001/* Integer.java -- object wrapper for int
002   Copyright (C) 1998, 1999, 2001, 2002, 2004, 2005
003   Free Software Foundation, Inc.
004
005This file is part of GNU Classpath.
006
007GNU Classpath is free software; you can redistribute it and/or modify
008it under the terms of the GNU General Public License as published by
009the Free Software Foundation; either version 2, or (at your option)
010any later version.
011
012GNU Classpath is distributed in the hope that it will be useful, but
013WITHOUT ANY WARRANTY; without even the implied warranty of
014MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015General Public License for more details.
016
017You should have received a copy of the GNU General Public License
018along with GNU Classpath; see the file COPYING.  If not, write to the
019Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02002110-1301 USA.
021
022Linking this library statically or dynamically with other modules is
023making a combined work based on this library.  Thus, the terms and
024conditions of the GNU General Public License cover the whole
025combination.
026
027As a special exception, the copyright holders of this library give you
028permission to link this library with independent modules to produce an
029executable, regardless of the license terms of these independent
030modules, and to copy and distribute the resulting executable under
031terms of your choice, provided that you also meet, for each linked
032independent module, the terms and conditions of the license of that
033module.  An independent module is a module which is not derived from
034or based on this library.  If you modify this library, you may extend
035this exception to your version of the library, but you are not
036obligated to do so.  If you do not wish to do so, delete this
037exception statement from your version. */
038
039
040package 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 * @author Ian Rogers
056 * @since 1.0
057 * @status updated to 1.5
058 */
059public final class Integer extends Number implements Comparable<Integer>
060{
061  /**
062   * Compatible with JDK 1.0.2+.
063   */
064  private static final long serialVersionUID = 1360826667806852920L;
065
066  /**
067   * The minimum value an <code>int</code> can represent is -2147483648 (or
068   * -2<sup>31</sup>).
069   */
070  public static final int MIN_VALUE = 0x80000000;
071
072  /**
073   * The maximum value an <code>int</code> can represent is 2147483647 (or
074   * 2<sup>31</sup> - 1).
075   */
076  public static final int MAX_VALUE = 0x7fffffff;
077
078  /**
079   * The primitive type <code>int</code> is represented by this
080   * <code>Class</code> object.
081   * @since 1.1
082   */
083  public static final Class<Integer> TYPE = (Class<Integer>) VMClassLoader.getPrimitiveClass('I');
084
085  /**
086   * The number of bits needed to represent an <code>int</code>.
087   * @since 1.5
088   */
089  public static final int SIZE = 32;
090
091  // This caches some Integer values, and is used by boxing
092  // conversions via valueOf().  We must cache at least -128..127;
093  // these constants control how much we actually cache.
094  private static final int MIN_CACHE = -128;
095  private static final int MAX_CACHE = 127;
096  private static final Integer[] intCache = new Integer[MAX_CACHE - MIN_CACHE + 1];
097  static
098  {
099    for (int i=MIN_CACHE; i <= MAX_CACHE; i++)
100      intCache[i - MIN_CACHE] = new Integer(i);
101  }
102
103  /**
104   * The immutable value of this Integer.
105   *
106   * @serial the wrapped int
107   */
108  private final int value;
109
110  /**
111   * Create an <code>Integer</code> object representing the value of the
112   * <code>int</code> argument.
113   *
114   * @param value the value to use
115   */
116  public Integer(int value)
117  {
118    this.value = value;
119  }
120
121  /**
122   * Create an <code>Integer</code> object representing the value of the
123   * argument after conversion to an <code>int</code>.
124   *
125   * @param s the string to convert
126   * @throws NumberFormatException if the String does not contain an int
127   * @see #valueOf(String)
128   */
129  public Integer(String s)
130  {
131    value = parseInt(s, 10, false);
132  }
133
134  /**
135   * Return the size of a string large enough to hold the given number
136   *
137   * @param num the number we want the string length for (must be positive)
138   * @param radix the radix (base) that will be used for the string
139   * @return a size sufficient for a string of num
140   */
141  private static int stringSize(int num, int radix) {
142    int exp;
143    if (radix < 4)
144      {
145        exp = 1;
146      }
147    else if (radix < 8)
148      {
149        exp = 2;
150      }
151    else if (radix < 16)
152      {
153        exp = 3;
154      }
155    else if (radix < 32)
156      {
157        exp = 4;
158      }
159    else
160      {
161        exp = 5;
162      }
163    int size=0;
164    do
165      {
166        num >>>= exp;
167        size++;
168      }
169    while(num != 0);
170    return size;
171  }
172
173  /**
174   * Converts the <code>int</code> to a <code>String</code> using
175   * the specified radix (base). If the radix exceeds
176   * <code>Character.MIN_RADIX</code> or <code>Character.MAX_RADIX</code>, 10
177   * is used instead. If the result is negative, the leading character is
178   * '-' ('\\u002D'). The remaining characters come from
179   * <code>Character.forDigit(digit, radix)</code> ('0'-'9','a'-'z').
