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 or an ASCII plus sign {@code '+'}
395 * (<code>'\u002B'</code>) to indicate a positive value. The
396 * resulting integer value is returned.
397 *
398 * <p>An exception of type {@code NumberFormatException} is
399 * thrown if any of the following situations occurs:
400 * <ul>
401 * <li>The first argument is {@code null} or is a string of
402 * length zero.
403 *
404 * <li>The radix is either smaller than
405 * {@link java.lang.Character#MIN_RADIX} or
406 * larger than {@link java.lang.Character#MAX_RADIX}.
407 *
408 * <li>Any character of the string is not a digit of the specified
409 * radix, except that the first character may be a minus sign
410 * {@code '-'} (<code>'\u002D'</code>) or plus sign
411 * {@code '+'} (<code>'\u002B'</code>) provided that the
412 * string is longer than length 1.
413 *
414 * <li>The value represented by the string is not a value of type
415 * {@code int}.
416 * </ul>
417 *
418 * <p>Examples:
419 * <blockquote><pre>
420 * parseInt("0", 10) returns 0
421 * parseInt("473", 10) returns 473
422 * parseInt("+42", 10) returns 42
423 * parseInt("-0", 10) returns 0
424 * parseInt("-FF", 16) returns -255
425 * parseInt("1100110", 2) returns 102
426 * parseInt("2147483647", 10) returns 2147483647
427 * parseInt("-2147483648", 10) returns -2147483648
428 * parseInt("2147483648", 10) throws a NumberFormatException
429 * parseInt("99", 8) throws a NumberFormatException
430 * parseInt("Kona", 10) throws a NumberFormatException
431 * parseInt("Kona", 27) returns 411787
432 * </pre></blockquote>
433 *
434 * @param s the {@code String} containing the integer
435 * representation to be parsed
436 * @param radix the radix to be used while parsing {@code s}.
437 * @return the integer represented by the string argument in the
438 * specified radix.
439 * @exception NumberFormatException if the {@code String}
440 * does not contain a parsable {@code int}.
441 */
442 public static int parseInt(String s, int radix)
443 throws NumberFormatException
444 {
445 if (s == null) {
446 throw new NumberFormatException("null");
447 }
448
449 if (radix < Character.MIN_RADIX) {
450 throw new NumberFormatException("radix " + radix +
451 " less than Character.MIN_RADIX");
452 }
453
454 if (radix > Character.MAX_RADIX) {
455 throw new NumberFormatException("radix " + radix +
456 " greater than Character.MAX_RADIX");
457 }
458
459 int result = 0;
460 boolean negative = false;
461 int i = 0, len = s.length();
462 int limit = -Integer.MAX_VALUE;
463 int multmin;
464 int digit;
465
466 if (len > 0) {
467 char firstChar = s.charAt(0);
468 if (firstChar < '0') { // Possible leading "+" or "-"
469 if (firstChar == '-') {
470 negative = true;
471 limit = Integer.MIN_VALUE;
472 } else if (firstChar != '+')
473 throw NumberFormatException.forInputString(s);
474
475 if (len == 1) // Cannot have lone "+" or "-"
476 throw NumberFormatException.forInputString(s);
477 i++;
478 }
479 multmin = limit / radix;
480 while (i < len) {
481 // Accumulating negatively avoids surprises near MAX_VALUE
482 digit = Character.digit(s.charAt(i++),radix);
483 if (digit < 0) {
484 throw NumberFormatException.forInputString(s);
485 }
486 if (result < multmin) {
487 throw NumberFormatException.forInputString(s);
488 }
489 result *= radix;
490 if (result < limit + digit) {
491 throw NumberFormatException.forInputString(s);
492 }
493 result -= digit;
494 }
495 } else {
496 throw NumberFormatException.forInputString(s);
497 }
498 return negative ? result : -result;
499 }
500
501 /**
502 * Parses the string argument as a signed decimal integer. The
503 * characters in the string must all be decimal digits, except
504 * that the first character may be an ASCII minus sign {@code '-'}
505 * (<code>'\u002D'</code>) to indicate a negative value or an
506 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
507 * indicate a positive value. The resulting integer value is
508 * returned, exactly as if the argument and the radix 10 were
509 * given as arguments to the {@link #parseInt(java.lang.String,
510 * int)} method.
511 *
512 * @param s a {@code String} containing the {@code int}
513 * representation to be parsed
514 * @return the integer value represented by the argument in decimal.
