001 /* Integer.java -- object wrapper for int
002 Copyright (C) 1998, 1999, 2001, 2002, 2004, 2005
003 Free Software Foundation, Inc.
004
005 This file is part of GNU Classpath.
006
007 GNU Classpath is free software; you can redistribute it and/or modify
008 it under the terms of the GNU General Public License as published by
009 the Free Software Foundation; either version 2, or (at your option)
010 any later version.
011
012 GNU Classpath is distributed in the hope that it will be useful, but
013 WITHOUT ANY WARRANTY; without even the implied warranty of
014 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 General Public License for more details.
016
017 You should have received a copy of the GNU General Public License
018 along with GNU Classpath; see the file COPYING. If not, write to the
019 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
020 02110-1301 USA.
021
022 Linking this library statically or dynamically with other modules is
023 making a combined work based on this library. Thus, the terms and
024 conditions of the GNU General Public License cover the whole
025 combination.
026
027 As a special exception, the copyright holders of this library give you
028 permission to link this library with independent modules to produce an
029 executable, regardless of the license terms of these independent
030 modules, and to copy and distribute the resulting executable under
031 terms of your choice, provided that you also meet, for each linked
032 independent module, the terms and conditions of the license of that
033 module. An independent module is a module which is not derived from
034 or based on this library. If you modify this library, you may extend
035 this exception to your version of the library, but you are not
036 obligated to do so. If you do not wish to do so, delete this
037 exception statement from your version. */
038
039
040 package java.lang;
041
042 /**
043 * Instances of class <code>Integer</code> represent primitive
044 * <code>int</code> values.
045 *
046 * Additionally, this class provides various helper functions and variables
047 * related to ints.
048 *
049 * @author Paul Fisher
050 * @author John Keiser
051 * @author Warren Levy
052 * @author Eric Blake (ebb9@email.byu.edu)
053 * @author Tom Tromey (tromey@redhat.com)
054 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
055 * @since 1.0
056 * @status updated to 1.5
057 */
058 public final class Integer extends Number implements Comparable<Integer>
059 {
060 /**
061 * Compatible with JDK 1.0.2+.
062 */
063 private static final long serialVersionUID = 1360826667806852920L;
064
065 /**
066 * The minimum value an <code>int</code> can represent is -2147483648 (or
067 * -2<sup>31</sup>).
068 */
069 public static final int MIN_VALUE = 0x80000000;
070
071 /**
072 * The maximum value an <code>int</code> can represent is 2147483647 (or
073 * 2<sup>31</sup> - 1).
074 */
075 public static final int MAX_VALUE = 0x7fffffff;
076
077 /**
078 * The primitive type <code>int</code> is represented by this
079 * <code>Class</code> object.
080 * @since 1.1
081 */
082 public static final Class<Integer> TYPE = (Class<Integer>) VMClassLoader.getPrimitiveClass('I');
083
084 /**
085 * The number of bits needed to represent an <code>int</code>.
086 * @since 1.5
087 */
088 public static final int SIZE = 32;
089
090 // This caches some Integer values, and is used by boxing
091 // conversions via valueOf(). We must cache at least -128..127;
092 // these constants control how much we actually cache.
093 private static final int MIN_CACHE = -128;
094 private static final int MAX_CACHE = 127;
095 private static Integer[] intCache = new Integer[MAX_CACHE - MIN_CACHE + 1];
096
097 /**
098 * The immutable value of this Integer.
099 *
100 * @serial the wrapped int
101 */
102 private final int value;
103
104 /**
105 * Create an <code>Integer</code> object representing the value of the
106 * <code>int</code> argument.
107 *
108 * @param value the value to use
109 */
110 public Integer(int value)
111 {
112 this.value = value;
113 }
114
115 /**
116 * Create an <code>Integer</code> object representing the value of the
117 * argument after conversion to an <code>int</code>.