180   *
181   * @param num the <code>int</code> to convert to <code>String</code>
182   * @param radix the radix (base) to use in the conversion
183   * @return the <code>String</code> representation of the argument
184   */
185  public static String toString(int num, int radix)
186  {
187    if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
188      radix = 10;
189
190    // Is the value negative?
191    boolean isNeg = num < 0;
192
193    // Is the string a single character?
194    if (!isNeg && num < radix)
195      return new String(digits, num, 1, true);
196
197    // Compute string size and allocate buffer
198    // account for a leading '-' if the value is negative
199    int size;
200    int i;
201    char[] buffer;
202    if (isNeg)
203      {
204        num = -num;
205
206        // When the value is MIN_VALUE, it overflows when made positive
207        if (num < 0)
208          {
209            i = size = stringSize(MAX_VALUE, radix) + 2;
210            buffer = new char[size];
211            buffer[--i] = digits[(int) (-(num + radix) % radix)];
212            num = -(num / radix);
213          }
214        else
215          {
216            i = size = stringSize(num, radix) + 1;
217            buffer = new char[size];
218          }
219      }
220    else
221      {
222        i = size = stringSize(num, radix);
223        buffer = new char[size];
224      }
225
226    do
227      {
228        buffer[--i] = digits[num % radix];
229        num /= radix;
230      }
231    while (num > 0);
232
233    if (isNeg)
234      buffer[--i] = '-';
235
236    // Package constructor avoids an array copy.
237    return new String(buffer, i, size - i, true);
238  }
239
240  /**
241   * Converts the <code>int</code> to a <code>String</code> assuming it is
242   * unsigned in base 16.
243   *
244   * @param i the <code>int</code> to convert to <code>String</code>
245   * @return the <code>String</code> representation of the argument
246   */
247  public static String toHexString(int i)
248  {
249    return toUnsignedString(i, 4);
250  }
251
252  /**
253   * Converts the <code>int</code> to a <code>String</code> assuming it is
254   * unsigned in base 8.
255   *
256   * @param i the <code>int</code> to convert to <code>String</code>
257   * @return the <code>String</code> representation of the argument
258   */
259  public static String toOctalString(int i)
260  {
261    return toUnsignedString(i, 3);
262  }
263
264  /**
265   * Converts the <code>int</code> to a <code>String</code> assuming it is
266   * unsigned in base 2.
267   *
268   * @param i the <code>int</code> to convert to <code>String</code>
269   * @return the <code>String</code> representation of the argument
270   */
271  public static String toBinaryString(int i)
272  {
273    return toUnsignedString(i, 1);
274  }
275
276  /**
277   * Converts the <code>int</code> to a <code>String</code> and assumes
278   * a radix of 10.
279   *
280   * @param i the <code>int</code> to convert to <code>String</code>
281   * @return the <code>String</code> representation of the argument
282   * @see #toString(int, int)
283   */
284  public static String toString(int i)
285  {
286    // This is tricky: in libgcj, String.valueOf(int) is a fast native
287    // implementation.  In Classpath it just calls back to
288    // Integer.toString(int, int).
289    return String.valueOf(i);
290  }
291
292  /**
293   * Converts the specified <code>String</code> into an <code>int</code>
294   * using the specified radix (base). The string must not be <code>null</code>
295   * or empty. It may begin with an optional '-', which will negate the answer,
296   * provided that there are also valid digits. Each digit is parsed as if by
297   * <code>Character.digit(d, radix)</code>, and must be in the range
298   * <code>0</code> to <code>radix - 1</code>. Finally, the result must be
299   * within <code>MIN_VALUE</code> to <code>MAX_VALUE</code>, inclusive.
