1 /*
2 * Copyright 1994-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.lang;
27
28 /**
29 * The {@code Integer} class wraps a value of the primitive type
30 * {@code int} in an object. An object of type {@code Integer}
31 * contains a single field whose type is {@code int}.
32 *
33 * <p>In addition, this class provides several methods for converting
34 * an {@code int} to a {@code String} and a {@code String} to an
35 * {@code int}, as well as other constants and methods useful when
36 * dealing with an {@code int}.
37 *
38 * <p>Implementation note: The implementations of the "bit twiddling"
39 * methods (such as {@link #highestOneBit(int) highestOneBit} and
40 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
41 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
42 * Delight</i>, (Addison Wesley, 2002).
43 *
44 * @author Lee Boynton
45 * @author Arthur van Hoff
46 * @author Josh Bloch
47 * @author Joseph D. Darcy
48 * @since JDK1.0
49 */
50 public final class Integer extends Number implements Comparable<Integer> {
51 /**
52 * A constant holding the minimum value an {@code int} can
53 * have, -2<sup>31</sup>.
54 */
55 public static final int MIN_VALUE = 0x80000000;
56
57 /**
58 * A constant holding the maximum value an {@code int} can
59 * have, 2<sup>31</sup>-1.
60 */
61 public static final int MAX_VALUE = 0x7fffffff;
62
63 /**
64 * The {@code Class} instance representing the primitive type
65 * {@code int}.
66 *
67 * @since JDK1.1
68 */
69 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
70
71 /**
72 * All possible chars for representing a number as a String
73 */
74 final static char[] digits = {
75 '0' , '1' , '2' , '3' , '4' , '5' ,
76 '6' , '7' , '8' , '9' , 'a' , 'b' ,
77 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
78 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
79 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
80 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
81 };
82
83 /**
84 * Returns a string representation of the first argument in the
85 * radix specified by the second argument.
86 *
87 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
88 * or larger than {@code Character.MAX_RADIX}, then the radix
89 * {@code 10} is used instead.
90 *
91 * <p>If the first argument is negative, the first element of the
92 * result is the ASCII minus character {@code '-'}
93 * (<code>'\u002D'</code>). If the first argument is not
94 * negative, no sign character appears in the result.
95 *
96 * <p>The remaining characters of the result represent the magnitude
97 * of the first argument. If the magnitude is zero, it is
98 * represented by a single zero character {@code '0'}
99 * (<code>'\u0030'</code>); otherwise, the first character of
100 * the representation of the magnitude will not be the zero
101 * character. The following ASCII characters are used as digits:
102 *
103 * <blockquote>
104 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
105 * </blockquote>
106 *
107 * These are <code>'\u0030'</code> through
108 * <code>'\u0039'</code> and <code>'\u0061'</code> through
109 * <code>'\u007A'</code>. If {@code radix} is
110 * <var>N</var>, then the first <var>N</var> of these characters
111 * are used as radix-<var>N</var> digits in the order shown. Thus,
112 * the digits for hexadecimal (radix 16) are
113 * {@code 0123456789abcdef}. If uppercase letters are
114 * desired, the {@link java.lang.String#toUpperCase()} method may
115 * be called on the result:
116 *
117 * <blockquote>
118 * {@code Integer.toString(n, 16).toUpperCase()}
119 * </blockquote>
120 *
121 * @param i an integer to be converted to a string.
122 * @param radix the radix to use in the string representation.
123 * @return a string representation of the argument in the specified radix.
124 * @see java.lang.Character#MAX_RADIX
125 * @see java.lang.Character#MIN_RADIX
126 */
127 public static String toString(int i, int radix) {
128
129 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
130 radix = 10;
131
132 /* Use the faster version */
133 if (radix == 10) {
134 return toString(i);
135 }
136
137 char buf[] = new char[33];
138 boolean negative = (i < 0);
139 int charPos = 32;
140
141 if (!negative) {
142 i = -i;
143 }
144
145 while (i <= -radix) {
146 buf[charPos--] = digits[-(i % radix)];
147 i = i / radix;
148 }
149 buf[charPos] = digits[-i];
150
151 if (negative) {
152 buf[--charPos] = '-';
153 }
154
155 return new String(buf, charPos, (33 - charPos));
156 }
157
158 /**
159 * Returns a string representation of the integer argument as an
160 * unsigned integer in base 16.
