如何在Java项目中实现多线程的阻塞与唤醒

//测试sleep（）方法class Thread7 implements Runnable{  @Override  public void run() {    for(int i=0;i<50;i++){      System.out.println(Thread.currentThread().getName()+"num="+i);      try {        Thread.sleep(500);      } catch (InterruptedException e) {        e.printStackTrace();      }    }  }}class Thread8 implements Runnable{  @Override  public void run() {    for(int i=0;i<1000;i++){      System.out.println(Thread.currentThread().getName()+"num="+i);    }  }}public static void main(String[] args) {        //测试sleep（）方法    Thread7 t7=new Thread7();    Thread8 t8=new Thread8();    Thread t81=new Thread(t8, "饺子");    Thread t71=new Thread(t7, "包子");    Thread t72=new Thread(t7, "面包");    t71.start();    t81.start();    t72.start();  }