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 @Override
922 public int hashCode() {
923 return Integer.hashCode(value);
924 }
925
926 /**
927 * Returns a hash code for a {@code int} value; compatible with
928 * {@code Integer.hashCode()}.
929 *
930 * @since 1.8
931 *
932 * @return a hash code value for a {@code int} value.
933 */
934 public static int hashCode(int value) {
935 return value;
936 }
937
938 /**
939 * Compares this object to the specified object. The result is
940 * {@code true} if and only if the argument is not
941 * {@code null} and is an {@code Integer} object that
942 * contains the same {@code int} value as this object.
943 *
944 * @param obj the object to compare with.
945 * @return {@code true} if the objects are the same;
946 * {@code false} otherwise.
947 */
948 public boolean equals(Object obj) {
949 if (obj instanceof Integer) {
950 return value == ((Integer)obj).intValue();
951 }
952 return false;
953 }
954
955 /**
956 * Determines the integer value of the system property with the
957 * specified name.
958 *
959 * <p>The first argument is treated as the name of a system
960 * property. System properties are accessible through the {@link
961 * java.lang.System#getProperty(java.lang.String)} method. The
962 * string value of this property is then interpreted as an integer
963 * value using the grammar supported by {@link Integer#decode decode} and
964 * an {@code Integer} object representing this value is returned.
965 *
966 * <p>If there is no property with the specified name, if the
967 * specified name is empty or {@code null}, or if the property
968 * does not have the correct numeric format, then {@code null} is
969 * returned.
970 *
971 * <p>In other words, this method returns an {@code Integer}
972 * object equal to the value of:
973 *
974 * <blockquote>
975 * {@code getInteger(nm, null)}
976 * </blockquote>
977 *
978 * @param nm property name.
979 * @return the {@code Integer} value of the property.
980 * @throws SecurityException for the same reasons as
981 * {@link System#getProperty(String) System.getProperty}
982 * @see java.lang.System#getProperty(java.lang.String)
983 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
984 */
985 public static Integer getInteger(String nm) {
986 return getInteger(nm, null);
987 }
988
989 /**
990 * Determines the integer value of the system property with the
991 * specified name.
992 *
993 * <p>The first argument is treated as the name of a system
994 * property. System properties are accessible through the {@link
995 * java.lang.System#getProperty(java.lang.String)} method. The
996 * string value of this property is then interpreted as an integer
997 * value using the grammar supported by {@link Integer#decode decode} and
998 * an {@code Integer} object representing this value is returned.
999 *
1000 * <p>The second argument is the default value. An {@code Integer} object
1001 * that represents the value of the second argument is returned if there
1002 * is no property of the specified name, if the property does not have
1003 * the correct numeric format, or if the specified name is empty or
1004 * {@code null}.
1005 *
1006 * <p>In other words, this method returns an {@code Integer} object
1007 * equal to the value of:
1008 *
1009 * <blockquote>
1010 * {@code getInteger(nm, new Integer(val))}
1011 * </blockquote>
1012 *
1013 * but in practice it may be implemented in a manner such as:
1014 *
1015 * <blockquote><pre>
1016 * Integer result = getInteger(nm, null);
1017 * return (result == null) ? new Integer(val) : result;
1018 * </pre></blockquote>
1019 *
1020 * to avoid the unnecessary allocation of an {@code Integer}
1021 * object when the default value is not needed.
1022 *
1023 * @param nm property name.
1024 * @param val default value.
1025 * @return the {@code Integer} value of the property.
1026 * @throws SecurityException for the same reasons as
1027 * {@link System#getProperty(String) System.getProperty}
1028 * @see java.lang.System#getProperty(java.lang.String)
1029 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1030 */
1031 public static Integer getInteger(String nm, int val) {
1032 Integer result = getInteger(nm, null);
1033 return (result == null) ? Integer.valueOf(val) : result;
1034 }
1035
1036 /**
1037 * Returns the integer value of the system property with the
1038 * specified name. The first argument is treated as the name of a
1039 * system property. System properties are accessible through the
1040 * {@link java.lang.System#getProperty(java.lang.String)} method.