300   * Unlike Double.parseDouble, you may not have a leading '+'.
301   *
302   * @param str the <code>String</code> to convert
303   * @param radix the radix (base) to use in the conversion
304   * @return the <code>String</code> argument converted to <code>int</code>
305   * @throws NumberFormatException if <code>s</code> cannot be parsed as an
306   *         <code>int</code>
307   */
308  public static int parseInt(String str, int radix)
309  {
310    return parseInt(str, radix, false);
311  }
312
313  /**
314   * Converts the specified <code>String</code> into an <code>int</code>.
315   * This function assumes a radix of 10.
316   *
317   * @param s the <code>String</code> to convert
318   * @return the <code>int</code> value of <code>s</code>
319   * @throws NumberFormatException if <code>s</code> cannot be parsed as an
320   *         <code>int</code>
321   * @see #parseInt(String, int)
322   */
323  public static int parseInt(String s)
324  {
325    return parseInt(s, 10, false);
326  }
327
328  /**
329   * Creates a new <code>Integer</code> object using the <code>String</code>
330   * and specified radix (base).
331   *
332   * @param s the <code>String</code> to convert
333   * @param radix the radix (base) to convert with
334   * @return the new <code>Integer</code>
335   * @throws NumberFormatException if <code>s</code> cannot be parsed as an
336   *         <code>int</code>
337   * @see #parseInt(String, int)
338   */
339  public static Integer valueOf(String s, int radix)
340  {
341    return valueOf(parseInt(s, radix, false));
342  }
343
344  /**
345   * Creates a new <code>Integer</code> object using the <code>String</code>,
346   * assuming a radix of 10.
347   *
348   * @param s the <code>String</code> to convert
349   * @return the new <code>Integer</code>
350   * @throws NumberFormatException if <code>s</code> cannot be parsed as an
351   *         <code>int</code>
352   * @see #Integer(String)
353   * @see #parseInt(String)
354   */
355  public static Integer valueOf(String s)
356  {
357    return valueOf(parseInt(s, 10, false));
358  }
359
360  /**
361   * Returns an <code>Integer</code> object wrapping the value.
362   * In contrast to the <code>Integer</code> constructor, this method
363   * will cache some values.  It is used by boxing conversion.
364   *
365   * @param val the value to wrap
366   * @return the <code>Integer</code>
367   */
368  public static Integer valueOf(int val)
369  {
370    if (val < MIN_CACHE || val > MAX_CACHE)
371      return new Integer(val);
372    else
373      return intCache[val - MIN_CACHE];
374  }
375
376  /**
377   * Return the value of this <code>Integer</code> as a <code>byte</code>.
378   *
379   * @return the byte value
380   */
381  public byte byteValue()
382  {
383    return (byte) value;
384  }
385
386  /**
387   * Return the value of this <code>Integer</code> as a <code>short</code>.
388   *
389   * @return the short value
390   */
391  public short shortValue()
392  {
393    return (short) value;
394  }
395
396  /**
397   * Return the value of this <code>Integer</code>.
398   * @return the int value
399   */
400  public int intValue()
401  {
402    return value;
403  }
404
405  /**
406   * Return the value of this <code>Integer</code> as a <code>long</code>.
407   *
408   * @return the long value
409   */
410  public long longValue()
411  {
412    return value;
413  }
414
415  /**
416   * Return the value of this <code>Integer</code> as a <code>float</code>.
417   *
418   * @return the float value
419   */
420  public float floatValue()
421  {
422    return value;
423  }
424
425  /**
426   * Return the value of this <code>Integer</code> as a <code>double</code>.
427   *
428   * @return the double value
429   */
430  public double doubleValue()
431  {
432    return value;
433  }
434
435  /**
436   * Converts the <code>Integer</code> value to a <code>String</code> and
437   * assumes a radix of 10.
438   *
439   * @return the <code>String</code> representation
440   */
441  public String toString()
442  {
443    return String.valueOf(value);
444  }
445
446  /**
447   * Return a hashcode representing this Object. <code>Integer</code>'s hash
448   * code is simply its value.
449   *
450   * @return this Object's hash code
451   */
452  public int hashCode()
453  {
454    return value;
455  }
456
457  /**
458   * Returns <code>true</code> if <code>obj</code> is an instance of
459   * <code>Integer</code> and represents the same int value.
