Absract Classes and Interfaces

Question 1

What is an abstract class?

Answer 1

An abstract class is:

1. A special type of class that cannot be instantiated.
2. It contains at least 1 abstract method and can contain concrete methods.
3. It is “contract-based”. Abstract methods MUST be overridden in the subclass.

Question 2

What is an interface?

Answer 2

An interface is:

1. A special type of class that cannot be instantiated
2. It specifies what a class does, but not how it implements it.
3. It lacks instance variables.
4. It is characterized by behavior.

Question 3

How is inheritance between classes and interfaces?

Answer 3

Classes can inherit interfaces; from 0 to many.

Question 4

How is inheritance between an interface to another interface?

Answer 4

Interfaces can extend other interfaces; from 0 to many.