libjava/classpath/gnu/java/security/util/IntegerUtil.java

/* IntegerUtil.java -- JDK 5 Integer methods with 1.4 API
   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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module.  An independent module is a module which is not derived from
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this exception to your version of the library, but you are not
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exception statement from your version. */


package gnu.java.security.util;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Utility class which offers Integer related methods found in RI's version 5
 * but written with RI's 1.4 API.
 */
public abstract class IntegerUtil
{
  /** Maximum size of our cache of constructed Integers. */
  private static final int CACHE_SIZE = 100;
  /** LRU (Least Recently Used) cache, of the last accessed 100 Integers. */
  private static final Map cache = new LinkedHashMap(CACHE_SIZE + 1, 0.75F, true)
  {
    public boolean removeEldestEntry(Map.Entry entry)
    {
      return size() > CACHE_SIZE;
    }
  };

  /** Trivial private constructor to enforce Singleton usage. */
  private IntegerUtil()
  {
    super();
  }

  /**
   * Similar to {@link Integer#valueOf(String)} except it caches the result in
   * a local LRU cache of 100 elements, organized by access order.
   * <p>
   * This method MUST be used in the gnu.java.security and gnu.javax.crypto
   * packages to ensure they would work with a version 1.4 only of the Java
   * class library API.
   *
   * @param aString a string representation of an integer.
   * @return the {@link Integer} object representing the designated string.
   */
  public static final Integer valueOf(String aString)
  {
    Integer result;
    synchronized (cache)
    {
      result = (Integer) cache.get(aString);
      if (result == null)
        {
          result = Integer.valueOf(aString);
          cache.put(aString, result);
        }
    }
    return result;
  }

  /**
   * Simulates the <code>valueOf(int)</code> method found in {@link Integer} of
   * the RI's version 1.5 using a local LRU cache of 100 elements, organized by
   * access order.
   * <p>
   * This method MUST be used in the gnu.java.security and gnu.javax.crypto
   * packages to ensure they would work with a version 1.4 only of the Java
   * class library API.
   *
   * @param anInt a decimal integer.
   * @return the {@link Integer} object representing the designated primitive.
   */
  public static final Integer valueOf(int anInt)
  {
    return valueOf(Integer.toString(anInt, 10));
  }
}