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1   /*** 
2    * 
3    * Copyright 2004 Protique Ltd
4    * 
5    * Licensed under the Apache License, Version 2.0 (the "License"); 
6    * you may not use this file except in compliance with the License. 
7    * You may obtain a copy of the License at 
8    * 
9    * http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS, 
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
14   * See the License for the specific language governing permissions and 
15   * limitations under the License. 
16   * 
17   **/
18  package org.codehaus.activemq.util;
19  
20  import java.util.LinkedHashMap;
21  import java.util.Map;
22  
23  /***
24   * Represnts an LRUCache of a fixed maximum size which by default will
25   * remove items based on access order but can be used to use insertion order
26   *
27   * @version $Revision: 1.2 $
28   */
29  public class LRUCache extends LinkedHashMap {
30      private static final long serialVersionUID = -5754338187296859149L;
31  
32      protected static final int DEFAULT_INITIAL_CAPACITY = 1000;
33      protected static final float DEFAULT_LOAD_FACTOR = (float) 0.75;
34  
35      private int maxSize;
36  
37      public LRUCache(int initialCapacity, float loadFactor, boolean accessOrder, int maxSize) {
38          super(initialCapacity, loadFactor, accessOrder);
39          this.maxSize = maxSize;
40      }
41  
42      public LRUCache(int maxSize) {
43          this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, true, maxSize);
44      }
45  
46      public LRUCache(int maxSize, boolean accessOrder) {
47          this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, accessOrder, maxSize);
48      }
49  
50      protected boolean removeEldestEntry(Map.Entry eldest) {
51          return size() > maxSize;
52      }
53  }