1 /*
2 * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.lang.annotation.Native;
29
30 /**
31 * The {@code Integer} class wraps a value of the primitive type
32 * {@code int} in an object. An object of type {@code Integer}
33 * contains a single field whose type is {@code int}.
34 *
35 * <p>In addition, this class provides several methods for converting
36 * an {@code int} to a {@code String} and a {@code String} to an
37 * {@code int}, as well as other constants and methods useful when
38 * dealing with an {@code int}.
39 *
40 * <p>Implementation note: The implementations of the "bit twiddling"
41 * methods (such as {@link #highestOneBit(int) highestOneBit} and
42 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
43 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
44 * Delight</i>, (Addison Wesley, 2002).
45 *
46 * @author Lee Boynton
47 * @author Arthur van Hoff
48 * @author Josh Bloch
49 * @author Joseph D. Darcy
50 * @since JDK1.0
51 */
52 public final class Integer extends Number implements Comparable<Integer> {
53 /**
54 * A constant holding the minimum value an {@code int} can
55 * have, -2<sup>31</sup>.
56 */
57 @Native public static final int MIN_VALUE = 0x80000000;
58
59 /**
60 * A constant holding the maximum value an {@code int} can
61 * have, 2<sup>31</sup>-1.
62 */
63 @Native public static final int MAX_VALUE = 0x7fffffff;
64
65 /**
66 * The {@code Class} instance representing the primitive type
67 * {@code int}.
68 *
69 * @since JDK1.1
70 */
71 @SuppressWarnings("unchecked")
72 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
73
74 /**
75 * All possible chars for representing a number as a String
76 */
77 final static char[] digits = {
78 '0' , '1' , '2' , '3' , '4' , '5' ,
79 '6' , '7' , '8' , '9' , 'a' , 'b' ,
80 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
81 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
82 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
83 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
84 };
85
86 /**
87 * Returns a string representation of the first argument in the
88 * radix specified by the second argument.
89 *
90 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
91 * or larger than {@code Character.MAX_RADIX}, then the radix
92 * {@code 10} is used instead.
93 *
94 * <p>If the first argument is negative, the first element of the
95 * result is the ASCII minus character {@code '-'}
96 * ({@code '\u005Cu002D'}). If the first argument is not
97 * negative, no sign character appears in the result.
98 *
99 * <p>The remaining characters of the result represent the magnitude
100 * of the first argument. If the magnitude is zero, it is
101 * represented by a single zero character {@code '0'}
102 * ({@code '\u005Cu0030'}); otherwise, the first character of
103 * the representation of the magnitude will not be the zero
104 * character. The following ASCII characters are used as digits:
105 *
106 * <blockquote>
107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
108 * </blockquote>
109 *
110 * These are {@code '\u005Cu0030'} through
111 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
112 * {@code '\u005Cu007A'}. If {@code radix} is
113 * <var>N</var>, then the first <var>N</var> of these characters
114 * are used as radix-<var>N</var> digits in the order shown. Thus,
115 * the digits for hexadecimal (radix 16) are
116 * {@code 0123456789abcdef}. If uppercase letters are
117 * desired, the {@link java.lang.String#toUpperCase()} method may
118 * be called on the result:
119 *
120 * <blockquote>
121 * {@code Integer.toString(n, 16).toUpperCase()}
122 * </blockquote>
123 *
124 * @param i an integer to be converted to a string.
125 * @param radix the radix to use in the string representation.
126 * @return a string representation of the argument in the specified radix.
127 * @see java.lang.Character#MAX_RADIX
128 * @see java.lang.Character#MIN_RADIX
129 */
130 public static String toString(int i, int radix) {
131 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
132 radix = 10;
133
134 /* Use the faster version */
135 if (radix == 10) {
136 return toString(i);
137 }
138
139 char buf[] = new char[33];
140 boolean negative = (i < 0);
141 int charPos = 32;
142
143 if (!negative) {
144 i = -i;
145 }
146
147 while (i <= -radix) {
148 buf[charPos--] = digits[-(i % radix)];
149 i = i / radix;
150 }
151 buf[charPos] = digits[-i];
152
153 if (negative) {
154 buf[--charPos] = '-';
155 }
156
157 return new String(buf, charPos, (33 - charPos));
158 }
159
160 /**
161 * Returns a string representation of the first argument as an
162 * unsigned integer value in the radix specified by the second
163 * argument.
164 *
165 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
166 * or larger than {@code Character.MAX_RADIX}, then the radix
167 * {@code 10} is used instead.
168 *
169 * <p>Note that since the first argument is treated as an unsigned
170 * value, no leading sign character is printed.
171 *
172 * <p>If the magnitude is zero, it is represented by a single zero
173 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
174 * the first character of the representation of the magnitude will
175 * not be the zero character.
176 *
177 * <p>The behavior of radixes and the characters used as digits
178 * are the same as {@link #toString(int, int) toString}.
179 *
180 * @param i an integer to be converted to an unsigned string.
181 * @param radix the radix to use in the string representation.
182 * @return an unsigned string representation of the argument in the specified radix.
183 * @see #toString(int, int)
184 * @since 1.8
185 */
186 public static String toUnsignedString(int i, int radix) {
187 return Long.toUnsignedString(toUnsignedLong(i), radix);
188 }
189
190 /**
191 * Returns a string representation of the integer argument as an
192 * unsigned integer in base 16.
193 *
194 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
195 * if the argument is negative; otherwise, it is equal to the
196 * argument. This value is converted to a string of ASCII digits
197 * in hexadecimal (base 16) with no extra leading
198 * {@code 0}s.
199 *
200 * <p>The value of the argument can be recovered from the returned
201 * string {@code s} by calling {@link
202 * Integer#parseUnsignedInt(String, int)
203 * Integer.parseUnsignedInt(s, 16)}.
204 *
205 * <p>If the unsigned magnitude is zero, it is represented by a
206 * single zero character {@code '0'} ({@code '\u005Cu0030'});
207 * otherwise, the first character of the representation of the
208 * unsigned magnitude will not be the zero character. The
209 * following characters are used as hexadecimal digits:
210 *
211 * <blockquote>
212 * {@code 0123456789abcdef}
213 * </blockquote>
214 *
215 * These are the characters {@code '\u005Cu0030'} through
216 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
217 * {@code '\u005Cu0066'}. If uppercase letters are
218 * desired, the {@link java.lang.String#toUpperCase()} method may
219 * be called on the result:
220 *
221 * <blockquote>
222 * {@code Integer.toHexString(n).toUpperCase()}
223 * </blockquote>
224 *
225 * @param i an integer to be converted to a string.