161 *
162 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
163 * if the argument is negative; otherwise, it is equal to the
164 * argument. This value is converted to a string of ASCII digits
165 * in hexadecimal (base 16) with no extra leading
166 * {@code 0}s. If the unsigned magnitude is zero, it is
167 * represented by a single zero character {@code '0'}
168 * (<code>'\u0030'</code>); otherwise, the first character of
169 * the representation of the unsigned magnitude will not be the
170 * zero character. The following characters are used as
171 * hexadecimal digits:
172 *
173 * <blockquote>
174 * {@code 0123456789abcdef}
175 * </blockquote>
176 *
177 * These are the characters <code>'\u0030'</code> through
178 * <code>'\u0039'</code> and <code>'\u0061'</code> through
179 * <code>'\u0066'</code>. If uppercase letters are
180 * desired, the {@link java.lang.String#toUpperCase()} method may
181 * be called on the result:
182 *
183 * <blockquote>
184 * {@code Integer.toHexString(n).toUpperCase()}
185 * </blockquote>
186 *
187 * @param i an integer to be converted to a string.
188 * @return the string representation of the unsigned integer value
189 * represented by the argument in hexadecimal (base 16).
190 * @since JDK1.0.2
191 */
192 public static String toHexString(int i) {
193 return toUnsignedString(i, 4);
194 }
195
196 /**
197 * Returns a string representation of the integer argument as an
198 * unsigned integer in base 8.
199 *
200 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
201 * if the argument is negative; otherwise, it is equal to the
202 * argument. This value is converted to a string of ASCII digits
203 * in octal (base 8) with no extra leading {@code 0}s.
204 *
205 * <p>If the unsigned magnitude is zero, it is represented by a
206 * single zero character {@code '0'}
207 * (<code>'\u0030'</code>); otherwise, the first character of
208 * the representation of the unsigned magnitude will not be the
209 * zero character. The following characters are used as octal
210 * digits:
211 *
212 * <blockquote>
213 * {@code 01234567}
214 * </blockquote>
215 *
216 * These are the characters <code>'\u0030'</code> through
217 * <code>'\u0037'</code>.
218 *
219 * @param i an integer to be converted to a string.
220 * @return the string representation of the unsigned integer value
221 * represented by the argument in octal (base 8).
222 * @since JDK1.0.2
223 */
224 public static String toOctalString(int i) {
225 return toUnsignedString(i, 3);
226 }
227
228 /**
229 * Returns a string representation of the integer argument as an
230 * unsigned integer in base 2.
231 *
232 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
233 * if the argument is negative; otherwise it is equal to the
234 * argument. This value is converted to a string of ASCII digits
235 * in binary (base 2) with no extra leading {@code 0}s.
236 * If the unsigned magnitude is zero, it is represented by a
237 * single zero character {@code '0'}
238 * (<code>'\u0030'</code>); otherwise, the first character of
239 * the representation of the unsigned magnitude will not be the
240 * zero character. The characters {@code '0'}
241 * (<code>'\u0030'</code>) and {@code '1'}
242 * (<code>'\u0031'</code>) are used as binary digits.
243 *
244 * @param i an integer to be converted to a string.
245 * @return the string representation of the unsigned integer value
246 * represented by the argument in binary (base 2).
247 * @since JDK1.0.2
248 */
249 public static String toBinaryString(int i) {
250 return toUnsignedString(i, 1);
251 }
252
253 /**
254 * Convert the integer to an unsigned number.
255 */
256 private static String toUnsignedString(int i, int shift) {
257 char[] buf = new char[32];
258 int charPos = 32;
259 int radix = 1 << shift;
260 int mask = radix - 1;
261 do {
262 buf[--charPos] = digits[i & mask];
263 i >>>= shift;
264 } while (i != 0);
265
266 return new String(buf, charPos, (32 - charPos));
267 }
268
269
270 final static char [] DigitTens = {
271 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
272 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
273 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
274 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
275 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
276 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
277 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
278 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
279 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
280 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
281 } ;
282
283 final static char [] DigitOnes = {
284 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
285 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
286 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
287 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
288 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
289 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
290 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
291 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
292 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
293 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
294 } ;
295
296 // I use the "invariant division by multiplication" trick to
297 // accelerate Integer.toString. In particular we want to
298 // avoid division by 10.
299 //
300 // The "trick" has roughly the same performance characteristics
301 // as the "classic" Integer.toString code on a non-JIT VM.
302 // The trick avoids .rem and .div calls but has a longer code
303 // path and is thus dominated by dispatch overhead. In the
304 // JIT case the dispatch overhead doesn't exist and the
305 // "trick" is considerably faster than the classic code.
306 //
307 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
308 // sequence.
309 //
310 // RE: Division by Invariant Integers using Multiplication
311 // T Gralund, P Montgomery
312 // ACM PLDI 1994
313 //
314
315 /**
316 * Returns a {@code String} object representing the
317 * specified integer. The argument is converted to signed decimal
318 * representation and returned as a string, exactly as if the
319 * argument and radix 10 were given as arguments to the {@link
320 * #toString(int, int)} method.
