Objectives

Write methods and constructors

Use parameters to provide methods with input

Return values from methods

Query / Modify object state with methods

Specifications

Getting started

Download the HW3Starter.zip starter project from Moodle and import it into Eclipse.

Overview

In this homework you will write constructors and methods for a SnackMachine class that emulates a device where you can put some money in, select multiple items (gum, candy, and/or chips, in any quantity), and complete your order, receiving change if appropriate. The SnackMachine class in the starter project has the following instance variables and their getter methods:

gumPrice: the cost of one pack of gum

candyPrice: the cost of one bag of candy

chipsPrice: the cost of one bag of chips

gumInOrder: the total number of packs of gum currently in your order

candyInOrder: the total number of bags of candy currently in your order

chipsInOrder: the total number of bags of chips currently in your order

totalSales: the total sales (in dollars) sold by the machine (not just for the current order, but cumulative over all orders)

paymentTendered: the amount of money the user has put into the machine

Write the constructor

The constructor should have three parameters for the gum, candy, and chip prices (in that order).

The body of the constructor should set ALL of the instance variables. If an instance variable does not have an associated parameter then it should be set to zero.

Test by uncommenting all the code in the TestConstructor class and running it as a JUnit test. Fix any errors you find.

Refactor the constructor

Refactor a public changePrices() method from the constructor. This method will change the prices of the gum, candy, and chips, in that order.

Test the changePrices() method by uncommenting the code in the TestChangePrices class and running it as a JUnit test. Fix any errors that that you find.

Refactor a private helper method to reset the gumInOrder, candyInOrder, chipsInOrder, and paymentTendered instance variables to zero. Call this method resetOrder.

Refactor a private helper to reset totalSales to zero. Call this method resetMachine.

Re-run all tests and make sure you haven't introduced any new bugs.

Adding money

Write a putInMoney method that adds money to the current order (i.e., the paymentTendered) variable.

Uncomment the code in TestPutInMoney and run the JUnit tests. Fix any errors. If you have syntax errors, you have probably named your method incorrectly, or do not have the right number or type(s) of parameters. Rethink the needs of your method.

Adding items to the order

Write an addGumToOrder method that adds one or more packs of gum to the order.

Uncomment the code in TestAddGumToOrder and run the JUnit tests. Fix any errors.

Repeat steps 1 and 2 for addCandyToOrder and addChipsToOrder.

Calculating the total for the order

Write a getOrderTotal method that returns the total cost of the order, based on the price and quantity of each item.

Uncomment the code in TestGetOrderTotal and run the JUnit tests. Fix any errors.

Completing an order

Write a completeOrder method that "completes the order", i.e.,

figures out how much change (if any) is needed

increases the total sales by the order total

resets the order

returns the change

Uncomment the code in TestCompleteOrder and run the JUnit tests. Fix any errors.

Export the project

Export the project to a ZIP file FirstnameLastnameHW3.zip.

Upload the ZIP file to your Moodle account.

END OF EXERCISE

Submission notes

When uploading your file to Moodle, verify that you are uploading the correct one and verify the zip file is named FirstnameLastnameHW3 and submit the zip file in Moodle by the due date.

If you do not follow the specified naming convention, three points will be deducted from the score you would have received.

Grading breakdown

10 pts. Exercise completed successfully with at most only a minor error.

7 pts. Exercise is missing some functionality.

4 pts. Exercise is missing most of the major functionality.

0 pts. Exercise not submitted, does not compile, or barely started.