515 * @exception NumberFormatException if the string does not contain a
516 * parsable integer.
517 */
518 public static int parseInt(String s) throws NumberFormatException {
519 return parseInt(s,10);
520 }
521
522 /**
523 * Returns an {@code Integer} object holding the value
524 * extracted from the specified {@code String} when parsed
525 * with the radix given by the second argument. The first argument
526 * is interpreted as representing a signed integer in the radix
527 * specified by the second argument, exactly as if the arguments
528 * were given to the {@link #parseInt(java.lang.String, int)}
529 * method. The result is an {@code Integer} object that
530 * represents the integer value specified by the string.
531 *
532 * <p>In other words, this method returns an {@code Integer}
533 * object equal to the value of:
534 *
535 * <blockquote>
536 * {@code new Integer(Integer.parseInt(s, radix))}
537 * </blockquote>
538 *
539 * @param s the string to be parsed.
540 * @param radix the radix to be used in interpreting {@code s}
541 * @return an {@code Integer} object holding the value
542 * represented by the string argument in the specified
543 * radix.
544 * @exception NumberFormatException if the {@code String}
545 * does not contain a parsable {@code int}.
546 */
547 public static Integer valueOf(String s, int radix) throws NumberFormatException {
548 return new Integer(parseInt(s,radix));
549 }
550
551 /**
552 * Returns an {@code Integer} object holding the
553 * value of the specified {@code String}. The argument is
554 * interpreted as representing a signed decimal integer, exactly
555 * as if the argument were given to the {@link
556 * #parseInt(java.lang.String)} method. The result is an
557 * {@code Integer} object that represents the integer value
558 * specified by the string.
559 *
560 * <p>In other words, this method returns an {@code Integer}
561 * object equal to the value of:
562 *
563 * <blockquote>
564 * {@code new Integer(Integer.parseInt(s))}
565 * </blockquote>
566 *
567 * @param s the string to be parsed.
568 * @return an {@code Integer} object holding the value
569 * represented by the string argument.
570 * @exception NumberFormatException if the string cannot be parsed
571 * as an integer.
572 */
573 public static Integer valueOf(String s) throws NumberFormatException
574 {
575 return new Integer(parseInt(s, 10));
576 }
577
578 private static class IntegerCache {
579 private IntegerCache(){}
580
581 static final Integer cache[] = new Integer[-(-128) + 127 + 1];
582
583 static {
584 for(int i = 0; i < cache.length; i++)
585 cache[i] = new Integer(i - 128);
586 }
587 }
588
589 /**
590 * Returns an {@code Integer} instance representing the specified
591 * {@code int} value. If a new {@code Integer} instance is not
592 * required, this method should generally be used in preference to
593 * the constructor {@link #Integer(int)}, as this method is likely
594 * to yield significantly better space and time performance by
595 * caching frequently requested values.
596 *
597 * @param i an {@code int} value.
598 * @return an {@code Integer} instance representing {@code i}.
599 * @since 1.5
600 */
601 public static Integer valueOf(int i) {
602 final int offset = 128;
603 if (i >= -128 && i <= 127) { // must cache
604 return IntegerCache.cache[i + offset];
605 }
606 return new Integer(i);
607 }
608
609 /**
610 * The value of the {@code Integer}.
611 *
612 * @serial
613 */
614 private final int value;
615
616 /**
617 * Constructs a newly allocated {@code Integer} object that
618 * represents the specified {@code int} value.
619 *
620 * @param value the value to be represented by the
621 * {@code Integer} object.
622 */
623 public Integer(int value) {
624 this.value = value;
625 }
626
627 /**
628 * Constructs a newly allocated {@code Integer} object that
629 * represents the {@code int} value indicated by the
630 * {@code String} parameter. The string is converted to an
631 * {@code int} value in exactly the manner used by the
632 * {@code parseInt} method for radix 10.
633 *
634 * @param s the {@code String} to be converted to an
635 * {@code Integer}.
636 * @exception NumberFormatException if the {@code String} does not
637 * contain a parsable integer.
638 * @see java.lang.Integer#parseInt(java.lang.String, int)
639 */
640 public Integer(String s) throws NumberFormatException {
641 this.value = parseInt(s, 10);
642 }
643
644 /**
645 * Returns the value of this {@code Integer} as a
646 * {@code byte}.
647 */
648 public byte byteValue() {
649 return (byte)value;
650 }
651
652 /**
653 * Returns the value of this {@code Integer} as a
654 * {@code short}.
