Lab 4

September 25, 2007 This will be an individual assignment, everyone should do their own work, on your own, etc. etc.

You will take the CashRegister class and manipulate the class to do a few extra things.
First:

You will type in the CashRegister class from the book (pages 130, 131). If you didn't bring your book I will have handouts in the lab for you to see the class. Make sure you understand where the instance fields are, the methods, returnValues, input parameters, etc. etc. Compile Often. Understand the code.
After you get it typed in and it compiles you will create another class to test it. Start a new class and type in the CashRegisterTester class from page 131 in the book.
Now enhance the CashRegister class by adding separate methods enterDollars, enterQuarters, enterDimes, enterNickels, and enterPennies.
Complete each method with returnValues, input parameters and all the code that goes with each method to complete what the method should be accomplishing.

Use this Tester class to make sure your five new methods work:

	public class CashRegisterTester2
	{
		public static void main(String [] args)
		{
			CashRegister register = new CashRegister();
			register.recordPurchase(20.37);
			register.enterDollars(20);
			register.enterQuarters(2);
			System.out.println("Change: " + register.giveChange());
			System.out.println("Expected: 0.13");
		}
	}

Now Enhance the CashRegister class so that it keeps track of the total number of items in a sale. Count all the recorded purchases and supply a method:

int getItemCount()
That returns the number of items of the current purchase. Remember to reset the count at the end of the purchase.

New Stuff

This program has a new feature we haven't talked about yet and that's a constant. A constant is a variable that can't be changed anywhere in the program.
The keyword for a constant is final. When you declare a instance field as a final you have to give it a value at the time of declaration and that value can't change throughout the program. Here is one of the constants in this program:

public static final double QUARTER_VALUE = 0.25;

The book also calls them static, but a final doesn't have to be static. For now make sure you use them the same way the book uses them.
The other thing that you should see in a final is the variable name is always in all capital letters. This tells other programmers that the variable is a constant.