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>'\u002D'</code>). If the first argument is not
97 * negative, no sign character appears in the result.
98 *
99 * <p>The remaining characters of the result represent the magnitude
100 * of the first argument. If the magnitude is zero, it is
101 * represented by a single zero character {@code '0'}
102 * (<code>'\u0030'</code>); otherwise, the first character of
103 * the representation of the magnitude will not be the zero
104 * character. The following ASCII characters are used as digits:
105 *
106 * <blockquote>
107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
108 * </blockquote>
109 *
110 * These are <code>'\u0030'</code> through
111 * <code>'\u0039'</code> and <code>'\u0061'</code> through
112 * <code>'\u007A'</code>. If {@code radix} is
113 * <var>N</var>, then the first <var>N</var> of these characters
114 * are used as radix-<var>N</var> digits in the order shown. Thus,
115 * the digits for hexadecimal (radix 16) are
116 * {@code 0123456789abcdef}. If uppercase letters are
117 * desired, the {@link java.lang.String#toUpperCase()} method may
118 * be called on the result:
119 *
120 * <blockquote>
121 * {@code Integer.toString(n, 16).toUpperCase()}
122 * </blockquote>
123 *
124 * @param i an integer to be converted to a string.
125 * @param radix the radix to use in the string representation.
126 * @return a string representation of the argument in the specified radix.
127 * @see java.lang.Character#MAX_RADIX
128 * @see java.lang.Character#MIN_RADIX
129 */
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 string in the radix specified by the second argument.
163 *
164 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
165 * or larger than {@code Character.MAX_RADIX}, then the radix
166 * {@code 10} is used instead.
167 *
168 * <p>Note that since the first argument is treated as an unsigned
169 * value, no leading sign character is printed.
170 *
171 * <p>If the magnitude is zero, it is represented by a single zero
172 * character {@code '0'} (<code>'\u0030'</code>); otherwise,
173 * the first character of the representation of the magnitude will
174 * not be the zero character.
175 *
176 * <p>The behavior of radixes and the characters used as digits
177 * are the same as {@link #toString(int, int) toString}.
178 *
179 * @param i an integer to be converted to an unsigned string.
180 * @param radix the radix to use in the string representation.
181 * @return an unsigned string representation of the argument in the specified radix.
182 * @see #toString(int, int)
183 * @since 1.8
184 */
185 public static String toUnsignedString(int i, int radix) {
186 return Long.toString(toUnsignedLong(i), radix);
187 }
188
189 /**
190 * Returns a string representation of the integer argument as an
191 * unsigned integer in base 16.
192 *
193 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
194 * if the argument is negative; otherwise, it is equal to the
195 * argument. This value is converted to a string of ASCII digits
196 * in hexadecimal (base 16) with no extra leading
197 * {@code 0}s.
198 *
199 * <p>The value of the argument can be recovered from the returned
200 * string {@code s} by calling {@link
201 * Integer#parseUnsignedInt(String, int)
202 * Integer.parseUnsignedInt(s, 16)}.
203 *
204 * <p>If the unsigned magnitude is zero, it is represented by a
205 * single zero character {@code '0'} (<code>'\u0030'</code>);
206 * otherwise, the first character of the representation of the
207 * unsigned magnitude will not be the zero character. The
208 * following characters are used as hexadecimal digits:
209 *
210 * <blockquote>
211 * {@code 0123456789abcdef}
212 * </blockquote>
213 *
214 * These are the characters <code>'\u0030'</code> through
215 * <code>'\u0039'</code> and <code>'\u0061'</code> through
216 * <code>'\u0066'</code>. If uppercase letters are
217 * desired, the {@link java.lang.String#toUpperCase()} method may
218 * be called on the result:
219 *
220 * <blockquote>
221 * {@code Integer.toHexString(n).toUpperCase()}
222 * </blockquote>
223 *
224 * @param i an integer to be converted to a string.
225 * @return the string representation of the unsigned integer value
226 * represented by the argument in hexadecimal (base 16).
227 * @see #parseUnsignedInt(String, int)
228 * @see #toUnsignedString(int, int)
229 * @since JDK1.0.2
230 */
231 public static String toHexString(int i) {
232 return toUnsignedString0(i, 4);
233 }
234
235 /**
236 * Returns a string representation of the integer argument as an
237 * unsigned integer in base 8.
238 *
239 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
240 * if the argument is negative; otherwise, it is equal to the
241 * argument. This value is converted to a string of ASCII digits
242 * in octal (base 8) with no extra leading {@code 0}s.
243 *
244 * <p>The value of the argument can be recovered from the returned
245 * string {@code s} by calling {@link
246 * Integer#parseUnsignedInt(String, int)
247 * Integer.parseUnsignedInt(s, 8)}.
248 *
249 * <p>If the unsigned magnitude is zero, it is represented by a
250 * single zero character {@code '0'} (<code>'\u0030'</code>);
251 * otherwise, the first character of the representation of the
252 * unsigned magnitude will not be the zero character. The
253 * following characters are used as octal digits:
254 *
255 * <blockquote>
256 * {@code 01234567}
257 * </blockquote>
258 *
259 * These are the characters <code>'\u0030'</code> through
260 * <code>'\u0037'</code>.
261 *
262 * @param i an integer to be converted to a string.
263 * @return the string representation of the unsigned integer value
264 * represented by the argument in octal (base 8).
265 * @see #parseUnsignedInt(String, int)
266 * @see #toUnsignedString(int, int)
267 * @since JDK1.0.2
268 */
269 public static String toOctalString(int i) {
270 return toUnsignedString0(i, 3);
271 }
272
273 /**
274 * Returns a string representation of the integer argument as an
275 * unsigned integer in base 2.
276 *
277 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
278 * if the argument is negative; otherwise it is equal to the
279 * argument. This value is converted to a string of ASCII digits
280 * in binary (base 2) with no extra leading {@code 0}s.
