Screenshot of the application

The main form just has a list of words and a button. When you press the button a subform pops up with a text field for you to enter a new word. When you enter a word, it is added to the list on the main form.

The code in this project can be adapted to your needs. It shows you how to:

Separate the interface from the logic of the program
Maintain and add to a list of objects (in this case strings)
Pop out a subform and have it pass information back to the main form
Update a listbox in the UI from the back-end logic

You will need all of these skills when you develop your own applications.

AppLogic Class

Has a way of holding a list of strings
Has a way of keeping count of how many strings there are
Can accept new strings and add them to the list
Can return the list of strings

Note: This is not a UI class. It knows nothing about the UI.

MainForm Class

This is the main form. Look principally at the button press code buttonActionPerformed. It:

instantiates and displays the subform
gets the text entered into the subform
asks the applogic to add the text
asks the applogic for the new list so it can update its listbox

SubForm Class

This is the subform. It allows you to enter a new word. Note particularly how we had to code a new method called getText() to allow the subform to give its text back to the parent.