460   *
461   * @param obj the object to compare
462   * @return whether these Objects are semantically equal
463   */
464  public boolean equals(Object obj)
465  {
466    return obj instanceof Integer && value == ((Integer) obj).value;
467  }
468
469  /**
470   * Get the specified system property as an <code>Integer</code>. The
471   * <code>decode()</code> method will be used to interpret the value of
472   * the property.
473   *
474   * @param nm the name of the system property
475   * @return the system property as an <code>Integer</code>, or null if the
476   *         property is not found or cannot be decoded
477   * @throws SecurityException if accessing the system property is forbidden
478   * @see System#getProperty(String)
479   * @see #decode(String)
480   */
481  public static Integer getInteger(String nm)
482  {
483    return getInteger(nm, null);
484  }
485
486  /**
487   * Get the specified system property as an <code>Integer</code>, or use a
488   * default <code>int</code> value if the property is not found or is not
489   * decodable. The <code>decode()</code> method will be used to interpret
490   * the value of the property.
491   *
492   * @param nm the name of the system property
493   * @param val the default value
494   * @return the value of the system property, or the default
495   * @throws SecurityException if accessing the system property is forbidden
496   * @see System#getProperty(String)
497   * @see #decode(String)
498   */
499  public static Integer getInteger(String nm, int val)
500  {
501    Integer result = getInteger(nm, null);
502    return result == null ? valueOf(val) : result;
503  }
504
505  /**
506   * Get the specified system property as an <code>Integer</code>, or use a
507   * default <code>Integer</code> value if the property is not found or is
508   * not decodable. The <code>decode()</code> method will be used to
509   * interpret the value of the property.
510   *
511   * @param nm the name of the system property
512   * @param def the default value
513   * @return the value of the system property, or the default
514   * @throws SecurityException if accessing the system property is forbidden
515   * @see System#getProperty(String)
516   * @see #decode(String)
517   */
518  public static Integer getInteger(String nm, Integer def)
519  {
520    if (nm == null || "".equals(nm))
521      return def;
522    nm = System.getProperty(nm);
523    if (nm == null)
524      return def;
525    try
526      {
527        return decode(nm);
528      }
529    catch (NumberFormatException e)
530      {
531        return def;
532      }
533  }
534
535  /**
536   * Convert the specified <code>String</code> into an <code>Integer</code>.
537   * The <code>String</code> may represent decimal, hexadecimal, or
538   * octal numbers.
539   *
540   * <p>The extended BNF grammar is as follows:<br>
541   * <pre>
542   * <em>DecodableString</em>:
543   *      ( [ <code>-</code> ] <em>DecimalNumber</em> )
544   *    | ( [ <code>-</code> ] ( <code>0x</code> | <code>0X</code>
545   *              | <code>#</code> ) <em>HexDigit</em> { <em>HexDigit</em> } )
546   *    | ( [ <code>-</code> ] <code>0</code> { <em>OctalDigit</em> } )
547   * <em>DecimalNumber</em>:
548   *        <em>DecimalDigit except '0'</em> { <em>DecimalDigit</em> }
549   * <em>DecimalDigit</em>:
550   *        <em>Character.digit(d, 10) has value 0 to 9</em>
551   * <em>OctalDigit</em>:
552   *        <em>Character.digit(d, 8) has value 0 to 7</em>
553   * <em>DecimalDigit</em>:
554   *        <em>Character.digit(d, 16) has value 0 to 15</em>
555   * </pre>
556   * Finally, the value must be in the range <code>MIN_VALUE</code> to
557   * <code>MAX_VALUE</code>, or an exception is thrown.
558   *
559   * @param str the <code>String</code> to interpret
560   * @return the value of the String as an <code>Integer</code>
561   * @throws NumberFormatException if <code>s</code> cannot be parsed as a
562   *         <code>int</code>
563   * @throws NullPointerException if <code>s</code> is null
564   * @since 1.2
565   */
566  public static Integer decode(String str)
567  {
568    return valueOf(parseInt(str, 10, true));
569  }
570
571  /**
572   * Compare two Integers numerically by comparing their <code>int</code>
573   * values. The result is positive if the first is greater, negative if the
574   * second is greater, and 0 if the two are equal.