281 *
282 * <p>The value of the argument can be recovered from the returned
283 * string {@code s} by calling {@link
284 * Integer#parseUnsignedInt(String, int)
285 * Integer.parseUnsignedInt(s, 2)}.
286 *
287 * <p>If the unsigned magnitude is zero, it is represented by a
288 * single zero character {@code '0'} (<code>'\u0030'</code>);
289 * otherwise, the first character of the representation of the
290 * unsigned magnitude will not be the zero character. The
291 * characters {@code '0'} (<code>'\u0030'</code>) and {@code
292 * '1'} (<code>'\u0031'</code>) are used as binary digits.
293 *
294 * @param i an integer to be converted to a string.
295 * @return the string representation of the unsigned integer value
296 * represented by the argument in binary (base 2).
297 * @see #parseUnsignedInt(String, int)
298 * @see #toUnsignedString(int, int)
299 * @since JDK1.0.2
300 */
301 public static String toBinaryString(int i) {
302 return toUnsignedString0(i, 1);
303 }
304
305 /**
306 * Convert the integer to an unsigned number.
307 */
308 private static String toUnsignedString0(int i, int shift) {
309 char[] buf = new char[32];
310 int charPos = 32;
311 int radix = 1 << shift;
312 int mask = radix - 1;
313 do {
314 buf[--charPos] = digits[i & mask];
315 i >>>= shift;
316 } while (i != 0);
317
318 return new String(buf, charPos, (32 - charPos));
319 }
320
321
322 final static char [] DigitTens = {
323 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
324 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
325 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
326 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
327 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
328 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
329 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
330 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
331 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
332 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
333 } ;
334
335 final static char [] DigitOnes = {
336 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
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 } ;
347
348 // I use the "invariant division by multiplication" trick to
349 // accelerate Integer.toString. In particular we want to
350 // avoid division by 10.
351 //
352 // The "trick" has roughly the same performance characteristics
353 // as the "classic" Integer.toString code on a non-JIT VM.
354 // The trick avoids .rem and .div calls but has a longer code
355 // path and is thus dominated by dispatch overhead. In the
356 // JIT case the dispatch overhead doesn't exist and the
357 // "trick" is considerably faster than the classic code.
358 //
359 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
360 // sequence.
361 //
362 // RE: Division by Invariant Integers using Multiplication
363 // T Gralund, P Montgomery
364 // ACM PLDI 1994
365 //
366
367 /**
368 * Returns a {@code String} object representing the
369 * specified integer. The argument is converted to signed decimal
370 * representation and returned as a string, exactly as if the
371 * argument and radix 10 were given as arguments to the {@link
372 * #toString(int, int)} method.
373 *
374 * @param i an integer to be converted.
375 * @return a string representation of the argument in base 10.
376 */
377 public static String toString(int i) {
378 if (i == Integer.MIN_VALUE)
379 return "-2147483648";
380 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
381 char[] buf = new char[size];
382 getChars(i, size, buf);
383 return new String(0, size, buf);
384 }
385
386 /**
387 * Returns a string representation of the argument as an unsigned
388 * string.
389 *
390 * The argument is converted to unsigned decimal representation
391 * and returned as a string exactly as if the argument and radix
392 * 10 were given as arguments to the {@link #toUnsignedString(int,
393 * int)} method.
394 *
395 * @param i an integer to be converted to an unsigned string.
396 * @return an unsigned string representation of the argument.
397 * @see #toUnsignedString(int, int)
398 * @since 1.8
399 */
400 public static String toUnsignedString(int i) {
401 return Long.toString(toUnsignedLong(i));
402 }
403
404 /**
405 * Places characters representing the integer i into the
406 * character array buf. The characters are placed into
407 * the buffer backwards starting with the least significant
408 * digit at the specified index (exclusive), and working
409 * backwards from there.
410 *
411 * Will fail if i == Integer.MIN_VALUE
412 */
413 static void getChars(int i, int index, char[] buf) {
414 int q, r;
415 int charPos = index;
416 char sign = 0;
417
418 if (i < 0) {
419 sign = '-';
420 i = -i;
421 }
422
423 // Generate two digits per iteration
424 while (i >= 65536) {
425 q = i / 100;
426 // really: r = i - (q * 100);
427 r = i - ((q << 6) + (q << 5) + (q << 2));
428 i = q;
429 buf [--charPos] = DigitOnes[r];
430 buf [--charPos] = DigitTens[r];
431 }
432
433 // Fall thru to fast mode for smaller numbers
434 // assert(i <= 65536, i);
435 for (;;) {
436 q = (i * 52429) >>> (16+3);
437 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
438 buf [--charPos] = digits [r];
439 i = q;
440 if (i == 0) break;
441 }
442 if (sign != 0) {
443 buf [--charPos] = sign;
444 }
445 }
446
447 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
448 99999999, 999999999, Integer.MAX_VALUE };
449
450 // Requires positive x
451 static int stringSize(int x) {
452 for (int i=0; ; i++)
453 if (x <= sizeTable[i])
454 return i+1;
455 }
456
457 /**
458 * Parses the string argument as a signed integer in the radix
459 * specified by the second argument. The characters in the string
460 * must all be digits of the specified radix (as determined by
461 * whether {@link java.lang.Character#digit(char, int)} returns a
462 * nonnegative value), except that the first character may be an
463 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to
464 * indicate a negative value or an ASCII plus sign {@code '+'}
465 * (<code>'\u002B'</code>) to indicate a positive value. The
466 * resulting integer value is returned.
467 *
468 * <p>An exception of type {@code NumberFormatException} is
469 * thrown if any of the following situations occurs:
470 * <ul>
471 * <li>The first argument is {@code null} or is a string of
472 * length zero.
