Java小游戏--通过Enter计算自身手速

  System.out.print("游戏马上开始,请准备,按Enter键开始:");

        Scanner sc = new Scanner(System.in);

        sc.nextLine();
        System.out.println("游戏开始!!!");
        //游戏开始

        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.SECOND, cal.get(Calendar.SECOND) + 20);//二十秒的时间

        Date end = cal.getTime();
        long endlong = end.getTime();

        int count = 1;
        while (endlong - new Date().getTime() >= 0) {
            sc.nextLine();
            System.out.print("你按了第" + count + "次Enter键");
            count++;
        }
        System.out.println();
        System.out.println("游戏结束!! !");
        System.out.println("你一共在20秒内按了" + count + "次Enter");

        double Pin = count / 20.0;

        DecimalFormat dec = new DecimalFormat(".##");
        System.out.println("您的频率是" + dec.format(Pin) + "秒/次");
    }