001package org.apache.commons.jcs.engine.memory.mru;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.io.IOException;
023
024import org.apache.commons.jcs.engine.behavior.ICacheElement;
025import org.apache.commons.jcs.engine.memory.AbstractDoubleLinkedListMemoryCache;
026import org.apache.commons.jcs.engine.memory.util.MemoryElementDescriptor;
027
028/**
029 * The most recently used items move to the front of the list and get spooled to disk if the cache
030 * hub is configured to use a disk cache.
031 */
032public class MRUMemoryCache<K, V>
033    extends AbstractDoubleLinkedListMemoryCache<K, V>
034{
035    /**
036     * Adds the item to the front of the list. A put doesn't count as a usage.
037     * <p>
038     * It's not clear if the put operation should be different. Perhaps this should remove the oldest
039     * if full, and then put.
040     * <p>
041     * @param ce
042     * @return MemoryElementDescriptor the new node
043     * @throws IOException
044     */
045    @Override
046    protected MemoryElementDescriptor<K, V> adjustListForUpdate( ICacheElement<K, V> ce )
047        throws IOException
048    {
049        return addFirst( ce );
050    }
051
052    /**
053     * Makes the item the last in the list.
054     * <p>
055     * @param me
056     */
057    @Override
058    protected void adjustListForGet( MemoryElementDescriptor<K, V> me )
059    {
060        list.makeLast( me );
061    }
062}