What are some good Object Oriented Design (OOD) interview questions?

Question

I'm looking to prepare for a job interview and I wanted to go over some good Object Oriented Design (OOD) questions.

Here are some of the OOD concepts that should give a good starting point:

1. inheritance
2. multiple inheritance
3. encapsulation
4. abstraction
5. composition
6. polymorphism
7. overriding polymorphism

Would you please suggest any other OOD question(s)/topics that should be reviewed?

Answer 1

Adding to your list of items/topics, you should also consider giving a glimpse on following topics :

• Data Hiding
• Interfaces
• Abstract classes
• Overloading Polymorphism
• Delegation (alternate to inheritance)

Also, I would suggest you to read some good OOD books like

• Head First Object Oriented Analysis and Design
• Design Patterns Explained - [Allan Shalloway]
• Design Patterns : Elements of Reusable Object-Oriented Software - [Erich Gamma]

Also, have a look at this link.

Answer 2

Patterns. Design patterns, mostly, but also mega-patterns like MVC, MVVM and so on. Look at anti-patterns as well, like god object and tarball.

Answer 3

What is a singleton pattern? When/Why would you use it? What are the positives/negatives in using that pattern? What is a strategy pattern? When/Why... (etc) What is a factory pattern? When/Why... (etc)

Pick a couple of the more "common" patterns and see if they have at least been exposed to them. You can also give a small, bad programming example and have the candidate refactor it. You can see how they approach a problem.

Ask them to draw a picture of one of the patterns on a white board using UML (doesn't have to be perfect, but will show if they have actually used any of it).

When I interview developers I would ask them about version control systems. I didn't really care what they used, but that they actually did use them (and their attitudes towards them). I know that's not OOD, but I just threw my 2c in :)