Source for gnu.java.security.util.IntegerUtil

   1: /* IntegerUtil.java -- JDK 5 Integer methods with 1.4 API
   2:    Copyright (C) 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.security.util;
  40: 
  41: import java.util.LinkedHashMap;
  42: import java.util.Map;
  43: 
  44: /**
  45:  * Utility class which offers Integer related methods found in RI's version 5
  46:  * but written with RI's 1.4 API.
  47:  */
  48: public abstract class IntegerUtil
  49: {
  50:   /** Maximum size of our cache of constructed Integers. */
  51:   private static final int CACHE_SIZE = 100;
  52:   /** LRU (Least Recently Used) cache, of the last accessed 100 Integers. */
  53:   private static final Map cache = new LinkedHashMap(CACHE_SIZE + 1, 0.75F, true)
  54:   {
  55:     public boolean removeEldestEntry(Map.Entry entry)
  56:     {
  57:       return size() > CACHE_SIZE;
  58:     }
  59:   };
  60: 
  61:   /** Trivial private constructor to enforce Singleton usage. */
  62:   private IntegerUtil()
  63:   {
  64:     super();
  65:   }
  66: 
  67:   /**
  68:    * Similar to {@link Integer#valueOf(String)} except it caches the result in
  69:    * a local LRU cache of 100 elements, organized by access order.
  70:    * <p>
  71:    * This method MUST be used in the gnu.java.security and gnu.javax.crypto
  72:    * packages to ensure they would work with a version 1.4 only of the Java
  73:    * class library API.
  74:    *
  75:    * @param aString a string representation of an integer.
  76:    * @return the {@link Integer} object representing the designated string.
  77:    */
  78:   public static final Integer valueOf(String aString)
  79:   {
  80:     Integer result;
  81:     synchronized (cache)
  82:     {
  83:       result = (Integer) cache.get(aString);
  84:       if (result == null)
  85:         {
  86:           result = Integer.valueOf(aString);
  87:           cache.put(aString, result);
  88:         }
  89:     }
  90:     return result;
  91:   }
  92: 
  93:   /**
  94:    * Simulates the <code>valueOf(int)</code> method found in {@link Integer} of
  95:    * the RI's version 1.5 using a local LRU cache of 100 elements, organized by
  96:    * access order.
  97:    * <p>
  98:    * This method MUST be used in the gnu.java.security and gnu.javax.crypto
  99:    * packages to ensure they would work with a version 1.4 only of the Java
 100:    * class library API.
 101:    *
 102:    * @param anInt a decimal integer.
 103:    * @return the {@link Integer} object representing the designated primitive.
 104:    */
 105:   public static final Integer valueOf(int anInt)
 106:   {
 107:     return valueOf(Integer.toString(anInt, 10));
 108:   }
 109: }