6.读写锁

/**
 * @author wuyimin
 * @create 2021-07-08-20:12
 * @description 允许同时读，不允许同时写或者同时写和读
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache cache = new MyCache();
        //写入操作
        for (int i = 0; i < 5; i++) {
            final int temp=i;
            new Thread(()->{
                cache.put(temp+"",temp);
            },String.valueOf(i)).start();
        }

        //读取操作
        for (int i = 0; i < 5; i++) {
            final int temp=i;
            new Thread(()->{
                cache.get(temp+"");
            },String.valueOf(i)).start();
        }
    }
}
/*
自定义缓存
 */
class MyCache{
    private volatile Map<String,Object> map=new HashMap<>();
    //读写锁
    private ReentrantReadWriteLock lock=new ReentrantReadWriteLock();
    //存，写
    public void put(String key,Object value){
        lock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"开始写");
            map.put(key,value);
            System.out.println(Thread.currentThread().getName()+"完成写");
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            lock.writeLock().unlock();
        }
    }
    //取，读
    public void get(String key){
        lock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"开始读");
            Object o=map.get(key);
            System.out.println(Thread.currentThread().getName()+"完成读");
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            lock.readLock().unlock();
        }
    }
}