1041 * The string value of this property is then interpreted as an
1042 * integer value, as per the {@link Integer#decode decode} method,
1043 * and an {@code Integer} object representing this value is
1044 * returned; in summary:
1045 *
1046 * <ul><li>If the property value begins with the two ASCII characters
1047 * {@code 0x} or the ASCII character {@code #}, not
1048 * followed by a minus sign, then the rest of it is parsed as a
1049 * hexadecimal integer exactly as by the method
1050 * {@link #valueOf(java.lang.String, int)} with radix 16.
1051 * <li>If the property value begins with the ASCII character
1052 * {@code 0} followed by another character, it is parsed as an
1053 * octal integer exactly as by the method
1054 * {@link #valueOf(java.lang.String, int)} with radix 8.
1055 * <li>Otherwise, the property value is parsed as a decimal integer
1056 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1057 * with radix 10.
1058 * </ul>
1059 *
1060 * <p>The second argument is the default value. The default value is
1061 * returned if there is no property of the specified name, if the
1062 * property does not have the correct numeric format, or if the
1063 * specified name is empty or {@code null}.
1064 *
1065 * @param nm property name.
1066 * @param val default value.
1067 * @return the {@code Integer} value of the property.
1068 * @throws SecurityException for the same reasons as
1069 * {@link System#getProperty(String) System.getProperty}
1070 * @see System#getProperty(java.lang.String)
1071 * @see System#getProperty(java.lang.String, java.lang.String)
1072 */
1073 public static Integer getInteger(String nm, Integer val) {
1074 String v = null;
1075 try {
1076 v = System.getProperty(nm);
1077 } catch (IllegalArgumentException | NullPointerException e) {
1078 }
1079 if (v != null) {
1080 try {
1081 return Integer.decode(v);
1082 } catch (NumberFormatException e) {
1083 }
1084 }
1085 return val;
1086 }
1087
1088 /**
1089 * Decodes a {@code String} into an {@code Integer}.
1090 * Accepts decimal, hexadecimal, and octal numbers given
1091 * by the following grammar:
1092 *
1093 * <blockquote>
1094 * <dl>
1095 * <dt><i>DecodableString:</i>
1096 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1097 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1098 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1099 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1100 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1101 * <p>
1102 * <dt><i>Sign:</i>
1103 * <dd>{@code -}
1104 * <dd>{@code +}
1105 * </dl>
1106 * </blockquote>
1107 *
1108 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1109 * are as defined in section 3.10.1 of
1110 * <cite>The Java™ Language Specification</cite>,
1111 * except that underscores are not accepted between digits.
1112 *
1113 * <p>The sequence of characters following an optional
1114 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1115 * "{@code #}", or leading zero) is parsed as by the {@code
1116 * Integer.parseInt} method with the indicated radix (10, 16, or
1117 * 8). This sequence of characters must represent a positive
1118 * value or a {@link NumberFormatException} will be thrown. The
1119 * result is negated if first character of the specified {@code
1120 * String} is the minus sign. No whitespace characters are
1121 * permitted in the {@code String}.
1122 *
1123 * @param nm the {@code String} to decode.
1124 * @return an {@code Integer} object holding the {@code int}
1125 * value represented by {@code nm}
1126 * @exception NumberFormatException if the {@code String} does not
1127 * contain a parsable integer.
1128 * @see java.lang.Integer#parseInt(java.lang.String, int)
1129 */
1130 public static Integer decode(String nm) throws NumberFormatException {
1131 int radix = 10;
1132 int index = 0;
1133 boolean negative = false;
1134 Integer result;
1135
1136 if (nm.length() == 0)
1137 throw new NumberFormatException("Zero length string");
1138 char firstChar = nm.charAt(0);
1139 // Handle sign, if present
1140 if (firstChar == '-') {
1141 negative = true;
1142 index++;
1143 } else if (firstChar == '+')
1144 index++;
1145
1146 // Handle radix specifier, if present
1147 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1148 index += 2;
1149 radix = 16;
1150 }
1151 else if (nm.startsWith("#", index)) {
1152 index ++;
1153 radix = 16;
1154 }
1155 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1156 index ++;
1157 radix = 8;
1158 }
1159
1160 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1161 throw new NumberFormatException("Sign character in wrong position");
1162
1163 try {
1164 result = Integer.valueOf(nm.substring(index), radix);
1165 result = negative ? Integer.valueOf(-result.intValue()) : result;
1166 } catch (NumberFormatException e) {
1167 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1168 // handles this case, and causes any genuine format error to be
1169 // rethrown.