473 *
474 * <li>The radix is either smaller than
475 * {@link java.lang.Character#MIN_RADIX} or
476 * larger than {@link java.lang.Character#MAX_RADIX}.
477 *
478 * <li>Any character of the string is not a digit of the specified
479 * radix, except that the first character may be a minus sign
480 * {@code '-'} (<code>'\u002D'</code>) or plus sign
481 * {@code '+'} (<code>'\u002B'</code>) provided that the
482 * string is longer than length 1.
483 *
484 * <li>The value represented by the string is not a value of type
485 * {@code int}.
486 * </ul>
487 *
488 * <p>Examples:
489 * <blockquote><pre>
490 * parseInt("0", 10) returns 0
491 * parseInt("473", 10) returns 473
492 * parseInt("+42", 10) returns 42
493 * parseInt("-0", 10) returns 0
494 * parseInt("-FF", 16) returns -255
495 * parseInt("1100110", 2) returns 102
496 * parseInt("2147483647", 10) returns 2147483647
497 * parseInt("-2147483648", 10) returns -2147483648
498 * parseInt("2147483648", 10) throws a NumberFormatException
499 * parseInt("99", 8) throws a NumberFormatException
500 * parseInt("Kona", 10) throws a NumberFormatException
501 * parseInt("Kona", 27) returns 411787
502 * </pre></blockquote>
503 *
504 * @param s the {@code String} containing the integer
505 * representation to be parsed
506 * @param radix the radix to be used while parsing {@code s}.
507 * @return the integer represented by the string argument in the
508 * specified radix.
509 * @exception NumberFormatException if the {@code String}
510 * does not contain a parsable {@code int}.
511 */
512 public static int parseInt(String s, int radix)
513 throws NumberFormatException
514 {
515 /*
516 * WARNING: This method may be invoked early during VM initialization
517 * before IntegerCache is initialized. Care must be taken to not use
518 * the valueOf method.
519 */
520
521 if (s == null) {
522 throw new NumberFormatException("null");
523 }
524
525 if (radix < Character.MIN_RADIX) {
526 throw new NumberFormatException("radix " + radix +
527 " less than Character.MIN_RADIX");
528 }
529
530 if (radix > Character.MAX_RADIX) {
531 throw new NumberFormatException("radix " + radix +
532 " greater than Character.MAX_RADIX");
533 }
534
535 int result = 0;
536 boolean negative = false;
537 int i = 0, len = s.length();
538 int limit = -Integer.MAX_VALUE;
539 int multmin;
540 int digit;
541
542 if (len > 0) {
543 char firstChar = s.charAt(0);
544 if (firstChar < '0') { // Possible leading "+" or "-"
545 if (firstChar == '-') {
546 negative = true;
547 limit = Integer.MIN_VALUE;
548 } else if (firstChar != '+')
549 throw NumberFormatException.forInputString(s);
550
551 if (len == 1) // Cannot have lone "+" or "-"
552 throw NumberFormatException.forInputString(s);
553 i++;
554 }
555 multmin = limit / radix;
556 while (i < len) {
557 // Accumulating negatively avoids surprises near MAX_VALUE
558 digit = Character.digit(s.charAt(i++),radix);
559 if (digit < 0) {
560 throw NumberFormatException.forInputString(s);
561 }
562 if (result < multmin) {
563 throw NumberFormatException.forInputString(s);
564 }
565 result *= radix;
566 if (result < limit + digit) {
567 throw NumberFormatException.forInputString(s);
568 }
569 result -= digit;
570 }
571 } else {
572 throw NumberFormatException.forInputString(s);
573 }
574 return negative ? result : -result;
575 }
576
577 /**
578 * Parses the string argument as a signed decimal integer. The
579 * characters in the string must all be decimal digits, except
580 * that the first character may be an ASCII minus sign {@code '-'}
581 * (<code>'\u002D'</code>) to indicate a negative value or an
582 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
583 * indicate a positive value. The resulting integer value is
584 * returned, exactly as if the argument and the radix 10 were
585 * given as arguments to the {@link #parseInt(java.lang.String,
586 * int)} method.
587 *
588 * @param s a {@code String} containing the {@code int}
589 * representation to be parsed
590 * @return the integer value represented by the argument in decimal.
591 * @exception NumberFormatException if the string does not contain a
592 * parsable integer.
593 */
594 public static int parseInt(String s) throws NumberFormatException {
595 return parseInt(s,10);
596 }
597
598 /**
599 * Parses the string argument as an unsigned integer in the radix
600 * specified by the second argument. An unsigned integer maps the
601 * values usually associated with negative numbers to positive
602 * numbers larger than {@code MAX_VALUE}.
603 *
604 * The characters in the string must all be digits of the
605 * specified radix (as determined by whether {@link
606 * java.lang.Character#digit(char, int)} returns a nonnegative
607 * value), except that the first character may be an ASCII plus
608 * sign {@code '+'} (<code>'\u002B'</code>). The resulting
609 * integer value is returned.
610 *
611 * <p>An exception of type {@code NumberFormatException} is
612 * thrown if any of the following situations occurs:
613 * <ul>
614 * <li>The first argument is {@code null} or is a string of
615 * length zero.
616 *
617 * <li>The radix is either smaller than
618 * {@link java.lang.Character#MIN_RADIX} or
619 * larger than {@link java.lang.Character#MAX_RADIX}.
620 *
621 * <li>Any character of the string is not a digit of the specified
622 * radix, except that the first character may be a plus sign
623 * {@code '+'} (<code>'\u002B'</code>) provided that the
624 * string is longer than length 1.
625 *
626 * <li>The value represented by the string is larger than the
627 * largest unsigned {@code int}, 2<sup>32</sup>-1.
628 *
629 * </ul>
630 *
631 *
632 * @param s the {@code String} containing the unsigned integer
633 * representation to be parsed
634 * @param radix the radix to be used while parsing {@code s}.
