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