Object Oriented Programming

Question 1

What does the (+) symbol tell us in a diagram?

Answer 1

An instance variable or method is public.

This means it can be fully accessed and used by other objects.

Question 2

What does the (-) symbol show us in a UML diagram?

Answer 2

That an instance variable or method is private.

This means it cannot be directly accessed or used by other objects.

Question 3

What is the purpose of encapsulation?

Answer 3

To make changes to private properties using the methods provided.

Question 4

What is a sub-class?

Answer 4

A class that is derived from an existing class.

Question 5

What is the purpose of inheritance?

Answer 5

To copy all of the data items and methods from the superclass when a sub-class is created.

Question 6

What does polymorphism allow?

Answer 6

Different sub-classes and the superclass they are derived from to behave differently when the same method is invoked.

Question 7

What does an array of objects allow in OOP?

Answer 7

An instance variable to become an array which contains several instances of another class.