高併發下對緩存加鎖的經典實現

package cn.hutool.core.lang;

import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;

/**
 * 簡單緩存，無超時實現，使用{@link WeakHashMap}實現緩存自動清理
 * @author Looly
 *
 * @param <K> 鍵類型
 * @param <V> 值類型
 */
public class SimpleCache<K, V> {
	/** 池 */
	private final Map<K, V> cache = new WeakHashMap<>();
	
	private final ReentrantReadWriteLock cacheLock = new ReentrantReadWriteLock();
	private final ReadLock readLock = cacheLock.readLock();
	private final WriteLock writeLock = cacheLock.writeLock();

	/**
	 * 從緩存池中查找值
	 * 
	 * @param key 鍵
	 * @return 值
	 */
	public V get(K key) {
		// 嘗試讀取緩存
		readLock.lock();
		V value;
		try {
			value = cache.get(key);
		} finally {
			readLock.unlock();
		}
		return value;
	}
	
	/**
	 * 放入緩存
	 * @param key 鍵
	 * @param value 值
	 * @return 值
	 */
	public V put(K key, V value){
		writeLock.lock();
		try {
			cache.put(key, value);
		} finally {
			writeLock.unlock();
		}
		return value;
	}

	/**
	 * 移除緩存
	 * 
	 * @param key 鍵
	 * @return 移除的值
	 */
	public V remove(K key) {
		writeLock.lock();
		try {
			return cache.remove(key);
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 清空緩存池
	 */
	public void clear() {
		writeLock.lock();
		try {
			this.cache.clear();
		} finally {
			writeLock.unlock();
		}
	}
}