This exercise implements an application to maintain a customer data.

Console

Operation

This application begins by displaying a menu with five choices: list, add, del, help, and exit.

• If the user enters list, the application displays the customer data that's stored in a text file.
• If the user enters add, the application prompts the user to enter data for a customer and saves that data to the text file.
• If the user enters del, the application prompts the user for an email address and deletes the corresponding customer from the text file.
• If the user enters help, the application displays the menu again.
• If the user enters exit, the application displays a goodbye message and exits.

Specifications

• Create a class named Customer that stores data for the user's email address, first name, and last name.
• Create interfaces named CustomerReader and CustomerWriter that define the methods that will be used to read and write customer data to a customer file. In addition, create an interface named CustomerConstants that contains three constants that specify the display size of a customer's email address (30), first name (15), and last name (15). Then, create an interface named CustomerDAO that inherits all three of these interfaces.
• Create a class named CustomerTextFile that implements the methods specified by the CustomerDAO interface. Store the customer data in a text file named "customers.txt" in the same directory as this class. If the customers.txt file doesn't exist, this class should create it. This class should use buffered I/O streams, and it should close all I/O streams when they're no longer needed.
• Create a class named DAOFactory that contains a method named getCustomerDAO. This method should return an instance of the CustomerTextFile class.
• Create a CustomerMaintApp class that displays the prompts shown in the console output and accepts the user entries. This class should use the DAOFactory class to get a CustomerDAO object. Then, it should use the methods of the CustomerDAO object to read customer data from the file and to write customer data to the file.
• Use the Validator class or a variation of it to validate the user's entries. Non-empty strings are required for the email address, first name, and last name.
• Use spaces to align the customer data in columns on the console. To do that, you can create a utility class named StringUtils with a method that adds the necessary spaces to a string to reach a specified length.

Option

For this exercise you have the option of creating GUI to maintain the customer data. It's more work, but it will help for the final test. The choice is yours.