321 *
322 * @param i an integer to be converted.
323 * @return a string representation of the argument in base 10.
324 */
325 public static String toString(int i) {
326 if (i == Integer.MIN_VALUE)
327 return "-2147483648";
328 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
329 char[] buf = new char[size];
330 getChars(i, size, buf);
331 return new String(0, size, buf);
332 }
333
334 /**
335 * Places characters representing the integer i into the
336 * character array buf. The characters are placed into
337 * the buffer backwards starting with the least significant
338 * digit at the specified index (exclusive), and working
339 * backwards from there.
340 *
341 * Will fail if i == Integer.MIN_VALUE
342 */
343 static void getChars(int i, int index, char[] buf) {
344 int q, r;
345 int charPos = index;
346 char sign = 0;
347
348 if (i < 0) {
349 sign = '-';
350 i = -i;
351 }
352
353 // Generate two digits per iteration
354 while (i >= 65536) {
355 q = i / 100;
356 // really: r = i - (q * 100);
357 r = i - ((q << 6) + (q << 5) + (q << 2));
358 i = q;
359 buf [--charPos] = DigitOnes[r];
360 buf [--charPos] = DigitTens[r];
361 }
362
363 // Fall thru to fast mode for smaller numbers
364 // assert(i <= 65536, i);
365 for (;;) {
366 q = (i * 52429) >>> (16+3);
367 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
368 buf [--charPos] = digits [r];
369 i = q;
370 if (i == 0) break;
371 }
372 if (sign != 0) {
373 buf [--charPos] = sign;
374 }
375 }
376
377 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
378 99999999, 999999999, Integer.MAX_VALUE };
379
380 // Requires positive x
381 static int stringSize(int x) {
382 for (int i=0; ; i++)
383 if (x <= sizeTable[i])
384 return i+1;
385 }
386
387 /**
388 * Parses the string argument as a signed integer in the radix
389 * specified by the second argument. The characters in the string
390 * must all be digits of the specified radix (as determined by
391 * whether {@link java.lang.Character#digit(char, int)} returns a
392 * nonnegative value), except that the first character may be an
393 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to
394 * indicate a negative value. The resulting integer value is
395 * returned.
396 *
397 * <p>An exception of type {@code NumberFormatException} is
398 * thrown if any of the following situations occurs:
399 * <ul>
400 * <li>The first argument is {@code null} or is a string of
401 * length zero.
402 *
403 * <li>The radix is either smaller than
404 * {@link java.lang.Character#MIN_RADIX} or
405 * larger than {@link java.lang.Character#MAX_RADIX}.
406 *
407 * <li>Any character of the string is not a digit of the specified
408 * radix, except that the first character may be a minus sign
409 * {@code '-'} (<code>'\u002D'</code>) provided that the
410 * string is longer than length 1.
411 *
412 * <li>The value represented by the string is not a value of type
413 * {@code int}.
414 * </ul>
415 *
416 * <p>Examples:
417 * <blockquote><pre>
418 * parseInt("0", 10) returns 0
419 * parseInt("473", 10) returns 473
420 * parseInt("-0", 10) returns 0
421 * parseInt("-FF", 16) returns -255
422 * parseInt("1100110", 2) returns 102
423 * parseInt("2147483647", 10) returns 2147483647
424 * parseInt("-2147483648", 10) returns -2147483648
425 * parseInt("2147483648", 10) throws a NumberFormatException
426 * parseInt("99", 8) throws a NumberFormatException
427 * parseInt("Kona", 10) throws a NumberFormatException
428 * parseInt("Kona", 27) returns 411787
429 * </pre></blockquote>
430 *
431 * @param s the {@code String} containing the integer
432 * representation to be parsed
433 * @param radix the radix to be used while parsing {@code s}.
434 * @return the integer represented by the string argument in the
435 * specified radix.
436 * @exception NumberFormatException if the {@code String}
437 * does not contain a parsable {@code int}.
