INFO-I211 Lab 4
Graphical User Interface

Due date: see Oncourse Modules or Assignments
50 points

Learning Objectives

1. Be able to develop a simple GUI (graphical user interface) in Java.
2. Use the if/else statement.
3. Be familiar with some useful Unix commands.

Part A: GUI

Instructions

In Lab 3, you developed one of the following programs:

• PP 3.1 User name generator
• PP 3.5 Sphere volume and surface area with formatting
• PP 3.6 Area of triangle with formatting

This program had a console-based, text user interface.

Modify the program (or a copy of the program) to give it a graphical user interface (GUI).

Your GUI must have these components:

• One or more JTextfields for user input.
  • Each of these needs to be identified with a JLabel, similar to the prompt in the text version of the program.
• A JButton to compute the result.
• One or more JLabels (or non-editable JTextfields) to display the result of the computation.
• A JButton to quit from the program.

You should be able to enter new data and have your program compute and display results for as many times as the first button is clicked, and quit when the second button is clicked.

Stage 1: GUI (One Working Button)

Prerequisite: Chapters 1–4, including GUI material.

Build the graphical user interface. It needs the components listed above.

• If you use a JTextField (instead of a JLabel) for the result, call result.setEditable(false) so the user cannot enter text in it. You can use result.setText("text") to change what it displays, the same as a JLabel. A JTextField may be less pretty than a JLabel, but its width is more stable.
• For now, assume that the only button clicked is the one to compute the result, and your actionPerformed method only has to deal with this case. Use the “X” window close control to quit from the program.
• Don’t worry too much about the layout (geometrical arrangement) of the GUI components. Simply let the JPanel arrange its components using its default layout manager. We will learn how to control layout in a later chapter.

Stage 2: GUI (Two Working Buttons)

Prerequisite: Sections 5.1–5.2 (if statement) and 5.7 (determining event sources).

• Modify your actionPerformed method, using an if/else statement to discriminate between the two possible event sources (the compute and quit buttons).
  • To respond to the quit button, make the static method call System.exit(0).
  • The compute button should now compute and display the result; the quit button should now quit from the program, closing its window.

Part B. Useful Unix Commands.

Read Unix Tutorial Six: Other Useful Unix Commands and try out the commands as suggested there, or in other ways.

• Quotas are not implemented on merlin, so the quota command will give you no output.

• Run the file command on the files in your project (i.e., for this lab—Java source and class files, screenshot files, etc.). Capture the output and turn it in as a text file (preferred) or screenshot.

What to Turn in

Turn in, as attachments in Oncourse Assignments:

• Java source code.
• Screenshots showing your program’s result for some test data (show two or three different cases).
• Text file or screenshot showing the results of the file command.

Grading Criteria

• 35 points, correctness
  • 5 for continued correctness of the project from Lab 3
  • 30 for GUI
• 10 points, program style.
• 5 points, output of file command

The Coding Standards for chapters 1–6 apply to this assignment.