/*
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */


package org.apache.commons.collections;

import java.lang.ref.*;


/**
 *  <p>A {@link WeakReference} class that passes calls to {@link #hashCode()}
 *  and {@link #equals(Object)} to the referenced object.  This class replaces
 *  the objects is a {@link WeakHashSet} so that they may be dereferenced during
 *  garbage collection.</p>
 *
 *  @see WeakHashSet
 *  @see WeakReference
 */
class WeakHashSetElement
    extends WeakReference {

    // Holds the last-known value of the referenced object's hash code
    int     lastKnownHashCode;


    /**
     *  Implements the {@link WeakReference#WeakReference(Object,ReferenceQueue)}
     *  constructor.
     */
    WeakHashSetElement(
        Object          referencedObject,
        ReferenceQueue  cleanupQueue
    ) {

        super( referencedObject, cleanupQueue );
        lastKnownHashCode = 0;

    }


    /**
     *  Return the referenced object's hash code.  If the object has been
     *  dereferenced, it uses the value that was returned the last time this
     *  method was called.
     */
    public int hashCode(
    ) {

        if( get( ) != null ) {

            lastKnownHashCode = get( ).hashCode( );

        }
        return lastKnownHashCode;

    }


    /**
     *  Passes the call to the other object's {@link Object#equals(Object)}
     *  method, passing the referenced object as its parameter.  It is done this
     *  way in case the referenced object has been dereferenced, which passes a
     *  <code>null</code> to the other object.
     */
    public boolean equals(
        Object  otherObject
    ) {

        return otherObject.equals( get( ) );

    }

}