IdentityHashSet.java

/*
 * Created on Apr 27, 2013
 * Created by Paul Gardner
 * 
 * Copyright 2013 Azureus Software, Inc.  All rights reserved.
 * 
 * This program 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; version 2 of the License only.
 * 
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */


package com.aelitis.azureus.core.util;


import java.util.*;

public class 
IdentityHashSet<E> 
	extends AbstractSet<E>
{
	private IdentityHashMap<E,Object> 	identity_map;


	public 
	IdentityHashSet() 
	{
		identity_map = new IdentityHashMap<E,Object>();
	}
	
	public IdentityHashSet(
		Collection<? extends E> 	set ) 
	{
		identity_map = new IdentityHashMap<E,Object>( Math.max((int)(set.size()/.75f) + 1, 16 ));
		
		addAll(set);
	}
	
	public int 
	size() 
	{
		return( identity_map.size());
	}
		
	public boolean 
	contains(
		Object entry )
	{
		return( identity_map.containsKey( entry ));
	}
	

	public boolean 
	add(
		E entry )
	{
		return( identity_map.put( entry, "" ) == null );
	}
	
	public boolean 
	remove(
		Object entry ) 
	{
		return( identity_map.remove( entry ) != null );
	}
	
	public void 
	clear() 
	{
		identity_map.clear();
	}

	public Iterator<E> 
	iterator() 
	{
		return identity_map.keySet().iterator();
	}
}