读写锁 ReentrantReadWriteLock-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_40577921/article/details/100922291

本文介绍了一个使用Java并发包中ReentrantReadWriteLock实现的简单缓存类MyCache。通过读写锁机制，该缓存类能够允许多个读操作同时进行，而写操作则必须独占锁，确保数据的一致性和安全性。示例代码展示了如何在多线程环境下正确地使用读写锁来提高并发性能。

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package com.itjava.interview;


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

//读写锁  ReentrantReadWriteLock
class MyCache {

    private volatile Map<String, Object> map = new HashMap<>();
    //读写锁
    private ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();

    public void put(String key, Object value) {

        //写锁 写必须要锁
        rwLock.writeLock().lock();
        try {

            System.out.println(Thread.currentThread().getName() + "\t正在写入：" + key);
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + "\t写入完成。");

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            rwLock.writeLock().unlock();
        }


    }

    public void get(String key) {

        //读加锁  readLock  读都不需要顺序
        rwLock.readLock().lock();
        try {

            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "\t正在读取：");
            Object result = map.get(key);
            System.out.println(Thread.currentThread().getName() + "\t读取完成：" + result);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            rwLock.readLock().unlock();
        }

    }

}

public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache myCache = new MyCache();

        for (int i = 0; i <= 5; i++) {
            final int tempInt = i;
            new Thread(() -> {
                myCache.put(tempInt + "", tempInt + "");
            }, String.valueOf(i)).start();
        }

        for (int i = 0; i <= 5; i++) {
            final int tempInt = i;
            new Thread(() -> {
                myCache.get(tempInt + "");
            }, String.valueOf(i)).start();
        }
    }
}