9、编写一个 Java 程序实现多线程，在线程中输出线程的名字，隔300毫秒输出一次，共 输出20次。
//programme name TestThread;
//声明一个子线程类Threaddemo;
class ThreadDemo extends Thread{ public ThreadDemo(String str){ super(str);
}
public void run(){
for(int i=0;i<20;i++){
System.out.print(""+this.getName());
Try{
Sleep(300);
}catch(InterruptedException e){
System.out.println(e.getMessage();
Return;
}
}
System.out.println(" /end");
}
public class TestThread {
public static void main(String args\[\]){
ThreadDemo thread1=new ThreadDemo("T1");
ThreadDemo thread2=new ThreadDemo("T2");
ThreadDemo thread3=new ThreadDemo("T3");
thread1.start();
thread2.start();
thread3.start();