public class Ex8_2 {

    public static void main(String[] args) {
        //创建并命名每个线程
        TestThread thread1 = new TestThread("thread1");
        TestThread thread2 = new TestThread("thread2");
        TestThread thread3 = new TestThread("thread3");
System.out.println("Starting threads");
 thread1.start(); // 启动线程1
        thread2.start(); // 启动线程2
        thread3.start(); // 启动线程3
 System.out.println("Threads started, main ends\n");}  }
class TestThread extends Thread {private int sleepTime;
 public TestThread(String name)//构造函数
    { super(name);  //调用基类构造函数为线程命名
      sleepTime = (int) (Math.random()*600);//获得随机休息毫秒数
    } @Override
    public void run() //run方法是线程启动并开始运行后要执行的方法
    {
        try {
            System.out.println(
                    getName() + " going to sleep for " + sleepTime);

            Thread.sleep(sleepTime); //线程休眠
        } catch (InterruptedException exception) {
            exception.printStackTrace();
        }
        System.out.println(getName() + " finished");//运行结束，给出提示信息
    }
}