1 /*
2 * Copyright 1994-2009 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 import java.util.Properties;
29
30 /**
31 * The {@code Integer} class wraps a value of the primitive type
32 * {@code int} in an object. An object of type {@code Integer}
33 * contains a single field whose type is {@code int}.
34 *
35 * <p>In addition, this class provides several methods for converting
36 * an {@code int} to a {@code String} and a {@code String} to an
37 * {@code int}, as well as other constants and methods useful when
38 * dealing with an {@code int}.
39 *
40 * <p>Implementation note: The implementations of the "bit twiddling"
41 * methods (such as {@link #highestOneBit(int) highestOneBit} and
42 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
43 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
44 * Delight</i>, (Addison Wesley, 2002).
45 *
46 * @author Lee Boynton
47 * @author Arthur van Hoff
48 * @author Josh Bloch
49 * @author Joseph D. Darcy
50 * @since JDK1.0
51 */
52 public final class Integer extends Number implements Comparable<Integer> {
53 /**
54 * A constant holding the minimum value an {@code int} can
55 * have, -2<sup>31</sup>.
56 */
57 public static final int MIN_VALUE = 0x80000000;
58
59 /**
60 * A constant holding the maximum value an {@code int} can
61 * have, 2<sup>31</sup>-1.
62 */
63 public static final int MAX_VALUE = 0x7fffffff;
64
65 /**
66 * The {@code Class} instance representing the primitive type
67 * {@code int}.
68 *
69 * @since JDK1.1
70 */
71 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
72
73 /**
74 * All possible chars for representing a number as a String
75 */
76 final static char[] digits = {
77 '0' , '1' , '2' , '3' , '4' , '5' ,
78 '6' , '7' , '8' , '9' , 'a' , 'b' ,
79 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
80 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
81 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
82 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
83 };
84
85 /**
86 * Returns a string representation of the first argument in the
87 * radix specified by the second argument.
88 *
89 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
90 * or larger than {@code Character.MAX_RADIX}, then the radix
91 * {@code 10} is used instead.
92 *
93 * <p>If the first argument is negative, the first element of the
94 * result is the ASCII minus character {@code '-'}
95 * (<code>'\u002D'</code>). If the first argument is not
96 * negative, no sign character appears in the result.
97 *
98 * <p>The remaining characters of the result represent the magnitude
99 * of the first argument. If the magnitude is zero, it is
100 * represented by a single zero character {@code '0'}
101 * (<code>'\u0030'</code>); otherwise, the first character of
102 * the representation of the magnitude will not be the zero
103 * character. The following ASCII characters are used as digits:
104 *
105 * <blockquote>
106 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
107 * </blockquote>
108 *
109 * These are <code>'\u0030'</code> through
110 * <code>'\u0039'</code> and <code>'\u0061'</code> through
111 * <code>'\u007A'</code>. If {@code radix} is
112 * <var>N</var>, then the first <var>N</var> of these characters
113 * are used as radix-<var>N</var> digits in the order shown. Thus,
114 * the digits for hexadecimal (radix 16) are
115 * {@code 0123456789abcdef}. If uppercase letters are
116 * desired, the {@link java.lang.String#toUpperCase()} method may
117 * be called on the result:
118 *
119 * <blockquote>
120 * {@code Integer.toString(n, 16).toUpperCase()}
121 * </blockquote>
122 *
123 * @param i an integer to be converted to a string.
124 * @param radix the radix to use in the string representation.
125 * @return a string representation of the argument in the specified radix.
126 * @see java.lang.Character#MAX_RADIX
127 * @see java.lang.Character#MIN_RADIX
128 */
129 public static String toString(int i, int radix) {
130
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 integer argument as an
162 * unsigned integer in base 16.
163 *
164 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
165 * if the argument is negative; otherwise, it is equal to the
166 * argument. This value is converted to a string of ASCII digits
167 * in hexadecimal (base 16) with no extra leading
168 * {@code 0}s. If the unsigned magnitude is zero, it is
169 * represented by a single zero character {@code '0'}
170 * (<code>'\u0030'</code>); otherwise, the first character of
171 * the representation of the unsigned magnitude will not be the
172 * zero character. The following characters are used as
173 * hexadecimal digits:
174 *
175 * <blockquote>
176 * {@code 0123456789abcdef}
177 * </blockquote>
178 *
179 * These are the characters <code>'\u0030'</code> through
180 * <code>'\u0039'</code> and <code>'\u0061'</code> through
181 * <code>'\u0066'</code>. If uppercase letters are
182 * desired, the {@link java.lang.String#toUpperCase()} method may
183 * be called on the result:
184 *
185 * <blockquote>
186 * {@code Integer.toHexString(n).toUpperCase()}
187 * </blockquote>
188 *
189 * @param i an integer to be converted to a string.
190 * @return the string representation of the unsigned integer value
191 * represented by the argument in hexadecimal (base 16).
