J.3. Class Screen

Class Screen (Fig. J.2) represents the screen of the ATM and encapsulates all aspects of displaying output to the user. Class Screen simulates a real ATM's screen with the computer monitor and outputs text messages using standard console output methods Console.Write and Console.WriteLine. In the design portion of this case study, we endowed class Screen with one operationDisplayMessage. For greater flexibility in displaying messages to the Screen, we now declare three Screen methodsDisplayMessage, DisplayMessageLine and DisplayDollarAmount.

Method DisplayMessage (lines 811) takes a string as an argument and prints it to the screen using Console.Write. The cursor stays on the same line, making this method appropriate for displaying prompts to the user. Method DisplayMessageLine (lines 1417) does the same using Console.WriteLine, which outputs a newline to move the cursor to the next line. Finally, method DisplayDollarAmount (lines 2023) outputs a properly formatted dollar amount (e.g., $1,234.56). Line 22 uses method Console.Write to output a decimal value formatted as currency with a dollar sign, two decimal places and commas to increase the readability of large dollar amounts.

J 4 Class Keypad