655 */
656 public short shortValue() {
657 return (short)value;
658 }
659
660 /**
661 * Returns the value of this {@code Integer} as an
662 * {@code int}.
663 */
664 public int intValue() {
665 return value;
666 }
667
668 /**
669 * Returns the value of this {@code Integer} as a
670 * {@code long}.
671 */
672 public long longValue() {
673 return (long)value;
674 }
675
676 /**
677 * Returns the value of this {@code Integer} as a
678 * {@code float}.
679 */
680 public float floatValue() {
681 return (float)value;
682 }
683
684 /**
685 * Returns the value of this {@code Integer} as a
686 * {@code double}.
687 */
688 public double doubleValue() {
689 return (double)value;
690 }
691
692 /**
693 * Returns a {@code String} object representing this
694 * {@code Integer}'s value. The value is converted to signed
695 * decimal representation and returned as a string, exactly as if
696 * the integer value were given as an argument to the {@link
697 * java.lang.Integer#toString(int)} method.
698 *
699 * @return a string representation of the value of this object in
700 * base 10.
701 */
702 public String toString() {
703 return String.valueOf(value);
704 }
705
706 /**
707 * Returns a hash code for this {@code Integer}.
708 *
709 * @return a hash code value for this object, equal to the
710 * primitive {@code int} value represented by this
711 * {@code Integer} object.
712 */
713 public int hashCode() {
714 return value;
715 }
716
717 /**
718 * Compares this object to the specified object. The result is
719 * {@code true} if and only if the argument is not
720 * {@code null} and is an {@code Integer} object that
721 * contains the same {@code int} value as this object.
722 *
723 * @param obj the object to compare with.
724 * @return {@code true} if the objects are the same;
725 * {@code false} otherwise.
726 */
727 public boolean equals(Object obj) {
728 if (obj instanceof Integer) {
729 return value == ((Integer)obj).intValue();
730 }
731 return false;
732 }
733
734 /**
735 * Determines the integer value of the system property with the
736 * specified name.
737 *
738 * <p>The first argument is treated as the name of a system property.
739 * System properties are accessible through the
740 * {@link java.lang.System#getProperty(java.lang.String)} method. The
741 * string value of this property is then interpreted as an integer
742 * value and an {@code Integer} object representing this value is
743 * returned. Details of possible numeric formats can be found with
744 * the definition of {@code getProperty}.
745 *
746 * <p>If there is no property with the specified name, if the specified name
747 * is empty or {@code null}, or if the property does not have
748 * the correct numeric format, then {@code null} is returned.
749 *
750 * <p>In other words, this method returns an {@code Integer}
751 * object equal to the value of:
752 *
753 * <blockquote>
754 * {@code getInteger(nm, null)}
755 * </blockquote>
756 *
757 * @param nm property name.
758 * @return the {@code Integer} value of the property.
759 * @see java.lang.System#getProperty(java.lang.String)
760 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
761 */
762 public static Integer getInteger(String nm) {
763 return getInteger(nm, null);
764 }
765
766 /**
767 * Determines the integer value of the system property with the
768 * specified name.
769 *
770 * <p>The first argument is treated as the name of a system property.
771 * System properties are accessible through the {@link
772 * java.lang.System#getProperty(java.lang.String)} method. The
773 * string value of this property is then interpreted as an integer
774 * value and an {@code Integer} object representing this value is
775 * returned. Details of possible numeric formats can be found with
776 * the definition of {@code getProperty}.
777 *
778 * <p>The second argument is the default value. An {@code Integer} object
779 * that represents the value of the second argument is returned if there
780 * is no property of the specified name, if the property does not have
781 * the correct numeric format, or if the specified name is empty or
782 * {@code null}.
783 *
784 * <p>In other words, this method returns an {@code Integer} object
785 * equal to the value of:
786 *
787 * <blockquote>
788 * {@code getInteger(nm, new Integer(val))}
789 * </blockquote>
790 *
791 * but in practice it may be implemented in a manner such as:
792 *
793 * <blockquote><pre>
794 * Integer result = getInteger(nm, null);
795 * return (result == null) ? new Integer(val) : result;
796 * </pre></blockquote>
797 *
798 * to avoid the unnecessary allocation of an {@code Integer}
799 * object when the default value is not needed.
800 *
801 * @param nm property name.
802 * @param val default value.
803 * @return the {@code Integer} value of the property.