192 * @since JDK1.0.2
193 */
194 public static String toHexString(int i) {
195 return toUnsignedString(i, 4);
196 }
197
198 /**
199 * Returns a string representation of the integer argument as an
200 * unsigned integer in base 8.
201 *
202 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
203 * if the argument is negative; otherwise, it is equal to the
204 * argument. This value is converted to a string of ASCII digits
205 * in octal (base 8) with no extra leading {@code 0}s.
206 *
207 * <p>If the unsigned magnitude is zero, it is represented by a
208 * single zero character {@code '0'}
209 * (<code>'\u0030'</code>); otherwise, the first character of
210 * the representation of the unsigned magnitude will not be the
211 * zero character. The following characters are used as octal
212 * digits:
213 *
214 * <blockquote>
215 * {@code 01234567}
216 * </blockquote>
217 *
218 * These are the characters <code>'\u0030'</code> through
219 * <code>'\u0037'</code>.
220 *
221 * @param i an integer to be converted to a string.
222 * @return the string representation of the unsigned integer value
223 * represented by the argument in octal (base 8).
224 * @since JDK1.0.2
225 */
226 public static String toOctalString(int i) {
227 return toUnsignedString(i, 3);
228 }
229
230 /**
231 * Returns a string representation of the integer argument as an
232 * unsigned integer in base 2.
233 *
234 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
235 * if the argument is negative; otherwise it is equal to the
236 * argument. This value is converted to a string of ASCII digits
237 * in binary (base 2) with no extra leading {@code 0}s.
238 * If the unsigned magnitude is zero, it is represented by a
239 * single zero character {@code '0'}
240 * (<code>'\u0030'</code>); otherwise, the first character of
241 * the representation of the unsigned magnitude will not be the
242 * zero character. The characters {@code '0'}
243 * (<code>'\u0030'</code>) and {@code '1'}
244 * (<code>'\u0031'</code>) are used as binary digits.
245 *
246 * @param i an integer to be converted to a string.
247 * @return the string representation of the unsigned integer value
248 * represented by the argument in binary (base 2).
249 * @since JDK1.0.2
250 */
251 public static String toBinaryString(int i) {
252 return toUnsignedString(i, 1);
253 }
254
255 /**
256 * Convert the integer to an unsigned number.
257 */
258 private static String toUnsignedString(int i, int shift) {
259 char[] buf = new char[32];
260 int charPos = 32;
261 int radix = 1 << shift;
262 int mask = radix - 1;
263 do {
264 buf[--charPos] = digits[i & mask];
265 i >>>= shift;
266 } while (i != 0);
267
268 return new String(buf, charPos, (32 - charPos));
269 }
270
271
272 final static char [] DigitTens = {
273 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
274 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
275 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
276 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
277 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
278 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
279 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
280 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
281 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
282 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
283 } ;
284
285 final static char [] DigitOnes = {
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 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
295 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
296 } ;
297
298 // I use the "invariant division by multiplication" trick to
299 // accelerate Integer.toString. In particular we want to
300 // avoid division by 10.
301 //
302 // The "trick" has roughly the same performance characteristics
303 // as the "classic" Integer.toString code on a non-JIT VM.
304 // The trick avoids .rem and .div calls but has a longer code
305 // path and is thus dominated by dispatch overhead. In the
306 // JIT case the dispatch overhead doesn't exist and the
307 // "trick" is considerably faster than the classic code.
308 //
309 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
310 // sequence.
311 //
312 // RE: Division by Invariant Integers using Multiplication
313 // T Gralund, P Montgomery
314 // ACM PLDI 1994
315 //
316
317 /**
318 * Returns a {@code String} object representing the
319 * specified integer. The argument is converted to signed decimal
320 * representation and returned as a string, exactly as if the
321 * argument and radix 10 were given as arguments to the {@link
322 * #toString(int, int)} method.
323 *
324 * @param i an integer to be converted.
325 * @return a string representation of the argument in base 10.
326 */
327 public static String toString(int i) {
328 if (i == Integer.MIN_VALUE)
329 return "-2147483648";
330 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
331 char[] buf = new char[size];
332 getChars(i, size, buf);
333 return new String(0, size, buf);
334 }
335
336 /**
337 * Places characters representing the integer i into the
338 * character array buf. The characters are placed into
339 * the buffer backwards starting with the least significant
340 * digit at the specified index (exclusive), and working
341 * backwards from there.
