Java:使用Executorservice和future作为计时器时如何打破循环？

Question

我正在尝试为一个简单的数学测验制作一个计时器，用户需要在 10 秒内回答问题，当时间超过时，它将加载到下一个问题。我找到了实现 Executorservice 和 future 的解决方案，但是当用户输入整数以外的其他输入时，它不断重复无效输入循环(数字格式异常)，我遇到了问题> 在我的游戏课上。

希望了解以下内容有用:MathQuestion 类(生成数学问题的地方)、Game(启动游戏回合)和 GameTimer 类。

游戏类:-

  //for 10 rounds of game
   for (int i=0; i<rounds; ++i)
   {
       System.out.println("*************************************");
       System.out.println("\nRound " + (i+1)
               + "\nEnter 'x' to quit game");

       System.out.println("\nQuestion:");
      //call method to generate question and get correct answer
      result = quiz.Questions();
      System.out.println("You have 10 seconds");

     //to make sure we read a line or interrupt it for the timer
     ExecutorService ex = Executors.newSingleThreadExecutor();
      try
     {
     //retrieve the actual result at a later point in time.
     Future<String> ans = ex.submit(new GameTimer());
     try {

      boolean validInput = false;

      do
      {

           System.out.println("\nEnter your answer: ");//prompt user input answer
          //10 secs wait to obtain result from player
          //wait until callable complete before return result
            answer = ans.get(10, TimeUnit.SECONDS);
           //answer = scan.nextLine();
           try
           {
               //valid player input
               pAnswer = Double.parseDouble(answer.trim()) ; //convert to double
               validInput = true;

           }catch (NumberFormatException e){ //other input other than integers *this the repeated loop  
            System.out.println("Invalid input. Please try again.");
            validInput = false;
            ans = ex.submit(new GameTimer()); //resubmit task solution
            }

           if (answer.trim().equalsIgnoreCase("x")) //player quit game
           {
               quit=true;
               break;
           }

      }while (!validInput);
    if (quit)
    {
     break;
    }
            //for correct answer
            if (Math.abs(Double.parseDouble(answer) - quiz.answer)  <= 0.01) {
            //add 10 points
            this.gamer.setScore(score+=10); 
            System.out.println("You got it right!");
        } 
        else //wrong answwer
        {
            //subtract 10 points
            this.gamer.setScore(score-=10);;
            System.out.println("You got it wrong!");

        }
        } catch (InterruptedException ex1) {
            Logger.getLogger(Game.class.getName()).log(Level.SEVERE, null, ex1);
        } catch (ExecutionException ex1) {
            Logger.getLogger(Game.class.getName()).log(Level.SEVERE, null, ex1);
        } catch (TimeoutException ex1) {
            System.out.println ("\nTime's up! Better luck next time~");
        }
    }finally {
      ex.shutdownNow(); //stop all running tasks and shut the executor down immediately.
    }

    }     

GameTimer 类:-

public class GameTimer implements Callable<String>  {


public String call() throws IOException {
BufferedReader inp = new BufferedReader(new InputStreamReader(System.in));
String input = "";
while ("".equals(input)) {
  try {
    while (!inp.ready()) {
      Thread.sleep(1000);
    }
    input = inp.readLine();
  } catch (InterruptedException e) {
    return null;
  }
} 
return input;
}
}

这是输出循环问题的图片:loop problem

我已经尝试寻找计时器的解决方案很长一段时间了，如果有人可以提供帮助，我将非常感激。非常感谢。

*附加:有没有办法显示计时器倒计时(例如:10 9 8..)，但当新的秒计数出现时删除前一秒？

(不删除建议也有帮助，谢谢!)

Answer 1

你不能一直重新调用get。您的任务是可执行文件，您提交它然后它就会运行。你调用 .get ，它就会得到你的执行结果。您需要重新提交任务，例如:

catch (NumberFormatException e){ //other input other than integers *this the repeated loop  
    System.out.println("Invalid input. Please try again.");
    validInput = false;
    ans = ex.submit(new GameTimer());
}

您可能想要跟踪自每次调用 get 时使用相同的超时以来所耗时。

在我看来，您应该将错误处理放在可调用中。

final String question = "Enter double value";
Callable<Double> getDouble = ()-{

     BufferedReader inp = new BufferedReader(neww InputStreamReader(System.in));
     while (!Thread.currentThread().isInterupted()) {
         System.out.println(question);
         try {
             String input = inp.readLine();
             Double v = Double.parseDouble(v);
             return v;
         } catch(Exception e){
             if( Thread.currentThread().isInterrupted()){
                 return null;
             }
             System.out.println("Invalid Input, try again");
         }
     } 

}

现在，当您提交任务时，您不必担心无效的 double 值，因为它是在可调用任务中处理的。

Future<Double> ans = ex.submit(getDouble);
Double v = ans.get(10, TimeUnit.SECONDS);

这会留下一个问题:任务即使被取消，仍然会等待标准输入。解决此问题的最简单方法是告诉用户按 Enter 键继续。