多线程(2)

练习:创建两个线程,和主线程交替运行

package exercise;class Thread1 extends Thread{    public void run(){        for (int i = 0; i < 20; i++) {            System.out.println("thread1_____"+i);        }    }}class Thread2 extends Thread{    public void run(){        for(int i = 0;i<20;i++){            System.out.println("thread2___"+i);        }    }}public class Test {    public static void main(String[] args) {        // TODO Auto-generated method stub        Thread1 thread1 = new Thread1();        Thread2 thread2 = new Thread2();        thread1.start();        thread2.start();        for(int i = 0;i<20;i++){            System.out.println("main___"+i);        }    }}