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OOPs Interview Questions and Answers

Introduction

Most Popular OOPs Interview Questions And Answers

Knowledge of object-oriented programming languages such as Java, C++, and Python is one of the most valued skills an organization demands. Multiple ways are there for candidates to widen their OOPs knowledge and ace the OOPs interview questions.

To begin with, the object-oriented programming system deals with implementing a programming language model around an object rather than logic or procedural programming. OOP is modeled around objects that interact with one another.

We have jotted down the ideal answers to the top OOPs questions in this article, which are the most asked OOPs interview questions. 

 

List of Top OOPs Interview Questions And Answers In 2026

Having a thorough read on the sample OOPs interview questions and answers pretty much caters to an idea of questions to expect.

The comprehensive segment includes the OOPs interview questions and answers that will boost your preparation for the next Object-Oriented Programming interview questions.

If you worry about how to prepare OOPs viva questions! Here is the curated list of top interview questions and answers in OOPs.

 

Basic OOPs Interview Questions and Answers

Here is a rundown of the answers to the OOPs basic interview questions for beginners or professionals.

1. What is an Object-Oriented Programming language?

OOPs are abbreviated as ‘Object Oriented Programming Systems’. The programming languages that execute objects and related processes following the Object-Oriented Programming paradigm, or OOP, are known as Object-Oriented Programming languages.

Java, Python, C++, Lisp, and Perl are examples of popular object-oriented programming languages.

2. What are some major Object-Oriented Programming languages?

Some of the major Object-Oriented Programming languages include:

- C++
- Java
- Javascript
- Python
- PHP, and many more. 

3. What are the main features of OOPs?

Here are the main features of OOPs;

- Data Abstraction
- Encapsulation
- Inheritance
- Polymorphism 

4. What are the core concepts of OOPS?

The OOPS core concepts are:

- Abstraction
- Association
- Aggregation
- Composition
- Encapsulation
- Inheritance
- Polymorphism 

5. What is an Object?

An object is a basic run-time entity of an object-oriented system. It is an instance of a class, and any number of instances of a class can be created. It has its own state, behavior, and identity. Objects are created from a user-defined or predefined template called a class.

6. What are the types of Inheritance in OOPS?

The different types of inheritance in OOPs are as follows:

- Single Inheritance
- Multiple Inheritance
- Multi-level Inheritance
- Multi-path Inheritance
- Hierarchical Inheritance
- Hybrid Inheritance

Suggested Read: C# Interview Questions And Answers - UPDATED 2026

 

Advanced OOPs Interview Questions and Answers

Given below are the OOPs interview questions for freshers at an advanced level.

1. What are the 7 OOPs concepts?

The four main theoretical principles of object-oriented programming are abstraction, encapsulation, inheritance, and polymorphism.

Java operates with three further OOP concepts: aggregation, association, and composition.

2. What is Structured Programming?

Structured Programming refers to an approach to program development that brings high-quality programs with definitive control flow.

This method highlights an approach that makes it easy to test, maintain, modify, and debug.

Most programming paradigms comprise structured programming with the OOP model.

3. What is encapsulation?

In the OOPs concept, encapsulation is binding together the data and the functions that define, manipulate, and safeguard them from getters and setters under a single unit. One can apply encapsulation using access modifiers (public, private, and protected).

For example, make member variables of a class private and provide public getter and setter methods.

4. What is Polymorphism?

Polymorphism is derived from the Greek word “poly”, which means “many”, and “morph”, implying “form.”

In an object-oriented programming system, polymorphism is the process of representing one form (a property, function, or object) in multiple forms.

It is divided into two types:

Method Overloading (compile time): also known as static binding and early binding.

Method Overriding (run time): also known as dynamic binding and late binding.

5. What is multiple inheritance?

Multiple inheritance is an inheritance type where a class inherits attributes and methods from more than one base class (or a parent class).

It has two class levels: base class and derived class.

 

 

6. What is the meaning of the “IS-A” and “HAS-A” relationship?

The “IS-A” is an inheritance relationship. The classes that inherit from the base classes are known as subclasses or child classes (base object). 

Whereas “HAS-A” is a composite relationship. One object that contains a reference to an instance of another class of a similar class.

 

Intermediate Oops Interview Questions and Answers

Here are the OOPs practice questions with the answers at an intermediate level for experienced professionals or freshers.

1. What is a constructor?

A constructor is a special method of a class in a program that gets invoked implicitly when we create an object of the class.

It does not have any return type, cannot be overridden in Java, and cannot be inherited by a subclass.

