001 /**
002 *
003 * Copyright 2004 Protique Ltd
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 **/
018 package org.activemq.util;
019
020 import java.util.LinkedHashMap;
021 import java.util.Map;
022
023 /**
024 * Represnts an LRUCache of a fixed maximum size which by default will
025 * remove items based on access order but can be used to use insertion order
026 *
027 * @version $Revision: 1.1.1.1 $
028 */
029 public class LRUCache extends LinkedHashMap {
030 private static final long serialVersionUID = -5754338187296859149L;
031
032 protected static final int DEFAULT_INITIAL_CAPACITY = 1000;
033 protected static final float DEFAULT_LOAD_FACTOR = (float) 0.75;
034
035 private int maxSize;
036
037 public LRUCache(int initialCapacity, float loadFactor, boolean accessOrder, int maxSize) {
038 super(initialCapacity, loadFactor, accessOrder);
039 this.maxSize = maxSize;
040 }
041
042 public LRUCache(int maxSize) {
043 this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, true, maxSize);
044 }
045
046 public LRUCache(int maxSize, boolean accessOrder) {
047 this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, accessOrder, maxSize);
048 }
049
050 protected boolean removeEldestEntry(Map.Entry eldest) {
051 return size() > maxSize;
052 }
053 }