JAVA concurrent programming 4

Description: Code first, and notes will be added later. 
public class ScheduleTest1 { 

    private static long start; 

    private static ScheduledExecutorService executorService = Executors.newScheduledThreadPool(2); 

    /** 
     * If timer.schedule plus sleep, the output is 1001 6005 
     * The sleep of the first thread will affect the second 
     * If the first thread hangs up, the next thread will not execute * 
     timer is related to the system time 
     * 
     * The above problems will not occur when using executorService 
     * 
     * @param args 
     */ 
    public static void main(String [] args) { 
        TimerTask task = new TimerTask() { 
            @Override 
            public void run() { 
// System.out.println(System.currentTimeMillis()-start); 
// try {
//                    Thread.sleep(5000);
//                } catch (InterruptedException e) {
//                    e.printStackTrace();
//                }
                throw new RuntimeException();
            }
        };

        TimerTask task1 = new TimerTask() {
            @Override
            public void run() {
                System.out.println(System.currentTimeMillis()-start);
            }
        };

        Timer timer = new Timer();
        start = System.currentTimeMillis();
//        //1s后执行
//        timer.schedule(task,1000);
//        //3s后执行
//        timer.schedule(task1,3000);

        executorService.schedule(task,1000, TimeUnit.MILLISECONDS);
        executorService.schedule(task1,3000, TimeUnit.MILLISECONDS);
    }
}