ScheduledExecutorService的使用 (如何关闭一个任务)

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

public class ScheduledExecutorServiceTest
{
       public static void main(String[] args) throws InterruptedException,ExecutionException
       {
              //*1
               ScheduledExecutorService service=Executors.newScheduledThreadPool(2);
               //*2
               Runnable task1=new Runnable()
               {
                    public void run()
                    {
                       System.out.println("Taskrepeating.");
                    }
               };
               //*3
               final ScheduledFuture future1=service.scheduleAtFixedRate(task1,0,1,TimeUnit.SECONDS);
               //*4
               ScheduledFuture future2=service.schedule(new Callable()
            {
                    public String call()
                    {
                            future1.cancel(true);
                            return "taskcancelled!";
                    }
               },10,TimeUnit.SECONDS);
               System.out.println(future2.get());
     //*5
     service.shutdown();
   }
}

这个例子有两个任务，第一个任务每隔一秒打印一句“Taskrepeating”,第二个任务在5秒钟后取消第一个任务。