342 *
343 * Will fail if i == Integer.MIN_VALUE
344 */
345 static void getChars(int i, int index, char[] buf) {
346 int q, r;
347 int charPos = index;
348 char sign = 0;
349
350 if (i < 0) {
351 sign = '-';
352 i = -i;
353 }
354
355 // Generate two digits per iteration
356 while (i >= 65536) {
357 q = i / 100;
358 // really: r = i - (q * 100);
359 r = i - ((q << 6) + (q << 5) + (q << 2));
360 i = q;
361 buf [--charPos] = DigitOnes[r];
362 buf [--charPos] = DigitTens[r];
363 }
364
365 // Fall thru to fast mode for smaller numbers
366 // assert(i <= 65536, i);
367 for (;;) {
368 q = (i * 52429) >>> (16+3);
369 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
370 buf [--charPos] = digits [r];
371 i = q;
372 if (i == 0) break;
373 }
374 if (sign != 0) {
375 buf [--charPos] = sign;
376 }
377 }
378
379 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
380 99999999, 999999999, Integer.MAX_VALUE };
381
382 // Requires positive x
383 static int stringSize(int x) {
384 for (int i=0; ; i++)
385 if (x <= sizeTable[i])
386 return i+1;
387 }
388
389 /**
390 * Parses the string argument as a signed integer in the radix
391 * specified by the second argument. The characters in the string
392 * must all be digits of the specified radix (as determined by
393 * whether {@link java.lang.Character#digit(char, int)} returns a
394 * nonnegative value), except that the first character may be an
395 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to
396 * indicate a negative value or an ASCII plus sign {@code '+'}
397 * (<code>'\u002B'</code>) to indicate a positive value. The
398 * resulting integer value is returned.
399 *
400 * <p>An exception of type {@code NumberFormatException} is
401 * thrown if any of the following situations occurs:
402 * <ul>
403 * <li>The first argument is {@code null} or is a string of
404 * length zero.
405 *
406 * <li>The radix is either smaller than
407 * {@link java.lang.Character#MIN_RADIX} or
408 * larger than {@link java.lang.Character#MAX_RADIX}.
409 *
410 * <li>Any character of the string is not a digit of the specified
411 * radix, except that the first character may be a minus sign
412 * {@code '-'} (<code>'\u002D'</code>) or plus sign
413 * {@code '+'} (<code>'\u002B'</code>) provided that the
414 * string is longer than length 1.
415 *
416 * <li>The value represented by the string is not a value of type
417 * {@code int}.
418 * </ul>
419 *
420 * <p>Examples:
421 * <blockquote><pre>
422 * parseInt("0", 10) returns 0
423 * parseInt("473", 10) returns 473
424 * parseInt("+42", 10) returns 42
425 * parseInt("-0", 10) returns 0
426 * parseInt("-FF", 16) returns -255
427 * parseInt("1100110", 2) returns 102
428 * parseInt("2147483647", 10) returns 2147483647
429 * parseInt("-2147483648", 10) returns -2147483648
430 * parseInt("2147483648", 10) throws a NumberFormatException
431 * parseInt("99", 8) throws a NumberFormatException
432 * parseInt("Kona", 10) throws a NumberFormatException
433 * parseInt("Kona", 27) returns 411787
434 * </pre></blockquote>
435 *
436 * @param s the {@code String} containing the integer
437 * representation to be parsed
438 * @param radix the radix to be used while parsing {@code s}.
439 * @return the integer represented by the string argument in the
440 * specified radix.
441 * @exception NumberFormatException if the {@code String}
442 * does not contain a parsable {@code int}.
443 */
444 public static int parseInt(String s, int radix)
445 throws NumberFormatException
446 {
447 /*
448 * WARNING: This method may be invoked early during VM initialization
449 * before IntegerCache is initialized. Care must be taken to not use
450 * the valueOf method.
451 */
452
453 if (s == null) {
454 throw new NumberFormatException("null");
455 }
456
457 if (radix < Character.MIN_RADIX) {
458 throw new NumberFormatException("radix " + radix +
459 " less than Character.MIN_RADIX");
460 }
461
462 if (radix > Character.MAX_RADIX) {
463 throw new NumberFormatException("radix " + radix +
464 " greater than Character.MAX_RADIX");
465 }
466
467 int result = 0;
468 boolean negative = false;
469 int i = 0, len = s.length();
470 int limit = -Integer.MAX_VALUE;
471 int multmin;
472 int digit;
473
474 if (len > 0) {
475 char firstChar = s.charAt(0);
476 if (firstChar < '0') { // Possible leading "+" or "-"
477 if (firstChar == '-') {
478 negative = true;
479 limit = Integer.MIN_VALUE;
480 } else if (firstChar != '+')
481 throw NumberFormatException.forInputString(s);
482
483 if (len == 1) // Cannot have lone "+" or "-"
484 throw NumberFormatException.forInputString(s);
485 i++;
486 }
487 multmin = limit / radix;
488 while (i < len) {
489 // Accumulating negatively avoids surprises near MAX_VALUE
490 digit = Character.digit(s.charAt(i++),radix);
491 if (digit < 0) {
492 throw NumberFormatException.forInputString(s);
493 }
494 if (result < multmin) {
495 throw NumberFormatException.forInputString(s);
496 }
497 result *= radix;
498 if (result < limit + digit) {
499 throw NumberFormatException.forInputString(s);
500 }
501 result -= digit;
502 }
503 } else {
504 throw NumberFormatException.forInputString(s);
505 }
506 return negative ? result : -result;
507 }
508
509 /**
510 * Parses the string argument as a signed decimal integer. The
511 * characters in the string must all be decimal digits, except
512 * that the first character may be an ASCII minus sign {@code '-'}
513 * (<code>'\u002D'</code>) to indicate a negative value or an
514 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
515 * indicate a positive value. The resulting integer value is
516 * returned, exactly as if the argument and the radix 10 were
517 * given as arguments to the {@link #parseInt(java.lang.String,
518 * int)} method.
