LRUCache xref

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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  }