635 * @return the integer represented by the string argument in the
636 * specified radix.
637 * @throws NumberFormatException if the {@code String}
638 * does not contain a parsable {@code int}.
639 * @since 1.8
640 */
641 public static int parseUnsignedInt(String s, int radix)
642 throws NumberFormatException {
643 if (s == null) {
644 throw new NumberFormatException("null");
645 }
646
647 int len = s.length();
648 if (len > 0) {
649 char firstChar = s.charAt(0);
650 if (firstChar == '-') {
651 throw new
652 NumberFormatException(String.format("Illegal leading minus sign " +
653 "on unsigned string %s.", s));
654 } else {
655 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
656 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
657 return parseInt(s, radix);
658 } else {
659 long ell = Long.parseLong(s, radix);
660 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
661 return (int) ell;
662 } else {
663 throw new
664 NumberFormatException(String.format("String value %s exceeds " +
665 "range of unsigned int.", s));
666 }
667 }
668 }
669 } else {
670 throw NumberFormatException.forInputString(s);
671 }
672 }
673
674 /**
675 * Parses the string argument as an unsigned decimal integer. The
676 * characters in the string must all be decimal digits, except
677 * that the first character may be an an ASCII plus sign {@code
678 * '+'} (<code>'\u002B'</code>). The resulting integer value
679 * is returned, exactly as if the argument and the radix 10 were
680 * given as arguments to the {@link
681 * #parseUnsignedInt(java.lang.String, int)} method.
682 *
683 * @param s a {@code String} containing the unsigned {@code int}
684 * representation to be parsed
685 * @return the unsigned integer value represented by the argument in decimal.
686 * @throws NumberFormatException if the string does not contain a
687 * parsable unsigned integer.
688 * @since 1.8
689 */
690 public static int parseUnsignedInt(String s) throws NumberFormatException {
691 return parseUnsignedInt(s, 10);
692 }
693
694 /**
695 * Returns an {@code Integer} object holding the value
696 * extracted from the specified {@code String} when parsed
697 * with the radix given by the second argument. The first argument
698 * is interpreted as representing a signed integer in the radix
699 * specified by the second argument, exactly as if the arguments
700 * were given to the {@link #parseInt(java.lang.String, int)}
701 * method. The result is an {@code Integer} object that
702 * represents the integer value specified by the string.
703 *
704 * <p>In other words, this method returns an {@code Integer}
705 * object equal to the value of:
706 *
707 * <blockquote>
708 * {@code new Integer(Integer.parseInt(s, radix))}
709 * </blockquote>
710 *
711 * @param s the string to be parsed.
712 * @param radix the radix to be used in interpreting {@code s}
713 * @return an {@code Integer} object holding the value
714 * represented by the string argument in the specified
715 * radix.
716 * @exception NumberFormatException if the {@code String}
717 * does not contain a parsable {@code int}.
718 */
719 public static Integer valueOf(String s, int radix) throws NumberFormatException {
720 return Integer.valueOf(parseInt(s,radix));
721 }
722
723 /**
724 * Returns an {@code Integer} object holding the
725 * value of the specified {@code String}. The argument is
726 * interpreted as representing a signed decimal integer, exactly
727 * as if the argument were given to the {@link
728 * #parseInt(java.lang.String)} method. The result is an
729 * {@code Integer} object that represents the integer value
730 * specified by the string.
731 *
732 * <p>In other words, this method returns an {@code Integer}
733 * object equal to the value of:
734 *
735 * <blockquote>
736 * {@code new Integer(Integer.parseInt(s))}
737 * </blockquote>
738 *
739 * @param s the string to be parsed.
740 * @return an {@code Integer} object holding the value
741 * represented by the string argument.
742 * @exception NumberFormatException if the string cannot be parsed
743 * as an integer.
744 */
745 public static Integer valueOf(String s) throws NumberFormatException {
746 return Integer.valueOf(parseInt(s, 10));
747 }
748
749 /**
750 * Cache to support the object identity semantics of autoboxing for values between
751 * -128 and 127 (inclusive) as required by JLS.
752 *
753 * The cache is initialized on first usage. The size of the cache
754 * may be controlled by the -XX:AutoBoxCacheMax=<size> option.
755 * During VM initialization, java.lang.Integer.IntegerCache.high property
756 * may be set and saved in the private system properties in the
757 * sun.misc.VM class.
758 */
759
760 private static class IntegerCache {
761 static final int low = -128;
762 static final int high;
763 static final Integer cache[];
764
765 static {
766 // high value may be configured by property
767 int h = 127;
768 String integerCacheHighPropValue =
769 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
770 if (integerCacheHighPropValue != null) {
771 int i = parseInt(integerCacheHighPropValue);
772 i = Math.max(i, 127);
773 // Maximum array size is Integer.MAX_VALUE
774 h = Math.min(i, Integer.MAX_VALUE - (-low));
775 }
776 high = h;
777
778 cache = new Integer[(high - low) + 1];
779 int j = low;
780 for(int k = 0; k < cache.length; k++)
781 cache[k] = new Integer(j++);
782 }
783
784 private IntegerCache() {}
785 }
786
787 /**
788 * Returns an {@code Integer} instance representing the specified
789 * {@code int} value. If a new {@code Integer} instance is not
790 * required, this method should generally be used in preference to
791 * the constructor {@link #Integer(int)}, as this method is likely
792 * to yield significantly better space and time performance by
793 * caching frequently requested values.
794 *
795 * This method will always cache values in the range -128 to 127,
796 * inclusive, and may cache other values outside of this range.
797 *
798 * @param i an {@code int} value.
799 * @return an {@code Integer} instance representing {@code i}.
800 * @since 1.5
801 */
802 public static Integer valueOf(int i) {
803 assert IntegerCache.high >= 127;
804 if (i >= IntegerCache.low && i <= IntegerCache.high)
805 return IntegerCache.cache[i + (-IntegerCache.low)];
806 return new Integer(i);
807 }
808
809 /**
810 * The value of the {@code Integer}.
