关于ReentrantReadWriteLock小实例-优快云博客

本文链接：https://blog.youkuaiyun.com/limj625/article/details/55505127

本文介绍了一个使用Java实现的简单并发编程案例，通过ReentrantReadWriteLock实现读写锁机制，确保了多线程环境下数据的一致性和安全性。案例中定义了一个Person类，用于演示如何在多线程环境下进行数据的读写操作。

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package cn.test.thread;


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

/**
 * Created by lim on 2017/2/16.
 */
public class TestThread {

    public static void main(String[] args)throws Exception{

        final Person person = new Person();
        final Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    int i = 0;
                    //while (true)  {
                       // i++;
                        person.write("A","A");
                        //Thread.sleep(1000);
                   // }
                } catch (InterruptedException e) {
                    System.out.println("此线程已被挂起...");
                    //e.printStackTrace();
                }
            }
        });

//        Thread t11 = new Thread(new Runnable() {
//            @Override
//            public void run() {
//                System.out.println("取到了："+person.read("A2").toString());
//            }
//        });

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("取到了："+person.read("A1").toString());
            }
        });
        //t11.start();
        t1.start();
        t2.start();
        Thread.sleep(2000);
        // interrupt 只能打断阻塞的线程
        // 如果想打断正在运行的线程，我的方法：需要打断的业务中添加 Thread.sleep(100)
        t1.interrupt();
    }
}

class Person{

    Map<String, Object> rmap = new HashMap<String, Object>();
    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
    Lock r = lock.readLock();
    Lock w = lock.writeLock();

    public void write(String key, String msg) throws InterruptedException{
        try {
            // 加写入锁
            // （ 如果你乐意<脑残>也可以加读锁，这样向map放值的动作变为可多个线程同时执行的了）
            w.lock();
            int i = 0;
            while(true){
                i++;
                System.out.println("开始放入第...."+" :"+msg+i);
                rmap.put(key+i,msg+i);
//                try {
//                    Thread.sleep(1000);
//                } catch (InterruptedException e) {
//                    //e.printStackTrace();
//                }
                if(i >= 20){
                    break;
                }
            }
        } finally {
            w.unlock();
        }
    }

    public Object read(String key) {
        Object obj = null;
        try {
            // 加读锁
            r.lock();
            obj = rmap.get(key);
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            r.unlock();
        }
        return obj;
    }
}