575   *
576   * @param i the Integer to compare
577   * @return the comparison
578   * @since 1.2
579   */
580  public int compareTo(Integer i)
581  {
582    if (value == i.value)
583      return 0;
584    // Returns just -1 or 1 on inequality; doing math might overflow.
585    return value > i.value ? 1 : -1;
586  }
587
588  /**
589   * Compares two unboxed int values.
590   * The result is positive if the first is greater, negative if the second
591   * is greater, and 0 if the two are equal.
592   *
593   * @param x First value to compare.
594   * @param y Second value to compare.
595   *
596   * @return positive int if the first value is greater, negative if the second
597   * is greater, and 0 if the two are equal.
598   * @since 1.7
599   */
600  public static int compare(int x, int y)
601  {
602    return Integer.valueOf(x).compareTo(Integer.valueOf(y));
603  }
604
605  /**
606   * Return the number of bits set in x.
607   * @param x value to examine
608   * @since 1.5
609   */
610  public static int bitCount(int x)
611  {
612    // Successively collapse alternating bit groups into a sum.
613    x = ((x >> 1) & 0x55555555) + (x & 0x55555555);
614    x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
615    x = ((x >> 4) & 0x0f0f0f0f) + (x & 0x0f0f0f0f);
616    x = ((x >> 8) & 0x00ff00ff) + (x & 0x00ff00ff);
617    return ((x >> 16) & 0x0000ffff) + (x & 0x0000ffff);
618  }
619
620  /**
621   * Rotate x to the left by distance bits.
622   * @param x the value to rotate
623   * @param distance the number of bits by which to rotate
624   * @since 1.5
625   */
626  public static int rotateLeft(int x, int distance)
627  {
628    // This trick works because the shift operators implicitly mask
629    // the shift count.
630    return (x << distance) | (x >>> - distance);
631  }
632
633  /**
634   * Rotate x to the right by distance bits.
635   * @param x the value to rotate
636   * @param distance the number of bits by which to rotate
637   * @since 1.5
638   */
639  public static int rotateRight(int x, int distance)
640  {
641    // This trick works because the shift operators implicitly mask
642    // the shift count.
643    return (x << - distance) | (x >>> distance);
644  }
645
646  /**
647   * Find the highest set bit in value, and return a new value
648   * with only that bit set.
649   * @param value the value to examine
650   * @since 1.5
651   */
652  public static int highestOneBit(int value)
653  {
654    value |= value >>> 1;
655    value |= value >>> 2;
656    value |= value >>> 4;
657    value |= value >>> 8;
658    value |= value >>> 16;
659    return value ^ (value >>> 1);
660  }
661
662  /**
663   * Return the number of leading zeros in value.
664   * @param value the value to examine
665   * @since 1.5
666   */
667  public static int numberOfLeadingZeros(int value)
668  {
669    value |= value >>> 1;
670    value |= value >>> 2;
671    value |= value >>> 4;
672    value |= value >>> 8;
673    value |= value >>> 16;
674    return bitCount(~value);
675  }
676
677  /**
678   * Find the lowest set bit in value, and return a new value
679   * with only that bit set.
680   * @param value the value to examine
681   * @since 1.5
682   */
683  public static int lowestOneBit(int value)
684  {
685    // Classic assembly trick.
686    return value & - value;
687  }
688
689  /**
690   * Find the number of trailing zeros in value.
691   * @param value the value to examine
692   * @since 1.5
693   */
694  public static int numberOfTrailingZeros(int value)
695  {
696    return bitCount((value & -value) - 1);
697  }
698
699  /**
700   * Return 1 if x is positive, -1 if it is negative, and 0 if it is
701   * zero.
702   * @param x the value to examine
703   * @since 1.5
704   */
705  public static int signum(int x)
706  {
707    return (x >> 31) | (-x >>> 31);
708
709    // The LHS propagates the sign bit through every bit in the word;
710    // if X < 0, every bit is set to 1, else 0.  if X > 0, the RHS
711    // negates x and shifts the resulting 1 in the sign bit to the
712    // LSB, leaving every other bit 0.
713
714    // Hacker's Delight, Section 2-7
715  }
716
717  /**
718   * Reverse the bytes in val.