811 *
812 * @serial
813 */
814 private final int value;
815
816 /**
817 * Constructs a newly allocated {@code Integer} object that
818 * represents the specified {@code int} value.
819 *
820 * @param value the value to be represented by the
821 * {@code Integer} object.
822 */
823 public Integer(int value) {
824 this.value = value;
825 }
826
827 /**
828 * Constructs a newly allocated {@code Integer} object that
829 * represents the {@code int} value indicated by the
830 * {@code String} parameter. The string is converted to an
831 * {@code int} value in exactly the manner used by the
832 * {@code parseInt} method for radix 10.
833 *
834 * @param s the {@code String} to be converted to an
835 * {@code Integer}.
836 * @exception NumberFormatException if the {@code String} does not
837 * contain a parsable integer.
838 * @see java.lang.Integer#parseInt(java.lang.String, int)
839 */
840 public Integer(String s) throws NumberFormatException {
841 this.value = parseInt(s, 10);
842 }
843
844 /**
845 * Returns the value of this {@code Integer} as a {@code byte}
846 * after a narrowing primitive conversion.
847 * @jls 5.1.3 Narrowing Primitive Conversions
848 */
849 public byte byteValue() {
850 return (byte)value;
851 }
852
853 /**
854 * Returns the value of this {@code Integer} as a {@code short}
855 * after a narrowing primitive conversion.
856 * @jls 5.1.3 Narrowing Primitive Conversions
857 */
858 public short shortValue() {
859 return (short)value;
860 }
861
862 /**
863 * Returns the value of this {@code Integer} as an
864 * {@code int}.
865 */
866 public int intValue() {
867 return value;
868 }
869
870 /**
871 * Returns the value of this {@code Integer} as a {@code long}
872 * after a widening primitive conversion.
873 * @jls 5.1.2 Widening Primitive Conversions
874 */
875 public long longValue() {
876 return (long)value;
877 }
878
879 /**
880 * Returns the value of this {@code Integer} as a {@code float}
881 * after a widening primitive conversion.
882 * @jls 5.1.2 Widening Primitive Conversions
883 */
884 public float floatValue() {
885 return (float)value;
886 }
887
888 /**
889 * Returns the value of this {@code Integer} as a {@code double}
890 * after a widening primitive conversion.
891 * @jls 5.1.2 Widening Primitive Conversions
892 */
893 public double doubleValue() {
894 return (double)value;
895 }
896
897 /**
898 * Returns a {@code String} object representing this
899 * {@code Integer}'s value. The value is converted to signed
900 * decimal representation and returned as a string, exactly as if
901 * the integer value were given as an argument to the {@link
902 * java.lang.Integer#toString(int)} method.
903 *
904 * @return a string representation of the value of this object in
905 * base 10.
906 */
907 public String toString() {
908 return toString(value);
909 }
910
911 /**
912 * Returns a hash code for this {@code Integer}.
913 *
914 * @return a hash code value for this object, equal to the
915 * primitive {@code int} value represented by this
916 * {@code Integer} object.
917 */
918 public int hashCode() {
919 return value;
920 }
921
922 /**
923 * Compares this object to the specified object. The result is
924 * {@code true} if and only if the argument is not
925 * {@code null} and is an {@code Integer} object that
926 * contains the same {@code int} value as this object.
927 *
928 * @param obj the object to compare with.
929 * @return {@code true} if the objects are the same;
930 * {@code false} otherwise.
931 */
932 public boolean equals(Object obj) {
933 if (obj instanceof Integer) {
934 return value == ((Integer)obj).intValue();
935 }
936 return false;
937 }
938
939 /**
940 * Determines the integer value of the system property with the
941 * specified name.
942 *
943 * <p>The first argument is treated as the name of a system
944 * property. System properties are accessible through the {@link
945 * java.lang.System#getProperty(java.lang.String)} method. The
946 * string value of this property is then interpreted as an integer
947 * value using the grammar supported by {@link Integer#decode decode} and
948 * an {@code Integer} object representing this value is returned.
949 *
950 * <p>If there is no property with the specified name, if the
951 * specified name is empty or {@code null}, or if the property
952 * does not have the correct numeric format, then {@code null} is
953 * returned.
954 *
955 * <p>In other words, this method returns an {@code Integer}
956 * object equal to the value of:
957 *
958 * <blockquote>
959 * {@code getInteger(nm, null)}
960 * </blockquote>
961 *
962 * @param nm property name.
963 * @return the {@code Integer} value of the property.
964 * @throws SecurityException for the same reasons as
965 * {@link System#getProperty(String) System.getProperty}
966 * @see java.lang.System#getProperty(java.lang.String)
967 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
968 */
969 public static Integer getInteger(String nm) {
970 return getInteger(nm, null);
971 }
972
973 /**
974 * Determines the integer value of the system property with the
975 * specified name.
976 *
977 * <p>The first argument is treated as the name of a system
978 * property. System properties are accessible through the {@link
979 * java.lang.System#getProperty(java.lang.String)} method. The
980 * string value of this property is then interpreted as an integer
981 * value using the grammar supported by {@link Integer#decode decode} and
982 * an {@code Integer} object representing this value is returned.
983 *
984 * <p>The second argument is the default value. An {@code Integer} object
985 * that represents the value of the second argument is returned if there
986 * is no property of the specified name, if the property does not have
987 * the correct numeric format, or if the specified name is empty or
988 * {@code null}.
