使用ReadWriteLock实现模拟缓存

 

 

使用ReadWriteLock的读写锁 实现 模拟缓存的 功能

 

 

package cn.zto.lock;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

//模仿缓存
public class CacheDateTest {
	
	ReadWriteLock rwl = new ReentrantReadWriteLock();
	Map map = new HashMap();
	
	public Object get(Object key){
		
		rwl.readLock().lock();
		
		Object value = null;
		boolean flag ;
		value = map.get(key);
		
		if (value == null) {
			flag = false;
			rwl.readLock().unlock();
			rwl.writeLock().lock();
			if (!flag) {
				value = " 初始化 ";
				map.put(key, value);
				flag = true;
			}
			rwl.writeLock().unlock();
			rwl.readLock().lock();
		}
		
		rwl.readLock().unlock();
		return value;
	}
	
}