notify()与notifyAll()

男娘i 2022-06-16 10:52 183阅读 0赞

notifyAll()调用时，并非唤醒所有的等待线程，而是当nofityAll()因某个特定锁而被调用时，只有等待这个锁的任务才会被唤醒。

class Blocker{
        synchronized void waitingCall(){
            try {
                while(!Thread.interrupted()){
                    wait();
                    System.out.println(Thread.currentThread()+" ");
                }
            } catch (InterruptedException e) {
                //Ok to exit this way
            }
        }
        synchronized void prod(){
            notify();
        }
        synchronized void prodAll(){
            notifyAll();
        }
    }
    class Task implements Runnable{
        static Blocker blocker=new Blocker();
    
        @Override
        public void run() {
            blocker.waitingCall();
        }
    }
    class Task2 implements Runnable{
        static Blocker blocker=new Blocker();
    
        @Override
        public void run() {
            blocker.waitingCall();
        }
    }
    public class NotifyVsNotifyAll {
        public static void main(String[] args) throws Exception{
            ExecutorService exec= Executors.newCachedThreadPool();
            for(int i=0;i<5;i++)
                exec.execute(new Task());
            exec.execute(new Task2());
            Timer timer=new Timer();
            timer.scheduleAtFixedRate(new TimerTask() {
                boolean prod=true;
                @Override
                public void run() {
                    if(prod){
                        System.out.println("\nnotify()");
                        Task.blocker.prod();
                        prod=false;
                    }else{
                        System.out.println("\nnotifyAll() ");
                        Task.blocker.prodAll();
                        prod=true;
                    }
                }
            },400,400);
            TimeUnit.SECONDS.sleep(5);
            timer.cancel();
            System.out.println("\nTimer canceled");
            TimeUnit.MILLISECONDS.sleep(500);
            System.out.println("Task2.blocker.prodAll()");
            Task2.blocker.prodAll();
            TimeUnit.MILLISECONDS.sleep(500);
            System.out.println("\nShutting down");
            exec.shutdown();
        }
    }

Task和Task2每个都有自己的Blocker对象，因此每个Task对象都会在Task.blocker上阻塞，而每个Task2都会在Task2.blocker上阻塞。