The
949 * string value of this property is then interpreted as an integer
950 * value using the grammar supported by {@link Integer#decode decode} and
951 * an {@code Integer} object representing this value is returned.
952 *
953 * <p>If there is no property with the specified name, if the
954 * specified name is empty or {@code null}, or if the property
955 * does not have the correct numeric format, then {@code null} is
956 * returned.
957 *
958 * <p>In other words, this method returns an {@code Integer}
959 * object equal to the value of:
960 *
961 * <blockquote>
962 * {@code getInteger(nm, null)}
963 * </blockquote>
964 *
965 * @param nm property name.
966 * @return the {@code Integer} value of the property.
967 * @throws SecurityException for the same reasons as
968 * {@link System#getProperty(String) System.getProperty}
969 * @see java.lang.System#getProperty(java.lang.String)
970 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
971 */
972 public static Integer getInteger(String nm) {
973 return getInteger(nm, null);
974 }
975
976 /**
977 * Determines the integer value of the system property with the
978 * specified name.
979 *
980 * <p>The first argument is treated as the name of a system
981 * property. System properties are accessible through the {@link
982 * java.lang.System#getProperty(java.lang.String)} method. The
983 * string value of this property is then interpreted as an integer
984 * value using the grammar supported by {@link Integer#decode decode} and
985 * an {@code Integer} object representing this value is returned.
986 *
987 * <p>The second argument is the default value. An {@code Integer} object
988 * that represents the value of the second argument is returned if there
989 * is no property of the specified name, if the property does not have
990 * the correct numeric format, or if the specified name is empty or
991 * {@code null}.
992 *
993 * <p>In other words, this method returns an {@code Integer} object
994 * equal to the value of:
995 *
996 * <blockquote>
997 * {@code getInteger(nm, new Integer(val))}
998 * </blockquote>
999 *
1000 * but in practice it may be implemented in a manner such as:
1001 *
1002 * <blockquote><pre>
1003 * Integer result = getInteger(nm, null);
1004 * return (result == null) ? new Integer(val) : result;
1005 * </pre></blockquote>
1006 *
1007 * to avoid the unnecessary allocation of an {@code Integer}
1008 * object when the default value is not needed.
1009 *
1010 * @param nm property name.
1011 * @param val default value.
1012 * @return the {@code Integer} value of the property.
1013 * @throws SecurityException for the same reasons as
1014 * {@link System#getProperty(String) System.getProperty}
1015 * @see java.lang.System#getProperty(java.lang.String)
1016 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1017 */
1018 public static Integer getInteger(String nm, int val) {
1019 Integer result = getInteger(nm, null);
1020 return (result == null) ? Integer.valueOf(val) : result;
1021 }
1022
1023 /**
1024 * Returns the integer value of the system property with the
1025 * specified name. The first argument is treated as the name of a
1026 * system property. System properties are accessible through the
1027 * {@link java.lang.System#getProperty(java.lang.String)} method.
1028 * The string value of this property is then interpreted as an
1029 * integer value, as per the {@link Integer#decode decode} method,
1030 * and an {@code Integer} object representing this value is
1031 * returned; in summary:
1032 *
1033 * <ul><li>If the property value begins with the two ASCII characters
1034 * {@code 0x} or the ASCII character {@code #}, not
1035 * followed by a minus sign, then the rest of it is parsed as a
1036 * hexadecimal integer exactly as by the method
1037 * {@link #valueOf(java.lang.String, int)} with radix 16.
1038 * <li>If the property value begins with the ASCII character
1039 * {@code 0} followed by another character, it is parsed as an
1040 * octal integer exactly as by the method
1041 * {@link #valueOf(java.lang.String, int)} with radix 8.
1042 * <li>Otherwise, the property value is parsed as a decimal integer
1043 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1044 * with radix 10.
1045 * </ul>
1046 *
1047 * <p>The second argument is the default value. The default value is
1048 * returned if there is no property of the specified name, if the
1049 * property does not have the correct numeric format, or if the
1050 * specified name is empty or {@code null}.
