OOPs Interview Questions and Answers(2023)

What is Object-Oriented Programming?

Object-oriented programming is a programming module centered around OBJECTS. The objects are real-world instances of entities like a class that have the characteristics and behavior of the class template. Most programming languages (C, C++, Python, Java) are multi-paradigm and support object-oriented programming.

Object-oriented programming (OOPs) is the foundation of the programming world. As a candidate, you should be ready to answer OOPs interview questions and answers to do well in an interview on programming knowledge. In this article, we will discuss the main OOPs Interview Questions.

How to Prepare for a Technical Interview

Nowadays, recruiters look for candidates with technical knowledge and good soft skills. Soft skills demonstrate a polished persona, whereas strong technical knowledge gives the candidate an edge over the other applicants.

Let us look at the essential questions in progression, starting with some basic questions followed by advanced questions. Please remember, the interviewer may ask several other questions. We have mentioned the common questions that are most likely to feature in an interview.

Basic OOPs Interview Questions for Freshers

1. What do you mean by OOPs?

OOPs is a programming paradigm used to define objects. The objects can be real-world instances like class having their characteristics and behaviors.

2. Why are OOPs popular?

• OOPs, are considered to be a more flexible and comfortable style for programming.
• It helps to write, manage, and maintain complex codes easily.
• The main features of OOPs provide an easier path for solving complex codes for the programmer. For this reason, OOPs are popular in the programming world.

3. Name some object-oriented programming languages.

The major object-oriented programming languages are C, C++, Java, Python, and PHP.

4. What is the importance of OOPs in programming?

• The OOPs help understand the software easily without actually going through the implementation.
• The readability and the understanding of the code increases.
• This question is one of the key OOPs Interview Questions For Freshers.

5. What are the main features of OOPs?

The main features of OOPs are Inheritance, Polymorphism, Encapsulation, and Data Abstraction.

6. Name some advantages of OOPs.

The OOPs have many advantages in programming. Some advantages are

• It promotes the reuse of codes, thus ensuring redundancy.
• OOPs, can create, handle, and maintain complex programming.
• Data Abstraction hides the unnecessary details in OOPs.
• OOPs, work on the bottom-up approach, whereas the structured programming paradigm operates on a top-down approach.
• The OOPs are flexible because of polymorphism.

7. Name some other programming paradigms.

There are two kinds of programming paradigms. They are:

• The Imperative Programming Paradigm talks about how to execute the program.
• The Declarative Programming paradigm talks about things to execute. It frames program logic.

8. What do you mean by structured programming?

• Structured programming is a programming method that has a complete structural control flow.
• The structure is a block that contains a set of rules and has a defined control flow.

So, these are some basic OOPs Interview Questions And Answers. Candidates will benefit from thorough awareness of these object-oriented programming concepts to do well in the interview.

Advanced OOPs Interview Questions For Experienced Candidates

We have now covered the most common basic questions. Let us move on to the advanced OOPs Interview Questions.

1. What is an object?

The object contains the instance of the class for all the members. Their behaviours are defined in the class template. An object in the real world is an actual entity with which a user interacts. So, the object takes space and has that behaviour.

2. What is a class?

The class is the blueprint that contains values known as member data or member and behavior or functions. So, when the object is created, it takes the data and functions that are defined by the class.

3. What is encapsulation?

Encapsulation involves keeping everything necessary inside a capsule before starting the job and sending it to the user. In simpler words, one removes all the unnecessary data and sends only the required data.

4. What is abstraction?

Abstraction is a central component of OOPs. It is the process of hiding unnecessary data from the data.

5. Does the inheritance have any limitations?

• There are certain limitations to inheritance.
• The time taken to process is more as it moves through many classes.
• The two classes involved in inheritance are tightly coupled. When one wants to make a change, it is necessary to make nested changes in both classes.
• Inheritance is also complicated. So, if the implementation is not proper, it may result in the wrong output.

6. What is compile-time polymorphism, and state the differences with runtime polymorphism?

• When a polymorphism occurs at compile-time, it is called compile-time polymorphism or static polymorphism.
• When a polymorphism occurs at run time, it is called runtime polymorphism.
• In compile-time polymorphism, the compiler decides the value or the shape of the entity, whereas, in runtime, the execution determines it.

7. Name the differences between an abstract class and an interface.

• The main difference between an abstract class and an interface is in implementing the inheritance.
• An interface is implemented. That is why, for an interface, the subclass should define all the methods and provide the implementation.
• On the other hand, the abstract class is inherited, so the subclass should define the abstract method if and only if the subclass is using it.
• The abstract class can have abstract and non-abstract methods.

8. What is a constructor?

The constructors are methods that share the same name, just like their class name. They are used to initialize the objects.

9. Name the different constructors.

There are three kinds of constructors. The types are default constructor, parameterized constructor, and copy constructor.

10. What is a copy constructor?

The sole purpose of a copy constructor is to create a clone of one object to the other. The clone and the original object are exactly alike in all aspects, including its value.

11. What is a destructor?

Destructors are special methods to remove unused data and memory taken up by an object. The destructors are automatically operated when destroying the object.

12. How much memory does a class take?

The class does not take any memory, as it is a blueprint upon which objects are formed. When the objects are created, they provide the class and the methods, thus consuming memory.

13. What do you mean by garbage collection in OOPs?

Some objects can cause memory-related errors causing system failure. So, garbage collection is the process of handling memory in the program. In this process, the unwanted objects are removed and cleared of the memory.

14. What is inheritance? What are the different kinds of inheritance?

• Inheritance is developing an object or class using another object or class definition. Its implementation is simple and also allows the reuse of codes.
• There are five kinds of inheritance. The types of inheritance are single inheritance, multiple inheritance, multi-level inheritance, hierarchical inheritance, and hybrid inheritance.

15. What would be the output of the following code?

• The output for this code is- If the integer size is 4 bytes, the output would be 80.

• The output of this code is - Inside B. The above code is a multi-level hierarchy. So, it is searched linearly to identify a matching function. Here, it is present in both classes of A and B.

The interview may include several other programs. Candidates will need to strengthen their technical base to provide the output of these programs. For further support in the interview preparation, check out the top 10 skills to become a full-stack developer.

How To Be Interview-Ready

Through various courses like full-stack development, candidates can gain insight into the technical languages that can help them in their professional careers. We at Board Infinity offer many such courses that can help candidates excel in the technical stream.

There are several questions asked during a technical interview. This article has covered the most common OOPs Interview Questions And Answers, and candidates can use these to cover their bases. The candidates can ensure that they are interview-ready by strengthening their foundation in programming.