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/* 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.

You should have received a copy of the GNU General Public License

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

conditions of the GNU General Public License cover the whole

combination.

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

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

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));

  }

}