OOPs interview questions and How to Answer Them

An object-oriented programming (OOP) system is important to overall programming. You’ll want to brush up on OOP fundamentals if you're scheduled for a job interview. Whether interviewing for a C++ developer, Python developer, or software engineering position, you’ll want to show the interviewer your familiarity with all aspects of OOPs. 

Before your scheduled interview, you should research the company to learn more about its IT department, software development, and the programming languages they prefer to work with. If you know someone who works for the company, that’s even better because you can ask questions about the preferences and procedures they follow. You can reach out to anyone you know who works with object-oriented programming and inquire about the interview questions they were asked. 

The following interview questions will help you study and prepare for your interview. The more prepared you are for the interaction, the more likely you’ll make an outstanding impression. 

What is OOPs?

Object-oriented programming (OOP) combines data attributes with functions into units called objects. OOP languages are class-based and include Java, Python,  C++, and others.

Common interview questions

When applying for a role in OOPs, it is essential to come to the interview prepared to answer relevant questions. Review some common interview questions and sample answers to learn beforehand and increase your confidence on interview day. 

Below are some examples:

Tell us about yourself

Why they’re asking this: They want to know why you feel you’re the right person for the position.

How to answer: This is a common icebreaker question used for jobs of all types. It’s also an excellent opportunity to tell the interviewer why you’re interested in OOPs, what your education and experience are, and what value you bring to the job. 

Focus your answer on your experience working with and learning about OOPs. For example, you could focus on your previous jobs, volunteer experience, internships, or IT skills. If you lack education or experience, consider sharing other experiences you’ve had that showcase your work ethic and professionalism.

Similar questions the interviewer might ask: 

• How did you become interested in OOPs?

• Tell me about your background in OOPs

• Why should we hire you? 

What is OOPs? 

Why they’re asking this: They want to know if you thoroughly understand object-oriented programming. 

How to answer: You should describe OOPs, the four pillars, and an overview. You can also talk about how inheritance, abstraction, polymorphism, and encapsulation

work in conjunction with one another.

Similar questions an interviewer might ask: 

• How would you describe OOPs to someone with no computer experience?

• How can object-oriented programming benefit a company? 

• Can you explain OOPs in simple terms?

Why is OOPs important? 

Why they’re asking this: They want to know how you validate the importance of object-oriented programming. 

How to answer: Discuss how OOPs has made it possible to develop mobile applications and their problem-solving benefits. Talk about how it makes it easier for programmers to organise and update software applications.

Similar questions the interviewer might ask: 

• Why is OOPs important to our company? 

• How important is OOPs in the day-to-day operations of a company? 

• Why OOPs is important to software developers?

Explain the basic concepts of object-oriented programming

Why they’re asking this: Most interviewers will ask this question to ensure you are solid on the basic concepts of inheritance, encapsulation, polymorphism, and abstraction.

How to answer: Explain how the object-oriented programing system works using the four building blocks and their importance in the programming environment. Discuss what they are, how you define them, each concept’s importance in OOPs, and how they interact. 

Similar questions the interviewer might ask: 

• Explain the difference between encapsulation and inheritance

• How can you apply polymorphism to programming? 

• What are the benefits of abstraction? 

Explain the difference between procedural programming, and OOPs

Why they’re asking this: Interviewers ask this question to assess your knowledge of procedural programming and OOPS. 

How to answer:  Object-oriented language is based on real-world objects, while procedural is based on functions. Object-oriented language focuses on object behaviour, and procedural language deals with execution. Talk about how object-oriented language encapsulates data, and procedural language exposes data. 

Similar questions the interviewer might ask:

• Is OOPs easier than procedural programming?

• Do you prefer OOPs or procedural languages? 

• How does procedural language expose data? 

Name four of the most widely used OOP languages

Why they’re asking this: The interviewer wants to ensure you know the commonly used languages. 

How to answer: If you’re asked to name some widely used OOP languages, you can choose from Python, Java, C++, C#, Ruby, PHP, and TypeScript. Since Python and Java are the most commonly used, you should consider naming them at the top of your list while ensuring you also discuss how you use each. For example, Java is excellent for building applications, and Python offers versatility for creating apps, data analysis, and automation. 