226 * @return the string representation of the unsigned integer value
227 * represented by the argument in hexadecimal (base 16).
228 * @see #parseUnsignedInt(String, int)
229 * @see #toUnsignedString(int, int)
230 * @since JDK1.0.2
231 */
232 public static String toHexString(int i) {
233 return toUnsignedString0(i, 4);
234 }
235
236 /**
237 * Returns a string representation of the integer argument as an
238 * unsigned integer in base 8.
239 *
240 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
241 * if the argument is negative; otherwise, it is equal to the
242 * argument. This value is converted to a string of ASCII digits
243 * in octal (base 8) with no extra leading {@code 0}s.
244 *
245 * <p>The value of the argument can be recovered from the returned
246 * string {@code s} by calling {@link
247 * Integer#parseUnsignedInt(String, int)
248 * Integer.parseUnsignedInt(s, 8)}.
249 *
250 * <p>If the unsigned magnitude is zero, it is represented by a
251 * single zero character {@code '0'} ({@code '\u005Cu0030'});
252 * otherwise, the first character of the representation of the
253 * unsigned magnitude will not be the zero character. The
254 * following characters are used as octal digits:
255 *
256 * <blockquote>
257 * {@code 01234567}
258 * </blockquote>
259 *
260 * These are the characters {@code '\u005Cu0030'} through
261 * {@code '\u005Cu0037'}.
262 *
263 * @param i an integer to be converted to a string.
264 * @return the string representation of the unsigned integer value
265 * represented by the argument in octal (base 8).
266 * @see #parseUnsignedInt(String, int)
267 * @see #toUnsignedString(int, int)
268 * @since JDK1.0.2
269 */
270 public static String toOctalString(int i) {
271 return toUnsignedString0(i, 3);
272 }
273
274 /**
275 * Returns a string representation of the integer argument as an
276 * unsigned integer in base 2.
277 *
278 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
279 * if the argument is negative; otherwise it is equal to the
280 * argument. This value is converted to a string of ASCII digits
281 * in binary (base 2) with no extra leading {@code 0}s.
282 *
283 * <p>The value of the argument can be recovered from the returned
284 * string {@code s} by calling {@link
285 * Integer#parseUnsignedInt(String, int)
286 * Integer.parseUnsignedInt(s, 2)}.
287 *
288 * <p>If the unsigned magnitude is zero, it is represented by a
289 * single zero character {@code '0'} ({@code '\u005Cu0030'});
290 * otherwise, the first character of the representation of the
291 * unsigned magnitude will not be the zero character. The
292 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
293 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
294 *
295 * @param i an integer to be converted to a string.
296 * @return the string representation of the unsigned integer value
297 * represented by the argument in binary (base 2).
298 * @see #parseUnsignedInt(String, int)
299 * @see #toUnsignedString(int, int)
300 * @since JDK1.0.2
301 */
302 public static String toBinaryString(int i) {
303 return toUnsignedString0(i, 1);
304 }
305
306 /**
307 * Convert the integer to an unsigned number.
308 */
309 private static String toUnsignedString0(int val, int shift) {
310 // assert shift > 0 && shift <=5 : "Illegal shift value";
311 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
312 int chars = Math.max(((mag + (shift - 1)) / shift), 1);
313 char[] buf = new char[chars];
314
315 formatUnsignedInt(val, shift, buf, 0, chars);
316
317 // Use special constructor which takes over "buf".
318 return new String(buf, true);
319 }
320
321 /**
322 * Format a long (treated as unsigned) into a character buffer.
323 * @param val the unsigned int to format
324 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
325 * @param buf the character buffer to write to
326 * @param offset the offset in the destination buffer to start at
327 * @param len the number of characters to write
328 * @return the lowest character location used
329 */
330 static int formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
331 int charPos = len;
332 int radix = 1 << shift;
333 int mask = radix - 1;
334 do {
335 buf[offset + --charPos] = Integer.digits[val & mask];
336 val >>>= shift;
337 } while (val != 0 && charPos > 0);
338
339 return charPos;
340 }
341
342 final static char [] DigitTens = {
343 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
344 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
345 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
346 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
347 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
348 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
349 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
350 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
351 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
352 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
353 } ;
354
355 final static char [] DigitOnes = {
356 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
357 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
358 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
359 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
360 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
361 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
362 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
363 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
364 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
365 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
366 } ;
367
368 // I use the "invariant division by multiplication" trick to
369 // accelerate Integer.toString. In particular we want to
370 // avoid division by 10.
371 //
372 // The "trick" has roughly the same performance characteristics
373 // as the "classic" Integer.toString code on a non-JIT VM.
374 // The trick avoids .rem and .div calls but has a longer code
375 // path and is thus dominated by dispatch overhead. In the
376 // JIT case the dispatch overhead doesn't exist and the
377 // "trick" is considerably faster than the classic code.
378 //
379 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
380 // sequence.
381 //
382 // RE: Division by Invariant Integers using Multiplication
383 // T Gralund, P Montgomery
384 // ACM PLDI 1994
385 //
386
387 /**
388 * Returns a {@code String} object representing the
389 * specified integer. The argument is converted to signed decimal
390 * representation and returned as a string, exactly as if the
391 * argument and radix 10 were given as arguments to the {@link
392 * #toString(int, int)} method.
393 *
394 * @param i an integer to be converted.
395 * @return a string representation of the argument in base 10.
396 */
397 public static String toString(int i) {
398 if (i == Integer.MIN_VALUE)
399 return "-2147483648";
400 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
401 char[] buf = new char[size];
402 getChars(i, size, buf);
403 return new String(buf, true);
404 }
405
406 /**
407 * Returns a string representation of the argument as an unsigned
408 * decimal value.
409 *
410 * The argument is converted to unsigned decimal representation
411 * and returned as a string exactly as if the argument and radix
412 * 10 were given as arguments to the {@link #toUnsignedString(int,
413 * int)} method.
414 *
415 * @param i an integer to be converted to an unsigned string.
416 * @return an unsigned string representation of the argument.
417 * @see #toUnsignedString(int, int)
418 * @since 1.8
419 */
420 public static String toUnsignedString(int i) {
421 return Long.toString(toUnsignedLong(i));
422 }
423
424 /**
425 * Places characters representing the integer i into the
426 * character array buf. The characters are placed into
427 * the buffer backwards starting with the least significant
428 * digit at the specified index (exclusive), and working
429 * backwards from there.
