Java多线程之-Sleep方法详解

sleep方法详解

• 作用：我只想让线程在于其的时间执行，其他时候不要占用CPU资源。
• 特点
  • 不释放锁 包括synchronize 和lock 和wait不同

public class SleepDontReleaseMonitor implements Runnable {

    public static void main(String[] args) {
        SleepDontReleaseMonitor sleepDontReleaseMonitor = new SleepDontReleaseMonitor();
        Thread thread1 = new Thread(sleepDontReleaseMonitor);
        Thread thread2 =new Thread(sleepDontReleaseMonitor);
        thread1.start();
        thread2.start();
    }
    public void run() {
        syn();
    }

    private synchronized void syn()  {
        System.out.println("线程" + Thread.currentThread().getName()+"获取到monitor。");
        try{
            Thread.sleep(5000);
        }catch (Exception e){
            e.printStackTrace();
        }
        System.out.println("线程" + Thread.currentThread().getName()+"睡眠结束。退出同步代码块");
    }
}

可以看出线程在sleep()时并不会把锁给释放。

---

Sleep 同时也并不会释放Lock锁

public class SleepDontReleaseLcok implements  Runnable {
    private static final Lock lock = new ReentrantLock();
    public void run() {
        lock.lock();
        System.out.println("线程" +Thread.currentThread().getName() +"获取到了锁");
        try {
            Thread.sleep(5000);
            System.out.println("线程" +Thread.currentThread().getName() +"已经唤醒");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            lock.unlock();
        }

    }

    public static void main(String[] args) {
        SleepDontReleaseLcok sleepDontReleaseLcok = new SleepDontReleaseLcok();
        Thread  thread1 = new Thread(sleepDontReleaseLcok);
        Thread  thread2 = new Thread(sleepDontReleaseLcok);
        thread1.start();
        thread2.start();
    }
}

sleep方法响应中断

1. 抛出InterruptedException
2. 清除中断状态

public class SleepInterrupt implements  Runnable{
    public static void main(String[] args) throws InterruptedException {
        Thread thread1 =  new Thread(new SleepInterrupt());
        thread1.start();
        Thread.sleep(6500);
        thread1.interrupt();

    }

    public void run() {
        for(int i =0;i<10;i++){
            System.out.println(new Date());
            try{
                //sleep7小时 5 分钟 3秒
                TimeUnit.HOURS.sleep(7);
                TimeUnit.SECONDS.sleep(5);
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                System.out.println("被中断了!");
                e.printStackTrace();
            }

        }
    }
}

sleep方法可以让线程进入Watting状态,并且不占用CPU资源，但是不释放锁，直到规定时间后再执行，休眠期间如果被中断，会抛出异常并清除中断状态。

sleep方法—常见面试问题

wait/notify、sleep异同

• 相同
  • 阻塞(都会阻塞线程)
  • 响应中断(都会相应线程中断 并清除中断状态)
• 不同
  • 同步方法中(wait/notify 必须在同步方法块 中 而sleep不需要 为什么?线程更安全防止死锁和永久等待)
  • 释放锁(wait会释放锁 但是sleep不会)
  • 指定时间(sleep 要指定时间)
  • 所属类(wait/notify 属于Object 类 sleep 属于Thread类 为什么放Object类? java设计每一个类都是一把锁 对象头都有记录锁的字段)