Switch Calculator with Try Catch Exceptions

Scanner keyboard = new Scanner (System.in);

     try
     {
        System.out.print("Enter number:  ");
        double num1 = keyboard.nextDouble();
        System.out.print("Enter number:  ");
        double num2 = keyboard.nextDouble();
        System.out.print("Enter operator:  ");
        String op = keyboard.next();
        System.out.println(num1 + " " + op + " " + num2);
        switch(op) {
        case "+":
            System.out.println (num1 + num2);
             break;
        case "-":
            System.out.println  (num1 - num2);
            break;
        case "*":
            System.out.println (num1 * num2);
            break;
        case "/":
            System.out.println (num1 / num2);
            break;
        case "!":
        System.out.println(Math.pow(num1, num2));
        break;
        default:
                System.out.println("You have not entered a valid operator!");

          }
      }catch(Exception e) {
         System.out.println("You did not enter number!");

      }