438 */
439 public static int parseInt(String s, int radix)
440 throws NumberFormatException
441 {
442 if (s == null) {
443 throw new NumberFormatException("null");
444 }
445
446 if (radix < Character.MIN_RADIX) {
447 throw new NumberFormatException("radix " + radix +
448 " less than Character.MIN_RADIX");
449 }
450
451 if (radix > Character.MAX_RADIX) {
452 throw new NumberFormatException("radix " + radix +
453 " greater than Character.MAX_RADIX");
454 }
455
456 int result = 0;
457 boolean negative = false;
458 int i = 0, len = s.length();
459 int limit = -Integer.MAX_VALUE;
460 int multmin;
461 int digit;
462
463 if (len > 0) {
464 char firstChar = s.charAt(0);
465 if (firstChar < '0') { // Possible leading "-"
466 if (firstChar == '-') {
467 negative = true;
468 limit = Integer.MIN_VALUE;
469 } else
470 throw NumberFormatException.forInputString(s);
471
472 if (len == 1) // Cannot have lone "-"
473 throw NumberFormatException.forInputString(s);
474 i++;
475 }
476 multmin = limit / radix;
477 while (i < len) {
478 // Accumulating negatively avoids surprises near MAX_VALUE
479 digit = Character.digit(s.charAt(i++),radix);
480 if (digit < 0) {
481 throw NumberFormatException.forInputString(s);
482 }
483 if (result < multmin) {
484 throw NumberFormatException.forInputString(s);
485 }
486 result *= radix;
487 if (result < limit + digit) {
488 throw NumberFormatException.forInputString(s);
489 }
490 result -= digit;
491 }
492 } else {
493 throw NumberFormatException.forInputString(s);
494 }
495 return negative ? result : -result;
496 }
497
498 /**
499 * Parses the string argument as a signed decimal integer. The
500 * characters in the string must all be decimal digits, except
501 * that the first character may be an ASCII minus sign {@code '-'}
502 * (<code>'\u002D'</code>) to indicate a negative value. The
503 * resulting integer value is returned, exactly as if the argument
504 * and the radix 10 were given as arguments to the {@link
505 * #parseInt(java.lang.String, int)} method.
506 *
507 * @param s a {@code String} containing the {@code int}
508 * representation to be parsed
509 * @return the integer value represented by the argument in decimal.
510 * @exception NumberFormatException if the string does not contain a
511 * parsable integer.
512 */
513 public static int parseInt(String s) throws NumberFormatException {
514 return parseInt(s,10);
515 }
516
517 /**
518 * Returns an {@code Integer} object holding the value
519 * extracted from the specified {@code String} when parsed
520 * with the radix given by the second argument. The first argument
521 * is interpreted as representing a signed integer in the radix
522 * specified by the second argument, exactly as if the arguments
523 * were given to the {@link #parseInt(java.lang.String, int)}
524 * method. The result is an {@code Integer} object that
525 * represents the integer value specified by the string.
526 *
527 * <p>In other words, this method returns an {@code Integer}
528 * object equal to the value of:
529 *
530 * <blockquote>
531 * {@code new Integer(Integer.parseInt(s, radix))}
532 * </blockquote>
533 *
534 * @param s the string to be parsed.
535 * @param radix the radix to be used in interpreting {@code s}
536 * @return an {@code Integer} object holding the value
537 * represented by the string argument in the specified
538 * radix.
539 * @exception NumberFormatException if the {@code String}
540 * does not contain a parsable {@code int}.
541 */
542 public static Integer valueOf(String s, int radix) throws NumberFormatException {
543 return new Integer(parseInt(s,radix));
544 }
545
546 /**
547 * Returns an {@code Integer} object holding the
548 * value of the specified {@code String}. The argument is
549 * interpreted as representing a signed decimal integer, exactly
550 * as if the argument were given to the {@link
551 * #parseInt(java.lang.String)} method. The result is an
552 * {@code Integer} object that represents the integer value
553 * specified by the string.
554 *
555 * <p>In other words, this method returns an {@code Integer}
556 * object equal to the value of:
557 *
558 * <blockquote>
559 * {@code new Integer(Integer.parseInt(s))}
560 * </blockquote>
561 *
562 * @param s the string to be parsed.
563 * @return an {@code Integer} object holding the value
564 * represented by the string argument.
565 * @exception NumberFormatException if the string cannot be parsed
566 * as an integer.
567 */
568 public static Integer valueOf(String s) throws NumberFormatException
569 {
570 return new Integer(parseInt(s, 10));
571 }
572
573 private static class IntegerCache {
574 private IntegerCache(){}
575
576 static final Integer cache[] = new Integer[-(-128) + 127 + 1];
577
578 static {
579 for(int i = 0; i < cache.length; i++)
580 cache[i] = new Integer(i - 128);
581 }
582 }
583
584 /**
585 * Returns an {@code Integer} instance representing the specified
586 * {@code int} value. If a new {@code Integer} instance is not
587 * required, this method should generally be used in preference to
588 * the constructor {@link #Integer(int)}, as this method is likely
589 * to yield significantly better space and time performance by
590 * caching frequently requested values.
591 *
592 * @param i an {@code int} value.
593 * @return an {@code Integer} instance representing {@code i}.
594 * @since 1.5
595 */
596 public static Integer valueOf(int i) {
597 final int offset = 128;
598 if (i >= -128 && i <= 127) { // must cache
599 return IntegerCache.cache[i + offset];
600 }
601 return new Integer(i);
602 }
603
604 /**
605 * The value of the {@code Integer}.
