并发JUC之读写锁_juc 读写锁

• 读写锁:
  读读可以共存
  读写不能共存
  写写不能共存
  独占锁(写锁)
  共享锁(读锁)

public class ReadWriteLockTest {
    public static void main(String[] args) {
        MyCache myCache = new MyCache();
        for (int i = 1; i <= 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.put(temp+"",temp+"");
            },String.valueOf(i)).start();
        }
        for (int i = 1; i <= 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.get(temp+"");
            },String.valueOf(i)).start();
        }
    }
}

/**
 * 自定义缓存
 */
class MyCache{
    private volatile Map<String,Object> map = new HashMap<>();

    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    //存方法,写的过程
    public void put(String key,Object value){
        readWriteLock.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");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //取方法,读的过程
    public void get(String key){
        readWriteLock.readLock().lock();

        try {
            System.out.println(Thread.currentThread().getName()+"读取"+key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}
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