JUC系列十：ReentrantReadWriteLock

JUC系列十：ReentrantReadWriteLock 1.1、错误代码

package com.atguigu.juc;

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

class MyCache1 {
    private volatile Map map = new HashMap<>();

    public void put(String key, Object value) {
        System.out.println(Thread.currentThread().getName() + "t正在写" + key);
        //线程休眠，单位：秒
        try {
            TimeUnit.MILLISECONDS.sleep(300);
        } catch (Exception e) {
            e.printStackTrace();
        }
        map.put(key, value);
        System.out.println(Thread.currentThread().getName() + "t写完了" + key);
    }

    public Object get(String key) {
        Object result = null;
        System.out.println(Thread.currentThread().getName() + "t正在读" + key);
        //线程休眠，单位：毫秒
        try {
            TimeUnit.MILLISECONDS.sleep(300);
        } catch (Exception e) {
            e.printStackTrace();
        }
        result = map.get(key);
        System.out.println(Thread.currentThread().getName() + "t读完了" + result);
        return result;
    }
}


public class ReadWriteLockDemo1 {
    public static void main(String[] args) {
        MyCache1 myCache1 = new MyCache1();

        for (int i = 1; i <= 5; i++) {
            final int num = i;
            new Thread(() -> {
                myCache1.put(num + "", +num + "");
            }, String.valueOf(i)).start();
        }

        for (int i = 1; i <= 5; i++) {
            final int num = i;
            new Thread(() -> {
                myCache1.get(num + "");
            }, String.valueOf(i)).start();
        }
    }
}

1.2、正确代码

package com.atguigu.juc;

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

class MyCache2{
    private volatile Map map = new HashMap<>();
    private ReadWriteLock rwLock = new ReentrantReadWriteLock();

    public void put(String key,Object value){
        rwLock.writeLock().lock();
        try{
            System.out.println(Thread.currentThread().getName()+"t正在写"+key);
            //线程休眠，单位：毫秒
            try { TimeUnit.MILLISECONDS.sleep(300); } catch (Exception e) { e.printStackTrace(); }
            map.put(key,value);
            System.out.println(Thread.currentThread().getName()+"t写完了"+key);
            System.out.println();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            rwLock.writeLock().unlock();
        }
    }

    public Object get(String key){
        rwLock.readLock().lock();
        Object result = null;
        try{
            System.out.println(Thread.currentThread().getName()+"t正在读"+key);
            //线程休眠，单位：毫秒
            try { TimeUnit.MILLISECONDS.sleep(300); } catch (Exception e) { e.printStackTrace(); }
            result = map.get(key);
            System.out.println(Thread.currentThread().getName()+"t读完了"+result);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            rwLock.readLock().unlock();
        }

        return result;
    }
}

public class ReadWriteLockDemo2 {
    public static void main(String[] args) {
        MyCache2 myCache2 = new MyCache2();

        for (int i = 1; i <= 5; i++) {
            final int num = i;
            new Thread(() -> {
                myCache2.put(num + "", +num + "");
            }, String.valueOf(i)).start();
        }

        for (int i = 1; i <= 5; i++) {
            final int num = i;
            new Thread(() -> {
                myCache2.get(num + "");
            }, String.valueOf(i)).start();
        }
    }
}