JavaReferences : 34
Data Modeling 2 : 33
Equality and Object Copying : 32
Polymorphism : 31
Inheritance : 30
Data Modeling 1 : 29
Static : 28
Encapsulation : 27
Constructors : 26
Objects, Continued : 25
Introduction to Objects : 24
Compilation and Type Inference : 23
Practice with Collections : 22
Maps and Sets : 21
Lists and Type Parameters : 20
Imports and Libraries : 19
Multidimensional Arrays : 18
Practice with Strings : 17
null : 16
Algorithms and Strings : 15
Strings : 14
Functions and Algorithms : 13
Practice with Functions : 12
More About Functions : 11
Errors and Debugging : 10
Functions : 9
Practice with Loops and Algorithms : 8
Algorithms I : 7
Loops : 6
Arrays : 5
Compound Conditionals : 4
Conditional Expressions and Statements : 3
Operations on Variables : 2
Variables and Types : 1
Hello, world! : 0
Data Modeling 2
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 ChallengeWarm Up Debugging Challenge
But, as we frequently do, let’s warm up with another debugging challenge!
Modeling Office HoursModeling 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 RelationshipClasses 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:
Class Properties and MethodsClass 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.
Implementing Initial MethodsImplementing Initial Methods
Next, we’ll pick a pair of the methods on our Room class to implement.
Finishing UpFinishing 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!
Practice: Last 8
Create a public class called Last8.
You should expose two public methods:
add: adds a value, does not return a valuelast: returns an array containing the last 8 values that were added, in any order.
You do not need a constructor, but you can add an empty one if you need. 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 to save the values. Submissions that do will be marked incorrect.
Homework: Last 4 In Order
Create a public class called Last4Ordered.
You should expose two public methods:
add: adds a value, does not return a valuelast: 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.
Do not use a List to solve this problem.
More Practice
Need more practice? Head over to the practice page.