118 *
119 * @param s the string to convert
120 * @throws NumberFormatException if the String does not contain an int
121 * @see #valueOf(String)
122 */
123 public Integer(String s)
124 {
125 value = parseInt(s, 10, false);
126 }
127
128 /**
129 * Converts the <code>int</code> to a <code>String</code> using
130 * the specified radix (base). If the radix exceeds
131 * <code>Character.MIN_RADIX</code> or <code>Character.MAX_RADIX</code>, 10
132 * is used instead. If the result is negative, the leading character is
133 * '-' ('\\u002D'). The remaining characters come from
134 * <code>Character.forDigit(digit, radix)</code> ('0'-'9','a'-'z').
135 *
136 * @param num the <code>int</code> to convert to <code>String</code>
137 * @param radix the radix (base) to use in the conversion
138 * @return the <code>String</code> representation of the argument
139 */
140 public static String toString(int num, int radix)
141 {
142 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
143 radix = 10;
144
145 // For negative numbers, print out the absolute value w/ a leading '-'.
146 // Use an array large enough for a binary number.
147 char[] buffer = new char[33];
148 int i = 33;
149 boolean isNeg = false;
150 if (num < 0)
151 {
152 isNeg = true;
153 num = -num;
154
155 // When the value is MIN_VALUE, it overflows when made positive
156 if (num < 0)
157 {
158 buffer[--i] = digits[(int) (-(num + radix) % radix)];
159 num = -(num / radix);
160 }
161 }
162
163 do
164 {
165 buffer[--i] = digits[num % radix];
166 num /= radix;
167 }
168 while (num > 0);
169
170 if (isNeg)
171 buffer[--i] = '-';
172
173 // Package constructor avoids an array copy.
174 return new String(buffer, i, 33 - i, true);
175 }
176
177 /**
178 * Converts the <code>int</code> to a <code>String</code> assuming it is
179 * unsigned in base 16.
180 *
181 * @param i the <code>int</code> to convert to <code>String</code>
182 * @return the <code>String</code> representation of the argument
183 */
184 public static String toHexString(int i)
185 {
186 return toUnsignedString(i, 4);
187 }
188
189 /**
190 * Converts the <code>int</code> to a <code>String</code> assuming it is
191 * unsigned in base 8.
192 *
193 * @param i the <code>int</code> to convert to <code>String</code>
194 * @return the <code>String</code> representation of the argument
195 */
196 public static String toOctalString(int i)
197 {
198 return toUnsignedString(i, 3);
199 }
200
201 /**
202 * Converts the <code>int</code> to a <code>String</code> assuming it is
203 * unsigned in base 2.
204 *
205 * @param i the <code>int</code> to convert to <code>String</code>
206 * @return the <code>String</code> representation of the argument
207 */
208 public static String toBinaryString(int i)
209 {
210 return toUnsignedString(i, 1);
211 }
212
213 /**
214 * Converts the <code>int</code> to a <code>String</code> and assumes
215 * a radix of 10.
216 *
217 * @param i the <code>int</code> to convert to <code>String</code>
218 * @return the <code>String</code> representation of the argument
219 * @see #toString(int, int)
220 */
221 public static String toString(int i)
222 {
223 // This is tricky: in libgcj, String.valueOf(int) is a fast native
224 // implementation. In Classpath it just calls back to
225 // Integer.toString(int, int).
226 return String.valueOf(i);
227 }
228
229 /**
230 * Converts the specified <code>String</code> into an <code>int</code>
231 * using the specified radix (base). The string must not be <code>null</code>
232 * or empty. It may begin with an optional '-', which will negate the answer,
233 * provided that there are also valid digits. Each digit is parsed as if by
234 * <code>Character.digit(d, radix)</code>, and must be in the range
235 * <code>0</code> to <code>radix - 1</code>. Finally, the result must be
236 * within <code>MIN_VALUE</code> to <code>MAX_VALUE</code>, inclusive.
237 * Unlike Double.parseDouble, you may not have a leading '+'.
