5.线程休眠

控制当前线程休眠若干毫秒

Thread.sleep(毫秒)
Thread.sleep(毫秒,纳秒)

1秒 = 1000毫秒 1秒 = 1000000000纳秒（1000 1000 1000)

    @Test
    public void demo1() throws InterruptedException {
        for(int i = 20; i >= 0; i--) {
            Thread.sleep(1000);
            System.out.println("倒计时第" +i + "秒");
        }
    }

    @Test
    public static void main(String[] args) {
        new Thread() {
            @Override
            public void run() {
                for(int i = 0; i < 10; i++) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(getName());
                }
            }
        }.start();
        new Thread() {
            @Override
            public void run() {
                for(int i = 0; i < 10; i++) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(getName());
                }
            }
        }.start();
    }