0. Executive Summary

This is the second graded lab for CS2102.

1. Stated Aims

1. Learn how to write a class from scratch
2. Learn how to develop JUnit test case(s) to test the newly-defined class.
3. Learn how to modify an existing class

2. Background knowledge

1. Understand concept of class
2. Understand instance variable
3. Understand instance method

3. Setup

If you are in the Lab, perform the routine KH 202 setup or AK 120D setup; for now, ignore the "advanced setup" options. If you would like to set up  Eclipse on your personal computer, then (a) install Java JDK 1.5 if you need to as described in tools section (here); and (b) install Eclipse as described in tools section (here).

Make sure you have read pp. [177-194] from the textbook.

4. Individual Tasks

4.1 Design a Class Precinct

A Precinct represents "the lowest-level minor civil division in the United States". Each precinct has a name (i.e., "K12") an address where voters can vote (i.e., "130 Winter Street") and a total number of voters in the precinct (i.e., 673).

• Create a project in which to work (or reuse one of your own)
• Create a package "username.lab2"
• Create a class Precinct in this package.
• Create Precinct instance variables name, address, and population to reflect this data. Make name and address instance variables of type String, while population can be an int instance variable.

Now consider how instances of this class are to be used. Let's write a small program to create a new Precinct object and assign it some relevant information.

• Create a class in your lab package named "PrecinctProgram". Make sure that this class has a defined "public static void main (String args[])" method in which the following code is to be written.

To complete your class, add three methods:

• Create a public String toString() method to Precinct. It should return the String "Precinct: PREC-NAME, Address: PREC-ADDR, Population: PREC-POPULATION" where each of these capitalized words is replaced with the actual instance variable.
• Create a public void add (int num) method that increments the population by the given fixed amount.
• Create a public void remove (int num) method that decrements the population by the given fixed amount.

Now go back to your main method in PrecinctProgram, and update it to use these instance methods:

This "test" program is not going to be completely suitable for our purposes. We need something more formal and repeatable. The next task accomplishes this.

4.2 Design the JUnit test case

We will see how we use testing to validate each of our designs as we proceed. By starting testing early, we avoid numerous complications that occur because we either (a) run out of time to test; or (b) forget to test key units.

First, to become familiar with JUnit, follow the small example posted on the course tools page. In this tools page, you will create your first JUnit test case, to validate the add method.

For this lab, you are to:

• Write a test case (in its own instance method) that validates the remove method.
• Write a test case (in its own instance method) that validates the toString method. Note that you should validate the results on several possible permutations (change the name, change the address, change the population, etc...)

5. Follow-up Tasks

Your goal is to turnin the assignment file(s) (Precinct.java and PrecinctTest.java) by November 8th at 11:59 PM. The name of the assignment you should use is "lab2".

6. Change History