804 * @see java.lang.System#getProperty(java.lang.String)
805 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
806 */
807 public static Integer getInteger(String nm, int val) {
808 Integer result = getInteger(nm, null);
809 return (result == null) ? new Integer(val) : result;
810 }
811
812 /**
813 * Returns the integer value of the system property with the
814 * specified name. The first argument is treated as the name of a
815 * system property. System properties are accessible through the
816 * {@link java.lang.System#getProperty(java.lang.String)} method.
817 * The string value of this property is then interpreted as an
818 * integer value, as per the {@code Integer.decode} method,
819 * and an {@code Integer} object representing this value is
820 * returned.
821 *
822 * <ul><li>If the property value begins with the two ASCII characters
823 * {@code 0x} or the ASCII character {@code #}, not
824 * followed by a minus sign, then the rest of it is parsed as a
825 * hexadecimal integer exactly as by the method
826 * {@link #valueOf(java.lang.String, int)} with radix 16.
827 * <li>If the property value begins with the ASCII character
828 * {@code 0} followed by another character, it is parsed as an
829 * octal integer exactly as by the method
830 * {@link #valueOf(java.lang.String, int)} with radix 8.
831 * <li>Otherwise, the property value is parsed as a decimal integer
832 * exactly as by the method {@link #valueOf(java.lang.String, int)}
833 * with radix 10.
834 * </ul>
835 *
836 * <p>The second argument is the default value. The default value is
837 * returned if there is no property of the specified name, if the
838 * property does not have the correct numeric format, or if the
839 * specified name is empty or {@code null}.
840 *
841 * @param nm property name.
842 * @param val default value.
843 * @return the {@code Integer} value of the property.
844 * @see java.lang.System#getProperty(java.lang.String)
845 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
846 * @see java.lang.Integer#decode
847 */
848 public static Integer getInteger(String nm, Integer val) {
849 String v = null;
850 try {
851 v = System.getProperty(nm);
852 } catch (IllegalArgumentException e) {
853 } catch (NullPointerException e) {
854 }
855 if (v != null) {
856 try {
857 return Integer.decode(v);
858 } catch (NumberFormatException e) {
859 }
860 }
861 return val;
862 }
863
864 /**
865 * Decodes a {@code String} into an {@code Integer}.
866 * Accepts decimal, hexadecimal, and octal numbers given
867 * by the following grammar:
868 *
869 * <blockquote>
870 * <dl>
871 * <dt><i>DecodableString:</i>
872 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
873 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
874 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
875 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
876 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
877 * <p>
878 * <dt><i>Sign:</i>
879 * <dd>{@code -}
880 * <dd>{@code +}
881 * </dl>
882 * </blockquote>
883 *
884 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
885 * are defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">§3.10.1</a>
886 * of the <a href="http://java.sun.com/docs/books/jls/html/">Java
887 * Language Specification</a>.
888 *
889 * <p>The sequence of characters following an optional
890 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
891 * "{@code #}", or leading zero) is parsed as by the {@code
892 * Integer.parseInt} method with the indicated radix (10, 16, or
893 * 8). This sequence of characters must represent a positive
894 * value or a {@link NumberFormatException} will be thrown. The
895 * result is negated if first character of the specified {@code
896 * String} is the minus sign. No whitespace characters are
897 * permitted in the {@code String}.
898 *
899 * @param nm the {@code String} to decode.
900 * @return an {@code Integer} object holding the {@code int}
901 * value represented by {@code nm}
902 * @exception NumberFormatException if the {@code String} does not
903 * contain a parsable integer.
904 * @see java.lang.Integer#parseInt(java.lang.String, int)
905 */
906 public static Integer decode(String nm) throws NumberFormatException {
907 int radix = 10;
908 int index = 0;
909 boolean negative = false;
910 Integer result;
911
912 if (nm.length() == 0)
913 throw new NumberFormatException("Zero length string");
914 char firstChar = nm.charAt(0);
915 // Handle sign, if present
916 if (firstChar == '-') {
917 negative = true;
918 index++;
919 } else if (firstChar == '+')
920 index++;
921
922 // Handle radix specifier, if present
923 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
924 index += 2;
925 radix = 16;
926 }
927 else if (nm.startsWith("#", index)) {
928 index ++;
929 radix = 16;
930 }
931 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
932 index ++;
933 radix = 8;
934 }
935
936 if (nm.startsWith("-", index) || nm.startsWith("+", index))
937 throw new NumberFormatException("Sign character in wrong position");
938
939 try {
940 result = Integer.valueOf(nm.substring(index), radix);
941 result = negative ? new Integer(-result.intValue()) : result;
942 } catch (NumberFormatException e) {
943 // If number is Integer.MIN_VALUE, we'll end up here. The next line
944 // handles this case, and causes any genuine format error to be
945 // rethrown.