1051 *
1052 * @param nm property name.
1053 * @param val default value.
1054 * @return the {@code Integer} value of the property.
1055 * @throws SecurityException for the same reasons as
1056 * {@link System#getProperty(String) System.getProperty}
1057 * @see System#getProperty(java.lang.String)
1058 * @see System#getProperty(java.lang.String, java.lang.String)
1059 */
1060 public static Integer getInteger(String nm, Integer val) {
1061 String v = null;
1062 try {
1063 v = System.getProperty(nm);
1064 } catch (IllegalArgumentException | NullPointerException e) {
1065 }
1066 if (v != null) {
1067 try {
1068 return Integer.decode(v);
1069 } catch (NumberFormatException e) {
1070 }
1071 }
1072 return val;
1073 }
1074
1075 /**
1076 * Decodes a {@code String} into an {@code Integer}.
1077 * Accepts decimal, hexadecimal, and octal numbers given
1078 * by the following grammar:
1079 *
1080 * <blockquote>
1081 * <dl>
1082 * <dt><i>DecodableString:</i>
1083 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1084 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1085 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1086 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1087 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1088 * <p>
1089 * <dt><i>Sign:</i>
1090 * <dd>{@code -}
1091 * <dd>{@code +}
1092 * </dl>
1093 * </blockquote>
1094 *
1095 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1096 * are as defined in section 3.10.1 of
1097 * <cite>The Java™ Language Specification</cite>,
1098 * except that underscores are not accepted between digits.
1099 *
1100 * <p>The sequence of characters following an optional
1101 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1102 * "{@code #}", or leading zero) is parsed as by the {@code
1103 * Integer.parseInt} method with the indicated radix (10, 16, or
1104 * 8). This sequence of characters must represent a positive
1105 * value or a {@link NumberFormatException} will be thrown. The
1106 * result is negated if first character of the specified {@code
1107 * String} is the minus sign. No whitespace characters are
1108 * permitted in the {@code String}.
1109 *
1110 * @param nm the {@code String} to decode.
1111 * @return an {@code Integer} object holding the {@code int}
1112 * value represented by {@code nm}
1113 * @exception NumberFormatException if the {@code String} does not
1114 * contain a parsable integer.
1115 * @see java.lang.Integer#parseInt(java.lang.String, int)
1116 */
1117 public static Integer decode(String nm) throws NumberFormatException {
1118 int radix = 10;
1119 int index = 0;
1120 boolean negative = false;
1121 Integer result;
1122
1123 if (nm.length() == 0)
1124 throw new NumberFormatException("Zero length string");
1125 char firstChar = nm.charAt(0);
1126 // Handle sign, if present
1127 if (firstChar == '-') {
1128 negative = true;
1129 index++;
1130 } else if (firstChar == '+')
1131 index++;
1132
1133 // Handle radix specifier, if present
1134 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1135 index += 2;
1136 radix = 16;
1137 }
1138 else if (nm.startsWith("#", index)) {
1139 index ++;
1140 radix = 16;
1141 }
1142 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1143 index ++;
1144 radix = 8;
1145 }
1146
1147 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1148 throw new NumberFormatException("Sign character in wrong position");
1149
1150 try {
1151 result = Integer.valueOf(nm.substring(index), radix);
1152 result = negative ? Integer.valueOf(-result.intValue()) : result;
1153 } catch (NumberFormatException e) {
1154 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1155 // handles this case, and causes any genuine format error to be
1156 // rethrown.
1157 String constant = negative ? ("-" + nm.substring(index))
1158 : nm.substring(index);
1159 result = Integer.valueOf(constant, radix);
1160 }
1161 return result;
1162 }
1163
1164 /**
1165 * Compares two {@code Integer} objects numerically.
1166 *
1167 * @param anotherInteger the {@code Integer} to be compared.