238 *
239 * @param str the <code>String</code> to convert
240 * @param radix the radix (base) to use in the conversion
241 * @return the <code>String</code> argument converted to <code>int</code>
242 * @throws NumberFormatException if <code>s</code> cannot be parsed as an
243 * <code>int</code>
244 */
245 public static int parseInt(String str, int radix)
246 {
247 return parseInt(str, radix, false);
248 }
249
250 /**
251 * Converts the specified <code>String</code> into an <code>int</code>.
252 * This function assumes a radix of 10.
253 *
254 * @param s the <code>String</code> to convert
255 * @return the <code>int</code> value of <code>s</code>
256 * @throws NumberFormatException if <code>s</code> cannot be parsed as an
257 * <code>int</code>
258 * @see #parseInt(String, int)
259 */
260 public static int parseInt(String s)
261 {
262 return parseInt(s, 10, false);
263 }
264
265 /**
266 * Creates a new <code>Integer</code> object using the <code>String</code>
267 * and specified radix (base).
268 *
269 * @param s the <code>String</code> to convert
270 * @param radix the radix (base) to convert with
271 * @return the new <code>Integer</code>
272 * @throws NumberFormatException if <code>s</code> cannot be parsed as an
273 * <code>int</code>
274 * @see #parseInt(String, int)
275 */
276 public static Integer valueOf(String s, int radix)
277 {
278 return new Integer(parseInt(s, radix, false));
279 }
280
281 /**
282 * Creates a new <code>Integer</code> object using the <code>String</code>,
283 * assuming a radix of 10.
284 *
285 * @param s the <code>String</code> to convert
286 * @return the new <code>Integer</code>
287 * @throws NumberFormatException if <code>s</code> cannot be parsed as an
288 * <code>int</code>
289 * @see #Integer(String)
290 * @see #parseInt(String)
291 */
292 public static Integer valueOf(String s)
293 {
294 return new Integer(parseInt(s, 10, false));
295 }
296
297 /**
298 * Returns an <code>Integer</code> object wrapping the value.
299 * In contrast to the <code>Integer</code> constructor, this method
300 * will cache some values. It is used by boxing conversion.
301 *
302 * @param val the value to wrap
303 * @return the <code>Integer</code>
304 */
305 public static Integer valueOf(int val)
306 {
307 if (val < MIN_CACHE || val > MAX_CACHE)
308 return new Integer(val);
309 synchronized (intCache)
310 {
311 if (intCache[val - MIN_CACHE] == null)
312 intCache[val - MIN_CACHE] = new Integer(val);
313 return intCache[val - MIN_CACHE];
314 }
315 }
316
317 /**
318 * Return the value of this <code>Integer</code> as a <code>byte</code>.
319 *
320 * @return the byte value
321 */
322 public byte byteValue()
323 {
324 return (byte) value;
325 }
326
327 /**
328 * Return the value of this <code>Integer</code> as a <code>short</code>.
329 *
330 * @return the short value
331 */
332 public short shortValue()
333 {
334 return (short) value;
335 }
336
337 /**
338 * Return the value of this <code>Integer</code>.
339 * @return the int value
340 */
341 public int intValue()
342 {
343 return value;
344 }
345
346 /**
347 * Return the value of this <code>Integer</code> as a <code>long</code>.
348 *
349 * @return the long value
350 */
351 public long longValue()
352 {
353 return value;
354 }
355
356 /**
357 * Return the value of this <code>Integer</code> as a <code>float</code>.
358 *
359 * @return the float value
360 */
361 public float floatValue()
362 {
363 return value;
364 }
365
366 /**
367 * Return the value of this <code>Integer</code> as a <code>double</code>.
368 *
369 * @return the double value
370 */
371 public double doubleValue()
372 {
373 return value;
374 }
375
376 /**
377 * Converts the <code>Integer</code> value to a <code>String</code> and
378 * assumes a radix of 10.
379 *
380 * @return the <code>String</code> representation
381 */
382 public String toString()
383 {
384 return String.valueOf(value);
385 }
386
387 /**
388 * Return a hashcode representing this Object. <code>Integer</code>'s hash
389 * code is simply its value.