There are two types of Constructors, 

Implicit Constructors: They are internally created in the .NET Framework.

Explicit Constructors: They can declare explicit constructors as we prefer.

2. What is a destructor?

A destructor is a method that cannot be manually invoked in C#. It is automatically invoked when an object is to be destroyed.

The destructor clears allocated memory and frees resources by closing the files and database connections of the object to allocate to other processes.

It does not have a return type in C#, cannot be overloaded, and is public by default.

3. Is it possible for a class to inherit the constructor of its base class?

No, a class cannot inherit the constructor of its base class.

4. What are the types of constructors?

Each type of constructor differs from language to language.

Below are the feasible constructors accordingly:

- Copy constructor
- Default constructor
- Private constructor
- Parameterized constructor
- Static constructor

5. What is an interface?

The interface is an OOPs concept that contains methods but not their definitions. Interfaces, unlike classes, can only contain the signature of a class in C#. They do not contain detailed instructions or actions or any implementation.

Multiple interface inheritance with a single base is possible. You cannot create objects; any class that implements an interface defines the methods for the implementation of the interface.

6. What are access modifiers?

An access specifier is a special type of keyword to specify or define the visibility and scope of entities or a class member in C#.

C# has four access modifiers:

- Internal
- Protected
- Public
- Private

They play a crucial role in encapsulation.

 

Technical OOPs Interview Questions and Answers

Given below are the OOPs concepts interview questions along with answers at a technical level.

1. What is function overloading?

Function overloading is a process where there is a declaration of multiple functions with different parameters. It is an example of compile-time polymorphism.

2. What is operator overloading?

Operator overloading is a type of polymorphism that changes the function or implements operators to achieve different tasks.

An operator is overloaded to give a user-defined meaning to it.

3. What is the default access specifier in a class definition?

Private is the default access specifier in a class definition in C#.

4. What are virtual methods?

A virtual method, or virtual function, is a method or function that is compulsorily declared with the virtual keyword.

The virtual keyword signifies that this method can be overridden by an inherited class using the override keyword to achieve polymorphism.

5. What are the operators that cannot be overloaded?

Below are certain operators.

- Member Access or Dot Operator (.)
- Pointer to Member Operator (.*)
- sizeof operator
- Scope Resolution Operator (::)
- Ternary Operator (? :)

6. What are the advantages of OOPs?

The major advantages include,

- Code reusability via inheritance
- Data Security via Encapsulation
- Simple User Interface via Abstraction
- Structured class approach with objects to maintain code with easy detection of errors.
- Maintainability of objects
- Modifiability in an OO program
- Simple Structure 

7. Explain the multicast delegate.

A multicast delegate is a variable that has references from multiple functions. All the functions to which the multicast delegate is referenced are going to be invoked when the multicast delegate is invoked.

The two steps to create a multicast delegate involve;

+ or += to subscribe to the method or function with the delegate.
+= or -= to unsubscribe the method or function with the delegate.

 

Paradigms of programming apart from OOPs

Since we have had an understanding of OOP (object-oriented programming), now let’s look at some other important paradigms of programming.

Imperative programming—

This is a new type of programming paradigm that usually tells you about a task that is accomplished by specifying a very clear and well-structured sequence of instructions. This majorly includes writing code that directly changes the program's working. This also controls flow mechanisms such as loops and conditionals.

Declarative programming—

A type of programming paradigm that tells what the program should achieve, instead of just outlining the exact steps to achieve it. It tries to define the intended result or logic while leaving the details of execution to the underlying system or interpreter. 

Functional programming—

A declarative paradigm that focuses on performing computations by evaluating mathematical functions and avoiding changes in the working and mutable data.

 It relies on "pure functions," which consistently return the same output for the same input and do not cause any side effects. Some of its core principles are recursion, immutability, and the use of higher-order functions.

 

Difference between Structured Programming and Object-Oriented Programming

Object-oriented programming (OOP) and structured programming are two programming paradigms that have their own specific differences when it comes to software design and organization.

Structured programming is a foundational programming approach that tries to tell a very clear and organized code through the use of certain well-defined components. This method allows developers to create their own user-defined functions and aims to eliminate the problems caused by unconditional jumps (like goto statements), which in turn makes way for promoting a more logical and predictable program flow.

On the other hand, object-oriented programming (OOP) is a programming paradigm that organizes code by combining data and the functions that operate on that data into certain coordinated units called objects. It also supports certain key principles such as encapsulation, abstraction, inheritance, and polymorphism.

Along with this, it has certain built-in data-hiding mechanisms through which it is able to improve the security by limiting certain unauthorized access to internal object states. This approach makes use of real-world entities and explains who performs a task, rather than simply what needs to be done.