519 *
520 * @param s a {@code String} containing the {@code int}
521 * representation to be parsed
522 * @return the integer value represented by the argument in decimal.
523 * @exception NumberFormatException if the string does not contain a
524 * parsable integer.
525 */
526 public static int parseInt(String s) throws NumberFormatException {
527 return parseInt(s,10);
528 }
529
530 /**
531 * Returns an {@code Integer} object holding the value
532 * extracted from the specified {@code String} when parsed
533 * with the radix given by the second argument. The first argument
534 * is interpreted as representing a signed integer in the radix
535 * specified by the second argument, exactly as if the arguments
536 * were given to the {@link #parseInt(java.lang.String, int)}
537 * method. The result is an {@code Integer} object that
538 * represents the integer value specified by the string.
539 *
540 * <p>In other words, this method returns an {@code Integer}
541 * object equal to the value of:
542 *
543 * <blockquote>
544 * {@code new Integer(Integer.parseInt(s, radix))}
545 * </blockquote>
546 *
547 * @param s the string to be parsed.
548 * @param radix the radix to be used in interpreting {@code s}
549 * @return an {@code Integer} object holding the value
550 * represented by the string argument in the specified
551 * radix.
552 * @exception NumberFormatException if the {@code String}
553 * does not contain a parsable {@code int}.
554 */
555 public static Integer valueOf(String s, int radix) throws NumberFormatException {
556 return Integer.valueOf(parseInt(s,radix));
557 }
558
559 /**
560 * Returns an {@code Integer} object holding the
561 * value of the specified {@code String}. The argument is
562 * interpreted as representing a signed decimal integer, exactly
563 * as if the argument were given to the {@link
564 * #parseInt(java.lang.String)} method. The result is an
565 * {@code Integer} object that represents the integer value
566 * specified by the string.
567 *
568 * <p>In other words, this method returns an {@code Integer}
569 * object equal to the value of:
570 *
571 * <blockquote>
572 * {@code new Integer(Integer.parseInt(s))}
573 * </blockquote>
574 *
575 * @param s the string to be parsed.
576 * @return an {@code Integer} object holding the value
577 * represented by the string argument.
578 * @exception NumberFormatException if the string cannot be parsed
579 * as an integer.
580 */
581 public static Integer valueOf(String s) throws NumberFormatException {
582 return Integer.valueOf(parseInt(s, 10));
583 }
584
585 /**
586 * Cache to support the object identity semantics of autoboxing for values between
587 * -128 and 127 (inclusive) as required by JLS.
588 *
589 * The cache is initialized on first usage. During VM initialization the
590 * getAndRemoveCacheProperties method may be used to get and remove any system
591 * properites that configure the cache size. At this time, the size of the
592 * cache may be controlled by the -XX:AutoBoxCacheMax=<size> option.
593 */
594
595 // value of java.lang.Integer.IntegerCache.high property (obtained during VM init)
596 private static String integerCacheHighPropValue;
597
598 static void getAndRemoveCacheProperties() {
599 if (!sun.misc.VM.isBooted()) {
600 Properties props = System.getProperties();
601 integerCacheHighPropValue =
602 (String)props.remove("java.lang.Integer.IntegerCache.high");
603 if (integerCacheHighPropValue != null)
604 System.setProperties(props); // remove from system props
605 }
606 }
607
608 private static class IntegerCache {
609 static final int low = -128;
610 static final int high;
611 static final Integer cache[];
612
613 static {
614 // high value may be configured by property
615 int h = 127;
616 if (integerCacheHighPropValue != null) {
617 int i = parseInt(integerCacheHighPropValue);
618 i = Math.max(i, 127);
619 // Maximum array size is Integer.MAX_VALUE
620 h = Math.min(i, Integer.MAX_VALUE - (-low));
621 }
622 high = h;
623
624 cache = new Integer[(high - low) + 1];
625 int j = low;
626 for(int k = 0; k < cache.length; k++)
627 cache[k] = new Integer(j++);
628 }
629
630 private IntegerCache() {}
631 }
632
633 /**
634 * Returns an {@code Integer} instance representing the specified
635 * {@code int} value. If a new {@code Integer} instance is not
636 * required, this method should generally be used in preference to
637 * the constructor {@link #Integer(int)}, as this method is likely
638 * to yield significantly better space and time performance by
639 * caching frequently requested values.
640 *
641 * This method will always cache values in the range -128 to 127,
642 * inclusive, and may cache other values outside of this range.
643 *
644 * @param i an {@code int} value.
645 * @return an {@code Integer} instance representing {@code i}.