606 *
607 * @serial
608 */
609 private final int value;
610
611 /**
612 * Constructs a newly allocated {@code Integer} object that
613 * represents the specified {@code int} value.
614 *
615 * @param value the value to be represented by the
616 * {@code Integer} object.
617 */
618 public Integer(int value) {
619 this.value = value;
620 }
621
622 /**
623 * Constructs a newly allocated {@code Integer} object that
624 * represents the {@code int} value indicated by the
625 * {@code String} parameter. The string is converted to an
626 * {@code int} value in exactly the manner used by the
627 * {@code parseInt} method for radix 10.
628 *
629 * @param s the {@code String} to be converted to an
630 * {@code Integer}.
631 * @exception NumberFormatException if the {@code String} does not
632 * contain a parsable integer.
633 * @see java.lang.Integer#parseInt(java.lang.String, int)
634 */
635 public Integer(String s) throws NumberFormatException {
636 this.value = parseInt(s, 10);
637 }
638
639 /**
640 * Returns the value of this {@code Integer} as a
641 * {@code byte}.
642 */
643 public byte byteValue() {
644 return (byte)value;
645 }
646
647 /**
648 * Returns the value of this {@code Integer} as a
649 * {@code short}.
650 */
651 public short shortValue() {
652 return (short)value;
653 }
654
655 /**
656 * Returns the value of this {@code Integer} as an
657 * {@code int}.
658 */
659 public int intValue() {
660 return value;
661 }
662
663 /**
664 * Returns the value of this {@code Integer} as a
665 * {@code long}.
666 */
667 public long longValue() {
668 return (long)value;
669 }
670
671 /**
672 * Returns the value of this {@code Integer} as a
673 * {@code float}.
674 */
675 public float floatValue() {
676 return (float)value;
677 }
678
679 /**
680 * Returns the value of this {@code Integer} as a
681 * {@code double}.
682 */
683 public double doubleValue() {
684 return (double)value;
685 }
686
687 /**
688 * Returns a {@code String} object representing this
689 * {@code Integer}'s value. The value is converted to signed
690 * decimal representation and returned as a string, exactly as if
691 * the integer value were given as an argument to the {@link
692 * java.lang.Integer#toString(int)} method.
693 *
694 * @return a string representation of the value of this object in
695 * base 10.
696 */
697 public String toString() {
698 return String.valueOf(value);
699 }
700
701 /**
702 * Returns a hash code for this {@code Integer}.
703 *
704 * @return a hash code value for this object, equal to the
705 * primitive {@code int} value represented by this
706 * {@code Integer} object.
707 */
708 public int hashCode() {
709 return value;
710 }
711
712 /**
713 * Compares this object to the specified object. The result is
714 * {@code true} if and only if the argument is not
715 * {@code null} and is an {@code Integer} object that
716 * contains the same {@code int} value as this object.
717 *
718 * @param obj the object to compare with.
719 * @return {@code true} if the objects are the same;
720 * {@code false} otherwise.
721 */
722 public boolean equals(Object obj) {
723 if (obj instanceof Integer) {
724 return value == ((Integer)obj).intValue();
725 }
726 return false;
727 }
728
729 /**
730 * Determines the integer value of the system property with the
731 * specified name.
732 *
733 * <p>The first argument is treated as the name of a system property.
734 * System properties are accessible through the
735 * {@link java.lang.System#getProperty(java.lang.String)} method. The
736 * string value of this property is then interpreted as an integer
737 * value and an {@code Integer} object representing this value is
738 * returned. Details of possible numeric formats can be found with
739 * the definition of {@code getProperty}.
740 *
741 * <p>If there is no property with the specified name, if the specified name
742 * is empty or {@code null}, or if the property does not have
743 * the correct numeric format, then {@code null} is returned.
744 *
745 * <p>In other words, this method returns an {@code Integer}
746 * object equal to the value of:
747 *
748 * <blockquote>
749 * {@code getInteger(nm, null)}
750 * </blockquote>
751 *
752 * @param nm property name.
753 * @return the {@code Integer} value of the property.
754 * @see java.lang.System#getProperty(java.lang.String)
755 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
756 */
757 public static Integer getInteger(String nm) {
758 return getInteger(nm, null);
759 }
760
761 /**
762 * Determines the integer value of the system property with the
763 * specified name.
764 *
765 * <p>The first argument is treated as the name of a system property.
766 * System properties are accessible through the {@link
767 * java.lang.System#getProperty(java.lang.String)} method. The
768 * string value of this property is then interpreted as an integer
769 * value and an {@code Integer} object representing this value is
770 * returned. Details of possible numeric formats can be found with
771 * the definition of {@code getProperty}.