Similar questions the interviewer might ask:

• What are two common OOP languages?

• How would you describe Python and Java when used with OOPs?

• Describe your use of C++ and C#.

Describe some of the limitations of OOPs

Why they’re asking this: The interviewer wants to know if you know the limitations of OOPs. 

How to answer: Your answer will tell the interviewer how experienced you are with object-oriented programming. Some of the more common limitations you can speak of are its size requirements, its potential to run slower than other programs, and the time it will take you to get accustomed to it. 

If you’ve worked with OOPs, you can add your experience and opinions on their limitations. As a bonus, your answer can demonstrate to interviewers that you’re prepared for the challenges object-oriented programming might present.

Similar questions the interviewer might ask:

• How would you work around OOPs limitations? 

• How would you compensate for a slow-running program?

• How have you solved the size requirement limitations of OOPs?

What is garbage collection?

Why they’re asking this:

This is a less common question, but an interviewer might ask how in-depth your OOPs knowledge is.  

How to answer: Java and C# use garbage collection, often called GC, for memory management. A programming language that uses GC will release memory space that is no longer in use.

Similar questions the interviewer might ask:

• What is GC?

• How do you use garbage collection?

• Give an example of garbage collection.

Explain data abstraction

Why they’re asking this: The interviewer may ask this question to gauge your ability to explain in non-technical terms. 

How to answer: You can point out that it’s an important feature of object-oriented programming because it only allows the display of important information. For example,  you can explain how people can video conference on platforms such as Zoom and Google, yet the platforms hide how the connections occur. Users have no idea what goes on internally to connect them.

Similar questions the interviewer might ask: 

• Explain how video conferencing hides information from users. 

• How would you explain data abstraction to someone who has no computer experience?

• How can data abstraction benefit our company?

Name three types of variables in OOPs

Why they’re asking this: The interviewer wants to access your knowledge of variable types

How to answer: Three variable types you can name include:

• Primitive variables represent values such as float.

• Reference variables refer to objects in Java.

• Static variables occur during class loading, while class unloading destroys them. 

Similar questions the interviewer might ask: 

• Describe a primitive variable

• What are reference variables?

• How are static variables created? 

What are the rules for creating a constructor?

Why they’re asking this: The interviewer wants to ensure you know the rules for creating a constructor. 

How to answer: 

The rules for creating a constructor are standard and should be easy to recall. When creating a constructor, it must not have a return type, or you must mark it static. You cannot mark it abstract or override it. Most importantly, it must have the same name as the class name. This question offers you a good opportunity to show interviewers that you’re clear on the various types of constructors, including default, static, copy, private, and parameterised.

Similar questions the interviewer might ask: 

• Can you override a constructor?

• Does a constructor need to have the same name as the class name?

• How do you define a constructor? 

Other questions to expect

Your interviewer will likely give you scenarios and have you explain the proper concept to use. Be prepared to discuss various aspects of OOPs, including:

• Operators that can't overload

• Advantages of OOPs

• Differences between class and structure

• Types of access modifiers

Although you can’t prepare for scenario questions, you can ensure you’re well-versed in each concept and know how to apply each to real-life situations. Additionally, interviewers may ask challenging questions like how the position compares to others you applied for, your primary strengths and weaknesses, and your biggest failures. Tough questions provide insight into your character and help interviewers see your thoughts. 

Next steps

You’ll find many courses on Coursera for beginners and experienced developers working with object-oriented programming, Java, Python, and other programming languages. For example, you can complete Introduction to Object-Oriented Programming with Java, a course offered by LearnQuest, in about 17 hours. If you’re seeking an entry-level role in OOPs, this course can help enhance your skills. 

For aspiring software developers, the Object Oriented Programming in Java Specialisation, offered completely online by Duke University, takes approximately five months.

Google’s Crash Course on Python is a great way to refresh your Python programming skills, or if you’re new to programming, you can learn one of the most used languages in the global IT industry.