646 * @since 1.5
647 */
648 public static Integer valueOf(int i) {
649 assert IntegerCache.high >= 127;
650 if (i >= IntegerCache.low && i <= IntegerCache.high)
651 return IntegerCache.cache[i + (-IntegerCache.low)];
652 return new Integer(i);
653 }
654
655 /**
656 * The value of the {@code Integer}.
657 *
658 * @serial
659 */
660 private final int value;
661
662 /**
663 * Constructs a newly allocated {@code Integer} object that
664 * represents the specified {@code int} value.
665 *
666 * @param value the value to be represented by the
667 * {@code Integer} object.
668 */
669 public Integer(int value) {
670 this.value = value;
671 }
672
673 /**
674 * Constructs a newly allocated {@code Integer} object that
675 * represents the {@code int} value indicated by the
676 * {@code String} parameter. The string is converted to an
677 * {@code int} value in exactly the manner used by the
678 * {@code parseInt} method for radix 10.
679 *
680 * @param s the {@code String} to be converted to an
681 * {@code Integer}.
682 * @exception NumberFormatException if the {@code String} does not
683 * contain a parsable integer.
684 * @see java.lang.Integer#parseInt(java.lang.String, int)
685 */
686 public Integer(String s) throws NumberFormatException {
687 this.value = parseInt(s, 10);
688 }
689
690 /**
691 * Returns the value of this {@code Integer} as a
692 * {@code byte}.
693 */
694 public byte byteValue() {
695 return (byte)value;
696 }
697
698 /**
699 * Returns the value of this {@code Integer} as a
700 * {@code short}.
701 */
702 public short shortValue() {
703 return (short)value;
704 }
705
706 /**
707 * Returns the value of this {@code Integer} as an
708 * {@code int}.
709 */
710 public int intValue() {
711 return value;
712 }
713
714 /**
715 * Returns the value of this {@code Integer} as a
716 * {@code long}.
717 */
718 public long longValue() {
719 return (long)value;
720 }
721
722 /**
723 * Returns the value of this {@code Integer} as a
724 * {@code float}.
725 */
726 public float floatValue() {
727 return (float)value;
728 }
729
730 /**
731 * Returns the value of this {@code Integer} as a
732 * {@code double}.
733 */
734 public double doubleValue() {
735 return (double)value;
736 }
737
738 /**
739 * Returns a {@code String} object representing this
740 * {@code Integer}'s value. The value is converted to signed
741 * decimal representation and returned as a string, exactly as if
742 * the integer value were given as an argument to the {@link
743 * java.lang.Integer#toString(int)} method.
744 *
745 * @return a string representation of the value of this object in
746 * base 10.
747 */
748 public String toString() {
749 return String.valueOf(value);
750 }
751
752 /**
753 * Returns a hash code for this {@code Integer}.
754 *
755 * @return a hash code value for this object, equal to the
756 * primitive {@code int} value represented by this
757 * {@code Integer} object.
758 */
759 public int hashCode() {
760 return value;
761 }
762
763 /**
764 * Compares this object to the specified object. The result is
765 * {@code true} if and only if the argument is not
766 * {@code null} and is an {@code Integer} object that
767 * contains the same {@code int} value as this object.
768 *
769 * @param obj the object to compare with.
770 * @return {@code true} if the objects are the same;
771 * {@code false} otherwise.
772 */
773 public boolean equals(Object obj) {
774 if (obj instanceof Integer) {
775 return value == ((Integer)obj).intValue();
776 }
777 return false;
778 }
779
780 /**
781 * Determines the integer value of the system property with the
782 * specified name.
783 *
784 * <p>The first argument is treated as the name of a system property.
785 * System properties are accessible through the
786 * {@link java.lang.System#getProperty(java.lang.String)} method. The
787 * string value of this property is then interpreted as an integer
788 * value and an {@code Integer} object representing this value is
789 * returned. Details of possible numeric formats can be found with
790 * the definition of {@code getProperty}.
791 *
792 * <p>If there is no property with the specified name, if the specified name
793 * is empty or {@code null}, or if the property does not have
794 * the correct numeric format, then {@code null} is returned.
795 *
796 * <p>In other words, this method returns an {@code Integer}
797 * object equal to the value of:
798 *
799 * <blockquote>
800 * {@code getInteger(nm, null)}
801 * </blockquote>
802 *
803 * @param nm property name.
804 * @return the {@code Integer} value of the property.
805 * @see java.lang.System#getProperty(java.lang.String)
806 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
807 */
808 public static Integer getInteger(String nm) {
809 return getInteger(nm, null);
810 }
811
812 /**
813 * Determines the integer value of the system property with the
814 * specified name.
815 *
816 * <p>The first argument is treated as the name of a system property.
817 * System properties are accessible through the {@link
818 * java.lang.System#getProperty(java.lang.String)} method. The
819 * string value of this property is then interpreted as an integer
820 * value and an {@code Integer} object representing this value is
821 * returned. Details of possible numeric formats can be found with
822 * the definition of {@code getProperty}.
