public static void shutdown(){

         System.out.print("請輸入多少分鐘后關機:");
         Scanner scanner = new Scanner(System.in);
         int minute = scanner.nextInt()*60;
         Runtime runtime = Runtime.getRuntime();
         String shutdown = "shutdown -s -t "+minute;
         try {
             runtime.exec(shutdown);
         } catch (IOException e) {
             e.printStackTrace();
         }
     }