946 String constant = negative ? ("-" + nm.substring(index))
947 : nm.substring(index);
948 result = Integer.valueOf(constant, radix);
949 }
950 return result;
951 }
952
953 /**
954 * Compares two {@code Integer} objects numerically.
955 *
956 * @param anotherInteger the {@code Integer} to be compared.
957 * @return the value {@code 0} if this {@code Integer} is
958 * equal to the argument {@code Integer}; a value less than
959 * {@code 0} if this {@code Integer} is numerically less
960 * than the argument {@code Integer}; and a value greater
961 * than {@code 0} if this {@code Integer} is numerically
962 * greater than the argument {@code Integer} (signed
963 * comparison).
964 * @since 1.2
965 */
966 public int compareTo(Integer anotherInteger) {
967 int thisVal = this.value;
968 int anotherVal = anotherInteger.value;
969 return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1));
970 }
971
972
973 // Bit twiddling
974
975 /**
976 * The number of bits used to represent an {@code int} value in two's
977 * complement binary form.
978 *
979 * @since 1.5
980 */
981 public static final int SIZE = 32;
982
983 /**
984 * Returns an {@code int} value with at most a single one-bit, in the
985 * position of the highest-order ("leftmost") one-bit in the specified
986 * {@code int} value. Returns zero if the specified value has no
987 * one-bits in its two's complement binary representation, that is, if it
988 * is equal to zero.
989 *
990 * @return an {@code int} value with a single one-bit, in the position
991 * of the highest-order one-bit in the specified value, or zero if
992 * the specified value is itself equal to zero.
993 * @since 1.5
994 */
995 public static int highestOneBit(int i) {
996 // HD, Figure 3-1
997 i |= (i >> 1);
998 i |= (i >> 2);
999 i |= (i >> 4);
1000 i |= (i >> 8);
1001 i |= (i >> 16);
1002 return i - (i >>> 1);
1003 }
1004
1005 /**
1006 * Returns an {@code int} value with at most a single one-bit, in the
1007 * position of the lowest-order ("rightmost") one-bit in the specified
1008 * {@code int} value. Returns zero if the specified value has no
1009 * one-bits in its two's complement binary representation, that is, if it
1010 * is equal to zero.
1011 *
1012 * @return an {@code int} value with a single one-bit, in the position
1013 * of the lowest-order one-bit in the specified value, or zero if
1014 * the specified value is itself equal to zero.
1015 * @since 1.5
1016 */
1017 public static int lowestOneBit(int i) {
1018 // HD, Section 2-1
1019 return i & -i;
1020 }
1021
1022 /**
1023 * Returns the number of zero bits preceding the highest-order
1024 * ("leftmost") one-bit in the two's complement binary representation
1025 * of the specified {@code int} value. Returns 32 if the
1026 * specified value has no one-bits in its two's complement representation,
1027 * in other words if it is equal to zero.
1028 *
1029 * <p>Note that this method is closely related to the logarithm base 2.
1030 * For all positive {@code int} values x:
1031 * <ul>
1032 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1033 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1034 * </ul>
1035 *
1036 * @return the number of zero bits preceding the highest-order
1037 * ("leftmost") one-bit in the two's complement binary representation
1038 * of the specified {@code int} value, or 32 if the value
1039 * is equal to zero.
1040 * @since 1.5
1041 */
1042 public static int numberOfLeadingZeros(int i) {
1043 // HD, Figure 5-6
1044 if (i == 0)
1045 return 32;
1046 int n = 1;
1047 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1048 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1049 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1050 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1051 n -= i >>> 31;
1052 return n;
1053 }
1054
1055 /**
1056 * Returns the number of zero bits following the lowest-order ("rightmost")
1057 * one-bit in the two's complement binary representation of the specified
1058 * {@code int} value. Returns 32 if the specified value has no
1059 * one-bits in its two's complement representation, in other words if it is
1060 * equal to zero.
1061 *
1062 * @return the number of zero bits following the lowest-order ("rightmost")
1063 * one-bit in the two's complement binary representation of the
1064 * specified {@code int} value, or 32 if the value is equal
1065 * to zero.