823 *
824 * <p>The second argument is the default value. An {@code Integer} object
825 * that represents the value of the second argument is returned if there
826 * is no property of the specified name, if the property does not have
827 * the correct numeric format, or if the specified name is empty or
828 * {@code null}.
829 *
830 * <p>In other words, this method returns an {@code Integer} object
831 * equal to the value of:
832 *
833 * <blockquote>
834 * {@code getInteger(nm, new Integer(val))}
835 * </blockquote>
836 *
837 * but in practice it may be implemented in a manner such as:
838 *
839 * <blockquote><pre>
840 * Integer result = getInteger(nm, null);
841 * return (result == null) ? new Integer(val) : result;
842 * </pre></blockquote>
843 *
844 * to avoid the unnecessary allocation of an {@code Integer}
845 * object when the default value is not needed.
846 *
847 * @param nm property name.
848 * @param val default value.
849 * @return the {@code Integer} value of the property.
850 * @see java.lang.System#getProperty(java.lang.String)
851 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
852 */
853 public static Integer getInteger(String nm, int val) {
854 Integer result = getInteger(nm, null);
855 return (result == null) ? Integer.valueOf(val) : result;
856 }
857
858 /**
859 * Returns the integer value of the system property with the
860 * specified name. The first argument is treated as the name of a
861 * system property. System properties are accessible through the
862 * {@link java.lang.System#getProperty(java.lang.String)} method.
863 * The string value of this property is then interpreted as an
864 * integer value, as per the {@code Integer.decode} method,
865 * and an {@code Integer} object representing this value is
866 * returned.
867 *
868 * <ul><li>If the property value begins with the two ASCII characters
869 * {@code 0x} or the ASCII character {@code #}, not
870 * followed by a minus sign, then the rest of it is parsed as a
871 * hexadecimal integer exactly as by the method
872 * {@link #valueOf(java.lang.String, int)} with radix 16.
873 * <li>If the property value begins with the ASCII character
874 * {@code 0} followed by another character, it is parsed as an
875 * octal integer exactly as by the method
876 * {@link #valueOf(java.lang.String, int)} with radix 8.
877 * <li>Otherwise, the property value is parsed as a decimal integer
878 * exactly as by the method {@link #valueOf(java.lang.String, int)}
879 * with radix 10.
880 * </ul>
881 *
882 * <p>The second argument is the default value. The default value is
883 * returned if there is no property of the specified name, if the
884 * property does not have the correct numeric format, or if the
885 * specified name is empty or {@code null}.
886 *
887 * @param nm property name.
888 * @param val default value.
889 * @return the {@code Integer} value of the property.
890 * @see java.lang.System#getProperty(java.lang.String)
891 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
892 * @see java.lang.Integer#decode
893 */
894 public static Integer getInteger(String nm, Integer val) {
895 String v = null;
896 try {
897 v = System.getProperty(nm);
898 } catch (IllegalArgumentException e) {
899 } catch (NullPointerException e) {
900 }
901 if (v != null) {
902 try {
903 return Integer.decode(v);
904 } catch (NumberFormatException e) {
905 }
906 }
907 return val;
908 }
909
910 /**
911 * Decodes a {@code String} into an {@code Integer}.
912 * Accepts decimal, hexadecimal, and octal numbers given
913 * by the following grammar:
914 *
915 * <blockquote>
916 * <dl>
917 * <dt><i>DecodableString:</i>
918 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
919 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
920 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
921 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
922 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
923 * <p>
924 * <dt><i>Sign:</i>
925 * <dd>{@code -}
926 * <dd>{@code +}
927 * </dl>
928 * </blockquote>
929 *
930 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
931 * are defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">§3.10.1</a>
932 * of the <a href="http://java.sun.com/docs/books/jls/html/">Java
933 * Language Specification</a>.
934 *
935 * <p>The sequence of characters following an optional
936 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
937 * "{@code #}", or leading zero) is parsed as by the {@code
938 * Integer.parseInt} method with the indicated radix (10, 16, or
939 * 8). This sequence of characters must represent a positive
940 * value or a {@link NumberFormatException} will be thrown. The
941 * result is negated if first character of the specified {@code
942 * String} is the minus sign. No whitespace characters are
943 * permitted in the {@code String}.
944 *
945 * @param nm the {@code String} to decode.
946 * @return an {@code Integer} object holding the {@code int}
947 * value represented by {@code nm}
948 * @exception NumberFormatException if the {@code String} does not
949 * contain a parsable integer.
