try/catch problem

I want the program to give an error message after the first input if none of the required operators are inputted. But my try catch isn't working? Also when exit is inputted it still as operator the 2nd and 3rd questions ("Enter 1stnum & Enter 2ndnum" are both asked instead of exitting immediately. Is this more of a design issue or can it be overcome? Any comments would be welcomed.

import java.util.Scanner;































































import java.io.*;

class Monday {































































public static void main(String[] args) {































































double n1,n2;































































boolean check = true;

while(check) {































































System.out.println("Enter your operation: add, subtract, divide, multiply, or exit");































































try{































































Scanner myScan = new Scanner(System.in);

String op = myScan.next();

System.out.println("Enter your 1st number");































































n1 = myScan.nextDouble();































































System.out.println("Enter your 2nd number");































































n2 = myScan.nextDouble();

switch (op) {































































case"add":































































System.out.println("Your answer is "+ (n1 + n2));































































break;

case"subtract":































































System.out.println("Your answer is "+ (n1 - n2));































































break;

case"divide":































































System.out.println("Your answer is "+ (n1 / n2));































































break;

case"multiply":































































System.out.println("Your answer is "+ (n1 * n2)) ;































































break;

case"exit":































































System.out.println("Goodbye!");































































break;

}

if ("exit".equals(op))































































check = false;

} catch (Exception e) {































































System.out.println("This is my error");

}































































}































































}































































}