CIS 1068 (mini) Assignment 10
Perishable Grocery Item

Posted: Saturday, April 11

Due: Monday, April 20

20 points

This assignment builds directly on your work from Assignment 9. You'll extend the GroceryItem class by writing a subclass.

Background

Not everything on a grocery list has an expiration date. A bottle of dish soap doesn't expire. But milk, yogurt, and fresh produce all do.

We'd like to be able to represent items that have expiration dates alongside ordinary grocery items, treating them all as part of the same shopping list. Inheritance gives us a clean way to do this.

PerishableItem (8 points)

Implement a class PerishableItem that extends GroceryItem.

A PerishableItem has all the same fields as a GroceryItem — name, quantity, and estimated price — plus one additional private field:

• expirationDate: a String representing the date on which this item expires, in the format "YYYY-MM-DD" (e.g., "2026-04-20")

Your class should provide the following public methods:

• A constructor that accepts a name, quantity, estimated price, and expiration date, and uses super(...) to initialize the inherited fields
• An accessor and mutator for expirationDate
• isExpired(String today): returns true if expirationDate is strictly before today (both strings are in "YYYY-MM-DD" format, so a simple string comparison is sufficient)
• toString(): returns a nicely formatted summary that includes everything from GroceryItem's toString() plus the expiration date. Use super.toString() as your starting point.

Driver 1 (6 points)

Write a short driver that exercises PerishableItem directly:

• Create a few PerishableItem objects
• Print each one using toString()
• Call isExpired on each one and print whether it has expired

PerishableItem yogurt = new PerishableItem("Yogurt", 3, 1.19, "2026-04-12");
System.out.println(yogurt);
System.out.println("Expired: " + yogurt.isExpired("2026-04-08"));

Driver 2 (6 points)

Write a second driver that demonstrates something important about inheritance. Create a GroceryList and add a mix of plain GroceryItem objects and PerishableItem objects to it:

GroceryList groceries = new GroceryList();
groceries.addItem(new GroceryItem("Dish Soap", 1, 3.99));
groceries.addItem(new PerishableItem("Milk", 1, 4.29, "2026-04-15"));
groceries.addItem(new GroceryItem("Paper Towels", 2, 5.49));
groceries.addItem(new PerishableItem("Yogurt", 3, 1.19, "2026-04-12"));
System.out.println(groceries);

Bring your GroceryList from Assignment 9 into this project — you do not need to make any changes to it. GroceryList stores an array of GroceryItem objects, and since every PerishableItem is a GroceryItem, perishable items can be added to the list without GroceryList knowing anything about them.

When the list is printed, notice that the expiration date appears for perishable items and not for plain ones. GroceryList calls toString() on each element the same way, but Java is smart enough to call the right version of toString() depending on what kind of object it actually is. This is called polymorphism, and it's one of the most powerful ideas in object-oriented programming.

Implementation Notes

• PerishableItem should not redeclare any fields that are already in GroceryItem. Inherited fields belong to the parent class.
• Your PerishableItem constructor must call super(...) as its first statement to initialize the inherited fields. You cannot set them directly since they are private in GroceryItem.
• toString() in PerishableItem should call super.toString() rather than rebuilding the whole string from scratch. Think of it as: start with what GroceryItem already knows how to say, then add the expiration date.
• For isExpired, you don't need to parse the dates into any special type. Because the format is "YYYY-MM-DD", Java's ordinary string comparison (compareTo) gives you the correct chronological ordering.

what to submit

Upload PerishableItem.java, Driver1.java, and Driver2.java to Canvas. Include your GroceryItem.java and GroceryList.java from Assignment 9 as well — we need them to compile your code.

It's a good idea to confirm through the Canvas submission page that what you've intended to submit was uploaded. We will grade what you submit. If you submit a corrupted, empty, or otherwise incorrect file, this is what we'll grade. It is your responsibility to verify through the Canvas submission page that you've submitted the correct files and that they were uploaded properly.

If you're unsure about how to submit, please consult Canvas' tutorial or see us for help.