1168 * @return the value {@code 0} if this {@code Integer} is
1169 * equal to the argument {@code Integer}; a value less than
1170 * {@code 0} if this {@code Integer} is numerically less
1171 * than the argument {@code Integer}; and a value greater
1172 * than {@code 0} if this {@code Integer} is numerically
1173 * greater than the argument {@code Integer} (signed
1174 * comparison).
1175 * @since 1.2
1176 */
1177 public int compareTo(Integer anotherInteger) {
1178 return compare(this.value, anotherInteger.value);
1179 }
1180
1181 /**
1182 * Compares two {@code int} values numerically.
1183 * The value returned is identical to what would be returned by:
1184 * <pre>
1185 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1186 * </pre>
1187 *
1188 * @param x the first {@code int} to compare
1189 * @param y the second {@code int} to compare
1190 * @return the value {@code 0} if {@code x == y};
1191 * a value less than {@code 0} if {@code x < y}; and
1192 * a value greater than {@code 0} if {@code x > y}
1193 * @since 1.7
1194 */
1195 public static int compare(int x, int y) {
1196 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1197 }
1198
1199 /**
1200 * Compares two {@code int} values numerically treating the values
1201 * as unsigned.
1202 *
1203 * @param x the first {@code int} to compare
1204 * @param y the second {@code int} to compare
1205 * @return the value {@code 0} if {@code x == y}; a value less
1206 * than {@code 0} if {@code x < y} as unsigned values; and
1207 * a value greater than {@code 0} if {@code x > y} as
1208 * unsigned values
1209 * @since 1.8
1210 */
1211 public static int compareUnsigned(int x, int y) {
1212 return compare(x + MIN_VALUE, y + MIN_VALUE);
1213 }
1214
1215 /**
1216 * Converts the argument to a {@code long} by an unsigned
1217 * conversion. In an unsigned conversion to a {@code long}, the
1218 * high-order 32 bits of the {@code long} are zero and the
1219 * low-order 32 bits are equal to the bits of the integer
1220 * argument.
1221 *
1222 * Consequently, zero and positive {@code int} values are mapped
1223 * to a numerically equal {@code long} value and negative {@code
1224 * int} values are mapped to a {@code long} value equal to the
1225 * input plus 2<sup>32</sup>.
1226 *
1227 * @param x the value to convert to an unsigned {@code long}
1228 * @return the argument converted to {@code long} by an unsigned
1229 * conversion
1230 * @since 1.8
1231 */
1232 public static long toUnsignedLong(int x) {
1233 return ((long) x) & 0xffffffffL;
1234 }
1235
1236 /**
1237 * Returns the unsigned quotient of dividing the first argument by
1238 * the second where each argument and the result is interpreted as
1239 * an unsigned value.
1240 *
1241 * <p>Note that in two's complement arithmetic, the three other
1242 * basic arithmetic operations of add, subtract, and multiply are
1243 * bit-wise identical if the two operands are regarded as both
1244 * being signed or both being unsigned. Therefore separate {@code
1245 * addUnsigned}, etc. methods are not provided.
1246 *
1247 * @param dividend the value to be divided
1248 * @param divisor the value doing the dividing
1249 * @return the unsigned quotient of the first argument divided by
1250 * the second argument
1251 * @see #remainderUnsigned
1252 * @since 1.8
1253 */
1254 public static int divideUnsigned(int dividend, int divisor) {
1255 // In lieu of tricky code, for now just use long arithmetic.
1256 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1257 }
1258
1259 /**
1260 * Returns the unsigned remainder from dividing the first argument
1261 * by the second where each argument and the result is interpreted
1262 * as an unsigned value.
1263 *
1264 * @param dividend the value to be divided
1265 * @param divisor the value doing the dividing
1266 * @return the unsigned remainder of the first argument divided by
1267 * the second argument
1268 * @see #divideUnsigned
1269 * @since 1.8
1270 */
1271 public static int remainderUnsigned(int dividend, int divisor) {
1272 // In lieu of tricky code, for now just use long arithmetic.
