JUC-04

最新推荐文章于 2023-12-25 09:23:30 发布

原创最新推荐文章于 2023-12-25 09:23:30 发布 · 123 阅读

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#java #jvm #算法

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6、读写锁

ReadWriteLock

package com.bjw.rw;


import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/*
独占锁（写锁）
共享锁（读锁）
* ReadWriteLock
* 读-读 可以共存
* 读-写 不能共存
* 写-写 不能共存
* */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCacheLock myCache = new MyCacheLock();

        //写入
        for (int i = 1; i <= 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.put(temp+"",temp+"");
            },String.valueOf(i)).start();
        }

        //读取
        for (int i = 1; i <= 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.get(temp+"");
            },String.valueOf(i)).start();
        }
    }
}
/*
* 自定义缓存
* */
class MyCache {
    private volatile Map<String, Object> map = new HashMap<>();

    //存
    public void put(String key, Object value) {
        System.out.println(Thread.currentThread().getName()+"写入"+key);
        map.put(key, value);
        System.out.println(Thread.currentThread().getName()+"写入OK");
    }

    //取
    public void get(String key) {
        System.out.println(Thread.currentThread().getName()+"读取"+key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName()+"读取OK");
    }
}

//加锁的
class MyCacheLock {
    private volatile Map<String, Object> map = new HashMap<>();
    private ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    //存,写入的时候，只希望同时只有一个线程写
    public void put(String key, Object value) {
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"写入"+key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName()+"写入OK");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //取，读，所有人都可以读！
    public void get(String key) {
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"读取"+key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取OK");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}