1170 String constant = negative ? ("-" + nm.substring(index))
1171 : nm.substring(index);
1172 result = Integer.valueOf(constant, radix);
1173 }
1174 return result;
1175 }
1176
1177 /**
1178 * Compares two {@code Integer} objects numerically.
1179 *
1180 * @param anotherInteger the {@code Integer} to be compared.
1181 * @return the value {@code 0} if this {@code Integer} is
1182 * equal to the argument {@code Integer}; a value less than
1183 * {@code 0} if this {@code Integer} is numerically less
1184 * than the argument {@code Integer}; and a value greater
1185 * than {@code 0} if this {@code Integer} is numerically
1186 * greater than the argument {@code Integer} (signed
1187 * comparison).
1188 * @since 1.2
1189 */
1190 public int compareTo(Integer anotherInteger) {
1191 return compare(this.value, anotherInteger.value);
1192 }
1193
1194 /**
1195 * Compares two {@code int} values numerically.
1196 * The value returned is identical to what would be returned by:
1197 * <pre>
1198 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1199 * </pre>
1200 *
1201 * @param x the first {@code int} to compare
1202 * @param y the second {@code int} to compare
1203 * @return the value {@code 0} if {@code x == y};
1204 * a value less than {@code 0} if {@code x < y}; and
1205 * a value greater than {@code 0} if {@code x > y}
1206 * @since 1.7
1207 */
1208 public static int compare(int x, int y) {
1209 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1210 }
1211
1212 /**
1213 * Compares two {@code int} values numerically treating the values
1214 * as unsigned.
1215 *
1216 * @param x the first {@code int} to compare
1217 * @param y the second {@code int} to compare
1218 * @return the value {@code 0} if {@code x == y}; a value less
1219 * than {@code 0} if {@code x < y} as unsigned values; and
1220 * a value greater than {@code 0} if {@code x > y} as
1221 * unsigned values
1222 * @since 1.8
1223 */
1224 public static int compareUnsigned(int x, int y) {
1225 return compare(x + MIN_VALUE, y + MIN_VALUE);
1226 }
1227
1228 /**
1229 * Converts the argument to a {@code long} by an unsigned
1230 * conversion. In an unsigned conversion to a {@code long}, the
1231 * high-order 32 bits of the {@code long} are zero and the
1232 * low-order 32 bits are equal to the bits of the integer
1233 * argument.
1234 *
1235 * Consequently, zero and positive {@code int} values are mapped
1236 * to a numerically equal {@code long} value and negative {@code
1237 * int} values are mapped to a {@code long} value equal to the
1238 * input plus 2<sup>32</sup>.
1239 *
1240 * @param x the value to convert to an unsigned {@code long}
1241 * @return the argument converted to {@code long} by an unsigned
1242 * conversion
1243 * @since 1.8
1244 */
1245 public static long toUnsignedLong(int x) {
1246 return ((long) x) & 0xffffffffL;
1247 }
1248
1249 /**
1250 * Returns the unsigned quotient of dividing the first argument by
1251 * the second where each argument and the result is interpreted as
1252 * an unsigned value.
1253 *
1254 * <p>Note that in two's complement arithmetic, the three other
1255 * basic arithmetic operations of add, subtract, and multiply are
1256 * bit-wise identical if the two operands are regarded as both
1257 * being signed or both being unsigned. Therefore separate {@code
1258 * addUnsigned}, etc. methods are not provided.
1259 *
1260 * @param dividend the value to be divided
1261 * @param divisor the value doing the dividing
1262 * @return the unsigned quotient of the first argument divided by
1263 * the second argument
1264 * @see #remainderUnsigned
1265 * @since 1.8
1266 */
1267 public static int divideUnsigned(int dividend, int divisor) {
1268 // In lieu of tricky code, for now just use long arithmetic.
1269 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1270 }
1271
1272 /**
1273 * Returns the unsigned remainder from dividing the first argument
1274 * by the second where each argument and the result is interpreted
1275 * as an unsigned value.