989 *
990 * <p>In other words, this method returns an {@code Integer} object
991 * equal to the value of:
992 *
993 * <blockquote>
994 * {@code getInteger(nm, new Integer(val))}
995 * </blockquote>
996 *
997 * but in practice it may be implemented in a manner such as:
998 *
999 * <blockquote><pre>
1000 * Integer result = getInteger(nm, null);
1001 * return (result == null) ? new Integer(val) : result;
1002 * </pre></blockquote>
1003 *
1004 * to avoid the unnecessary allocation of an {@code Integer}
1005 * object when the default value is not needed.
1006 *
1007 * @param nm property name.
1008 * @param val default value.
1009 * @return the {@code Integer} value of the property.
1010 * @throws SecurityException for the same reasons as
1011 * {@link System#getProperty(String) System.getProperty}
1012 * @see java.lang.System#getProperty(java.lang.String)
1013 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1014 */
1015 public static Integer getInteger(String nm, int val) {
1016 Integer result = getInteger(nm, null);
1017 return (result == null) ? Integer.valueOf(val) : result;
1018 }
1019
1020 /**
1021 * Returns the integer value of the system property with the
1022 * specified name. The first argument is treated as the name of a
1023 * system property. System properties are accessible through the
1024 * {@link java.lang.System#getProperty(java.lang.String)} method.
1025 * The string value of this property is then interpreted as an
1026 * integer value, as per the {@link Integer#decode decode} method,
1027 * and an {@code Integer} object representing this value is
1028 * returned; in summary:
1029 *
1030 * <ul><li>If the property value begins with the two ASCII characters
1031 * {@code 0x} or the ASCII character {@code #}, not
1032 * followed by a minus sign, then the rest of it is parsed as a
1033 * hexadecimal integer exactly as by the method
1034 * {@link #valueOf(java.lang.String, int)} with radix 16.
1035 * <li>If the property value begins with the ASCII character
1036 * {@code 0} followed by another character, it is parsed as an
1037 * octal integer exactly as by the method
1038 * {@link #valueOf(java.lang.String, int)} with radix 8.
1039 * <li>Otherwise, the property value is parsed as a decimal integer
1040 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1041 * with radix 10.
1042 * </ul>
1043 *
1044 * <p>The second argument is the default value. The default value is
1045 * returned if there is no property of the specified name, if the
1046 * property does not have the correct numeric format, or if the
1047 * specified name is empty or {@code null}.
1048 *
1049 * @param nm property name.
1050 * @param val default value.
1051 * @return the {@code Integer} value of the property.
1052 * @throws SecurityException for the same reasons as
1053 * {@link System#getProperty(String) System.getProperty}
1054 * @see System#getProperty(java.lang.String)
1055 * @see System#getProperty(java.lang.String, java.lang.String)
1056 */
1057 public static Integer getInteger(String nm, Integer val) {
1058 String v = null;
1059 try {
1060 v = System.getProperty(nm);
1061 } catch (IllegalArgumentException | NullPointerException e) {
1062 }
1063 if (v != null) {
1064 try {
1065 return Integer.decode(v);
1066 } catch (NumberFormatException e) {
1067 }
1068 }
1069 return val;
1070 }
1071
1072 /**
1073 * Decodes a {@code String} into an {@code Integer}.
1074 * Accepts decimal, hexadecimal, and octal numbers given
1075 * by the following grammar:
1076 *
1077 * <blockquote>
1078 * <dl>
1079 * <dt><i>DecodableString:</i>
1080 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1081 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1082 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1083 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1084 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1085 * <p>
1086 * <dt><i>Sign:</i>
1087 * <dd>{@code -}
1088 * <dd>{@code +}
1089 * </dl>
1090 * </blockquote>
1091 *
1092 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1093 * are as defined in section 3.10.1 of
1094 * <cite>The Java™ Language Specification</cite>,
1095 * except that underscores are not accepted between digits.
1096 *
1097 * <p>The sequence of characters following an optional
1098 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1099 * "{@code #}", or leading zero) is parsed as by the {@code
1100 * Integer.parseInt} method with the indicated radix (10, 16, or
1101 * 8). This sequence of characters must represent a positive
1102 * value or a {@link NumberFormatException} will be thrown. The
1103 * result is negated if first character of the specified {@code
1104 * String} is the minus sign. No whitespace characters are
1105 * permitted in the {@code String}.
1106 *
1107 * @param nm the {@code String} to decode.
1108 * @return an {@code Integer} object holding the {@code int}
1109 * value represented by {@code nm}
1110 * @exception NumberFormatException if the {@code String} does not
1111 * contain a parsable integer.
1112 * @see java.lang.Integer#parseInt(java.lang.String, int)
1113 */
1114 public static Integer decode(String nm) throws NumberFormatException {
1115 int radix = 10;
1116 int index = 0;
1117 boolean negative = false;
1118 Integer result;
1119
1120 if (nm.length() == 0)
1121 throw new NumberFormatException("Zero length string");
1122 char firstChar = nm.charAt(0);
1123 // Handle sign, if present
1124 if (firstChar == '-') {
1125 negative = true;
1126 index++;
1127 } else if (firstChar == '+')
1128 index++;
1129
1130 // Handle radix specifier, if present
1131 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1132 index += 2;
1133 radix = 16;
1134 }
1135 else if (nm.startsWith("#", index)) {
1136 index ++;
1137 radix = 16;
1138 }
1139 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1140 index ++;
1141 radix = 8;
1142 }
1143
1144 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1145 throw new NumberFormatException("Sign character in wrong position");
1146
1147 try {
1148 result = Integer.valueOf(nm.substring(index), radix);
1149 result = negative ? Integer.valueOf(-result.intValue()) : result;
1150 } catch (NumberFormatException e) {
1151 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1152 // handles this case, and causes any genuine format error to be
1153 // rethrown.
1154 String constant = negative ? ("-" + nm.substring(index))
1155 : nm.substring(index);
1156 result = Integer.valueOf(constant, radix);
1157 }
1158 return result;
1159 }
1160
1161 /**
1162 * Compares two {@code Integer} objects numerically.
