engine/src/main/java/com/datatorrent/stram/util/LRUCache.java

/**
 * 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 com.datatorrent.stram.util;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * <p>LRUCache class.</p>
 *
 * @param <K> key
 * @param <V> value
 * @since 0.3.5
 */
public class LRUCache<K, V> extends LinkedHashMap<K, V>
{
  private static final long serialVersionUID = 1L;
  private final int capacity; // Maximum number of items in the cache.

  public LRUCache(int capacity, boolean accessOrder)
  {
    super(capacity + 1, 1.0f, accessOrder); // Pass 'true' for accessOrder.
    this.capacity = capacity;
  }

  @Override
  protected boolean removeEldestEntry(Map.Entry<K, V> entry)
  {
    return (size() > this.capacity);
  }

}