1 package org.apache.commons.jcs3.engine.memory.lru; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import java.io.IOException; 23 24 import org.apache.commons.jcs3.engine.behavior.ICacheElement; 25 import org.apache.commons.jcs3.engine.memory.AbstractDoubleLinkedListMemoryCache; 26 import org.apache.commons.jcs3.engine.memory.util.MemoryElementDescriptor; 27 28 /** 29 * A fast reference management system. The least recently used items move to the end of the list and 30 * get spooled to disk if the cache hub is configured to use a disk cache. Most of the cache 31 * bottlenecks are in IO. There are no io bottlenecks here, it's all about processing power. 32 * <p> 33 * Even though there are only a few adjustments necessary to maintain the double linked list, we 34 * might want to find a more efficient memory manager for large cache regions. 35 * <p> 36 * The LRUMemoryCache is most efficient when the first element is selected. The smaller the region, 37 * the better the chance that this will be the case. < .04 ms per put, p3 866, 1/10 of that per get 38 */ 39 public class LRUMemoryCache<K, V> 40 extends AbstractDoubleLinkedListMemoryCache<K, V> 41 { 42 /** 43 * Puts an item to the cache. Removes any pre-existing entries of the same key from the linked 44 * list and adds this one first. 45 * <p> 46 * @param ce The cache element, or entry wrapper 47 * @return MemoryElementDescriptor the new node 48 * @throws IOException 49 */ 50 @Override 51 protected MemoryElementDescriptor<K, V> adjustListForUpdate( final ICacheElement<K, V> ce ) 52 throws IOException 53 { 54 return addFirst( ce ); 55 } 56 57 /** 58 * Makes the item the first in the list. 59 * <p> 60 * @param me 61 */ 62 @Override 63 protected void adjustListForGet( final MemoryElementDescriptor<K, V> me ) 64 { 65 list.makeFirst( me ); 66 } 67 }