代码分析Java中线程的等待与唤醒
我们先来看一下实例代码:
classThreadAextendsThread{ publicThreadA(Stringname){ super(name); } publicvoidrun(){ synchronized(this){ System.out.println(Thread.currentThread().getName()+"callnotify()"); notify(); } } } publicclassWaitTest{ publicstaticvoidmain(String[]args){ ThreadAt1=newThreadA("t1"); synchronized(t1){ try{ //启动“线程t1” System.out.println(Thread.currentThread().getName()+"startt1"); t1.start(); //主线程等待t1通过notify()唤醒。 System.out.println(Thread.currentThread().getName()+"wait()"); t1.wait(); System.out.println(Thread.currentThread().getName()+"continue"); }catch(InterruptedExceptione){ e.printStackTrace(); } } } }
输出结果:mainstartt1->mainwait()->t1callnotify()->maincontinue
其实调用t1.start(),t1为就绪状态,只是main方法中,t1被main线程锁住了,t1.wait()的时候,让当前线程等待,其实是让main线程等待了,然后释放了t1锁,t1线程执行,打印t1callnotify(),然后唤醒main线程,最后结束;
这里说一下wait()与sleep()的区别,他们的共同点都是让线程休眠,但是wait()会释放对象同步锁,而sleep()不会;下面的代码t1结束之后才会运行t2;能够证实这一点;
publicclassSleepLockTest{ privatestaticObjectobj=newObject(); publicstaticvoidmain(String[]args){ ThreadAt1=newThreadA("t1"); ThreadAt2=newThreadA("t2"); t1.start(); t2.start(); } staticclassThreadAextendsThread{ publicThreadA(Stringname){ super(name); } publicvoidrun(){ synchronized(obj){ try{ for(inti=0;i<10;i++){ System.out.printf("%s:%d\n",this.getName(),i); //i能被4整除时,休眠100毫秒 if(i%4==0) Thread.sleep(100); } }catch(InterruptedExceptione){ e.printStackTrace(); } } } } }