这里的多线程中的sleep方法为什么不能用？小弟我加了try和catch,还是不行

public class ThreadTest{    public static void main(String[] args){        new ThreadTest().start();                }    public void start(){        ThreadNew tn = new ThreadNew();        Thread tn1 = new Thread(tn);        Thread tn2 = new Thread(tn);        Thread tn3 = new Thread(tn);            tn1.start();        tn2.start();        tn3.start();            }    }    class ThreadNew implements Runnable{        public void run(){        for(int i = 0;i <10000;i++){            System.out.println(" CURRENT:" + Thread.currentThread().getName());            sleep(1000);            }        }    }