content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.util;
  
  import java.util.LinkedHashMap;
  import java.util.Map;
  
  /**
   * A Simple LRU Cache
   * 
   * 
   * @param <K>
   * @param <V>
   */
  
  public class LRUCache<K, V> extends LinkedHashMap<K, V> {
      private static final long serialVersionUID = -342098639681884413L;
      protected int maxCacheSize = 10000;
  
      /**
       * Default constructor for an LRU Cache The default capacity is 10000
       */
      public LRUCache() {
          this(0,10000, 0.75f, true);
      }
  
      /**
       * Constructs a LRUCache with a maximum capacity
       * 
       * @param maximumCacheSize
       */
      public LRUCache(int maximumCacheSize) {
          this(0, maximumCacheSize, 0.75f, true);
      }
  
      /**
       * Constructs an empty <tt>LRUCache</tt> instance with the specified
       * initial capacity, maximumCacheSize,load factor and ordering mode.
       * 
       * @param initialCapacity the initial capacity.
       * @param maximumCacheSize
       * @param loadFactor the load factor.
       * @param accessOrder the ordering mode - <tt>true</tt> for access-order,
       *                <tt>false</tt> for insertion-order.
       * @throws IllegalArgumentException if the initial capacity is negative or
       *                 the load factor is non-positive.
       */
  
      public LRUCache(int initialCapacity, int maximumCacheSize, float loadFactor, boolean accessOrder) {
          super(initialCapacity, loadFactor, accessOrder);
          this.maxCacheSize = maximumCacheSize;
      }
  
      /**
       * @return Returns the maxCacheSize.
       */
      public int getMaxCacheSize() {
          return maxCacheSize;
      }
  
      /**
       * @param maxCacheSize The maxCacheSize to set.
       */
      public void setMaxCacheSize(int maxCacheSize) {
          this.maxCacheSize = maxCacheSize;
      }
  
      protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
          if( size() > maxCacheSize ) {
              onCacheEviction(eldest);
              return true;
          }
          return false;
      }
  
      protected void onCacheEviction(Map.Entry<K,V> eldest) {
      }
  
  }
  