950 * @see java.lang.Integer#parseInt(java.lang.String, int)
951 */
952 public static Integer decode(String nm) throws NumberFormatException {
953 int radix = 10;
954 int index = 0;
955 boolean negative = false;
956 Integer result;
957
958 if (nm.length() == 0)
959 throw new NumberFormatException("Zero length string");
960 char firstChar = nm.charAt(0);
961 // Handle sign, if present
962 if (firstChar == '-') {
963 negative = true;
964 index++;
965 } else if (firstChar == '+')
966 index++;
967
968 // Handle radix specifier, if present
969 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
970 index += 2;
971 radix = 16;
972 }
973 else if (nm.startsWith("#", index)) {
974 index ++;
975 radix = 16;
976 }
977 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
978 index ++;
979 radix = 8;
980 }
981
982 if (nm.startsWith("-", index) || nm.startsWith("+", index))
983 throw new NumberFormatException("Sign character in wrong position");
984
985 try {
986 result = Integer.valueOf(nm.substring(index), radix);
987 result = negative ? Integer.valueOf(-result.intValue()) : result;
988 } catch (NumberFormatException e) {
989 // If number is Integer.MIN_VALUE, we'll end up here. The next line
990 // handles this case, and causes any genuine format error to be
991 // rethrown.
992 String constant = negative ? ("-" + nm.substring(index))
993 : nm.substring(index);
994 result = Integer.valueOf(constant, radix);
995 }
996 return result;
997 }
998
999 /**
1000 * Compares two {@code Integer} objects numerically.
1001 *
1002 * @param anotherInteger the {@code Integer} to be compared.
1003 * @return the value {@code 0} if this {@code Integer} is
1004 * equal to the argument {@code Integer}; a value less than
1005 * {@code 0} if this {@code Integer} is numerically less
1006 * than the argument {@code Integer}; and a value greater
1007 * than {@code 0} if this {@code Integer} is numerically
1008 * greater than the argument {@code Integer} (signed
1009 * comparison).
1010 * @since 1.2
1011 */
1012 public int compareTo(Integer anotherInteger) {
1013 return compare(this.value, anotherInteger.value);
1014 }
1015
1016 /**
1017 * Compares two {@code int} values numerically.
1018 * The value returned is identical to what would be returned by:
1019 * <pre>
1020 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1021 * </pre>
1022 *
1023 * @param x the first {@code int} to compare
1024 * @param y the second {@code int} to compare
1025 * @return the value {@code 0} if {@code x == y};
1026 * a value less than {@code 0} if {@code x < y}; and
1027 * a value greater than {@code 0} if {@code x > y}
1028 * @since 1.7
1029 */
1030 public static int compare(int x, int y) {
1031 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1032 }
1033
1034
1035 // Bit twiddling
1036
1037 /**
1038 * The number of bits used to represent an {@code int} value in two's
1039 * complement binary form.
1040 *
1041 * @since 1.5
1042 */
1043 public static final int SIZE = 32;
1044
1045 /**
1046 * Returns an {@code int} value with at most a single one-bit, in the
1047 * position of the highest-order ("leftmost") one-bit in the specified
1048 * {@code int} value. Returns zero if the specified value has no
1049 * one-bits in its two's complement binary representation, that is, if it
1050 * is equal to zero.
1051 *
1052 * @return an {@code int} value with a single one-bit, in the position
1053 * of the highest-order one-bit in the specified value, or zero if
1054 * the specified value is itself equal to zero.
1055 * @since 1.5
1056 */
1057 public static int highestOneBit(int i) {
1058 // HD, Figure 3-1
1059 i |= (i >> 1);
1060 i |= (i >> 2);
1061 i |= (i >> 4);
1062 i |= (i >> 8);
1063 i |= (i >> 16);
1064 return i - (i >>> 1);
1065 }
1066
1067 /**
1068 * Returns an {@code int} value with at most a single one-bit, in the
1069 * position of the lowest-order ("rightmost") one-bit in the specified
1070 * {@code int} value. Returns zero if the specified value has no
1071 * one-bits in its two's complement binary representation, that is, if it
1072 * is equal to zero.
1073 *
1074 * @return an {@code int} value with a single one-bit, in the position
1075 * of the lowest-order one-bit in the specified value, or zero if
1076 * the specified value is itself equal to zero.
1077 * @since 1.5
1078 */
1079 public static int lowestOneBit(int i) {
1080 // HD, Section 2-1
1081 return i & -i;
1082 }
1083
1084 /**
1085 * Returns the number of zero bits preceding the highest-order
1086 * ("leftmost") one-bit in the two's complement binary representation
1087 * of the specified {@code int} value. Returns 32 if the
1088 * specified value has no one-bits in its two's complement representation,
1089 * in other words if it is equal to zero.
1090 *
1091 * <p>Note that this method is closely related to the logarithm base 2.
1092 * For all positive {@code int} values x:
1093 * <ul>
1094 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1095 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1096 * </ul>
1097 *
1098 * @return the number of zero bits preceding the highest-order
1099 * ("leftmost") one-bit in the two's complement binary representation
1100 * of the specified {@code int} value, or 32 if the value
1101 * is equal to zero.
1102 * @since 1.5
1103 */
1104 public static int numberOfLeadingZeros(int i) {
1105 // HD, Figure 5-6
1106 if (i == 0)
1107 return 32;
1108 int n = 1;
1109 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1110 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1111 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1112 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1113 n -= i >>> 31;
1114 return n;
1115 }
1116
1117 /**
1118 * Returns the number of zero bits following the lowest-order ("rightmost")
1119 * one-bit in the two's complement binary representation of the specified
1120 * {@code int} value. Returns 32 if the specified value has no
1121 * one-bits in its two's complement representation, in other words if it is
1122 * equal to zero.
