Java多线程-模拟一个缓存代理

示例

package com.zhihua.subject;

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

/**
 * 缓存代理
 * @author caizh
 *
 */
public class CacheDemo {

    private Map<String, Object> cache = new HashMap<>();
    private ReadWriteLock rWriteLock = new ReentrantReadWriteLock();
    public static void main(String[] args) {


    }

    public Object getData(String key) {
        rWriteLock.readLock().lock();
        Object value = null;
        try {
            value = cache.get(key);
            if(value == null) {
                rWriteLock.readLock().unlock();
                rWriteLock.readLock().lock();
                try {
                    if(value==null) {
                        value = "aaa";// 去获取到数据，并赋值
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    rWriteLock.writeLock().unlock();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            rWriteLock.readLock().unlock();
        }
        return value;
    }
}