1066 * @since 1.5
1067 */
1068 public static int numberOfTrailingZeros(int i) {
1069 // HD, Figure 5-14
1070 int y;
1071 if (i == 0) return 32;
1072 int n = 31;
1073 y = i <<16; if (y != 0) { n = n -16; i = y; }
1074 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1075 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1076 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1077 return n - ((i << 1) >>> 31);
1078 }
1079
1080 /**
1081 * Returns the number of one-bits in the two's complement binary
1082 * representation of the specified {@code int} value. This function is
1083 * sometimes referred to as the <i>population count</i>.
1084 *
1085 * @return the number of one-bits in the two's complement binary
1086 * representation of the specified {@code int} value.
1087 * @since 1.5
1088 */
1089 public static int bitCount(int i) {
1090 // HD, Figure 5-2
1091 i = i - ((i >>> 1) & 0x55555555);
1092 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1093 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1094 i = i + (i >>> 8);
1095 i = i + (i >>> 16);
1096 return i & 0x3f;
1097 }
1098
1099 /**
1100 * Returns the value obtained by rotating the two's complement binary
1101 * representation of the specified {@code int} value left by the
1102 * specified number of bits. (Bits shifted out of the left hand, or
1103 * high-order, side reenter on the right, or low-order.)
1104 *
1105 * <p>Note that left rotation with a negative distance is equivalent to
1106 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1107 * distance)}. Note also that rotation by any multiple of 32 is a
1108 * no-op, so all but the last five bits of the rotation distance can be
1109 * ignored, even if the distance is negative: {@code rotateLeft(val,
1110 * distance) == rotateLeft(val, distance & 0x1F)}.
1111 *
1112 * @return the value obtained by rotating the two's complement binary
1113 * representation of the specified {@code int} value left by the
1114 * specified number of bits.
1115 * @since 1.5
1116 */
1117 public static int rotateLeft(int i, int distance) {
1118 return (i << distance) | (i >>> -distance);
1119 }
1120
1121 /**
1122 * Returns the value obtained by rotating the two's complement binary
1123 * representation of the specified {@code int} value right by the
1124 * specified number of bits. (Bits shifted out of the right hand, or
1125 * low-order, side reenter on the left, or high-order.)
1126 *
1127 * <p>Note that right rotation with a negative distance is equivalent to
1128 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1129 * distance)}. Note also that rotation by any multiple of 32 is a
1130 * no-op, so all but the last five bits of the rotation distance can be
1131 * ignored, even if the distance is negative: {@code rotateRight(val,
1132 * distance) == rotateRight(val, distance & 0x1F)}.
1133 *
1134 * @return the value obtained by rotating the two's complement binary
1135 * representation of the specified {@code int} value right by the
1136 * specified number of bits.
1137 * @since 1.5
1138 */
1139 public static int rotateRight(int i, int distance) {
1140 return (i >>> distance) | (i << -distance);
1141 }
1142
1143 /**
1144 * Returns the value obtained by reversing the order of the bits in the
1145 * two's complement binary representation of the specified {@code int}
1146 * value.
1147 *
1148 * @return the value obtained by reversing order of the bits in the
1149 * specified {@code int} value.
1150 * @since 1.5
1151 */
1152 public static int reverse(int i) {
1153 // HD, Figure 7-1
1154 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1155 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1156 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1157 i = (i << 24) | ((i & 0xff00) << 8) |
1158 ((i >>> 8) & 0xff00) | (i >>> 24);
1159 return i;
1160 }
1161
1162 /**
1163 * Returns the signum function of the specified {@code int} value. (The
1164 * return value is -1 if the specified value is negative; 0 if the
1165 * specified value is zero; and 1 if the specified value is positive.)
1166 *
1167 * @return the signum function of the specified {@code int} value.
1168 * @since 1.5
1169 */
1170 public static int signum(int i) {
1171 // HD, Section 2-7
1172 return (i >> 31) | (-i >>> 31);
1173 }
1174
1175 /**
1176 * Returns the value obtained by reversing the order of the bytes in the
1177 * two's complement representation of the specified {@code int} value.
1178 *
1179 * @return the value obtained by reversing the bytes in the specified
1180 * {@code int} value.
1181 * @since 1.5
1182 */
1183 public static int reverseBytes(int i) {
1184 return ((i >>> 24) ) |
1185 ((i >> 8) & 0xFF00) |
1186 ((i << 8) & 0xFF0000) |
1187 ((i << 24));
1188 }
1189
1190 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1191 private static final long serialVersionUID = 1360826667806852920L;
1192 }
Save This Page