430 *
431 * Will fail if i == Integer.MIN_VALUE
432 */
433 static void getChars(int i, int index, char[] buf) {
434 int q, r;
435 int charPos = index;
436 char sign = 0;
437
438 if (i < 0) {
439 sign = '-';
440 i = -i;
441 }
442
443 // Generate two digits per iteration
444 while (i >= 65536) {
445 q = i / 100;
446 // really: r = i - (q * 100);
447 r = i - ((q << 6) + (q << 5) + (q << 2));
448 i = q;
449 buf [--charPos] = DigitOnes[r];
450 buf [--charPos] = DigitTens[r];
451 }
452
453 // Fall thru to fast mode for smaller numbers
454 // assert(i <= 65536, i);
455 for (;;) {
456 q = (i * 52429) >>> (16+3);
457 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
458 buf [--charPos] = digits [r];
459 i = q;
460 if (i == 0) break;
461 }
462 if (sign != 0) {
463 buf [--charPos] = sign;
464 }
465 }
466
467 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
468 99999999, 999999999, Integer.MAX_VALUE };
469
470 // Requires positive x
471 static int stringSize(int x) {
472 for (int i=0; ; i++)
473 if (x <= sizeTable[i])
474 return i+1;
475 }
476
477 /**
478 * Parses the string argument as a signed integer in the radix
479 * specified by the second argument. The characters in the string
480 * must all be digits of the specified radix (as determined by
481 * whether {@link java.lang.Character#digit(char, int)} returns a
482 * nonnegative value), except that the first character may be an
483 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
484 * indicate a negative value or an ASCII plus sign {@code '+'}
485 * ({@code '\u005Cu002B'}) to indicate a positive value. The
486 * resulting integer value is returned.
487 *
488 * <p>An exception of type {@code NumberFormatException} is
489 * thrown if any of the following situations occurs:
490 * <ul>
491 * <li>The first argument is {@code null} or is a string of
492 * length zero.
493 *
494 * <li>The radix is either smaller than
495 * {@link java.lang.Character#MIN_RADIX} or
496 * larger than {@link java.lang.Character#MAX_RADIX}.
497 *
498 * <li>Any character of the string is not a digit of the specified
499 * radix, except that the first character may be a minus sign
500 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
501 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
502 * string is longer than length 1.
503 *
504 * <li>The value represented by the string is not a value of type
505 * {@code int}.
506 * </ul>
507 *
508 * <p>Examples:
509 * <blockquote><pre>
510 * parseInt("0", 10) returns 0
511 * parseInt("473", 10) returns 473
512 * parseInt("+42", 10) returns 42
513 * parseInt("-0", 10) returns 0
514 * parseInt("-FF", 16) returns -255
515 * parseInt("1100110", 2) returns 102
516 * parseInt("2147483647", 10) returns 2147483647
517 * parseInt("-2147483648", 10) returns -2147483648
518 * parseInt("2147483648", 10) throws a NumberFormatException
519 * parseInt("99", 8) throws a NumberFormatException
520 * parseInt("Kona", 10) throws a NumberFormatException
521 * parseInt("Kona", 27) returns 411787
522 * </pre></blockquote>
523 *
524 * @param s the {@code String} containing the integer
525 * representation to be parsed
526 * @param radix the radix to be used while parsing {@code s}.
527 * @return the integer represented by the string argument in the
528 * specified radix.
529 * @exception NumberFormatException if the {@code String}
530 * does not contain a parsable {@code int}.
531 */
532 public static int parseInt(String s, int radix)
533 throws NumberFormatException
534 {
535 /*
536 * WARNING: This method may be invoked early during VM initialization
537 * before IntegerCache is initialized. Care must be taken to not use
538 * the valueOf method.
539 */
540
541 if (s == null) {
542 throw new NumberFormatException("null");
543 }
544
545 if (radix < Character.MIN_RADIX) {
546 throw new NumberFormatException("radix " + radix +
547 " less than Character.MIN_RADIX");
548 }
549
550 if (radix > Character.MAX_RADIX) {
551 throw new NumberFormatException("radix " + radix +
552 " greater than Character.MAX_RADIX");
553 }
554
555 int result = 0;
556 boolean negative = false;
557 int i = 0, len = s.length();
558 int limit = -Integer.MAX_VALUE;
559 int multmin;
560 int digit;
561
562 if (len > 0) {
563 char firstChar = s.charAt(0);
564 if (firstChar < '0') { // Possible leading "+" or "-"
565 if (firstChar == '-') {
566 negative = true;
567 limit = Integer.MIN_VALUE;
568 } else if (firstChar != '+')
569 throw NumberFormatException.forInputString(s);
570
571 if (len == 1) // Cannot have lone "+" or "-"
572 throw NumberFormatException.forInputString(s);
573 i++;
574 }
575 multmin = limit / radix;
576 while (i < len) {
577 // Accumulating negatively avoids surprises near MAX_VALUE
578 digit = Character.digit(s.charAt(i++),radix);
579 if (digit < 0) {
580 throw NumberFormatException.forInputString(s);
581 }
582 if (result < multmin) {
583 throw NumberFormatException.forInputString(s);
584 }
585 result *= radix;
586 if (result < limit + digit) {
587 throw NumberFormatException.forInputString(s);
588 }
589 result -= digit;
590 }
591 } else {
592 throw NumberFormatException.forInputString(s);
593 }
594 return negative ? result : -result;
595 }
596
597 /**
598 * Parses the string argument as a signed decimal integer. The
599 * characters in the string must all be decimal digits, except
600 * that the first character may be an ASCII minus sign {@code '-'}
601 * ({@code '\u005Cu002D'}) to indicate a negative value or an
602 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
603 * indicate a positive value. The resulting integer value is
604 * returned, exactly as if the argument and the radix 10 were
605 * given as arguments to the {@link #parseInt(java.lang.String,
606 * int)} method.
607 *
608 * @param s a {@code String} containing the {@code int}
609 * representation to be parsed
610 * @return the integer value represented by the argument in decimal.
611 * @exception NumberFormatException if the string does not contain a
612 * parsable integer.
613 */
614 public static int parseInt(String s) throws NumberFormatException {
615 return parseInt(s,10);
616 }
617
618 /**
619 * Parses the string argument as an unsigned integer in the radix
620 * specified by the second argument. An unsigned integer maps the
621 * values usually associated with negative numbers to positive
622 * numbers larger than {@code MAX_VALUE}.
