实现两线程的同步

public class WaitAndNotifyDemo {
    public static void main(String[] args) throws InterruptedException {
        MThread mThread = new MThread();            
        synchronized (mThread) {
            try {        
                mThread.start();
                // 主线程睡眠3s
                Thread.sleep(3000);
                System.out.println("before wait");
                // 阻塞主线程
                mThread.wait();
                System.out.println("after wait");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }            
        }        
    }
}

class MThread extends Thread {
    public void run() {
        synchronized (this) {
            System.out.println("before notify");            
            notify();
            System.out.println("after notify");    
        }
    }
}