772 *
773 * <p>The second argument is the default value. An {@code Integer} object
774 * that represents the value of the second argument is returned if there
775 * is no property of the specified name, if the property does not have
776 * the correct numeric format, or if the specified name is empty or
777 * {@code null}.
778 *
779 * <p>In other words, this method returns an {@code Integer} object
780 * equal to the value of:
781 *
782 * <blockquote>
783 * {@code getInteger(nm, new Integer(val))}
784 * </blockquote>
785 *
786 * but in practice it may be implemented in a manner such as:
787 *
788 * <blockquote><pre>
789 * Integer result = getInteger(nm, null);
790 * return (result == null) ? new Integer(val) : result;
791 * </pre></blockquote>
792 *
793 * to avoid the unnecessary allocation of an {@code Integer}
794 * object when the default value is not needed.
795 *
796 * @param nm property name.
797 * @param val default value.
798 * @return the {@code Integer} value of the property.
799 * @see java.lang.System#getProperty(java.lang.String)
800 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
801 */
802 public static Integer getInteger(String nm, int val) {
803 Integer result = getInteger(nm, null);
804 return (result == null) ? new Integer(val) : result;
805 }
806
807 /**
808 * Returns the integer value of the system property with the
809 * specified name. The first argument is treated as the name of a
810 * system property. System properties are accessible through the
811 * {@link java.lang.System#getProperty(java.lang.String)} method.
812 * The string value of this property is then interpreted as an
813 * integer value, as per the {@code Integer.decode} method,
814 * and an {@code Integer} object representing this value is
815 * returned.
816 *
817 * <ul><li>If the property value begins with the two ASCII characters
818 * {@code 0x} or the ASCII character {@code #}, not
819 * followed by a minus sign, then the rest of it is parsed as a
820 * hexadecimal integer exactly as by the method
821 * {@link #valueOf(java.lang.String, int)} with radix 16.
822 * <li>If the property value begins with the ASCII character
823 * {@code 0} followed by another character, it is parsed as an
824 * octal integer exactly as by the method
825 * {@link #valueOf(java.lang.String, int)} with radix 8.
826 * <li>Otherwise, the property value is parsed as a decimal integer
827 * exactly as by the method {@link #valueOf(java.lang.String, int)}
828 * with radix 10.
829 * </ul>
830 *
831 * <p>The second argument is the default value. The default value is
832 * returned if there is no property of the specified name, if the
833 * property does not have the correct numeric format, or if the
834 * specified name is empty or {@code null}.
835 *
836 * @param nm property name.
837 * @param val default value.
838 * @return the {@code Integer} value of the property.
839 * @see java.lang.System#getProperty(java.lang.String)
840 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
841 * @see java.lang.Integer#decode
842 */
843 public static Integer getInteger(String nm, Integer val) {
844 String v = null;
845 try {
846 v = System.getProperty(nm);
847 } catch (IllegalArgumentException e) {
848 } catch (NullPointerException e) {
849 }
850 if (v != null) {
851 try {
852 return Integer.decode(v);
853 } catch (NumberFormatException e) {
854 }
855 }
856 return val;
857 }
858
859 /**
860 * Decodes a {@code String} into an {@code Integer}.
861 * Accepts decimal, hexadecimal, and octal numbers given
862 * by the following grammar:
863 *
864 * <blockquote>
865 * <dl>
866 * <dt><i>DecodableString:</i>
867 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
868 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
869 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
870 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
871 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
872 * <p>
873 * <dt><i>Sign:</i>
874 * <dd>{@code -}
875 * </dl>
876 * </blockquote>
877 *
878 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
879 * are defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">§3.10.1</a>
880 * of the <a href="http://java.sun.com/docs/books/jls/html/">Java
881 * Language Specification</a>.
882 *
883 * <p>The sequence of characters following an (optional) negative
884 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
885 * "{@code #}", or leading zero) is parsed as by the {@code
886 * Integer.parseInt} method with the indicated radix (10, 16, or
887 * 8). This sequence of characters must represent a positive
888 * value or a {@link NumberFormatException} will be thrown. The
889 * result is negated if first character of the specified {@code
890 * String} is the minus sign. No whitespace characters are
891 * permitted in the {@code String}.
892 *
893 * @param nm the {@code String} to decode.
894 * @return an {@code Integer} object holding the {@code int}
895 * value represented by {@code nm}
896 * @exception NumberFormatException if the {@code String} does not
897 * contain a parsable integer.
