Object Oriented Programming Concepts and Interviews

haven't you imagined that OOP might not be the pinnacle of all knowledge? there are other ways to think, after all. Even more, there are lots problems out there where OOP isn't the best answer.

OOP is merely one way of coding. There are many Multi Paradigm Programming Languages that does not necessary need OOP to work. In fact, you also need to see what nature of the job is. For example, System Analysts that do little programming can not know OOP, but do well in his/her job.

On the other hand, there's proof (read it somewhere, can't remember where - probably on Stack Overflow blog or Joel on Software) that there are many graduates or freshmen in the industry that hardly know OOP or good programming practices. These people are probably the black sheeps in your team who will code poorly, have bad documentation and poor understanding of the code.

Who are you interviewing?

If the answer is fresh out of schools grad, then that's expected. In school a student gets to learn a lot of theory about OOP and the accompanying assignments are hardly long enough to make them understand the advantages of using OOP vs Procedural.

Disclaimer: I'm not a big fan of this test. But I must agree that failing it is a pretty good indication we don't know OO enough to state on our resume that we know OO.

A small exercice that requires just few minutes to complete for someone that know OO.

The question is: "What is the output on the following code?"

using System;

namespace Polymorphism
{
    class Animal
    {
        public void MakeSound() { Console.WriteLine("bip"); }
        public virtual void MakeSound2() { Console.WriteLine("bip"); }
        public void MakeSound3() { Console.WriteLine("bip"); }
    }

    class Dog : Animal
    {
        public void MakeSound() { Console.WriteLine("woof"); }
        public override void MakeSound2() { Console.WriteLine("woof"); }
        public new void MakeSound3() { Console.WriteLine("woof"); }
    }

    class Test
    {
        static void Main(string[] args)
        {
            Animal animal;
            Dog dog;

            animal = new Animal();
            dog = new Dog();
            animal.MakeSound();
            dog.MakeSound(); 

            animal = new Dog();
            animal.MakeSound();

            animal = new Animal();
            dog = new Dog();
            animal.MakeSound2();
            dog.MakeSound2();

            animal = new Dog();
            animal.MakeSound2();

            animal = new Animal();
            dog = new Dog();
            animal.MakeSound3();
            dog.MakeSound3();

            animal = new Dog();
            animal.MakeSound3();

            Console.ReadKey();
        }
    }
}

Oh and if you are a real a***ole, you can add this just before the Console.ReadKey(); statement:

    dog = new Animal();
    dog.MakeSound3();

And if being an a***ole is not enough, add this:

    dog = (Dog)new Animal();
    dog.MakeSound3();

I would like to answer the EDIT section of your question

I usually interview programmers with 2 to 5 years of experience.

If an interviewee has 2 to 5 year experience, OOP fundamentals is something that is expected and I don't think you are being over critical but just having a reasonable expectation.

• It's important to find out what other skills the interviewee has to offer
• By working in a large software development team I have learned more in three months then I have learned in 2 years at a smaller company. I think experience should be measured in successful projects, rather than years.
• Reasonable university graduates are likely to answer the majority of your OO related questions, but they are likely to have no or very little industrial experience to offer.

Because of these points, I think that you may be overcritical with your interviewees.

If you interviewed a fresh graduate, than you absolutely too critical.

I think what is important for a fresh graduate related to OOP are: medium - deep OOP knowledge, interest in programming and OOP, hard worker and some OOP college assignment. Some fresh graduates are lack of OOP experience in medium - large project. So I think a medium knowledge and interest in OOP will be enough.

Out of all the interview questions you've read about out there, I'm pretty sure that only a few were an actual OO problem and in their case it was probably a simple matter of proving facts about OOP.

Call it a personal sentiment, but the developers out there that are more concerned with software design probably feel disappointed that they'll never have to take an abstract specification and refine it into a solution of objects communicating with the notion of satisfying the specification requirements.

For most of the candidates out there, they'll be abusing to what the interviewing system has been reduced to and will generally focus on preparing data structure and algorithm implementations.