Homework 01 – Grocery Shopping

Topics: Classes and objects, encapsulation, constructors, visibility modifiers, getters, setters

Problem Description

It’s the weekend and that means you need to make a quick run to the grocery! You can now use your       knowledge of object-oriented programming to help keep track of all the things you are going to buy. To   do this you will create three files: Dairy.java, Bakery.java, and ShoppingCart.java to keep track of your groceries.

Solution Description

Create Dairy.java which will represent the things you buy from the Dairy section, Bakery.java to represent the things you buy from the Bakery section, and ShoppingCart.java which will hold all the things you have bought. You will be creating several fields and methods for each file. Based on  the description given for each variable and method, you will have to decide whether the variables and methods should be static, and whether they should be private or public. To make these decisions, you should carefully follow the guidelines on these keywords as covered in lecture. In some cases, your      program will still function with an incorrect keyword.

HINT: A lot of the code you will write can be reused. Try to think of what keywords you can use that will help you!

REMEMBER: Homeworks are different from PEs in that they state REQUIREMENTS. These requirements  may NOT always be stated in the ORDER in which you should implement them. For example, we may ask you to return a value and report an error, but these two requirements must be handled in the correct     order.

 Dairy.java                                                                                                                                  

This file defines a Dairy object.

All variables must not be allowed to be directly modified outside the class in which they are declared, unless otherwise stated in the description of the variable. The Dairy class must have these variables:

•    product – the name of the dairy product (example: cheese, milk, butter)

•    quantity – quantity of the product as a whole number

•    cost – the cost of one item of the product, as a Java default floating-point number (e.g., 4.99)

•    daysToExpiration – the number of days to expiration as a whole number

•    isConsumable – whether there are 3 or more days until expiration; If the number of days is less than 3, the product is not consumable. This value will not be passed as a parameter to the constructor.

o When isConsumable is initialized, print out “Good choice!” if the product is      consumable. Otherwise, print “Check the expiration date” . This should only be printed when isConsumable is first initialized.

Constructor(s):

•    A constructor that takes in the product, quantity, cost, and daysToExpiration

•    A constructor that takes in product and quantity. In this case, cost should be assumed to be 5.59 and daysToExpiration should be assumed to be 5.

•    A constructor that takes in no arguments. In this case, product should be “yoghurt”,     quantity should be 4, cost should be 3.99, and daysToExpiration should be 3.

•    NOTE: The constructor parameters should be in the order listed above. Assume that constructor inputs will be valid (i.e., product will not be null, cost will not be negative).

Methods:

All methods should have the proper visibility to be used where it is specified, they are used.

•    Getters and setters only as necessary

•    Any helper methods that you may need; ensure that these methods are not accessible outside of this class.

 Bakery.java                                                                                                                               

This file defines a Bakery object.

Variables:

All variables must not be allowed to be directly modified outside the class in which they are declared,    unless otherwise stated in the description of the variable. The Bakery class must have these variables:

•    product – the name of the bakery product (example: bread, bagel)

•    quantity – quantity of the product as a whole number

•    cost – the cost of one item of the product, as a floating-point number (e.g., 4.99)

Constructor(s):

•    A constructor that takes in product, quantity, and cost

•    NOTE: The constructor parameters should be in the order listed above. Assume that constructor inputs will be valid (i.e., product will not be null, cost will not be negative).

All methods should have the proper visibility to be used where it is specified, they are used.

•    Use getters and setters only as necessary

•    Any helper methods that you may need; ensure that these methods are not accessible outside of this class.

 ShoppingCart.java                                                                                                                   

This file defines a ShoppingCart object which contains Dairy and Bakery objects.

Variables:

All variables must not be allowed to be directly modified outside the class in which they are declared,  unless otherwise stated in the description of the variable. The ShoppingCart class must have these variables:

•    dairyItems – a value that represents the Dairy objects in your shopping cart, represented by an array of Dairy objects

•    bakeryItems – a value that represents the Bakery objects in your shopping cart, represented by an array of Bakery objects

Constructor(s):

•    A constructor that takes in dairyItems and bakeryItems.

•    A constructor that takes in no parameters and initializes bakeryItems to an array of size 2   and with one Bakery object at index 0 with the following values  <Bread, 1, 5.99> and initializes dairyItems to an empty array of size 4.

•    NOTE: The constructor parameters should be in the order listed above. Assume that constructor inputs will be valid (i.e., dairyItems will not be null, bakeryItems will not be null).

Methods:

All methods should have the proper visibility to be used where they are specified to be used.

•    addDairyItemAtIndex

o Given an index and a Dairy parameter, add that Dairy object to the index in the       dairyItems array and print out the name of the item that was previously at that index in the following format: “There was {product} here before.” and return the Dairy object that was previously placed there.

o If there was no item at the index, print out the name of the Dairy object added in the following format “{product} was added here.” and return null.

o If the index is invalid or if the Dairy object passed in is null, return null and print out “Cannot add Dairy item!”

