A simple GUI-based application in JAVA, the application should include at least the following:

2.1 Windows

At least 3 windows, each one of them has a number of components. The main window should have menus.

2.2 Components

A number of sufficient-various components depending on the application that you are building.

2.3 Layout mangers

Arrange the components in each window using different layout managers, when possible.

2.4 Storage

Your application obviously will take some input from the user and store them in a storage.

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Likewise, the application will retrieve some data from a storage and prints them out to the user. For this purpose, you can user either DB or files.

2.5 Exception handling

Use Exception handling where needed (e.g., when entering an invalid input).

2.6 Colors, Fonts, Images

Make your program as user-friendly as you can by using Colors, Fonts, and Images.