content: //  Copyright 2006, Clark N. Hobbie
  //
  //  This file is part of the util library.
  //
  //  The util library is free software; you can redistribute it and/or modify it
  //  under the terms of the Lesser GNU General Public License as published by
  //  the Free Software Foundation; either version 2.1 of the License, or (at
  //  your option) any later version.
  //
  //  The util library 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 Lesser GNU General Public
  //  License for more details.
  //
  //  You should have received a copy of the Lesser GNU General Public License
  //  along with the util library; if not, write to the Free Software Foundation,
  //  Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  //
  package com.lts.util;
  
  import java.util.AbstractSet;
  import java.util.IdentityHashMap;
  import java.util.Iterator;
  
  /**
   * An AbstractSet that is backed by an IdentityHashSet --- it uses "==" instead 
   * of Object.equals to determine if an object is in the set.
   */
  public class IdentityHashSet extends AbstractSet
  {
  	protected IdentityHashMap myMap = new IdentityHashMap();
  	
  	public int size()
  	{
  		return myMap.size();
  	}
  
  	public Iterator iterator()
  	{
  		return myMap.keySet().iterator();
  	}
  	
  	public boolean add (Object o)
  	{
  		boolean result = false;
  		
  		if (!myMap.containsKey(o))
  		{
  			myMap.put(o, o);
  			result = true;
  		}
  		
  		return result;
  	}
  	
  	public boolean remove (Object o)
  	{
  		return null != myMap.remove(o);
  	}
  
  }
  