1163 *
1164 * @param anotherInteger the {@code Integer} to be compared.
1165 * @return the value {@code 0} if this {@code Integer} is
1166 * equal to the argument {@code Integer}; a value less than
1167 * {@code 0} if this {@code Integer} is numerically less
1168 * than the argument {@code Integer}; and a value greater
1169 * than {@code 0} if this {@code Integer} is numerically
1170 * greater than the argument {@code Integer} (signed
1171 * comparison).
1172 * @since 1.2
1173 */
1174 public int compareTo(Integer anotherInteger) {
1175 return compare(this.value, anotherInteger.value);
1176 }
1177
1178 /**
1179 * Compares two {@code int} values numerically.
1180 * The value returned is identical to what would be returned by:
1181 * <pre>
1182 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1183 * </pre>
1184 *
1185 * @param x the first {@code int} to compare
1186 * @param y the second {@code int} to compare
1187 * @return the value {@code 0} if {@code x == y};
1188 * a value less than {@code 0} if {@code x < y}; and
1189 * a value greater than {@code 0} if {@code x > y}
1190 * @since 1.7
1191 */
1192 public static int compare(int x, int y) {
1193 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1194 }
1195
1196 /**
1197 * Compares two {@code int} values numerically treating the values
1198 * as unsigned.
1199 *
1200 * @param x the first {@code int} to compare
1201 * @param y the second {@code int} to compare
1202 * @return the value {@code 0} if {@code x == y}; a value less
1203 * than {@code 0} if {@code x < y} as unsigned values; and
1204 * a value greater than {@code 0} if {@code x > y} as
1205 * unsigned values
1206 * @since 1.8
1207 */
1208 public static int compareUnsigned(int x, int y) {
1209 return compare(x + MIN_VALUE, y + MIN_VALUE);
1210 }
1211
1212 /**
1213 * Converts the argument to a {@code long} by an unsigned
1214 * conversion. In an unsigned conversion to a {@code long}, the
1215 * high-order 32 bits of the {@code long} are zero and the
1216 * low-order 32 bits are equal to the bits of the integer
1217 * argument.
1218 *
1219 * @return the argument converted to {@code long} by an unsigned
1220 * conversion
1221 * @param x the value to convert to an unsigned {@code long}
1222 * @since 1.8
1223 */
1224 public static long toUnsignedLong(int x) {
1225 return ((long) x) & 0xffffffffL;
1226 }
1227
1228 /**
1229 * Returns the unsigned quotient of dividing the first argument by
1230 * the second where each argument and the result is interpreted as
1231 * an unsigned value.
1232 *
1233 * <p>Note that in two's complement arithmetic, the three other
1234 * basic arithmetic operations of add, subtract, and multiply are
1235 * bit-wise identical if the two operands are regarded as both
1236 * being signed or both being unsigned. Therefore separate {@code
1237 * addUnsigned}, etc. methods are not provided.
1238 *
1239 * @return the unsigned quotient of the first argument divided by
1240 * the second argument
1241 * @param dividend the value to be divided
1242 * @param divisor the value doing the dividing
1243 * @see #remainderUnsigned
1244 * @since 1.8
1245 */
1246 public static int divideUnsigned(int dividend, int divisor) {
1247 // In lieu of tricky code, for now just use long arithmetic.
1248 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1249 }
1250
1251 /**
1252 * Returns the unsigned remainder from dividing the first argument
1253 * by the second where each argument and the result is interpreted
1254 * as an unsigned value.
1255 *
1256 * @return the unsigned remainder of the first argument divided by
1257 * the second argument
1258 * @param dividend the value to be divided
1259 * @param divisor the value doing the dividing
1260 * @see #divideUnsigned
1261 * @since 1.8
1262 */
1263 public static int remainderUnsigned(int dividend, int divisor) {
1264 // In lieu of tricky code, for now just use long arithmetic.
1265 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1266 }
1267
1268
1269 // Bit twiddling
1270
1271 /**
1272 * The number of bits used to represent an {@code int} value in two's
1273 * complement binary form.
1274 *
1275 * @since 1.5
1276 */
1277 public static final int SIZE = 32;
1278
1279 /**
1280 * Returns an {@code int} value with at most a single one-bit, in the
1281 * position of the highest-order ("leftmost") one-bit in the specified
1282 * {@code int} value. Returns zero if the specified value has no
1283 * one-bits in its two's complement binary representation, that is, if it
1284 * is equal to zero.
1285 *
1286 * @return an {@code int} value with a single one-bit, in the position
1287 * of the highest-order one-bit in the specified value, or zero if
1288 * the specified value is itself equal to zero.
1289 * @since 1.5
1290 */
1291 public static int highestOneBit(int i) {
1292 // HD, Figure 3-1
1293 i |= (i >> 1);
1294 i |= (i >> 2);
1295 i |= (i >> 4);
1296 i |= (i >> 8);
1297 i |= (i >> 16);
1298 return i - (i >>> 1);
1299 }
1300
1301 /**
1302 * Returns an {@code int} value with at most a single one-bit, in the
1303 * position of the lowest-order ("rightmost") one-bit in the specified
1304 * {@code int} value. Returns zero if the specified value has no
1305 * one-bits in its two's complement binary representation, that is, if it
1306 * is equal to zero.
1307 *
1308 * @return an {@code int} value with a single one-bit, in the position
1309 * of the lowest-order one-bit in the specified value, or zero if
1310 * the specified value is itself equal to zero.
1311 * @since 1.5
1312 */
1313 public static int lowestOneBit(int i) {
1314 // HD, Section 2-1
1315 return i & -i;
1316 }
1317
1318 /**
1319 * Returns the number of zero bits preceding the highest-order
1320 * ("leftmost") one-bit in the two's complement binary representation
1321 * of the specified {@code int} value. Returns 32 if the
1322 * specified value has no one-bits in its two's complement representation,
1323 * in other words if it is equal to zero.
