ReentrantReadWriteLock

ReentrantReadWriteLock

ReentrantReadWriteLock:读写锁，在执行读操作时可以异步执行。读-读异步，读-写异步，写-写异步。

ReentrantLock是完全互斥排他的，效率低；

ReentrantReadWriteLock有两个锁：

• 读相关的锁：共享锁

• 写相关的锁：排他锁

package ReentranyReadWriteLock;
​
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
​
//ReentrantReadWriteLock:读读共享、读写互斥
public class Read_Write {
    public static void main(String[] args) {
        Service service = new Service();
        for(int i=0;i<5;i++){
            new MyThread1(service).start();
            new MyThread2(service).start();
        }
​
​
    }
}
class Service{
    private ReentrantReadWriteLock lock=new ReentrantReadWriteLock();
    //读操作
    public void read(){
        try {
            lock.readLock().lock();
            System.out.println("线程："+Thread.currentThread().getName()
                    +"读......"+System.currentTimeMillis());
            Thread.sleep(500);
            System.out.println("  线程："+Thread.currentThread().getName()
                    +"读......结束"+System.currentTimeMillis());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.readLock().unlock();
        }
    }
    public void write(){
        try {
            lock.writeLock().lock();
            System.out.println("线程："+Thread.currentThread().getName()+"写>>>>>>> "
                    +System.currentTimeMillis());
            Thread.sleep(500);
            System.out.println("  线程："+Thread.currentThread().getName()+"写>>>>>>>结束 "
                    +System.currentTimeMillis());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.writeLock().unlock();
        }
    }
    
​
}
class MyThread1 extends Thread{
    private Service service;
    public MyThread1(Service service){
        this.service=service;
    }
​
    @Override
    public void run() {
        service.read();
    }
}
class MyThread2 extends Thread{
    private Service service;
    public MyThread2(Service service){
        this.service=service;
    }
​
    @Override
    public void run() {
        service.write();
    }
}
/*
线程：Thread-0读......1609738706403
线程：Thread-2读......1609738706403
  线程：Thread-0读......结束1609738706918
  线程：Thread-2读......结束1609738706918
线程：Thread-3写>>>>>>> 1609738706918
  线程：Thread-3写>>>>>>>结束 1609738707434
线程：Thread-1写>>>>>>> 1609738707434
  线程：Thread-1写>>>>>>>结束 1609738707949
线程：Thread-5写>>>>>>> 1609738707949
  线程：Thread-5写>>>>>>>结束 1609738708465
线程：Thread-4读......1609738708465
线程：Thread-6读......1609738708465
  线程：Thread-6读......结束1609738708981
  线程：Thread-4读......结束1609738708981
线程：Thread-7写>>>>>>> 1609738708981
  线程：Thread-7写>>>>>>>结束 1609738709481
线程：Thread-8读......1609738709481
  线程：Thread-8读......结束1609738709996
线程：Thread-9写>>>>>>> 1609738709996
  线程：Thread-9写>>>>>>>结束 1609738710512
​
​
 */