Scanner sca1 = new Scanner(System.in);

  while (sca1.hasNext()) {

   String a = sca1.nextLine();

   char[] char1 = a.toCharArray();// 把字串轉字元陣列
   for (int i = 0; i < char1.length; i++) {
    char1[i] = (char) (char1[i] - 7);

   }

   for (int i = 0; i < char1.length; i++)
    System.out.print(char1[i]);
   System.out.print("\n");
  }