898 * @see java.lang.Integer#parseInt(java.lang.String, int)
899 */
900 public static Integer decode(String nm) throws NumberFormatException {
901 int radix = 10;
902 int index = 0;
903 boolean negative = false;
904 Integer result;
905
906 if (nm.length() == 0)
907 throw new NumberFormatException("Zero length string");
908 char firstChar = nm.charAt(0);
909 // Handle sign, if present
910 if (firstChar == '-') {
911 negative = true;
912 index++;
913 }
914
915 // Handle radix specifier, if present
916 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
917 index += 2;
918 radix = 16;
919 }
920 else if (nm.startsWith("#", index)) {
921 index ++;
922 radix = 16;
923 }
924 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
925 index ++;
926 radix = 8;
927 }
928
929 if (nm.startsWith("-", index))
930 throw new NumberFormatException("Sign character in wrong position");
931
932 try {
933 result = Integer.valueOf(nm.substring(index), radix);
934 result = negative ? new Integer(-result.intValue()) : result;
935 } catch (NumberFormatException e) {
936 // If number is Integer.MIN_VALUE, we'll end up here. The next line
937 // handles this case, and causes any genuine format error to be
938 // rethrown.
939 String constant = negative ? ("-" + nm.substring(index))
940 : nm.substring(index);
941 result = Integer.valueOf(constant, radix);
942 }
943 return result;
944 }
945
946 /**
947 * Compares two {@code Integer} objects numerically.
948 *
949 * @param anotherInteger the {@code Integer} to be compared.
950 * @return the value {@code 0} if this {@code Integer} is
951 * equal to the argument {@code Integer}; a value less than
952 * {@code 0} if this {@code Integer} is numerically less
953 * than the argument {@code Integer}; and a value greater
954 * than {@code 0} if this {@code Integer} is numerically
955 * greater than the argument {@code Integer} (signed
956 * comparison).
957 * @since 1.2
958 */
959 public int compareTo(Integer anotherInteger) {
960 int thisVal = this.value;
961 int anotherVal = anotherInteger.value;
962 return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1));
963 }
964
965
966 // Bit twiddling
967
968 /**
969 * The number of bits used to represent an {@code int} value in two's
970 * complement binary form.
971 *
972 * @since 1.5
973 */
974 public static final int SIZE = 32;
975
976 /**
977 * Returns an {@code int} value with at most a single one-bit, in the
978 * position of the highest-order ("leftmost") one-bit in the specified
979 * {@code int} value. Returns zero if the specified value has no
980 * one-bits in its two's complement binary representation, that is, if it
981 * is equal to zero.
982 *
983 * @return an {@code int} value with a single one-bit, in the position
984 * of the highest-order one-bit in the specified value, or zero if
985 * the specified value is itself equal to zero.
986 * @since 1.5
987 */
988 public static int highestOneBit(int i) {
989 // HD, Figure 3-1
990 i |= (i >> 1);
991 i |= (i >> 2);
992 i |= (i >> 4);
993 i |= (i >> 8);
994 i |= (i >> 16);
995 return i - (i >>> 1);
996 }
997
998 /**
999 * Returns an {@code int} value with at most a single one-bit, in the
1000 * position of the lowest-order ("rightmost") one-bit in the specified
1001 * {@code int} value. Returns zero if the specified value has no
1002 * one-bits in its two's complement binary representation, that is, if it
1003 * is equal to zero.
1004 *
1005 * @return an {@code int} value with a single one-bit, in the position
1006 * of the lowest-order one-bit in the specified value, or zero if
1007 * the specified value is itself equal to zero.
1008 * @since 1.5
1009 */
1010 public static int lowestOneBit(int i) {
1011 // HD, Section 2-1
1012 return i & -i;
1013 }
1014
1015 /**
1016 * Returns the number of zero bits preceding the highest-order
1017 * ("leftmost") one-bit in the two's complement binary representation
1018 * of the specified {@code int} value. Returns 32 if the
1019 * specified value has no one-bits in its two's complement representation,
1020 * in other words if it is equal to zero.
1021 *
1022 * <p>Note that this method is closely related to the logarithm base 2.
1023 * For all positive {@code int} values x:
1024 * <ul>
1025 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1026 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1027 * </ul>
1028 *
1029 * @return the number of zero bits preceding the highest-order
1030 * ("leftmost") one-bit in the two's complement binary representation
1031 * of the specified {@code int} value, or 32 if the value
1032 * is equal to zero.
1033 * @since 1.5
1034 */
1035 public static int numberOfLeadingZeros(int i) {
1036 // HD, Figure 5-6
1037 if (i == 0)
1038 return 32;
1039 int n = 1;
1040 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1041 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1042 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1043 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1044 n -= i >>> 31;
1045 return n;
1046 }
1047
1048 /**
1049 * Returns the number of zero bits following the lowest-order ("rightmost")
1050 * one-bit in the two's complement binary representation of the specified
1051 * {@code int} value. Returns 32 if the specified value has no
1052 * one-bits in its two's complement representation, in other words if it is
1053 * equal to zero.
