Cache based on SoftReference : SoftReference « Collections Data Structure « Java





Cache based on SoftReference

   
/*   Copyright 2004 The Apache Software Foundation
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *  limitations under the License.
 */
// Revised from xmlbeans

import java.util.HashMap;
import java.lang.ref.SoftReference;

/**
 * @author Cezar Andrei (cezar.andrei at bea.com)
 *         Date: Apr 26, 2005
 */
public class SoftCache
{
    private HashMap map = new HashMap();

    public Object get(Object key)
    {
        SoftReference softRef = (SoftReference)map.get(key);

        if (softRef==null)
            return null;

        return softRef.get();
    }

    public Object put(Object key, Object value)
    {
        SoftReference softRef = (SoftReference)map.put(key, new SoftReference(value));

        if (softRef==null)
            return null;

        Object oldValue = softRef.get();
        softRef.clear();

        return oldValue;
    }

    public Object remove(Object key)
    {
        SoftReference softRef = (SoftReference)map.remove(key);

        if (softRef==null)
            return null;

        Object oldValue = softRef.get();
        softRef.clear();

        return oldValue;
    }
}

   
    
    
  










Related examples in the same category

1.A soft reference holds onto its referent until memory becomes low.
2.A weak reference is used to determine when an object is no longer being referenced.
3.A phantom reference is used to determine when an object is just about to be reclaimed.
4.Testing SoftReference
5.Testing WeakReference
6.Testing PhantomReference
7.Soft ValueMap
8.An implementation of Set that manages a map of soft references to the set values.