001package org.apache.commons.jcs.engine.memory.lru; 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 * A fast reference management system. The least recently used items move to the end of the list and 030 * get spooled to disk if the cache hub is configured to use a disk cache. Most of the cache 031 * bottlenecks are in IO. There are no io bottlenecks here, it's all about processing power. 032 * <p> 033 * Even though there are only a few adjustments necessary to maintain the double linked list, we 034 * might want to find a more efficient memory manager for large cache regions. 035 * <p> 036 * The LRUMemoryCache is most efficient when the first element is selected. The smaller the region, 037 * the better the chance that this will be the case. < .04 ms per put, p3 866, 1/10 of that per get 038 */ 039public class LRUMemoryCache<K, V> 040 extends AbstractDoubleLinkedListMemoryCache<K, V> 041{ 042 /** 043 * Puts an item to the cache. Removes any pre-existing entries of the same key from the linked 044 * list and adds this one first. 045 * <p> 046 * @param ce The cache element, or entry wrapper 047 * @return MemoryElementDescriptor the new node 048 * @throws IOException 049 */ 050 @Override 051 protected MemoryElementDescriptor<K, V> adjustListForUpdate( ICacheElement<K, V> ce ) 052 throws IOException 053 { 054 return addFirst( ce ); 055 } 056 057 /** 058 * Makes the item the first in the list. 059 * <p> 060 * @param me 061 */ 062 @Override 063 protected void adjustListForGet( MemoryElementDescriptor<K, V> me ) 064 { 065 list.makeFirst( me ); 066 } 067}