com.mchange.v2.coalesce.AbstractWeakCoalescer Maven / Gradle / Ivy

/*
 * Distributed as part of mchange-commons-java 0.2.11
 *
 * Copyright (C) 2015 Machinery For Change, Inc.
 *
 * Author: Steve Waldman 
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of EITHER:
 *
 *     1) The GNU Lesser General Public License (LGPL), version 2.1, as 
 *        published by the Free Software Foundation
 *
 * OR
 *
 *     2) The Eclipse Public License (EPL), version 1.0
 *
 * You may choose which license to accept if you wish to redistribute
 * or modify this work. You may offer derivatives of this work
 * under the license you have chosen, or you may provide the same
 * choice of license which you have been offered here.
 *
 * This software 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.
 *
 * You should have received copies of both LGPL v2.1 and EPL v1.0
 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
 * If not, the text of these licenses are currently available at
 *
 * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 *  EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php 
 * 
 */

package com.mchange.v2.coalesce;

import java.util.*;
import java.lang.ref.WeakReference;

class AbstractWeakCoalescer implements Coalescer
{
    Map wcoalesced;

    AbstractWeakCoalescer( Map wcoalesced )
    { this.wcoalesced = wcoalesced; }

    public Object coalesce( Object o )
    {
	//System.err.println("AbstractWeakCoalescer.coalesce( " + o + " )");
	Object out = null;

	WeakReference wr = (WeakReference) wcoalesced.get( o );
	if ( wr != null ) 
	    out = wr.get(); //there is a conceivable race that would
    	                    //permit wr be cleared
	if ( out == null )
	    {
		wcoalesced.put( o , new WeakReference(o) );
		out = o;
	    }
	return out;
    }

    public int countCoalesced()
    { return wcoalesced.size(); }

    public Iterator iterator()
    { return new CoalescerIterator( wcoalesced.keySet().iterator() ); }
}