1276 *
1277 * @param dividend the value to be divided
1278 * @param divisor the value doing the dividing
1279 * @return the unsigned remainder of the first argument divided by
1280 * the second argument
1281 * @see #divideUnsigned
1282 * @since 1.8
1283 */
1284 public static int remainderUnsigned(int dividend, int divisor) {
1285 // In lieu of tricky code, for now just use long arithmetic.
1286 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1287 }
1288
1289
1290 // Bit twiddling
1291
1292 /**
1293 * The number of bits used to represent an {@code int} value in two's
1294 * complement binary form.
1295 *
1296 * @since 1.5
1297 */
1298 public static final int SIZE = 32;
1299
1300 /**
1301 * The number of bytes used to represent a {@code int} value in two's
1302 * complement binary form.
1303 *
1304 * @since 1.8
1305 */
1306 public static final int BYTES = SIZE / Byte.SIZE;
1307
1308 /**
1309 * Returns an {@code int} value with at most a single one-bit, in the
1310 * position of the highest-order ("leftmost") one-bit in the specified
1311 * {@code int} value. Returns zero if the specified value has no
1312 * one-bits in its two's complement binary representation, that is, if it
1313 * is equal to zero.
1314 *
1315 * @return an {@code int} value with a single one-bit, in the position
1316 * of the highest-order one-bit in the specified value, or zero if
1317 * the specified value is itself equal to zero.
1318 * @since 1.5
1319 */
1320 public static int highestOneBit(int i) {
1321 // HD, Figure 3-1
1322 i |= (i >> 1);
1323 i |= (i >> 2);
1324 i |= (i >> 4);
1325 i |= (i >> 8);
1326 i |= (i >> 16);
1327 return i - (i >>> 1);
1328 }
1329
1330 /**
1331 * Returns an {@code int} value with at most a single one-bit, in the
1332 * position of the lowest-order ("rightmost") one-bit in the specified
1333 * {@code int} value. Returns zero if the specified value has no
1334 * one-bits in its two's complement binary representation, that is, if it
1335 * is equal to zero.
1336 *
1337 * @return an {@code int} value with a single one-bit, in the position
1338 * of the lowest-order one-bit in the specified value, or zero if
1339 * the specified value is itself equal to zero.
1340 * @since 1.5
1341 */
1342 public static int lowestOneBit(int i) {
1343 // HD, Section 2-1
1344 return i & -i;
1345 }
1346
1347 /**
1348 * Returns the number of zero bits preceding the highest-order
1349 * ("leftmost") one-bit in the two's complement binary representation
1350 * of the specified {@code int} value. Returns 32 if the
1351 * specified value has no one-bits in its two's complement representation,
1352 * in other words if it is equal to zero.
1353 *
1354 * <p>Note that this method is closely related to the logarithm base 2.
1355 * For all positive {@code int} values x:
1356 * <ul>
1357 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1358 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1359 * </ul>
1360 *
1361 * @return the number of zero bits preceding the highest-order
1362 * ("leftmost") one-bit in the two's complement binary representation
1363 * of the specified {@code int} value, or 32 if the value
1364 * is equal to zero.
1365 * @since 1.5
1366 */
1367 public static int numberOfLeadingZeros(int i) {
1368 // HD, Figure 5-6
1369 if (i == 0)
1370 return 32;
1371 int n = 1;
1372 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1373 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1374 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1375 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1376 n -= i >>> 31;
1377 return n;
1378 }
1379
1380 /**
1381 * Returns the number of zero bits following the lowest-order ("rightmost")
1382 * one-bit in the two's complement binary representation of the specified
1383 * {@code int} value. Returns 32 if the specified value has no
1384 * one-bits in its two's complement representation, in other words if it is
1385 * equal to zero.
1386 *
1387 * @return the number of zero bits following the lowest-order ("rightmost")
1388 * one-bit in the two's complement binary representation of the
1389 * specified {@code int} value, or 32 if the value is equal
1390 * to zero.
1391 * @since 1.5
1392 */
1393 public static int numberOfTrailingZeros(int i) {
1394 // HD, Figure 5-14
1395 int y;
1396 if (i == 0) return 32;
1397 int n = 31;
1398 y = i <<16; if (y != 0) { n = n -16; i = y; }
1399 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1400 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1401 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1402 return n - ((i << 1) >>> 31);
1403 }
1404
1405 /**
1406 * Returns the number of one-bits in the two's complement binary
1407 * representation of the specified {@code int} value. This function is
1408 * sometimes referred to as the <i>population count</i>.
