package org.apache.ojb.broker.util;
   
   /* Copyright 2002-2005 The Apache Software Foundation
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * replacement for the JDK1.4 version
   * User: Matthew Baird
   * Date: Jul 8, 2003
   * Time: 8:37:00 AM
   */
  public final class IdentityHashMap extends HashMap
  {
  	private static final class IdentityKey
  	{
  		private final Object m_key;
  
  		public IdentityKey(final Object key)
  		{
  			m_key = key;
  		}
  
  		public boolean equals(final Object o)
  		{
  			return (o == m_key);
  		}
  
  		public int hashCode()
  		{
  			return System.identityHashCode(m_key);
  		}
  	}
  
  	/**
  	 * Constructor for IdentityHashMap.
  	 * @param initialCapacity
  	 * @param loadFactor
  	 */
  	public IdentityHashMap(final int initialCapacity, final float loadFactor)
  	{
  		super(initialCapacity, loadFactor);
  	}
  
  	/**
  	 * Constructor for IdentityHashMap.
  	 * @param initialCapacity
  	 */
  	public IdentityHashMap(final int initialCapacity)
  	{
  		super(initialCapacity);
  	}
  
  	/**
  	 * Constructor for IdentityHashMap.
  	 */
  	public IdentityHashMap()
  	{
  		super();
  	}
  
  	/**
  	 * Constructor for IdentityHashMap.
  	 * @param t
  	 */
  	public IdentityHashMap(final Map t)
  	{
  		super(t);
  	}
  
  	/**
  	 * @see java.util.Map#get(java.lang.Object)
  	 */
  	public Object get(final Object key)
  	{
  		return super.get(new IdentityKey(key));
  	}
  
  	/**
  	 * @see java.util.Map#put(java.lang.Object, java.lang.Object)
  	 */
  	public Object put(final Object key, final Object value)
  	{
  		return super.put(new IdentityKey(key), value);
  	}
 
 	/**
 	 * adds an object to the Map. new IdentityKey(obj) is used as key
 	 */
 	public Object add(final Object value)
 	{
 		final Object key = new IdentityKey(value);
 		if (!super.containsKey(key))
 		{
 			return super.put(key, value);
 		}
 		else
 		{
 			return null;
 		}
 	}
 
 	/**
 	 * @see java.util.Map#remove(java.lang.Object)
 	 */
 	public Object remove(final Object key)
 	{
 		return super.remove(new IdentityKey(key));
 	}
 
 	/**
 	 * @see java.util.Map#containsKey(java.lang.Object)
 	 */
 	public boolean containsKey(final Object key)
 	{
 		return super.containsKey(new IdentityKey(key));
 	}
 }