HW1: Duke-n-Donuts v1

Homework 1

Learning Objectives

This homework assignment is designed to help you learn several things. First, it will help you learn about data types, variables, literals, arithmetic operators, how utility classes are organized, static attributes, and declaring static methods. Second, it will help you become comfortable with some of the tools that you will be using throughout the semester. Third, it will help you become comfortable with the various policies (including submission policies) that you must comply with while working on homework assignments and programming assignments this semester.

Overview

A group of former JMU students have decided to open a bakery called Duke-n-Donuts. They have asked you to create a utility class named DonutPricer that they can use to calculate the price of a particular order. All types of donuts are priced the same way and all donuts are “delivered” in a box (that may be full or partially full). The number of donuts that fit in a full box is given by BOX_SIZE. The price of a full box of donuts is given by PRICE_PER_BOX and the price of an individual donut is given by PRICE_PER_INDIVIDUAL.

The Class to be Written

You must write the DonutPricer class.

The UML Class Diagram

The following UML class diagram provides an overview of the attributes and methods in this class (which must be in the default package).

Detailed Design Specifications

In addition to the specifications contained in the UML class diagram, this class must conform to the following specifications.

1. All of the “constants” must be declared to be final.
2. All of the methods that are passed a number of donuts and return a number (whether an int or a double) must return 0 when the number of donuts is less than or equal to 0. (Note: There is a method that is passed a number of donuts and returns a boolean. The specifications for that method are given below.)
3. numberOfFullBoxes() and numberOfBoxes() must return the number of full boxes and the total number of boxes required to hold the order. So, for example, an order of 98 donuts will require 8 full boxes and 9 boxes in total.
4. numberOfExtras() must return the number of donuts in the order that will be in a box that isn’t full. So, for example, an order of 98 donuts will have 2 extras (since 96 of the donuts will be in full boxes).
5. needAnExtraBox() must return true if there are extra donuts (i.e., donuts that won’t be in a full box) in the order and must return false otherwise. This method must not use an if statement, loop, or ternary operator.
6. priceFor() must return the price of an order of the given size. When a customer orders less than a full box, they pay the individual price for each donut. So, for example, an order of 6 donuts will have a price of $5.94. When a customer orders a full box, they pay the price of a full box. For example, an order of 12 donuts will have a price of $9.99. Finally, when a customer orders more than a full box, they pay the price of however many full boxes there are plus the cost of the extras. For example, an order of 98 donuts will have a price of $81.90 (8 boxes at $9.99 plus 2 extras at $0.99 each).
7. Methods must not duplicate the code in other methods unless it is absolutely necessary (e.g., for parameter validation). Instead, methods must invoke each other as needed.

An Existing Class

A main class (i.e., a class with a main() method) that you can use to test the DonutPricer class has already been written. It is named DonutPricerTest and the source code (i.e., the .java file) is available at:

📄 DonutPricerTest.java

Submission

You must submit (using Gradescope):

1. Your implementation of the DonutPricer class. Do not include the DonutPricerTest class.

There is no limit on the number of submissions and no penalty for excessive submissions. Note that your submission will not be graded if it does not comply with the specifications. So, if you do not complete the DonutPricer class your submission should include a stubbed-out version of all of the methods. This will allow you to potentially get credit for the methods that you do implement.

Grading

Your code will first be graded by Gradescope and then by the Professor. The grade you receive from Gradescope is the maximum grade that you can receive on the assignment

Gradescope Grading

Your code must compile (in Gradescope, this will be indicated in the section on “Does your code compile?”) and all class names and method signatures must comply with the specifications (in Gradescope, this will be indicated in the section on “Do your class names, method signatures, etc. comply with the specifications?”) for you to receive any points on this assignment. Gradescope will then grade your submission as follows:

Gradescope will provide you with hints, but may not completely identify the defects in your submission.

Manual Grading

After the due date, the Professor may manually review your code. At this time, points may be deducted for inelegant code, inappropriate variable names, bad comments, etc.

Recommended Process

Since nobody will be looking over your shoulder, you can use any process that you would like to use. However, it is strongly recommended that you use the process described here.

Get Started

1. Read and understand the entire assignment.
2. Create a project for this assignment named hw1. (Remember, do not create a module and create separate folders for source and class files).
3. Activate Checkstyle for this assignment.
4. Download DonutPricerTest.java to a directory outside of your Eclipse workspace (e.g., the downloads directory for this course).

Understand the Test Cases

1. Read and understand the test cases in DonutPricerTest.java.
2. By hand (i.e., using pencil and paper), calculate the expected answer for each of the test cases in DonutPricerTest.java.

Stub-Out DonutPricer.java

1. Create a version of the DonutPricer class that contains all of the methods (with appropriate signatures), each of which should return 0, 0.0, or false as appropriate. (Remember: All of the classes you write for this assignment must be in the default package. So, when you create a new class in Eclipse, make sure that the “Package” field is blank.)
2. Add the “javadoc” comments to the DonutPricer class and the methods in it. (Help on javadoc comments is available on the Department’s Wiki.)
3. Check the style of the DonutPricer class and make any necessary corrections.

Add DonutPricerTest.java to the Project

1. Add DonutPricerTest.java to the project. (Help on adding source files to a project is available on the Department’s Wiki.)
2. Make sure there are no compile-time errors in DonutPricerTest.java. If there are, you probably need to fix the stubbed-out version of DonutPricer.java (since there should be no syntax errors in DonutPricerTest.java).

Implement and Test the DonutPricer Class

1. Add the “constants”.
2. Add the numberOfFullBoxes() method.
3. Run the DonutPricerTest class and make sure that all of the answers returned by the numberOfFullBoxes() method are correct.
4. Debug numberOfFullBoxes() if necessary.
5. Add the numberOfExtras() method.
6. Run the DonutPricerTest class and make sure that all of the answers returned by the numberOfExtras() method are correct.
7. Debug numberOfExtras() if necessary.
8. Add the needAnExtraBox() method.
9. Run the DonutPricerTest class and make sure that all of the answers returned by the needAnExtraBox() method are correct.
10. Debug needAnExtraBox() if necessary.
11. Add the numberOfBoxes() method.
12. Run the DonutPricerTest class and make sure that all of the answers returned by the numberOfBoxes() method are correct.
13. Debug numberOfBoxes() if necessary.
14. Add the priceFor() method.
15. Run the DonutPricerTest class and make sure that all of the answers returned by the priceFor() method are correct.
16. Debug priceFor() if necessary.

Help

Help with Eclipse and help with Gradescope are available on the Department’s Wiki.

Questions to Think About

You don’t have to submit your answers to these questions, but you should try to answer them because they will help you determine whether or not you understand some of the important concepts covered in this assignment.

1. What compile-time errors (if any) do you get in DonutPricer.java class if you make the attributes non-static? Why?
2. What compile time errors (if any) do you get in DonutPricer.java if you make all of the methods non-static? Why?
3. What compile-time errors (if any) do you get in DonutPricerTest.java if you make the methods in DonutPricer.java non-static? Why?
4. Why does the recommended process have you test and debug each method immediately after you implement it?
5. Why does the recommended process have you implement the methods in the order it does? For example, why does it have you implement numberOfBoxes() after it has you implement numberOfExtraBoxes() and needAnExtraBox()?