1054 *
1055 * @return the number of zero bits following the lowest-order ("rightmost")
1056 * one-bit in the two's complement binary representation of the
1057 * specified {@code int} value, or 32 if the value is equal
1058 * to zero.
1059 * @since 1.5
1060 */
1061 public static int numberOfTrailingZeros(int i) {
1062 // HD, Figure 5-14
1063 int y;
1064 if (i == 0) return 32;
1065 int n = 31;
1066 y = i <<16; if (y != 0) { n = n -16; i = y; }
1067 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1068 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1069 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1070 return n - ((i << 1) >>> 31);
1071 }
1072
1073 /**
1074 * Returns the number of one-bits in the two's complement binary
1075 * representation of the specified {@code int} value. This function is
1076 * sometimes referred to as the <i>population count</i>.
1077 *
1078 * @return the number of one-bits in the two's complement binary
1079 * representation of the specified {@code int} value.
1080 * @since 1.5
1081 */
1082 public static int bitCount(int i) {
1083 // HD, Figure 5-2
1084 i = i - ((i >>> 1) & 0x55555555);
1085 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1086 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1087 i = i + (i >>> 8);
1088 i = i + (i >>> 16);
1089 return i & 0x3f;
1090 }
1091
1092 /**
1093 * Returns the value obtained by rotating the two's complement binary
1094 * representation of the specified {@code int} value left by the
1095 * specified number of bits. (Bits shifted out of the left hand, or
1096 * high-order, side reenter on the right, or low-order.)
1097 *
1098 * <p>Note that left rotation with a negative distance is equivalent to
1099 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1100 * distance)}. Note also that rotation by any multiple of 32 is a
1101 * no-op, so all but the last five bits of the rotation distance can be
1102 * ignored, even if the distance is negative: {@code rotateLeft(val,
1103 * distance) == rotateLeft(val, distance & 0x1F)}.
1104 *
1105 * @return the value obtained by rotating the two's complement binary
1106 * representation of the specified {@code int} value left by the
1107 * specified number of bits.
1108 * @since 1.5
1109 */
1110 public static int rotateLeft(int i, int distance) {
1111 return (i << distance) | (i >>> -distance);
1112 }
1113
1114 /**
1115 * Returns the value obtained by rotating the two's complement binary
1116 * representation of the specified {@code int} value right by the
1117 * specified number of bits. (Bits shifted out of the right hand, or
1118 * low-order, side reenter on the left, or high-order.)
1119 *
1120 * <p>Note that right rotation with a negative distance is equivalent to
1121 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1122 * distance)}. Note also that rotation by any multiple of 32 is a
1123 * no-op, so all but the last five bits of the rotation distance can be
1124 * ignored, even if the distance is negative: {@code rotateRight(val,
1125 * distance) == rotateRight(val, distance & 0x1F)}.
1126 *
1127 * @return the value obtained by rotating the two's complement binary
1128 * representation of the specified {@code int} value right by the
1129 * specified number of bits.
1130 * @since 1.5
1131 */
1132 public static int rotateRight(int i, int distance) {
1133 return (i >>> distance) | (i << -distance);
1134 }
1135
1136 /**
1137 * Returns the value obtained by reversing the order of the bits in the
1138 * two's complement binary representation of the specified {@code int}
1139 * value.
1140 *
1141 * @return the value obtained by reversing order of the bits in the
1142 * specified {@code int} value.
1143 * @since 1.5
1144 */
1145 public static int reverse(int i) {
1146 // HD, Figure 7-1
1147 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1148 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1149 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1150 i = (i << 24) | ((i & 0xff00) << 8) |
1151 ((i >>> 8) & 0xff00) | (i >>> 24);
1152 return i;
1153 }
1154
1155 /**
1156 * Returns the signum function of the specified {@code int} value. (The
1157 * return value is -1 if the specified value is negative; 0 if the
1158 * specified value is zero; and 1 if the specified value is positive.)
1159 *
1160 * @return the signum function of the specified {@code int} value.
1161 * @since 1.5
1162 */
1163 public static int signum(int i) {
1164 // HD, Section 2-7
1165 return (i >> 31) | (-i >>> 31);
1166 }
1167
1168 /**
1169 * Returns the value obtained by reversing the order of the bytes in the
1170 * two's complement representation of the specified {@code int} value.
1171 *
1172 * @return the value obtained by reversing the bytes in the specified
1173 * {@code int} value.
1174 * @since 1.5
1175 */
1176 public static int reverseBytes(int i) {
1177 return ((i >>> 24) ) |
1178 ((i >> 8) & 0xFF00) |
1179 ((i << 8) & 0xFF0000) |
1180 ((i << 24));
1181 }
1182
1183 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1184 private static final long serialVersionUID = 1360826667806852920L;
1185 }
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