1409 *
1410 * @return the number of one-bits in the two's complement binary
1411 * representation of the specified {@code int} value.
1412 * @since 1.5
1413 */
1414 public static int bitCount(int i) {
1415 // HD, Figure 5-2
1416 i = i - ((i >>> 1) & 0x55555555);
1417 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1418 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1419 i = i + (i >>> 8);
1420 i = i + (i >>> 16);
1421 return i & 0x3f;
1422 }
1423
1424 /**
1425 * Returns the value obtained by rotating the two's complement binary
1426 * representation of the specified {@code int} value left by the
1427 * specified number of bits. (Bits shifted out of the left hand, or
1428 * high-order, side reenter on the right, or low-order.)
1429 *
1430 * <p>Note that left rotation with a negative distance is equivalent to
1431 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1432 * distance)}. Note also that rotation by any multiple of 32 is a
1433 * no-op, so all but the last five bits of the rotation distance can be
1434 * ignored, even if the distance is negative: {@code rotateLeft(val,
1435 * distance) == rotateLeft(val, distance & 0x1F)}.
1436 *
1437 * @return the value obtained by rotating the two's complement binary
1438 * representation of the specified {@code int} value left by the
1439 * specified number of bits.
1440 * @since 1.5
1441 */
1442 public static int rotateLeft(int i, int distance) {
1443 return (i << distance) | (i >>> -distance);
1444 }
1445
1446 /**
1447 * Returns the value obtained by rotating the two's complement binary
1448 * representation of the specified {@code int} value right by the
1449 * specified number of bits. (Bits shifted out of the right hand, or
1450 * low-order, side reenter on the left, or high-order.)
1451 *
1452 * <p>Note that right rotation with a negative distance is equivalent to
1453 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1454 * distance)}. Note also that rotation by any multiple of 32 is a
1455 * no-op, so all but the last five bits of the rotation distance can be
1456 * ignored, even if the distance is negative: {@code rotateRight(val,
1457 * distance) == rotateRight(val, distance & 0x1F)}.
1458 *
1459 * @return the value obtained by rotating the two's complement binary
1460 * representation of the specified {@code int} value right by the
1461 * specified number of bits.
1462 * @since 1.5
1463 */
1464 public static int rotateRight(int i, int distance) {
1465 return (i >>> distance) | (i << -distance);
1466 }
1467
1468 /**
1469 * Returns the value obtained by reversing the order of the bits in the
1470 * two's complement binary representation of the specified {@code int}
1471 * value.
1472 *
1473 * @return the value obtained by reversing order of the bits in the
1474 * specified {@code int} value.
1475 * @since 1.5
1476 */
1477 public static int reverse(int i) {
1478 // HD, Figure 7-1
1479 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1480 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1481 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1482 i = (i << 24) | ((i & 0xff00) << 8) |
1483 ((i >>> 8) & 0xff00) | (i >>> 24);
1484 return i;
1485 }
1486
1487 /**
1488 * Returns the signum function of the specified {@code int} value. (The
1489 * return value is -1 if the specified value is negative; 0 if the
1490 * specified value is zero; and 1 if the specified value is positive.)
1491 *
1492 * @return the signum function of the specified {@code int} value.
1493 * @since 1.5
1494 */
1495 public static int signum(int i) {
1496 // HD, Section 2-7
1497 return (i >> 31) | (-i >>> 31);
1498 }
1499
1500 /**
1501 * Returns the value obtained by reversing the order of the bytes in the
1502 * two's complement representation of the specified {@code int} value.
1503 *
1504 * @return the value obtained by reversing the bytes in the specified
1505 * {@code int} value.
1506 * @since 1.5
1507 */
1508 public static int reverseBytes(int i) {
1509 return ((i >>> 24) ) |
1510 ((i >> 8) & 0xFF00) |
1511 ((i << 8) & 0xFF0000) |
1512 ((i << 24));
1513 }
1514
1515 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1516 private static final long serialVersionUID = 1360826667806852920L;
1517 }