390 *
391 * @return this Object's hash code
392 */
393 public int hashCode()
394 {
395 return value;
396 }
397
398 /**
399 * Returns <code>true</code> if <code>obj</code> is an instance of
400 * <code>Integer</code> and represents the same int value.
401 *
402 * @param obj the object to compare
403 * @return whether these Objects are semantically equal
404 */
405 public boolean equals(Object obj)
406 {
407 return obj instanceof Integer && value == ((Integer) obj).value;
408 }
409
410 /**
411 * Get the specified system property as an <code>Integer</code>. The
412 * <code>decode()</code> method will be used to interpret the value of
413 * the property.
414 *
415 * @param nm the name of the system property
416 * @return the system property as an <code>Integer</code>, or null if the
417 * property is not found or cannot be decoded
418 * @throws SecurityException if accessing the system property is forbidden
419 * @see System#getProperty(String)
420 * @see #decode(String)
421 */
422 public static Integer getInteger(String nm)
423 {
424 return getInteger(nm, null);
425 }
426
427 /**
428 * Get the specified system property as an <code>Integer</code>, or use a
429 * default <code>int</code> value if the property is not found or is not
430 * decodable. The <code>decode()</code> method will be used to interpret
431 * the value of the property.
432 *
433 * @param nm the name of the system property
434 * @param val the default value
435 * @return the value of the system property, or the default
436 * @throws SecurityException if accessing the system property is forbidden
437 * @see System#getProperty(String)
438 * @see #decode(String)
439 */
440 public static Integer getInteger(String nm, int val)
441 {
442 Integer result = getInteger(nm, null);
443 return result == null ? new Integer(val) : result;
444 }
445
446 /**
447 * Get the specified system property as an <code>Integer</code>, or use a
448 * default <code>Integer</code> value if the property is not found or is
449 * not decodable. The <code>decode()</code> method will be used to
450 * interpret the value of the property.
451 *
452 * @param nm the name of the system property
453 * @param def the default value
454 * @return the value of the system property, or the default
455 * @throws SecurityException if accessing the system property is forbidden
456 * @see System#getProperty(String)
457 * @see #decode(String)
458 */
459 public static Integer getInteger(String nm, Integer def)
460 {
461 if (nm == null || "".equals(nm))
462 return def;
463 nm = System.getProperty(nm);
464 if (nm == null)
465 return def;
466 try
467 {
468 return decode(nm);
469 }
470 catch (NumberFormatException e)
471 {
472 return def;
473 }
474 }
475
476 /**
477 * Convert the specified <code>String</code> into an <code>Integer</code>.
478 * The <code>String</code> may represent decimal, hexadecimal, or
479 * octal numbers.
480 *
481 * <p>The extended BNF grammar is as follows:<br>
482 * <pre>
483 * <em>DecodableString</em>:
484 * ( [ <code>-</code> ] <em>DecimalNumber</em> )
485 * | ( [ <code>-</code> ] ( <code>0x</code> | <code>0X</code>
486 * | <code>#</code> ) <em>HexDigit</em> { <em>HexDigit</em> } )
487 * | ( [ <code>-</code> ] <code>0</code> { <em>OctalDigit</em> } )
488 * <em>DecimalNumber</em>:
489 * <em>DecimalDigit except '0'</em> { <em>DecimalDigit</em> }
490 * <em>DecimalDigit</em>:
491 * <em>Character.digit(d, 10) has value 0 to 9</em>
492 * <em>OctalDigit</em>:
493 * <em>Character.digit(d, 8) has value 0 to 7</em>
494 * <em>DecimalDigit</em>:
495 * <em>Character.digit(d, 16) has value 0 to 15</em>
496 * </pre>
497 * Finally, the value must be in the range <code>MIN_VALUE</code> to
498 * <code>MAX_VALUE</code>, or an exception is thrown.