623 *
624 * The characters in the string must all be digits of the
625 * specified radix (as determined by whether {@link
626 * java.lang.Character#digit(char, int)} returns a nonnegative
627 * value), except that the first character may be an ASCII plus
628 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
629 * integer value is returned.
630 *
631 * <p>An exception of type {@code NumberFormatException} is
632 * thrown if any of the following situations occurs:
633 * <ul>
634 * <li>The first argument is {@code null} or is a string of
635 * length zero.
636 *
637 * <li>The radix is either smaller than
638 * {@link java.lang.Character#MIN_RADIX} or
639 * larger than {@link java.lang.Character#MAX_RADIX}.
640 *
641 * <li>Any character of the string is not a digit of the specified
642 * radix, except that the first character may be a plus sign
643 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
644 * string is longer than length 1.
645 *
646 * <li>The value represented by the string is larger than the
647 * largest unsigned {@code int}, 2<sup>32</sup>-1.
648 *
649 * </ul>
650 *
651 *
652 * @param s the {@code String} containing the unsigned integer
653 * representation to be parsed
654 * @param radix the radix to be used while parsing {@code s}.
655 * @return the integer represented by the string argument in the
656 * specified radix.
657 * @throws NumberFormatException if the {@code String}
658 * does not contain a parsable {@code int}.
659 * @since 1.8
660 */
661 public static int parseUnsignedInt(String s, int radix)
662 throws NumberFormatException {
663 if (s == null) {
664 throw new NumberFormatException("null");
665 }
666
667 int len = s.length();
668 if (len > 0) {
669 char firstChar = s.charAt(0);
670 if (firstChar == '-') {
671 throw new
672 NumberFormatException(String.format("Illegal leading minus sign " +
673 "on unsigned string %s.", s));
674 } else {
675 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
676 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
677 return parseInt(s, radix);
678 } else {
679 long ell = Long.parseLong(s, radix);
680 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
681 return (int) ell;
682 } else {
683 throw new
684 NumberFormatException(String.format("String value %s exceeds " +
685 "range of unsigned int.", s));
686 }
687 }
688 }
689 } else {
690 throw NumberFormatException.forInputString(s);
691 }
692 }
693
694 /**
695 * Parses the string argument as an unsigned decimal integer. The
696 * characters in the string must all be decimal digits, except
697 * that the first character may be an an ASCII plus sign {@code
698 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
699 * is returned, exactly as if the argument and the radix 10 were
700 * given as arguments to the {@link
701 * #parseUnsignedInt(java.lang.String, int)} method.
702 *
703 * @param s a {@code String} containing the unsigned {@code int}
704 * representation to be parsed
705 * @return the unsigned integer value represented by the argument in decimal.
706 * @throws NumberFormatException if the string does not contain a
707 * parsable unsigned integer.
708 * @since 1.8
709 */
710 public static int parseUnsignedInt(String s) throws NumberFormatException {
711 return parseUnsignedInt(s, 10);
712 }
713
714 /**
715 * Returns an {@code Integer} object holding the value
716 * extracted from the specified {@code String} when parsed
717 * with the radix given by the second argument. The first argument
718 * is interpreted as representing a signed integer in the radix
719 * specified by the second argument, exactly as if the arguments
720 * were given to the {@link #parseInt(java.lang.String, int)}
721 * method. The result is an {@code Integer} object that
722 * represents the integer value specified by the string.
723 *
724 * <p>In other words, this method returns an {@code Integer}
725 * object equal to the value of:
726 *
727 * <blockquote>
728 * {@code new Integer(Integer.parseInt(s, radix))}
729 * </blockquote>
730 *
731 * @param s the string to be parsed.
732 * @param radix the radix to be used in interpreting {@code s}
733 * @return an {@code Integer} object holding the value
734 * represented by the string argument in the specified
735 * radix.
736 * @exception NumberFormatException if the {@code String}
737 * does not contain a parsable {@code int}.
738 */
739 public static Integer valueOf(String s, int radix) throws NumberFormatException {
740 return Integer.valueOf(parseInt(s,radix));
741 }
742
743 /**
744 * Returns an {@code Integer} object holding the
745 * value of the specified {@code String}. The argument is
746 * interpreted as representing a signed decimal integer, exactly
747 * as if the argument were given to the {@link
748 * #parseInt(java.lang.String)} method. The result is an
749 * {@code Integer} object that represents the integer value
750 * specified by the string.
751 *
752 * <p>In other words, this method returns an {@code Integer}
753 * object equal to the value of:
754 *
755 * <blockquote>
756 * {@code new Integer(Integer.parseInt(s))}
757 * </blockquote>
758 *
759 * @param s the string to be parsed.
760 * @return an {@code Integer} object holding the value
761 * represented by the string argument.
762 * @exception NumberFormatException if the string cannot be parsed
763 * as an integer.
764 */
765 public static Integer valueOf(String s) throws NumberFormatException {
766 return Integer.valueOf(parseInt(s, 10));
767 }
768
769 /**
770 * Cache to support the object identity semantics of autoboxing for values between
771 * -128 and 127 (inclusive) as required by JLS.
772 *
773 * The cache is initialized on first usage. The size of the cache
774 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
775 * During VM initialization, java.lang.Integer.IntegerCache.high property
776 * may be set and saved in the private system properties in the
777 * sun.misc.VM class.
778 */
779
780 private static class IntegerCache {
781 static final int low = -128;
782 static final int high;
783 static final Integer cache[];
784
785 static {
786 // high value may be configured by property
787 int h = 127;
788 String integerCacheHighPropValue =
789 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
790 if (integerCacheHighPropValue != null) {
791 try {
792 int i = parseInt(integerCacheHighPropValue);
793 i = Math.max(i, 127);
794 // Maximum array size is Integer.MAX_VALUE
795 h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
796 } catch( NumberFormatException nfe) {
797 // If the property cannot be parsed into an int, ignore it.
798 }
799 }
800 high = h;
801
802 cache = new Integer[(high - low) + 1];
803 int j = low;
804 for(int k = 0; k < cache.length; k++)
805 cache[k] = new Integer(j++);
806
807 // range [-128, 127] must be interned (JLS7 5.1.7)
808 assert IntegerCache.high >= 127;
809 }
810
811 private IntegerCache() {}
812 }
813
814 /**
815 * Returns an {@code Integer} instance representing the specified
816 * {@code int} value. If a new {@code Integer} instance is not
817 * required, this method should generally be used in preference to
818 * the constructor {@link #Integer(int)}, as this method is likely
819 * to yield significantly better space and time performance by
820 * caching frequently requested values.