•    removeBakeryItemAtIndex

o Given an index, remove the Bakery item from bakeryItems at that index and print out “{product} was removed from the cart.” Return the Bakery object    that was removed.

o If the index is invalid, print “Invalid index entered.” and return null.

o If no object exists at that index, print “No Bakery item exists at this index!” and return null.

•    updateDairyQuantity

o Given the product name of the Dairy item (case-insensitive) and the new quantity, search and update the Dairy item’s quantity with the quantity passed in and        print out “Quantity of {product} was updated from {old quantity} to {new quantity}.”

o If the product name is not found or if the product entered was null, print “No such Dairy item exists in the cart!”

o Remember to check if the quantity entered is nonnegative. Else, print “Invalid quantity entered.”  and do not update the quantity.

o This method does not need to return anything.

o NOTE: You can assume that there are no duplicate items. That is, no two Dairy objects have the same product name.

•    displayItems

o This method takes in no parameters, simply print out the product name and     quantity, and cost of each item in both dairyItems and bakeryItems.

o Print each item’s details on a different line.

o For each Dairy object, print the following on its own line:

“Dairy Product: {product} Quantity: {quantity} Cost: {cost}” For each null object, print “null” on its own line. Cost should be displayed to 2 decimals.

o For each Bakery object, print the following on its own line:

“Bakery Product: {product} Quantity: {quantity} Cost: {cost}” For each null object, print “null” on its own line. Cost should be displayed to 2 decimals.

o Remember you cannot print out objects itself, you can only print out the variables associated with each object. How will you get that data?

o NOTE: the order of the items is important. First, print out all the Dairy items in order and then the Bakery items in order.

When writing your methods:

•    Include Getters and Setters only as necessary

•    Include any helper methods that you may need, but ensure that these methods are not accessible outside of this class.

•    HINT: You will likely run into a few exceptions (think of the empty spaces in the array), consider how you can prevent it from occurring using conditionals and consider what it is.

 Driver.java                                                                                                                                 

This file is used to test your code. You do not need to turn this in.

Methods:

•    main

o Create 3 Dairy objects and place them in an array.

o Create 3 Bakery objects and place them in an array.

o Create a ShoppingCart object with the arrays created previously.

o Create and add 1 Dairy object using addDairyItemAtIndex

o Remove 1 Bakery object using removeBakeryItemAtIndex

o Update the quantity of a Dairy object using updateDairyQuantity

o TIP: Print out the contents of dairyItems and BakeryItems using the           displayItems method to see the changes expected after adding, removing, or updating objects.

o TIP: Check the sample output given on the Ed clarification thread to make sure your program is running correctly.

o NOTE: This is to help you test your code, but it is not comprehensive. It is suggested you create more test cases. Great testing would include creating objects with each of the      constructors, invoking any public methods, and observing that the results are consistent with what you would expect.

You must run checkstyle on your submission (To learn more about Checkstyle, check out cs1331-style-   guide.pdf under CheckStyle Resources in the Modules section of Canvas.) The Checkstyle deduction cap for this assignment is 10 points. If you do not have Checkstyle yet, download it from Canvas -> Modules -> CheckStyle Resources -> checkstyle-8.28.jar. Place it in the same folder as the files you want to run     Checkstyle on. Run checkstyle on your code like so:

$ java -jar checkstyle-8.28.jar yourFileName.java

Starting audit...

Audit done.

The message above means there were no Checkstyle errors. If you had any errors, they would show up above this message, and the number at the end would be the points we would take off (limited by the  checkstyle cap mentioned in the Rubric section). In future homeworks we will be increasing this cap, so get into the habit of fixing these style errors early!

Turn-In Procedure

 Submission

To submit, upload the files listed below to the corresponding assignment on Gradescope:

•   Dairy.java

•   Bakery.java

•   ShoppingCart.java

Make sure you see the message stating the assignment was submitted successfully. From this point,      Gradescope will run a basic autograder on your submission as discussed in the next section. Any             autograder test are provided as a courtesy to help “sanity check” your work and you may not see all  the test cases used to grade your work. Autograder tests are NOT guaranteed to be released when the assignment is released, so YOU are responsible for thoroughly testing your submission on your own to  ensure you have fulfilled the requirements of this assignment. If you have questions about the                requirements given, reach out to a TA or Professor via our class discussion forum for clarification.

You can submit as many times as you want before the deadline, so feel free to resubmit as you make substantial progress on the homework. We will only grade your latest submission. Be sure to submit every file each time you resubmit.

 Gradescope Autograder

If an autograder is enabled for this assignment, you may be able to see the results of a few basic test     cases on your code. Typically, tests will correspond to a rubric item, and the score returned represents  the performance of your code on those rubric items only. If you fail a test, you can look at the output to determine what went wrong and resubmit once you have fixed the issue.

The Gradescope tests serve two main purposes:

•   Prevent upload mistakes (e.g. non-compiling code)