Object Oriented Design

Question 1

What are the main three categories of objects

Answer 1

Entity, Boundry and Control

Question 2

What is an entity object

Answer 2

An object that cooresponds with a real world object. Example: Chair, Person, Bike

Question 3

Give an example of a Boundry object

Answer 3

A Submit button on a page or a Service that makes a call to an api

Question 4

What is CRC and what does it stand for?

Answer 4

Is a technique (Class, Responsibility, Collaborator) thats used to represent information about Components, their connections and responsibilities.

Question 5

Can you give an example for a CRC card using a Bank User?

Answer 5

Bank User is the class, responsibilities would insert card and choose a task, the collaborator is the Bank Machine, Bank Card

Question 6

Name the four design principles

Answer 6

Abstraction, Encapsulation, Decomposition, Generalization

Question 7

Describe Abstraction

Answer 7

Idea of simplifying a concept to its essentials within some context

Question 8

Describe encapsulation

Answer 8

Involves 3 ideas:

1. Making some sort of capsule that has details on the inside which some of them you can access from the outside.
2. You expose certain data and functions of that object
3. You can restrict access to certain data and methods

Forms a self-contained object by bundling data and function it requires to work. Exposes an interface whereby other objects can access and use it and restricts access to certain details.

Question 9

Describe decomposition

Answer 9

Taking something as a whole and dividing it up into different parts.

Question 10

What are the three relationships in decomposition

Answer 10

Association, Aggregation, Composition

Question 11

What does a decomposition association mean?

Answer 11

It is some relationship. There is a loose relationship between two objects. Objects interact with each other for some time.

Question 12

What is decomposition Aggregation?

Answer 12

It is a has-a relationship where a whole has parts that belong to it. This is a weak relationship. Parts can belong to wholes but can also exist independently.

Question 13

What is Composition?

Answer 13

An exclusive containment of parts. A strong “has-a” relationship. The whole cannot exist without the part.

Question 14

How can a protected attribute be accessed?

Answer 14

1. By the encapuslating class
2. All Subclasses
3. All classes within the same package

Question 15

In what way can you implement Polymorphism in OOP?

Answer 15

By using interfaces