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Data Modeling 2

class Person
class Room

In this lesson we stop and put all that we’ve learned recently into action. We’ll complete another object modeling exercise together. But this time, we’ll make use of inheritance, polymorphism, and other new ideas that we recently learned. Welcome back!

Warm Up Debugging Challenge
Warm Up Debugging Challenge

But, as we frequently do, let’s warm up with another debugging challenge!

Define a public class named Counter with a single public instance method named increment. increment takes no parameters and returns an Int. The first time it is called it should return 0, the next 1, the next 2, and so on. Each instance of Counter should maintain its own counter.

Modeling Office Hours
Modeling Office Hours

Last time we did a game, and I said: I’m sorry we’re doing a game. This time we’re going to do something that may seem a bit like navel-gazing. And I’ll say: I’m sorry we’re doing something course-related. This is what I think about!

So let’s model office hours.

Classes and Relationship
Classes and Relationship

One way to begin object modeling is to think about what kind of entities we need to model and what kind of relationships they should have with each other. Let’s start there:

// Define our different classes

Class Properties and Methods
Class Properties and Methods

Next, let’s consider the kind of actions and methods that our objects need to support. That will help guide us as we add required instance variables.

// Outline the methods on our different classes
// These may require us adding certain instance variables as needed

Implementing Initial Methods
Implementing Initial Methods

Next, we’ll pick a pair of the methods on our Room class to implement.

// Implement some Room methods

Finishing Up
Finishing Up

Finally, we’ll finish at least a preliminary implementation of our office hours model. And then discuss how you could extend and improve it!

// Finish Room

Practice: Last 8

Created By: learncs.online Staff
/ Version: 2020.9.0

Create a class called Last8. You should expose two public methods:

  • add: adds a value, does not return a value
  • last: returns an array containing the last 8 values that were added, in any order.

You do not need a constructor. Until 8 values have been added you should return 0s in their place.

For example, here's how an instance of Last8 should work:

Do not create a huge array or use a list to save the values. Submissions that do will be marked incorrect.

Homework: Last 4 In Order

Created By: learncs.online Staff
/ Version: 2020.9.1

Create a public class called Last4Ordered. You should expose two public methods:

  • add: adds a value, does not return a value
  • last: returns an array containing the last 4 values that were added in the order they were added.

You do not need a constructor, but you can add an empty one if you need. Until 4 values have been added you should return 0s in their place.

For example, here's how an instance of Last4Ordered should work:

Do not create a huge array to save the values. Submissions that do will be marked incorrect.

This problem is harder than it looks! A suggestion is to handle the cases until the array is initially filled separately. Once four values have been added, you will need to shift values around before adding a new one.

More Practice

Need more practice? Head over to the practice page.