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    }