1324 *
1325 * <p>Note that this method is closely related to the logarithm base 2.
1326 * For all positive {@code int} values x:
1327 * <ul>
1328 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1329 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1330 * </ul>
1331 *
1332 * @return the number of zero bits preceding the highest-order
1333 * ("leftmost") one-bit in the two's complement binary representation
1334 * of the specified {@code int} value, or 32 if the value
1335 * is equal to zero.
1336 * @since 1.5
1337 */
1338 public static int numberOfLeadingZeros(int i) {
1339 // HD, Figure 5-6
1340 if (i == 0)
1341 return 32;
1342 int n = 1;
1343 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1344 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1345 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1346 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1347 n -= i >>> 31;
1348 return n;
1349 }
1350
1351 /**
1352 * Returns the number of zero bits following the lowest-order ("rightmost")
1353 * one-bit in the two's complement binary representation of the specified
1354 * {@code int} value. Returns 32 if the specified value has no
1355 * one-bits in its two's complement representation, in other words if it is
1356 * equal to zero.
1357 *
1358 * @return the number of zero bits following the lowest-order ("rightmost")
1359 * one-bit in the two's complement binary representation of the
1360 * specified {@code int} value, or 32 if the value is equal
1361 * to zero.
1362 * @since 1.5
1363 */
1364 public static int numberOfTrailingZeros(int i) {
1365 // HD, Figure 5-14
1366 int y;
1367 if (i == 0) return 32;
1368 int n = 31;
1369 y = i <<16; if (y != 0) { n = n -16; i = y; }
1370 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1371 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1372 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1373 return n - ((i << 1) >>> 31);
1374 }
1375
1376 /**
1377 * Returns the number of one-bits in the two's complement binary
1378 * representation of the specified {@code int} value. This function is
1379 * sometimes referred to as the <i>population count</i>.
1380 *
1381 * @return the number of one-bits in the two's complement binary
1382 * representation of the specified {@code int} value.
1383 * @since 1.5
1384 */
1385 public static int bitCount(int i) {
1386 // HD, Figure 5-2
1387 i = i - ((i >>> 1) & 0x55555555);
1388 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1389 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1390 i = i + (i >>> 8);
1391 i = i + (i >>> 16);
1392 return i & 0x3f;
1393 }
1394
1395 /**
1396 * Returns the value obtained by rotating the two's complement binary
1397 * representation of the specified {@code int} value left by the
1398 * specified number of bits. (Bits shifted out of the left hand, or
1399 * high-order, side reenter on the right, or low-order.)
1400 *
1401 * <p>Note that left rotation with a negative distance is equivalent to
1402 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1403 * distance)}. Note also that rotation by any multiple of 32 is a
1404 * no-op, so all but the last five bits of the rotation distance can be
1405 * ignored, even if the distance is negative: {@code rotateLeft(val,
1406 * distance) == rotateLeft(val, distance & 0x1F)}.
1407 *
1408 * @return the value obtained by rotating the two's complement binary
1409 * representation of the specified {@code int} value left by the
1410 * specified number of bits.
1411 * @since 1.5
1412 */
1413 public static int rotateLeft(int i, int distance) {
1414 return (i << distance) | (i >>> -distance);
1415 }
1416
1417 /**
1418 * Returns the value obtained by rotating the two's complement binary
1419 * representation of the specified {@code int} value right by the
1420 * specified number of bits. (Bits shifted out of the right hand, or
1421 * low-order, side reenter on the left, or high-order.)
1422 *
1423 * <p>Note that right rotation with a negative distance is equivalent to
1424 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1425 * distance)}. Note also that rotation by any multiple of 32 is a
1426 * no-op, so all but the last five bits of the rotation distance can be
1427 * ignored, even if the distance is negative: {@code rotateRight(val,
1428 * distance) == rotateRight(val, distance & 0x1F)}.
1429 *
1430 * @return the value obtained by rotating the two's complement binary
1431 * representation of the specified {@code int} value right by the
1432 * specified number of bits.
1433 * @since 1.5
1434 */
1435 public static int rotateRight(int i, int distance) {
1436 return (i >>> distance) | (i << -distance);
1437 }
1438
1439 /**
1440 * Returns the value obtained by reversing the order of the bits in the
1441 * two's complement binary representation of the specified {@code int}
1442 * value.
1443 *
1444 * @return the value obtained by reversing order of the bits in the
1445 * specified {@code int} value.
1446 * @since 1.5
1447 */
1448 public static int reverse(int i) {
1449 // HD, Figure 7-1
1450 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1451 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1452 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1453 i = (i << 24) | ((i & 0xff00) << 8) |
1454 ((i >>> 8) & 0xff00) | (i >>> 24);
1455 return i;
1456 }
1457
1458 /**
1459 * Returns the signum function of the specified {@code int} value. (The
1460 * return value is -1 if the specified value is negative; 0 if the
1461 * specified value is zero; and 1 if the specified value is positive.)
1462 *
1463 * @return the signum function of the specified {@code int} value.
1464 * @since 1.5
1465 */
1466 public static int signum(int i) {
1467 // HD, Section 2-7
1468 return (i >> 31) | (-i >>> 31);
1469 }
1470
1471 /**
1472 * Returns the value obtained by reversing the order of the bytes in the
1473 * two's complement representation of the specified {@code int} value.
1474 *
1475 * @return the value obtained by reversing the bytes in the specified
1476 * {@code int} value.
1477 * @since 1.5
1478 */
1479 public static int reverseBytes(int i) {
1480 return ((i >>> 24) ) |
1481 ((i >> 8) & 0xFF00) |
1482 ((i << 8) & 0xFF0000) |
1483 ((i << 24));
1484 }
1485
1486 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1487 private static final long serialVersionUID = 1360826667806852920L;
1488 }