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/*
 * The contents of this file are subject to the terms 
 * of the Common Development and Distribution License 
 * (the "License").  You may not use this file except 
 * in compliance with the License.
 * 
 * You can obtain a copy of the license at 
 * glassfish/bootstrap/legal/CDDLv1.0.txt or 
 * https://glassfish.dev.java.net/public/CDDLv1.0.html. 
 * See the License for the specific language governing 
 * permissions and limitations under the License.
 * 
 * When distributing Covered Code, include this CDDL 
 * HEADER in each file and include the License file at 
 * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable, 
 * add the following below this CDDL HEADER, with the 
 * fields enclosed by brackets "[]" replaced with your 
 * own identifying information: Portions Copyright [yyyy] 
 * [name of copyright owner]
 */
// Copyright (c) 1998, 2005, Oracle. All rights reserved.  
package oracle.toplink.essentials.internal.identitymaps;

import java.lang.ref.*;

/**
 * Purpose: A weak cache is identical to the weak identity map, however the weak
 * can be a performance problem for some types of apps because it can cause too much garbage collection
 * of objects read causing them to be re-read and re-built (this defeats the purpose of the cache).
 * The weak cache solves this through also holding a fixed number of objects is memory to improve caching.
 * 
Responsibilities:

 *  Guarantees identity
 * 
 Allows garbage collection
 * 
 Increases performance through maintaining a fixed size cache of MRU objects when memory is available
 * 
 The default size of the reference cache is half the max size
 * 
 * @since TOPLink/Java 1.2
 */
public class SoftCacheWeakIdentityMap extends HardCacheWeakIdentityMap {
    public SoftCacheWeakIdentityMap(int size) {
        super(size);
    }

    /**
     * Creates a Soft reference if Required
     * @param object is the domain object to cache.
     */
    public Object buildReference(Object object) {
        return new SoftReference(object);
    }

    /**
     * Checks if the object is null, or reference's object is null.
     * @param the object for hard or the reference for soft.
     */
    public boolean hasReference(Object reference) {
        return (reference != null) && (((SoftReference)reference).get() != null);
    }
}