Operations of Class Keypad
From the phrase “receives numeric input from the user” listed by class
Keypad in Fig. 22.16, we conclude that class
Keypad should perform a
getInput operation. Because the ATM’s keypad, unlike a computer keyboard, contains only the numbers 0–9, we specify that this operation returns an integer value. Recall from the requirements document that in different situations the user may be required to enter a different type of number (e.g., an account number, a PIN, the number of a menu option, a deposit amount as a number of cents). Class
Keypad simply obtains a numeric value for a client of the class—it does not determine whether the value meets any specific criteria. Any class that uses this operation must verify that the ...