719   * @since 1.5
720   */
721  public static int reverseBytes(int val)
722  {
723    return (  ((val >> 24) & 0xff)
724            | ((val >> 8) & 0xff00)
725            | ((val << 8) & 0xff0000)
726            | ((val << 24) & 0xff000000));
727  }
728
729  /**
730   * Reverse the bits in val.
731   * @since 1.5
732   */
733  public static int reverse(int val)
734  {
735    // Successively swap alternating bit groups.
736    val = ((val >> 1) & 0x55555555) + ((val << 1) & ~0x55555555);
737    val = ((val >> 2) & 0x33333333) + ((val << 2) & ~0x33333333);
738    val = ((val >> 4) & 0x0f0f0f0f) + ((val << 4) & ~0x0f0f0f0f);
739    val = ((val >> 8) & 0x00ff00ff) + ((val << 8) & ~0x00ff00ff);
740    return ((val >> 16) & 0x0000ffff) + ((val << 16) & ~0x0000ffff);
741  }
742
743  /**
744   * Helper for converting unsigned numbers to String.
745   *
746   * @param num the number
747   * @param exp log2(digit) (ie. 1, 3, or 4 for binary, oct, hex)
748   */
749  // Package visible for use by Long.
750  static String toUnsignedString(int num, int exp)
751  {
752    // Compute string length
753    int size = 1;
754    int copy = num >>> exp;
755    while (copy != 0)
756      {
757        size++;
758        copy >>>= exp;
759      }
760    // Quick path for single character strings
761    if (size == 1)
762      return new String(digits, num, 1, true);
763
764    // Encode into buffer
765    int mask = (1 << exp) - 1;
766    char[] buffer = new char[size];
767    int i = size;
768    do
769      {
770        buffer[--i] = digits[num & mask];
771        num >>>= exp;
772      }
773    while (num != 0);
774
775    // Package constructor avoids an array copy.
776    return new String(buffer, i, size - i, true);
777  }
778
779  /**
780   * Helper for parsing ints, used by Integer, Short, and Byte.
781   *
782   * @param str the string to parse
783   * @param radix the radix to use, must be 10 if decode is true
784   * @param decode if called from decode
785   * @return the parsed int value
786   * @throws NumberFormatException if there is an error
787   * @throws NullPointerException if decode is true and str if null
788   * @see #parseInt(String, int)
789   * @see #decode(String)
790   * @see Byte#parseByte(String, int)
791   * @see Short#parseShort(String, int)
792   */
793  static int parseInt(String str, int radix, boolean decode)
794  {
795    if (! decode && str == null)
796      throw new NumberFormatException();
797    int index = 0;
798    int len = str.length();
799    boolean isNeg = false;
800    if (len == 0)
801      throw new NumberFormatException("string length is null");
802    int ch = str.charAt(index);
803    if (ch == '-')
804      {
805        if (len == 1)
806          throw new NumberFormatException("pure '-'");
807        isNeg = true;
808        ch = str.charAt(++index);
809      }
810    else if (ch == '+')
811      {
812        if (len == 1)
813          throw new NumberFormatException("pure '+'");
814        ch = str.charAt(++index);
815      }
816    if (decode)
817      {
818        if (ch == '0')
819          {
820            if (++index == len)
821              return 0;
822            if ((str.charAt(index) & ~('x' ^ 'X')) == 'X')
823              {
824                radix = 16;
825                index++;
826              }
827            else
828              radix = 8;
829          }
830        else if (ch == '#')
831          {
832            radix = 16;
833            index++;
834          }
835      }
836    if (index == len)
837      throw new NumberFormatException("non terminated number: " + str);
838
839    int max = MAX_VALUE / radix;
840    // We can't directly write `max = (MAX_VALUE + 1) / radix'.
841    // So instead we fake it.
842    if (isNeg && MAX_VALUE % radix == radix - 1)
843      ++max;
844
845    int val = 0;
846    while (index < len)
847      {
848        if (val < 0 || val > max)
849          throw new NumberFormatException("number overflow (pos=" + index + ") : " + str);
850
851        ch = Character.digit(str.charAt(index++), radix);
852        val = val * radix + ch;
853        if (ch < 0 || (val < 0 && (! isNeg || val != MIN_VALUE)))
854          throw new NumberFormatException("invalid character at position " + index + " in " + str);
855      }
856    return isNeg ? -val : val;
857  }
858}