Top 50 OOPs Interview Questions (With Example Answers)
Updated 16 March 2023
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Preparing for industry-related questions in an interview could increase your chances of getting hired. For instance, if you are applying for a job that requires object-oriented programming (OOPs), you should review the common OOPs interview questions. Being prepared demonstrates to employers that you are worth their time and a qualified candidate to consider. In this article, we provide a list of the top 50 most commonly asked object-oriented programming based interview questions and some example answers to help you craft your own responses.
Read more: How to Prepare for a Job Interview
Top 40 OOPs interview questions
Here are the 40 most commonly asked OOPs interview questions:
What is encapsulation?
Define a structure.
What is the difference between a class and a structure?
When is an operator keyword used?
Do you know what cohesion is?
Do you know what coupling is?
What is the difference between coupling and cohesion?
Define an interface.
What is the importance of an interface?
Can you give an example of a virtual function?
What is the difference between a friend function and a virtual function?
What is a destructor?
Do you know what a ternary operator is?
What is another name for a ternary operator?
Define an abstract class.
Differentiate between an interface and an abstract class.
What is a monad?
What is a static constructor?
Differentiate between polymorphism and abstraction.
Give an example of a token.
Who created the first-ever object-oriented language?
Which is the first object-oriented programming language?
Which feature in the OOPs model lets a class derive the features of another class?
Can C language be used for demonstrating polymorphism?
Can you create an application in Java without the implementation of object-oriented programming concepts?
In a superclass, which member is not accessible to its subclass?
What is a garbage collector in object-oriented programming?
Define exceptions in object-oriented programming.
How is exception handling done in OOPs?
Define access specifiers.
How would you accomplish data abstraction?
Describe static polymorphism.
What is the significance of access specifiers in object-oriented programming?
Describe dynamic polymorphism.
Define a subclass.
What is a superclass?
Does inheritance have any limitations?
List the different inheritance types.
Define copy constructor.
Read more: 9 Interface Interview Questions In Java (With Answers)
Interview questions with example answers
Here are the example answers to some of the most common questions about OOPs:
1. What does OOPs stand for?
This is a straightforward question, and this makes answering this one correctly all the more important for you. Although the interviewer is asking for a basic definition, you must showcase your knowledge of the topic by adding a few additional details. Also, try and define the concept in an engaging manner.
Example: "OOPs stands for Object-Oriented Programming system, which is a term that Alan Key introduced in the late 1960s. It can be defined as programs that are groups of objects."
2. What are its four basic concepts?
The interviewer may ask this follow-up question to the previous question, depending on how detailed your answer to the previous question was. This question is often asked to gauge your understanding of the basic concepts and terminology.
Example: "The four basic concepts of objected oriented programming are abstraction, encapsulation, inheritance and polymorphism."
Read more: 23 Interview Tips: How to Get the Job
3. How would you describe polymorphism to someone?
Such questions are often asked to check both your knowledge of the basic concepts and your capability of processing the meaning of a question quickly and correctly. This question, in particular, aims to check how well you can communicate your ideas to others. This interviewer may use this question to gauge your ability to break down programming concepts in a way that anyone can understand them.
Example: "Polymorphism means assigning behaviours or values of a subclass to something that was already a part of the main class. In other words, polymorphism occurs when one particular symbol can have multiple meanings depending on the context it is in."
Related: 40 Common Java OOPS Interview Questions (With 4 Sample Responses)
4. What does abstraction mean in programming terminology?
This question tests your knowledge of the basic concepts. You must provide a detailed explanation in your answer. The best way to highlight your understanding of the concept is to include a simple example in your answer.
Example: "Abstraction can be defined as anything that simplifies technology for a user, like a power button. It masks the inner-workings of the technology itself so that the user only sees the surface level component needed to operate the technology."
5. What is a class?
Just like the previous question, this question also tests your knowledge of the basic concepts. Your answer should provide a proper definition of the term. You may also describe how this concept works within the OOPs system to make your response more comprehensive.
Example: "A class represents an object or grouping of data and acts as a blueprint for that particular type of object."
6. What makes object-oriented programming different from procedural programming?
This question tests your understanding of both types of programming. You should provide an in-depth answer describing in detail the basics of both types of programming and highlighting the main points of difference between the two.
Example: "In procedural programming, a program is broken down into individual procedures. In object-oriented programming, a program is referred to as a collection of objects. The structure of object-oriented programming makes it easy to reuse.
This makes it a much more time-effective programming method, as procedural programming requires a top-down method. This means that if changes need to be made to a particular code, every other instance of that code in the program must be found and manually changed, slowing productivity."
Read more: Essential C++ Interview Questions and Example Answers
7. Do you know what inheritance is?
This question tests how you react to the way the question has been asked, in addition to testing your knowledge of the basic concepts. This question, unlike the earlier questions, asks you if you understand the concept. You must stay composed when such questions come up and answer confidently. Calmly state that you do know the concept, and then describe the concept briefly.
Example: "Yes, I do know what inheritance is. Inheritance is where a class has the same makeup as another class."
8. Can you tell me the difference between a class and an object?
This question tests your understanding of both the concepts together. You should provide an in-depth answer describing in proper detail the basics of both the concepts and highlight the main points of difference between the two.
Example: "An object is an example of a class with its own traits and ability to hold information, while a class serves as the blueprint of an object. In other words, a class is an unchanging template. The object can be viewed as the template's finished product, creating an instance of the class with its unique data."
9. Can you describe the difference between method overriding and overloading?
These two OOPs concepts sound very similar; however, they differ in their applications. By asking you this question, the interviewer is trying to gauge how clearly you understand the difference between the two concepts.
Example: "The difference between method overriding and method overloading is that overriding uses dynamic binding where it has the same methods but different arguments that may or may not be able to return the same value to an original class. Overloading uses static binding where it has the same methods and arguments which return the same value to an original class and its child class."
Read more: How to Introduce Yourself in an Interview
10. What are the two subcategories of inheritance?
This question tests the depth of your knowledge about this OOPs concept. You should name the two subcategories and then describe both briefly to demonstrate your understanding.
Example: "The two subcategories for inheritance are single inheritance and multiple inheritance. Single inheritance refers to an instance when the inheritance of one class is applied to only one other class. In contrast, multiple inheritance refers to an inheritance of a class being applied to multiple classes."
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