821 *
822 * This method will always cache values in the range -128 to 127,
823 * inclusive, and may cache other values outside of this range.
824 *
825 * @param i an {@code int} value.
826 * @return an {@code Integer} instance representing {@code i}.
827 * @since 1.5
828 */
829 public static Integer valueOf(int i) {
830 if (i >= IntegerCache.low && i <= IntegerCache.high)
831 return IntegerCache.cache[i + (-IntegerCache.low)];
832 return new Integer(i);
833 }
834
835 /**
836 * The value of the {@code Integer}.
837 *
838 * @serial
839 */
840 private final int value;
841
842 /**
843 * Constructs a newly allocated {@code Integer} object that
844 * represents the specified {@code int} value.
845 *
846 * @param value the value to be represented by the
847 * {@code Integer} object.
848 */
849 public Integer(int value) {
850 this.value = value;
851 }
852
853 /**
854 * Constructs a newly allocated {@code Integer} object that
855 * represents the {@code int} value indicated by the
856 * {@code String} parameter. The string is converted to an
857 * {@code int} value in exactly the manner used by the
858 * {@code parseInt} method for radix 10.
859 *
860 * @param s the {@code String} to be converted to an
861 * {@code Integer}.
862 * @exception NumberFormatException if the {@code String} does not
863 * contain a parsable integer.
864 * @see java.lang.Integer#parseInt(java.lang.String, int)
865 */
866 public Integer(String s) throws NumberFormatException {
867 this.value = parseInt(s, 10);
868 }
869
870 /**
871 * Returns the value of this {@code Integer} as a {@code byte}
872 * after a narrowing primitive conversion.
873 * @jls 5.1.3 Narrowing Primitive Conversions
874 */
875 public byte byteValue() {
876 return (byte)value;
877 }
878
879 /**
880 * Returns the value of this {@code Integer} as a {@code short}
881 * after a narrowing primitive conversion.
882 * @jls 5.1.3 Narrowing Primitive Conversions
883 */
884 public short shortValue() {
885 return (short)value;
886 }
887
888 /**
889 * Returns the value of this {@code Integer} as an
890 * {@code int}.
891 */
892 public int intValue() {
893 return value;
894 }
895
896 /**
897 * Returns the value of this {@code Integer} as a {@code long}
898 * after a widening primitive conversion.
899 * @jls 5.1.2 Widening Primitive Conversions
900 * @see Integer#toUnsignedLong(int)
901 */
902 public long longValue() {
903 return (long)value;
904 }
905
906 /**
907 * Returns the value of this {@code Integer} as a {@code float}
908 * after a widening primitive conversion.
909 * @jls 5.1.2 Widening Primitive Conversions
910 */
911 public float floatValue() {
912 return (float)value;
913 }
914
915 /**
916 * Returns the value of this {@code Integer} as a {@code double}
917 * after a widening primitive conversion.
918 * @jls 5.1.2 Widening Primitive Conversions
919 */
920 public double doubleValue() {
921 return (double)value;
922 }
923
924 /**
925 * Returns a {@code String} object representing this
926 * {@code Integer}'s value. The value is converted to signed
927 * decimal representation and returned as a string, exactly as if
928 * the integer value were given as an argument to the {@link
929 * java.lang.Integer#toString(int)} method.
930 *
931 * @return a string representation of the value of this object in
932 * base 10.
933 */
934 public String toString() {
935 return toString(value);
936 }
937
938 /**
939 * Returns a hash code for this {@code Integer}.
940 *
941 * @return a hash code value for this object, equal to the
942 * primitive {@code int} value represented by this
943 * {@code Integer} object.
944 */
945 @Override
946 public int hashCode() {
947 return Integer.hashCode(value);
948 }
949
950 /**
951 * Returns a hash code for a {@code int} value; compatible with
952 * {@code Integer.hashCode()}.
953 *
954 * @since 1.8
955 *
956 * @return a hash code value for a {@code int} value.
957 */
958 public static int hashCode(int value) {
959 return value;
960 }
961
962 /**
963 * Compares this object to the specified object. The result is
964 * {@code true} if and only if the argument is not
965 * {@code null} and is an {@code Integer} object that
966 * contains the same {@code int} value as this object.
967 *
968 * @param obj the object to compare with.
969 * @return {@code true} if the objects are the same;
970 * {@code false} otherwise.
971 */
972 public boolean equals(Object obj) {
973 if (obj instanceof Integer) {
974 return value == ((Integer)obj).intValue();
975 }
976 return false;
977 }
978
979 /**
980 * Determines the integer value of the system property with the
981 * specified name.
982 *
983 * <p>The first argument is treated as the name of a system
984 * property. System properties are accessible through the {@link
985 * java.lang.System#getProperty(java.lang.String)} method. The
986 * string value of this property is then interpreted as an integer
987 * value using the grammar supported by {@link Integer#decode decode} and
988 * an {@code Integer} object representing this value is returned.
989 *
990 * <p>If there is no property with the specified name, if the
991 * specified name is empty or {@code null}, or if the property
992 * does not have the correct numeric format, then {@code null} is
993 * returned.
994 *
995 * <p>In other words, this method returns an {@code Integer}
996 * object equal to the value of:
997 *
998 * <blockquote>
999 * {@code getInteger(nm, null)}
1000 * </blockquote>
1001 *
1002 * @param nm property name.
1003 * @return the {@code Integer} value of the property.
1004 * @throws SecurityException for the same reasons as
1005 * {@link System#getProperty(String) System.getProperty}
1006 * @see java.lang.System#getProperty(java.lang.String)
1007 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1008 */
1009 public static Integer getInteger(String nm) {
1010 return getInteger(nm, null);
1011 }
1012
1013 /**
1014 * Determines the integer value of the system property with the
1015 * specified name.
1016 *
1017 * <p>The first argument is treated as the name of a system
1018 * property. System properties are accessible through the {@link
1019 * java.lang.System#getProperty(java.lang.String)} method. The
1020 * string value of this property is then interpreted as an integer
1021 * value using the grammar supported by {@link Integer#decode decode} and
1022 * an {@code Integer} object representing this value is returned.
1023 *
1024 * <p>The second argument is the default value. An {@code Integer} object
1025 * that represents the value of the second argument is returned if there
1026 * is no property of the specified name, if the property does not have
1027 * the correct numeric format, or if the specified name is empty or
1028 * {@code null}.
