/*
 * Copyright (c) 2008-2016 Computer Network Information Center (CNIC), Chinese Academy of Sciences.
 * 
 * This file is part of Duckling project.
 *
 * Licensed 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 cn.vlabs.umt.common;

import java.util.LinkedHashMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class LRULinkedHashMap<K, V> extends LinkedHashMap<K, V> {

	private static final long serialVersionUID = 1L;

	private final int maxCapacity;

	private static final float DEFAULT_LOAD_FACTOR = 0.75f;

	private final Lock lock = new ReentrantLock();

	public LRULinkedHashMap(int maxCapacity) {
		super(maxCapacity, DEFAULT_LOAD_FACTOR, true);
		this.maxCapacity = maxCapacity;
	}

	@Override
	protected boolean removeEldestEntry(java.util.Map.Entry<K, V> eldest) {
		return size() > maxCapacity;
	}

	@Override
	public V get(Object key) {
		try {
			lock.lock();
			return super.get(key);
		} finally {
			lock.unlock();
		}
	}

	@Override
	public V put(K key, V value) {
		try {
			lock.lock();
			return super.put(key, value);
		} finally {
			lock.unlock();
		}
	}
}