Java项目中怎么让线程休眠

 // SleepTest.java的源码 class ThreadA extends Thread{   public ThreadA(String name){      super(name);    }    public synchronized void run() {      try {       for(int i=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();       }      } catch (InterruptedException e) {       e.printStackTrace();     }   }  }  public class SleepTest{    public static void main(String[] args){      ThreadA t1 = new ThreadA("t1");      t.start();    }  }