001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.camel.util;
018    
019    import java.util.LinkedHashMap;
020    import java.util.Map;
021    
022    /**
023     * A Least Recently Used Cache
024     *
025     * @version $Revision: 514 $
026     */
027    public class LRUCache<K, V> extends LinkedHashMap<K, V> {
028        private static final long serialVersionUID = -342098639681884413L;
029        private int maxCacheSize = 10000;
030    
031        public LRUCache(int maximumCacheSize) {
032            this(maximumCacheSize, maximumCacheSize, 0.75f, true);
033        }
034    
035        /**
036         * Constructs an empty <tt>LRUCache</tt> instance with the
037         * specified initial capacity, maximumCacheSize,load factor and ordering mode.
038         *
039         * @param initialCapacity  the initial capacity.
040         * @param maximumCacheSize
041         * @param loadFactor       the load factor.
042         * @param accessOrder      the ordering mode - <tt>true</tt> for
043         *                         access-order, <tt>false</tt> for insertion-order.
044         * @throws IllegalArgumentException if the initial capacity is negative
045         *                                  or the load factor is non positive.
046         */
047        public LRUCache(int initialCapacity, int maximumCacheSize, float loadFactor, boolean accessOrder) {
048            super(initialCapacity, loadFactor, accessOrder);
049            this.maxCacheSize = maximumCacheSize;
050        }
051    
052        /**
053         * Returns the maxCacheSize.
054         */
055        public int getMaxCacheSize() {
056            return maxCacheSize;
057        }
058    
059        protected boolean removeEldestEntry(Map.Entry entry) {
060            return size() > maxCacheSize;
061        }
062    }