LRUCache

package common;

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

/**
 *
 * @Title: LRUCache.java
 * @Copyright: Copyright (c) 2011
 * @Description: <br>LRUCache 本地缓存
 *               <br>
 * @Company: renren.com
 * @Created on 2014-1-14 下午1:25:55
 * @author youle.heng
 */
public class LRUCache <K, V> extends LinkedHashMap<K, V> {
   
    private static final long serialVersionUID = -8021134033779621716L;

    private final int maxCapacity;

    private static final float DEFAULT_LOAD_FACTOR = 0.75f;

    private final Lock lock = new ReentrantLock();

    public LRUCache(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;
    }

    /**
     * Weather contains someone Object according to a key
     * @param key
     */
    @Override
    public boolean containsKey(Object key) {
        lock.lock();
        try {
            return super.containsKey(key);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Get one Object according to a key
     * @param key
     */
    @Override
    public V get(Object key) {
        lock.lock();
        try {
            return super.get(key);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Put an Object to cache
     * @param key,value
     */
    @Override
    public V put(K key, V value) {
        lock.lock();
        try {
            return super.put(key, value);
        } finally {
            lock.unlock();
        }
    }

    /**
     * The cache's size
     */
    public int size() {
        lock.lock();
        try {
            return super.size();
        } finally {
            lock.unlock();
        }
    }

    /**
     * clear the cache
     */
    public void clear() {
        lock.lock();
        try {
            super.clear();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Delete one Object from cache
     *
     * @param key
     */
    public void delete(Object key) {
        lock.lock();
        try {
            super.remove(key);
        } finally {
            lock.unlock();
        }
    }

}

new 一个能存储50个值的LRUCache对象

LRUCache<String,String> mc = new LRUCache<String,String>(50);