499 *
500 * @param str the <code>String</code> to interpret
501 * @return the value of the String as an <code>Integer</code>
502 * @throws NumberFormatException if <code>s</code> cannot be parsed as a
503 * <code>int</code>
504 * @throws NullPointerException if <code>s</code> is null
505 * @since 1.2
506 */
507 public static Integer decode(String str)
508 {
509 return new Integer(parseInt(str, 10, true));
510 }
511
512 /**
513 * Compare two Integers numerically by comparing their <code>int</code>
514 * values. The result is positive if the first is greater, negative if the
515 * second is greater, and 0 if the two are equal.
516 *
517 * @param i the Integer to compare
518 * @return the comparison
519 * @since 1.2
520 */
521 public int compareTo(Integer i)
522 {
523 if (value == i.value)
524 return 0;
525 // Returns just -1 or 1 on inequality; doing math might overflow.
526 return value > i.value ? 1 : -1;
527 }
528
529 /**
530 * Return the number of bits set in x.
531 * @param x value to examine
532 * @since 1.5
533 */
534 public static int bitCount(int x)
535 {
536 // Successively collapse alternating bit groups into a sum.
537 x = ((x >> 1) & 0x55555555) + (x & 0x55555555);
538 x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
539 x = ((x >> 4) & 0x0f0f0f0f) + (x & 0x0f0f0f0f);
540 x = ((x >> 8) & 0x00ff00ff) + (x & 0x00ff00ff);
541 return ((x >> 16) & 0x0000ffff) + (x & 0x0000ffff);
542 }
543
544 /**
545 * Rotate x to the left by distance bits.
546 * @param x the value to rotate
547 * @param distance the number of bits by which to rotate
548 * @since 1.5
549 */
550 public static int rotateLeft(int x, int distance)
551 {
552 // This trick works because the shift operators implicitly mask
553 // the shift count.
554 return (x << distance) | (x >>> - distance);
555 }
556
557 /**
558 * Rotate x to the right by distance bits.
559 * @param x the value to rotate
560 * @param distance the number of bits by which to rotate
561 * @since 1.5
562 */
563 public static int rotateRight(int x, int distance)
564 {
565 // This trick works because the shift operators implicitly mask
566 // the shift count.
567 return (x << - distance) | (x >>> distance);
568 }
569
570 /**
571 * Find the highest set bit in value, and return a new value
572 * with only that bit set.
573 * @param value the value to examine
574 * @since 1.5
575 */
576 public static int highestOneBit(int value)
577 {
578 value |= value >>> 1;
579 value |= value >>> 2;
580 value |= value >>> 4;
581 value |= value >>> 8;
582 value |= value >>> 16;
583 return value ^ (value >>> 1);
584 }
585
586 /**
587 * Return the number of leading zeros in value.
588 * @param value the value to examine
589 * @since 1.5
590 */
591 public static int numberOfLeadingZeros(int value)
592 {
593 value |= value >>> 1;
594 value |= value >>> 2;
595 value |= value >>> 4;
596 value |= value >>> 8;
597 value |= value >>> 16;
598 return bitCount(~value);
599 }
600
601 /**
602 * Find the lowest set bit in value, and return a new value
603 * with only that bit set.
604 * @param value the value to examine
605 * @since 1.5
606 */
607 public static int lowestOneBit(int value)
608 {
609 // Classic assembly trick.
610 return value & - value;
611 }
612
613 /**
614 * Find the number of trailing zeros in value.
615 * @param value the value to examine
616 * @since 1.5
617 */
618 public static int numberOfTrailingZeros(int value)
619 {
620 return bitCount((value & -value) - 1);
621 }
622
623 /**
624 * Return 1 if x is positive, -1 if it is negative, and 0 if it is
625 * zero.
626 * @param x the value to examine
627 * @since 1.5
628 */
629 public static int signum(int x)
630 {
631 return x < 0 ? -1 : (x > 0 ? 1 : 0);
632 }
633
634 /**
635 * Reverse the bytes in val.
