Immutable Objects

Background

For this lab you will create a class named CSColor. Java already comes with its own Color class (check out the documentation and source code), but we are going to create a simple variant of that class. This lab was originally designed by Prof. Arch Harris with modifications by Chris Mayfield.

Objectives

• Implement methods that accept objects as parameters.

• Implement methods that return an object of the class.

Part 1: Getting Started

1. Download a copy of Main.java. This file provides the main method you will use to test your implementation of CSColor.

2. Download a copy of CSColor.java. Read the documentation for the CSColor class that this file implements.

3. Normally, to run a Java program that has the main method in a file named Main.java, you would run the following command.

   java Main

   But instead of sending the program output to the screen, we want the output to go to a file. So run today's lab with the following command.

   java Main > output.html

   This will create a file named output.html which you should view in a web browser.

Part 2: Implementation

1. Look at the parts of CSColor that have already been completed.

   • A number of constants have been defined. Those constants are public so they may be used outside of the class (you should note that those constants are referenced in Main.java).

   • Three instance variables are defined. Every CSColor object that is created will have its own copy of those three instance variables. Those instance variables are private so they can only be accessed by methods in the class.

   • The methods toString, add, and dim have already been finished. Look at those methods and ask questions about anything that you do not understand.

2. Implement the constructor. Recall that a constructor's job is to initialize an object to a particular state. Compile your Java files and run the main program as specified below. The top portion of the html file that outputs the constants should work properly after you complete the constructor.

3. Implement the other methods, one at a time. Rerun the program after implementing each method to test the implemented method. Make sure a method is working correctly before moving on to the next method.

4. When you have everything working, open two browser windows: one with your web page and one with the sample output page. Ask a TA or instructor to verify that your program produces the correct output.

Submit your CSColor.java file via Web-CAT.