1029 *
1030 * <p>In other words, this method returns an {@code Integer} object
1031 * equal to the value of:
1032 *
1033 * <blockquote>
1034 * {@code getInteger(nm, new Integer(val))}
1035 * </blockquote>
1036 *
1037 * but in practice it may be implemented in a manner such as:
1038 *
1039 * <blockquote><pre>
1040 * Integer result = getInteger(nm, null);
1041 * return (result == null) ? new Integer(val) : result;
1042 * </pre></blockquote>
1043 *
1044 * to avoid the unnecessary allocation of an {@code Integer}
1045 * object when the default value is not needed.
1046 *
1047 * @param nm property name.
1048 * @param val default value.
1049 * @return the {@code Integer} value of the property.
1050 * @throws SecurityException for the same reasons as
1051 * {@link System#getProperty(String) System.getProperty}
1052 * @see java.lang.System#getProperty(java.lang.String)
1053 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1054 */
1055 public static Integer getInteger(String nm, int val) {
1056 Integer result = getInteger(nm, null);
1057 return (result == null) ? Integer.valueOf(val) : result;
1058 }
1059
1060 /**
1061 * Returns the integer value of the system property with the
1062 * specified name. The first argument is treated as the name of a
1063 * system property. System properties are accessible through the
1064 * {@link java.lang.System#getProperty(java.lang.String)} method.
1065 * The string value of this property is then interpreted as an
1066 * integer value, as per the {@link Integer#decode decode} method,
1067 * and an {@code Integer} object representing this value is
1068 * returned; in summary:
1069 *
1070 * <ul><li>If the property value begins with the two ASCII characters
1071 * {@code 0x} or the ASCII character {@code #}, not
1072 * followed by a minus sign, then the rest of it is parsed as a
1073 * hexadecimal integer exactly as by the method
1074 * {@link #valueOf(java.lang.String, int)} with radix 16.
1075 * <li>If the property value begins with the ASCII character
1076 * {@code 0} followed by another character, it is parsed as an
1077 * octal integer exactly as by the method
1078 * {@link #valueOf(java.lang.String, int)} with radix 8.
1079 * <li>Otherwise, the property value is parsed as a decimal integer
1080 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1081 * with radix 10.
1082 * </ul>
1083 *
1084 * <p>The second argument is the default value. The default value is
1085 * returned if there is no property of the specified name, if the
1086 * property does not have the correct numeric format, or if the
1087 * specified name is empty or {@code null}.
1088 *
1089 * @param nm property name.
1090 * @param val default value.
1091 * @return the {@code Integer} value of the property.
1092 * @throws SecurityException for the same reasons as
1093 * {@link System#getProperty(String) System.getProperty}
1094 * @see System#getProperty(java.lang.String)
1095 * @see System#getProperty(java.lang.String, java.lang.String)
1096 */
1097 public static Integer getInteger(String nm, Integer val) {
1098 String v = null;
1099 try {
1100 v = System.getProperty(nm);
1101 } catch (IllegalArgumentException | NullPointerException e) {
1102 }
1103 if (v != null) {
1104 try {
1105 return Integer.decode(v);
1106 } catch (NumberFormatException e) {
1107 }
1108 }
1109 return val;
1110 }
1111
1112 /**
1113 * Decodes a {@code String} into an {@code Integer}.
1114 * Accepts decimal, hexadecimal, and octal numbers given
1115 * by the following grammar:
1116 *
1117 * <blockquote>
1118 * <dl>
1119 * <dt><i>DecodableString:</i>
1120 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1121 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1122 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1123 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1124 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1125 * <p>
1126 * <dt><i>Sign:</i>
1127 * <dd>{@code -}
1128 * <dd>{@code +}
1129 * </dl>
1130 * </blockquote>
1131 *
1132 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1133 * are as defined in section 3.10.1 of
1134 * <cite>The Java™ Language Specification</cite>,
1135 * except that underscores are not accepted between digits.
1136 *
1137 * <p>The sequence of characters following an optional
1138 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1139 * "{@code #}", or leading zero) is parsed as by the {@code
1140 * Integer.parseInt} method with the indicated radix (10, 16, or
1141 * 8). This sequence of characters must represent a positive
1142 * value or a {@link NumberFormatException} will be thrown. The
1143 * result is negated if first character of the specified {@code
1144 * String} is the minus sign. No whitespace characters are
1145 * permitted in the {@code String}.
1146 *
1147 * @param nm the {@code String} to decode.
1148 * @return an {@code Integer} object holding the {@code int}
1149 * value represented by {@code nm}
1150 * @exception NumberFormatException if the {@code String} does not
1151 * contain a parsable integer.
1152 * @see java.lang.Integer#parseInt(java.lang.String, int)
1153 */
1154 public static Integer decode(String nm) throws NumberFormatException {
1155 int radix = 10;
1156 int index = 0;
1157 boolean negative = false;
1158 Integer result;
1159
1160 if (nm.length() == 0)
1161 throw new NumberFormatException("Zero length string");
1162 char firstChar = nm.charAt(0);
1163 // Handle sign, if present
1164 if (firstChar == '-') {
1165 negative = true;
1166 index++;
1167 } else if (firstChar == '+')
1168 index++;
1169
1170 // Handle radix specifier, if present
1171 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1172 index += 2;
1173 radix = 16;
1174 }
1175 else if (nm.startsWith("#", index)) {
1176 index ++;
1177 radix = 16;
1178 }
1179 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1180 index ++;
1181 radix = 8;
1182 }
1183
1184 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1185 throw new NumberFormatException("Sign character in wrong position");
1186
1187 try {
1188 result = Integer.valueOf(nm.substring(index), radix);
1189 result = negative ? Integer.valueOf(-result.intValue()) : result;
1190 } catch (NumberFormatException e) {
1191 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1192 // handles this case, and causes any genuine format error to be
1193 // rethrown.
1194 String constant = negative ? ("-" + nm.substring(index))
1195 : nm.substring(index);
1196 result = Integer.valueOf(constant, radix);
1197 }
1198 return result;
1199 }
1200
1201 /**
1202 * Compares two {@code Integer} objects numerically.
1203 *
1204 * @param anotherInteger the {@code Integer} to be compared.
1205 * @return the value {@code 0} if this {@code Integer} is
1206 * equal to the argument {@code Integer}; a value less than
1207 * {@code 0} if this {@code Integer} is numerically less
1208 * than the argument {@code Integer}; and a value greater
1209 * than {@code 0} if this {@code Integer} is numerically
1210 * greater than the argument {@code Integer} (signed
1211 * comparison).