636 * @since 1.5
637 */
638 public static int reverseBytes(int val)
639 {
640 return ( ((val >> 24) & 0xff)
641 | ((val >> 8) & 0xff00)
642 | ((val << 8) & 0xff0000)
643 | ((val << 24) & 0xff000000));
644 }
645
646 /**
647 * Reverse the bits in val.
648 * @since 1.5
649 */
650 public static int reverse(int val)
651 {
652 // Successively swap alternating bit groups.
653 val = ((val >> 1) & 0x55555555) + ((val << 1) & ~0x55555555);
654 val = ((val >> 2) & 0x33333333) + ((val << 2) & ~0x33333333);
655 val = ((val >> 4) & 0x0f0f0f0f) + ((val << 4) & ~0x0f0f0f0f);
656 val = ((val >> 8) & 0x00ff00ff) + ((val << 8) & ~0x00ff00ff);
657 return ((val >> 16) & 0x0000ffff) + ((val << 16) & ~0x0000ffff);
658 }
659
660 /**
661 * Helper for converting unsigned numbers to String.
662 *
663 * @param num the number
664 * @param exp log2(digit) (ie. 1, 3, or 4 for binary, oct, hex)
665 */
666 // Package visible for use by Long.
667 static String toUnsignedString(int num, int exp)
668 {
669 // Use an array large enough for a binary number.
670 int mask = (1 << exp) - 1;
671 char[] buffer = new char[32];
672 int i = 32;
673 do
674 {
675 buffer[--i] = digits[num & mask];
676 num >>>= exp;
677 }
678 while (num != 0);
679
680 // Package constructor avoids an array copy.
681 return new String(buffer, i, 32 - i, true);
682 }
683
684 /**
685 * Helper for parsing ints, used by Integer, Short, and Byte.
686 *
687 * @param str the string to parse
688 * @param radix the radix to use, must be 10 if decode is true
689 * @param decode if called from decode
690 * @return the parsed int value
691 * @throws NumberFormatException if there is an error
692 * @throws NullPointerException if decode is true and str if null
693 * @see #parseInt(String, int)
694 * @see #decode(String)
695 * @see Byte#parseByte(String, int)
696 * @see Short#parseShort(String, int)
697 */
698 static int parseInt(String str, int radix, boolean decode)
699 {
700 if (! decode && str == null)
701 throw new NumberFormatException();
702 int index = 0;
703 int len = str.length();
704 boolean isNeg = false;
705 if (len == 0)
706 throw new NumberFormatException("string length is null");
707 int ch = str.charAt(index);
708 if (ch == '-' || ch == '+')
709 {
710 if (len == 1)
711 if (ch == '-')
712 throw new NumberFormatException("pure '-'");
713 else if (ch == '+')
714 throw new NumberFormatException("pure '+'");
715 isNeg = true;
716 ch = str.charAt(++index);
717 }
718 if (decode)
719 {
720 if (ch == '0')
721 {
722 if (++index == len)
723 return 0;
724 if ((str.charAt(index) & ~('x' ^ 'X')) == 'X')
725 {
726 radix = 16;
727 index++;
728 }
729 else
730 radix = 8;
731 }
732 else if (ch == '#')
733 {
734 radix = 16;
735 index++;
736 }
737 }
738 if (index == len)
739 throw new NumberFormatException("non terminated number: " + str);
740
741 int max = MAX_VALUE / radix;
742 // We can't directly write `max = (MAX_VALUE + 1) / radix'.
743 // So instead we fake it.
744 if (isNeg && MAX_VALUE % radix == radix - 1)
745 ++max;
746
747 int val = 0;
748 while (index < len)
749 {
750 if (val < 0 || val > max)
751 throw new NumberFormatException("number overflow (pos=" + index + ") : " + str);
752
753 ch = Character.digit(str.charAt(index++), radix);
754 val = val * radix + ch;
755 if (ch < 0 || (val < 0 && (! isNeg || val != MIN_VALUE)))
756 throw new NumberFormatException("invalid character at position " + index + " in " + str);
757 }
758 return isNeg ? -val : val;
759 }
760 }