多线程，休眠线程。

public class Demo03 {
    public static void main(String[] args) throws InterruptedException {
        Test01();
        new Thread(){
            public void run(){
                for(int i = 0;i<10;i++){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(this.getName()+"aaaaa");
                }
            }
        }.start();
        new Thread(){
            public void run(){
                for(int i = 0;i<10;i++){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(this.getName()+"bbbbbbb");
                }
            }
        }.start();
    }
    public static void Test01() throws InterruptedException {
        for(int i = 20; i >= 0; i--){
            Thread.sleep(1000);
            System.out.println("倒计时第"+i+"秒");
        }
    }
}