I can see a problem, I am afraid. You have got a method inside a display component which isn't part of the display. Testing whether the input is a number or not is part of your “business logic” and ought to be in a “business class”. Which isn't the opposite of economy class. You should have a method which tests whether the input is a number or not; the display class can take action, e.g. remove the entry from the text field.
There are better ways to test whether a String represents a number than catching Exceptions. You will find some suggestions in this thread from last Summer.