1212 * @since 1.2
1213 */
1214 public int compareTo(Integer anotherInteger) {
1215 return compare(this.value, anotherInteger.value);
1216 }
1217
1218 /**
1219 * Compares two {@code int} values numerically.
1220 * The value returned is identical to what would be returned by:
1221 * <pre>
1222 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1223 * </pre>
1224 *
1225 * @param x the first {@code int} to compare
1226 * @param y the second {@code int} to compare
1227 * @return the value {@code 0} if {@code x == y};
1228 * a value less than {@code 0} if {@code x < y}; and
1229 * a value greater than {@code 0} if {@code x > y}
1230 * @since 1.7
1231 */
1232 public static int compare(int x, int y) {
1233 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1234 }
1235
1236 /**
1237 * Compares two {@code int} values numerically treating the values
1238 * as unsigned.
1239 *
1240 * @param x the first {@code int} to compare
1241 * @param y the second {@code int} to compare
1242 * @return the value {@code 0} if {@code x == y}; a value less
1243 * than {@code 0} if {@code x < y} as unsigned values; and
1244 * a value greater than {@code 0} if {@code x > y} as
1245 * unsigned values
1246 * @since 1.8
1247 */
1248 public static int compareUnsigned(int x, int y) {
1249 return compare(x + MIN_VALUE, y + MIN_VALUE);
1250 }
1251
1252 /**
1253 * Converts the argument to a {@code long} by an unsigned
1254 * conversion. In an unsigned conversion to a {@code long}, the
1255 * high-order 32 bits of the {@code long} are zero and the
1256 * low-order 32 bits are equal to the bits of the integer
1257 * argument.
1258 *
1259 * Consequently, zero and positive {@code int} values are mapped
1260 * to a numerically equal {@code long} value and negative {@code
1261 * int} values are mapped to a {@code long} value equal to the
1262 * input plus 2<sup>32</sup>.
1263 *
1264 * @param x the value to convert to an unsigned {@code long}
1265 * @return the argument converted to {@code long} by an unsigned
1266 * conversion
1267 * @since 1.8
1268 */
1269 public static long toUnsignedLong(int x) {
1270 return ((long) x) & 0xffffffffL;
1271 }
1272
1273 /**
1274 * Returns the unsigned quotient of dividing the first argument by
1275 * the second where each argument and the result is interpreted as
1276 * an unsigned value.
1277 *
1278 * <p>Note that in two's complement arithmetic, the three other
1279 * basic arithmetic operations of add, subtract, and multiply are
1280 * bit-wise identical if the two operands are regarded as both
1281 * being signed or both being unsigned. Therefore separate {@code
1282 * addUnsigned}, etc. methods are not provided.
1283 *
1284 * @param dividend the value to be divided
1285 * @param divisor the value doing the dividing
1286 * @return the unsigned quotient of the first argument divided by
1287 * the second argument
1288 * @see #remainderUnsigned
1289 * @since 1.8
1290 */
1291 public static int divideUnsigned(int dividend, int divisor) {
1292 // In lieu of tricky code, for now just use long arithmetic.
1293 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1294 }
1295
1296 /**
1297 * Returns the unsigned remainder from dividing the first argument
1298 * by the second where each argument and the result is interpreted
1299 * as an unsigned value.
1300 *
1301 * @param dividend the value to be divided
1302 * @param divisor the value doing the dividing
1303 * @return the unsigned remainder of the first argument divided by
1304 * the second argument
1305 * @see #divideUnsigned
1306 * @since 1.8
1307 */
1308 public static int remainderUnsigned(int dividend, int divisor) {
1309 // In lieu of tricky code, for now just use long arithmetic.
1310 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1311 }
1312
1313
1314 // Bit twiddling
1315
1316 /**
1317 * The number of bits used to represent an {@code int} value in two's
1318 * complement binary form.
1319 *
1320 * @since 1.5
1321 */
1322 @Native public static final int SIZE = 32;
1323
1324 /**
1325 * The number of bytes used to represent a {@code int} value in two's
1326 * complement binary form.
1327 *
1328 * @since 1.8
1329 */
1330 public static final int BYTES = SIZE / Byte.SIZE;
1331
1332 /**
1333 * Returns an {@code int} value with at most a single one-bit, in the
1334 * position of the highest-order ("leftmost") one-bit in the specified
1335 * {@code int} value. Returns zero if the specified value has no
1336 * one-bits in its two's complement binary representation, that is, if it
1337 * is equal to zero.
1338 *
1339 * @return an {@code int} value with a single one-bit, in the position
1340 * of the highest-order one-bit in the specified value, or zero if
1341 * the specified value is itself equal to zero.
1342 * @since 1.5
1343 */
1344 public static int highestOneBit(int i) {
1345 // HD, Figure 3-1
1346 i |= (i >> 1);
1347 i |= (i >> 2);
1348 i |= (i >> 4);
1349 i |= (i >> 8);
1350 i |= (i >> 16);
1351 return i - (i >>> 1);
1352 }
1353
1354 /**
1355 * Returns an {@code int} value with at most a single one-bit, in the
1356 * position of the lowest-order ("rightmost") one-bit in the specified
1357 * {@code int} value. Returns zero if the specified value has no
1358 * one-bits in its two's complement binary representation, that is, if it
1359 * is equal to zero.
1360 *
1361 * @return an {@code int} value with a single one-bit, in the position
1362 * of the lowest-order one-bit in the specified value, or zero if
1363 * the specified value is itself equal to zero.
1364 * @since 1.5
1365 */
1366 public static int lowestOneBit(int i) {
1367 // HD, Section 2-1
1368 return i & -i;
1369 }
1370
1371 /**
1372 * Returns the number of zero bits preceding the highest-order
1373 * ("leftmost") one-bit in the two's complement binary representation
1374 * of the specified {@code int} value. Returns 32 if the
1375 * specified value has no one-bits in its two's complement representation,
1376 * in other words if it is equal to zero.
1377 *
1378 * <p>Note that this method is closely related to the logarithm base 2.
1379 * For all positive {@code int} values x:
1380 * <ul>
1381 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1382 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1383 * </ul>
1384 *
1385 * @return the number of zero bits preceding the highest-order
1386 * ("leftmost") one-bit in the two's complement binary representation
1387 * of the specified {@code int} value, or 32 if the value
1388 * is equal to zero.
