[Java] Thread 创建线程的第二种方法

public class Thread4{     public static void main(String[] args){         //利用多态         Thread t = new RunnableTest3();         t.start();     } } //用继承Thread父类的方法来定义 class RunnableTest3 extends Thread{     @Override         public void run(){             for(int i= 0;i<20;i++){                 String str = Thread.currentThread().getName();                 System.out.println(str+":"+i);             }         } }