多线程编程<二>

wait()与notify():

public class ThreadComDemo {
    public static void main(String[] args) {
        try {
            SyncOb sObj= new SyncOb();
            
            new MyThread("MyThread", sObj);
            
            for (int i = 0; i < 10; i++) {
                Thread.sleep(250);
                System.out.print(".");
            }
            System.out.println();
            
            sObj.goAhead();
        } catch (InterruptedException e) {
            System.out.println("Main thread interrupted.");
        }
    }
}


class MyThread implements Runnable {
    SyncOb syncOb;
    
    public MyThread( String name, SyncOb so) {
        syncOb = so;
        new Thread(this, name).start();
    }

    @Override
    public void run() {
        syncOb.waitFor();\\线程睡眠
    }
}

class SyncOb {
    boolean ready = false;
    synchronized void waitFor() {
        String thrdName = Thread.currentThread().getName();
        System.out.println(thrdName + " is entering waitFor().");
        
        System.out.println(thrdName + " calling wait() to wait for " + "notification to proceed.\n");
        
        //调用wait()方法，这会使线程睡眠，并且会释放该对象的监视器。这样就允许另一个线程使用对象。
        //在另一个线程进去同一个监视器并调用notify()之后，睡眠的线程会被唤醒。
        try {
            while(!ready) wait();//此处用的是while循环，而不是if.防止假唤醒。
        } catch (InterruptedException e) {
            System.out.println("Interrupted");
        }
        System.out.println(thrdName + " received notification and is" + " resuming execution.");
    }
    
    synchronized void goAhead() {
        String thrdName = Thread.currentThread().getName();
        System.out.println("\n" + thrdName + " thread calling notify() inside goAhead().\n" + 
        "This will let MyThread resume execution.\n");
        ready = true;
        notify();
    }
    
}