1123 *
1124 * @return the number of zero bits following the lowest-order ("rightmost")
1125 * one-bit in the two's complement binary representation of the
1126 * specified {@code int} value, or 32 if the value is equal
1127 * to zero.
1128 * @since 1.5
1129 */
1130 public static int numberOfTrailingZeros(int i) {
1131 // HD, Figure 5-14
1132 int y;
1133 if (i == 0) return 32;
1134 int n = 31;
1135 y = i <<16; if (y != 0) { n = n -16; i = y; }
1136 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1137 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1138 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1139 return n - ((i << 1) >>> 31);
1140 }
1141
1142 /**
1143 * Returns the number of one-bits in the two's complement binary
1144 * representation of the specified {@code int} value. This function is
1145 * sometimes referred to as the <i>population count</i>.
1146 *
1147 * @return the number of one-bits in the two's complement binary
1148 * representation of the specified {@code int} value.
1149 * @since 1.5
1150 */
1151 public static int bitCount(int i) {
1152 // HD, Figure 5-2
1153 i = i - ((i >>> 1) & 0x55555555);
1154 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1155 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1156 i = i + (i >>> 8);
1157 i = i + (i >>> 16);
1158 return i & 0x3f;
1159 }
1160
1161 /**
1162 * Returns the value obtained by rotating the two's complement binary
1163 * representation of the specified {@code int} value left by the
1164 * specified number of bits. (Bits shifted out of the left hand, or
1165 * high-order, side reenter on the right, or low-order.)
1166 *
1167 * <p>Note that left rotation with a negative distance is equivalent to
1168 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1169 * distance)}. Note also that rotation by any multiple of 32 is a
1170 * no-op, so all but the last five bits of the rotation distance can be
1171 * ignored, even if the distance is negative: {@code rotateLeft(val,
1172 * distance) == rotateLeft(val, distance & 0x1F)}.
1173 *
1174 * @return the value obtained by rotating the two's complement binary
1175 * representation of the specified {@code int} value left by the
1176 * specified number of bits.
1177 * @since 1.5
1178 */
1179 public static int rotateLeft(int i, int distance) {
1180 return (i << distance) | (i >>> -distance);
1181 }
1182
1183 /**
1184 * Returns the value obtained by rotating the two's complement binary
1185 * representation of the specified {@code int} value right by the
1186 * specified number of bits. (Bits shifted out of the right hand, or
1187 * low-order, side reenter on the left, or high-order.)
1188 *
1189 * <p>Note that right rotation with a negative distance is equivalent to
1190 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1191 * distance)}. Note also that rotation by any multiple of 32 is a
1192 * no-op, so all but the last five bits of the rotation distance can be
1193 * ignored, even if the distance is negative: {@code rotateRight(val,
1194 * distance) == rotateRight(val, distance & 0x1F)}.
1195 *
1196 * @return the value obtained by rotating the two's complement binary
1197 * representation of the specified {@code int} value right by the
1198 * specified number of bits.
1199 * @since 1.5
1200 */
1201 public static int rotateRight(int i, int distance) {
1202 return (i >>> distance) | (i << -distance);
1203 }
1204
1205 /**
1206 * Returns the value obtained by reversing the order of the bits in the
1207 * two's complement binary representation of the specified {@code int}
1208 * value.
1209 *
1210 * @return the value obtained by reversing order of the bits in the
1211 * specified {@code int} value.
1212 * @since 1.5
1213 */
1214 public static int reverse(int i) {
1215 // HD, Figure 7-1
1216 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1217 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1218 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1219 i = (i << 24) | ((i & 0xff00) << 8) |
1220 ((i >>> 8) & 0xff00) | (i >>> 24);
1221 return i;
1222 }
1223
1224 /**
1225 * Returns the signum function of the specified {@code int} value. (The
1226 * return value is -1 if the specified value is negative; 0 if the
1227 * specified value is zero; and 1 if the specified value is positive.)
1228 *
1229 * @return the signum function of the specified {@code int} value.
1230 * @since 1.5
1231 */
1232 public static int signum(int i) {
1233 // HD, Section 2-7
1234 return (i >> 31) | (-i >>> 31);
1235 }
1236
1237 /**
1238 * Returns the value obtained by reversing the order of the bytes in the
1239 * two's complement representation of the specified {@code int} value.
1240 *
1241 * @return the value obtained by reversing the bytes in the specified
1242 * {@code int} value.
1243 * @since 1.5
1244 */
1245 public static int reverseBytes(int i) {
1246 return ((i >>> 24) ) |
1247 ((i >> 8) & 0xFF00) |
1248 ((i << 8) & 0xFF0000) |
1249 ((i << 24));
1250 }
1251
1252 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1253 private static final long serialVersionUID = 1360826667806852920L;
1254 }