1273 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1274 }
1275
1276
1277 // Bit twiddling
1278
1279 /**
1280 * The number of bits used to represent an {@code int} value in two's
1281 * complement binary form.
1282 *
1283 * @since 1.5
1284 */
1285 public static final int SIZE = 32;
1286
1287 /**
1288 * Returns an {@code int} value with at most a single one-bit, in the
1289 * position of the highest-order ("leftmost") one-bit in the specified
1290 * {@code int} value. Returns zero if the specified value has no
1291 * one-bits in its two's complement binary representation, that is, if it
1292 * is equal to zero.
1293 *
1294 * @return an {@code int} value with a single one-bit, in the position
1295 * of the highest-order one-bit in the specified value, or zero if
1296 * the specified value is itself equal to zero.
1297 * @since 1.5
1298 */
1299 public static int highestOneBit(int i) {
1300 // HD, Figure 3-1
1301 i |= (i >> 1);
1302 i |= (i >> 2);
1303 i |= (i >> 4);
1304 i |= (i >> 8);
1305 i |= (i >> 16);
1306 return i - (i >>> 1);
1307 }
1308
1309 /**
1310 * Returns an {@code int} value with at most a single one-bit, in the
1311 * position of the lowest-order ("rightmost") one-bit in the specified
1312 * {@code int} value. Returns zero if the specified value has no
1313 * one-bits in its two's complement binary representation, that is, if it
1314 * is equal to zero.
1315 *
1316 * @return an {@code int} value with a single one-bit, in the position
1317 * of the lowest-order one-bit in the specified value, or zero if
1318 * the specified value is itself equal to zero.
1319 * @since 1.5
1320 */
1321 public static int lowestOneBit(int i) {
1322 // HD, Section 2-1
1323 return i & -i;
1324 }
1325
1326 /**
1327 * Returns the number of zero bits preceding the highest-order
1328 * ("leftmost") one-bit in the two's complement binary representation
1329 * of the specified {@code int} value. Returns 32 if the
1330 * specified value has no one-bits in its two's complement representation,
1331 * in other words if it is equal to zero.
1332 *
1333 * <p>Note that this method is closely related to the logarithm base 2.
1334 * For all positive {@code int} values x:
1335 * <ul>
1336 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1337 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1338 * </ul>
1339 *
1340 * @return the number of zero bits preceding the highest-order
1341 * ("leftmost") one-bit in the two's complement binary representation
1342 * of the specified {@code int} value, or 32 if the value
1343 * is equal to zero.
1344 * @since 1.5
1345 */
1346 public static int numberOfLeadingZeros(int i) {
1347 // HD, Figure 5-6
1348 if (i == 0)
1349 return 32;
1350 int n = 1;
1351 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1352 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1353 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1354 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1355 n -= i >>> 31;
1356 return n;
1357 }
1358
1359 /**
1360 * Returns the number of zero bits following the lowest-order ("rightmost")
1361 * one-bit in the two's complement binary representation of the specified
1362 * {@code int} value. Returns 32 if the specified value has no
1363 * one-bits in its two's complement representation, in other words if it is
1364 * equal to zero.
1365 *
1366 * @return the number of zero bits following the lowest-order ("rightmost")
1367 * one-bit in the two's complement binary representation of the
1368 * specified {@code int} value, or 32 if the value is equal
1369 * to zero.
1370 * @since 1.5
1371 */
1372 public static int numberOfTrailingZeros(int i) {
1373 // HD, Figure 5-14
1374 int y;
1375 if (i == 0) return 32;
1376 int n = 31;
1377 y = i <<16; if (y != 0) { n = n -16; i = y; }
1378 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1379 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1380 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1381 return n - ((i << 1) >>> 31);
1382 }
1383
1384 /**
1385 * Returns the number of one-bits in the two's complement binary
1386 * representation of the specified {@code int} value. This function is
1387 * sometimes referred to as the <i>population count</i>.