1389 * @since 1.5
1390 */
1391 public static int numberOfLeadingZeros(int i) {
1392 // HD, Figure 5-6
1393 if (i == 0)
1394 return 32;
1395 int n = 1;
1396 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1397 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1398 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1399 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1400 n -= i >>> 31;
1401 return n;
1402 }
1403
1404 /**
1405 * Returns the number of zero bits following the lowest-order ("rightmost")
1406 * one-bit in the two's complement binary representation of the specified
1407 * {@code int} value. Returns 32 if the specified value has no
1408 * one-bits in its two's complement representation, in other words if it is
1409 * equal to zero.
1410 *
1411 * @return the number of zero bits following the lowest-order ("rightmost")
1412 * one-bit in the two's complement binary representation of the
1413 * specified {@code int} value, or 32 if the value is equal
1414 * to zero.
1415 * @since 1.5
1416 */
1417 public static int numberOfTrailingZeros(int i) {
1418 // HD, Figure 5-14
1419 int y;
1420 if (i == 0) return 32;
1421 int n = 31;
1422 y = i <<16; if (y != 0) { n = n -16; i = y; }
1423 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1424 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1425 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1426 return n - ((i << 1) >>> 31);
1427 }
1428
1429 /**
1430 * Returns the number of one-bits in the two's complement binary
1431 * representation of the specified {@code int} value. This function is
1432 * sometimes referred to as the <i>population count</i>.
1433 *
1434 * @return the number of one-bits in the two's complement binary
1435 * representation of the specified {@code int} value.
1436 * @since 1.5
1437 */
1438 public static int bitCount(int i) {
1439 // HD, Figure 5-2
1440 i = i - ((i >>> 1) & 0x55555555);
1441 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1442 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1443 i = i + (i >>> 8);
1444 i = i + (i >>> 16);
1445 return i & 0x3f;
1446 }
1447
1448 /**
1449 * Returns the value obtained by rotating the two's complement binary
1450 * representation of the specified {@code int} value left by the
1451 * specified number of bits. (Bits shifted out of the left hand, or
1452 * high-order, side reenter on the right, or low-order.)
1453 *
1454 * <p>Note that left rotation with a negative distance is equivalent to
1455 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1456 * distance)}. Note also that rotation by any multiple of 32 is a
1457 * no-op, so all but the last five bits of the rotation distance can be
1458 * ignored, even if the distance is negative: {@code rotateLeft(val,
1459 * distance) == rotateLeft(val, distance & 0x1F)}.
1460 *
1461 * @return the value obtained by rotating the two's complement binary
1462 * representation of the specified {@code int} value left by the
1463 * specified number of bits.
1464 * @since 1.5
1465 */
1466 public static int rotateLeft(int i, int distance) {
1467 return (i << distance) | (i >>> -distance);
1468 }
1469
1470 /**
1471 * Returns the value obtained by rotating the two's complement binary
1472 * representation of the specified {@code int} value right by the
1473 * specified number of bits. (Bits shifted out of the right hand, or
1474 * low-order, side reenter on the left, or high-order.)
1475 *
1476 * <p>Note that right rotation with a negative distance is equivalent to
1477 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1478 * distance)}. Note also that rotation by any multiple of 32 is a
1479 * no-op, so all but the last five bits of the rotation distance can be
1480 * ignored, even if the distance is negative: {@code rotateRight(val,
1481 * distance) == rotateRight(val, distance & 0x1F)}.
1482 *
1483 * @return the value obtained by rotating the two's complement binary
1484 * representation of the specified {@code int} value right by the
1485 * specified number of bits.
1486 * @since 1.5
1487 */
1488 public static int rotateRight(int i, int distance) {
1489 return (i >>> distance) | (i << -distance);
1490 }
1491
1492 /**
1493 * Returns the value obtained by reversing the order of the bits in the
1494 * two's complement binary representation of the specified {@code int}
1495 * value.
1496 *
1497 * @return the value obtained by reversing order of the bits in the
1498 * specified {@code int} value.
1499 * @since 1.5
1500 */
1501 public static int reverse(int i) {
1502 // HD, Figure 7-1
1503 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1504 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1505 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1506 i = (i << 24) | ((i & 0xff00) << 8) |
1507 ((i >>> 8) & 0xff00) | (i >>> 24);
1508 return i;
1509 }
1510
1511 /**
1512 * Returns the signum function of the specified {@code int} value. (The
1513 * return value is -1 if the specified value is negative; 0 if the
1514 * specified value is zero; and 1 if the specified value is positive.)
1515 *
1516 * @return the signum function of the specified {@code int} value.
1517 * @since 1.5
1518 */
1519 public static int signum(int i) {
1520 // HD, Section 2-7
1521 return (i >> 31) | (-i >>> 31);
1522 }
1523
1524 /**
1525 * Returns the value obtained by reversing the order of the bytes in the
1526 * two's complement representation of the specified {@code int} value.
1527 *
1528 * @return the value obtained by reversing the bytes in the specified
1529 * {@code int} value.
1530 * @since 1.5
1531 */
1532 public static int reverseBytes(int i) {
1533 return ((i >>> 24) ) |
1534 ((i >> 8) & 0xFF00) |
1535 ((i << 8) & 0xFF0000) |
1536 ((i << 24));
1537 }
1538
1539 /**
1540 * Adds two integers together as per the + operator.
1541 *
1542 * @param a the first operand
1543 * @param b the second operand
1544 * @return the sum of {@code a} and {@code b}
1545 * @see java.util.function.BinaryOperator
1546 * @since 1.8
1547 */
1548 public static int sum(int a, int b) {
1549 return a + b;
1550 }
1551
1552 /**
1553 * Returns the greater of two {@code int} values
1554 * as if by calling {@link Math#max(int, int) Math.max}.
1555 *
1556 * @param a the first operand
1557 * @param b the second operand
1558 * @return the greater of {@code a} and {@code b}
1559 * @see java.util.function.BinaryOperator
1560 * @since 1.8
1561 */
1562 public static int max(int a, int b) {
1563 return Math.max(a, b);
1564 }
1565
1566 /**
1567 * Returns the smaller of two {@code int} values
1568 * as if by calling {@link Math#min(int, int) Math.min}.
1569 *
1570 * @param a the first operand
1571 * @param b the second operand
1572 * @return the smaller of {@code a} and {@code b}
1573 * @see java.util.function.BinaryOperator
1574 * @since 1.8
1575 */
1576 public static int min(int a, int b) {
1577 return Math.min(a, b);
1578 }
1579
1580 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1581 @Native private static final long serialVersionUID = 1360826667806852920L;
1582 }