JUC个人学习笔记7-读写锁

根据b站UP主狂神说JUC课程所写的个人学习笔记

视频地址：https://www.bilibili.com/video/BV1B7411L7tE?from=search&seid=14761503393031794075

ReadWriteLock 

读的时候可以多线程读，写的时候只能一个写

//独占锁(写锁)
//共享锁(读锁)
//1.读-读 可以共存2.读-写 不能共存3.写-写 不能共存
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCacheLock myCache = new MyCacheLock();
        //写入
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.put(temp+"",temp+"");
            },String.valueOf(i)).start();
        }
        //读取
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.get(temp+"");
            },String.valueOf(i)).start();
        }

    }

}
//加锁的
class MyCacheLock{
    private volatile Map<String,Object> map = new HashMap<>();
    //读写锁，更加细粒度的控制
    private ReentrantReadWriteLock reentrantReadWriteLock =  new ReentrantReadWriteLock();
    //写入的时候只希望一个线程写
    public void put(String key,Object value){
        reentrantReadWriteLock.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"+key);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            reentrantReadWriteLock.writeLock().unlock();
        }



    }
    //读的时候可以多线程读
    public void get(String key){
        //取
        reentrantReadWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"读取"+key);
            map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取ok"+key);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            reentrantReadWriteLock.readLock().unlock();
        }

    }
}
class MyCache{
    private volatile Map<String,Object> map = new HashMap<>();
    public void put(String key,Object value){
        System.out.println(Thread.currentThread().getName()+"写入"+key);
        map.put(key,value);
        //存
        System.out.println(Thread.currentThread().getName()+"写入ok"+key);


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