Project: address-book-v3t
Authors: David J. Barnes and Michael Kölling

This project is part of the material for chapter 12 of the book

   Objects First with Java - A Practical Introduction using BlueJ
   Fifth edition
   David J. Barnes and Michael Kölling
   Pearson Education, 2012

A simple address-book implementation.
This version includes some argument-validity checking.

How to start this project:
    Either: Create an AddressBook object and add
    contact details (such as name, address, and phone) to it.
    Or: create an AddressBookDemo and call its showInterface method.
    This will create a sample AddressBook along with a text
    interface for the purposes of interactive experimentation.