Write an object-oriented model of a pizza parlor. You can approach this at various levels.
Just an exercise in writing classes and interfaces. Model a pizza that can be made with different toppings. Pizza should probably be a class but you should define at least one interface and have multiple implementations of that interface. Make sure to follow the is-a/has-a rule for deciding when classes should implement an interface vs when classes should be linked by composition.
Your Pizza class should have some methods to compute values such as the pizza's price or cost to make (or both) based on the toppings. Does your restaurant serve any other kinds of food, e.g. salads? What are they made of? Are there ingredients that can be used both as a pizza topping or in a salad?
Extend your model from the pizza itself to the pizza parlor. Make a
PizzaParlor class that can track an inventory of ingredients and money earned
and provide methods to determine whether you can make a particular pizza or
salad. Maybe make a game where the player can order a pizza and you construct a
Pizza object and then use it to tell the customer how much it costs.
Model a pizza parlor using a discrete event simulation. You probably want to model customers arriving at random. (Technically the right way to model this is with an exponential distribution.) Then model how many pizzas you can make at one time (based on oven capacity) and keep track of how many customers are waiting for their pizza. Then think of some question you might want to answer if you were running a pizza parlor and see if you can answer it with a simualaton.
For instance if you simulate customers leaving who arrive when the line is too long you can track of how many customers are lost that way and then determine whether increasing your over capacity is a good investment.
Or you could model the possibility that a pizza will be burnt if the staff are too busy serving customers and don't take the pizza out in time and what that does to wait times to answer questios about staffing.