1388 *
1389 * @return the number of one-bits in the two's complement binary
1390 * representation of the specified {@code int} value.
1391 * @since 1.5
1392 */
1393 public static int bitCount(int i) {
1394 // HD, Figure 5-2
1395 i = i - ((i >>> 1) & 0x55555555);
1396 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1397 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1398 i = i + (i >>> 8);
1399 i = i + (i >>> 16);
1400 return i & 0x3f;
1401 }
1402
1403 /**
1404 * Returns the value obtained by rotating the two's complement binary
1405 * representation of the specified {@code int} value left by the
1406 * specified number of bits. (Bits shifted out of the left hand, or
1407 * high-order, side reenter on the right, or low-order.)
1408 *
1409 * <p>Note that left rotation with a negative distance is equivalent to
1410 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1411 * distance)}. Note also that rotation by any multiple of 32 is a
1412 * no-op, so all but the last five bits of the rotation distance can be
1413 * ignored, even if the distance is negative: {@code rotateLeft(val,
1414 * distance) == rotateLeft(val, distance & 0x1F)}.
1415 *
1416 * @return the value obtained by rotating the two's complement binary
1417 * representation of the specified {@code int} value left by the
1418 * specified number of bits.
1419 * @since 1.5
1420 */
1421 public static int rotateLeft(int i, int distance) {
1422 return (i << distance) | (i >>> -distance);
1423 }
1424
1425 /**
1426 * Returns the value obtained by rotating the two's complement binary
1427 * representation of the specified {@code int} value right by the
1428 * specified number of bits. (Bits shifted out of the right hand, or
1429 * low-order, side reenter on the left, or high-order.)
1430 *
1431 * <p>Note that right rotation with a negative distance is equivalent to
1432 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1433 * distance)}. Note also that rotation by any multiple of 32 is a
1434 * no-op, so all but the last five bits of the rotation distance can be
1435 * ignored, even if the distance is negative: {@code rotateRight(val,
1436 * distance) == rotateRight(val, distance & 0x1F)}.
1437 *
1438 * @return the value obtained by rotating the two's complement binary
1439 * representation of the specified {@code int} value right by the
1440 * specified number of bits.
1441 * @since 1.5
1442 */
1443 public static int rotateRight(int i, int distance) {
1444 return (i >>> distance) | (i << -distance);
1445 }
1446
1447 /**
1448 * Returns the value obtained by reversing the order of the bits in the
1449 * two's complement binary representation of the specified {@code int}
1450 * value.
1451 *
1452 * @return the value obtained by reversing order of the bits in the
1453 * specified {@code int} value.
1454 * @since 1.5
1455 */
1456 public static int reverse(int i) {
1457 // HD, Figure 7-1
1458 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1459 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1460 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1461 i = (i << 24) | ((i & 0xff00) << 8) |
1462 ((i >>> 8) & 0xff00) | (i >>> 24);
1463 return i;
1464 }
1465
1466 /**
1467 * Returns the signum function of the specified {@code int} value. (The
1468 * return value is -1 if the specified value is negative; 0 if the
1469 * specified value is zero; and 1 if the specified value is positive.)
1470 *
1471 * @return the signum function of the specified {@code int} value.
1472 * @since 1.5
1473 */
1474 public static int signum(int i) {
1475 // HD, Section 2-7
1476 return (i >> 31) | (-i >>> 31);
1477 }
1478
1479 /**
1480 * Returns the value obtained by reversing the order of the bytes in the
1481 * two's complement representation of the specified {@code int} value.
1482 *
1483 * @return the value obtained by reversing the bytes in the specified
1484 * {@code int} value.
1485 * @since 1.5
1486 */
1487 public static int reverseBytes(int i) {
1488 return ((i >>> 24) ) |
1489 ((i >> 8) & 0xFF00) |
1490 ((i << 8) & 0xFF0000) |
1491 ((i << 24));
1492 }
1493
1494 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1495 private static final long serialVersionUID = 1360826667806852920L;
1496 }