 

Advantages and Disadvantages of OOPs

Even though OOPs has several advantages, such as a well-maintained and organized code structure, there are also certain disadvantages that are associated with it.

 Here, we have tried to discuss some of the important advantages and disadvantages of OOPs.

Reutilization—

Various classes and objects can be reused in different segments of a program, along with various other programs, which indeed play a very important role in helping you complete your work and, at the same time, save a lot of your time and effort. 

Efficient handling of difficult problems—

OOPs, no doubt, plays a very essential role in breaking down various difficult problems into easier and smaller objects, which indeed makes the process very smooth and efficient.

Encapsulation—

Various data are packed together within an object, which in a way secures the data from certain illegal access. 

Now, since we know about the important advantages of OOPs, let's discuss some of the disadvantages associated with it.

Potential Performance Overhead:

Object-oriented programming can introduce performance overhead due to the management of objects and method resolution. These factors can often result in slower execution compared to more straightforward and procedural programming approaches, especially when it comes to certain performance-critical applications.

Limited Applicability Across All Domains:

Even though OOPs is highly effective for many types of software development, it is not always the best fit for every problem.

Certain tasks are better addressed using other paradigms, such as functional or logic programming. Applying OOP in such scenarios can lead to unnecessarily complicated and less efficient solutions.

Increased Difficulty and Steeper Learning Curve:

OOP mainly includes abstract concepts such as classes, objects, inheritance, polymorphism, and encapsulation, which at times can become quite difficult for beginners to understand. 

 

Conclusion

OOPs has a good call in business and with software publishers that demand skills to develop software as per their requirements. A career with OOPs knowledge is promising, as using the methodologies of OOPs is frequent.

The OOPs interview questions and answers preparation course will bridge success to your next OOPs work.

A candidate must be subjectively prepared and go in hand with OOPs concepts for the interview to crack the tricky OOPs interview questions.

 To explore certification programs in your field, chat with our experts, and find the certification that fits your career requirements.

Data Science Master Program
Java Certification Training
Full Stack Developer Master Program

Table of Contents

• Most Popular OOPs Interview Questions And Answers
• List of Top OOPs Interview Questions And Answers In 2026
• Basic OOPs Interview Questions and Answers
• Advanced OOPs Interview Questions and Answers
• Intermediate Oops Interview Questions and Answers
• Technical OOPs Interview Questions and Answers
• Paradigms of programming apart from OOPs
• Difference between Structured Programming and Object-Oriented Programming
• Advantages and Disadvantages of OOPs
• Conclusion

Most Popular OOPs Interview Questions And Answers

Knowledge of object-oriented programming languages such as Java, C++, and Python is one of the most valued skills an organization demands. Multiple ways are there for candidates to widen their OOPs knowledge and ace the OOPs interview questions.

To begin with, the object-oriented programming system deals with implementing a programming language model around an object rather than logic or procedural programming. OOP is modeled around objects that interact with one another.

We have jotted down the ideal answers to the top OOPs questions in this article, which are the most asked OOPs interview questions. 

List of Top OOPs Interview Questions And Answers In 2026

Having a thorough read on the sample OOPs interview questions and answers pretty much caters to an idea of questions to expect.

The comprehensive segment includes the OOPs interview questions and answers that will boost your preparation for the next Object-Oriented Programming interview questions.

If you worry about how to prepare OOPs viva questions! Here is the curated list of top interview questions and answers in OOPs.

Basic OOPs Interview Questions and Answers

Here is a rundown of the answers to the OOPs basic interview questions for beginners or professionals.

1. What is an Object-Oriented Programming language?

OOPs are abbreviated as ‘Object Oriented Programming Systems’. The programming languages that execute objects and related processes following the Object-Oriented Programming paradigm, or OOP, are known as Object-Oriented Programming languages.

Java, Python, C++, Lisp, and Perl are examples of popular object-oriented programming languages.

2. What are some major Object-Oriented Programming languages?

Some of the major Object-Oriented Programming languages include:

- C++
- Java
- Javascript
- Python
- PHP, and many more. 

3. What are the main features of OOPs?

Here are the main features of OOPs;

- Data Abstraction
- Encapsulation
- Inheritance
- Polymorphism 

4. What are the core concepts of OOPS?

The OOPS core concepts are:

- Abstraction
- Association
- Aggregation
- Composition
- Encapsulation
- Inheritance
- Polymorphism 

5. What is an Object?

An object is a basic run-time entity of an object-oriented system. It is an instance of a class, and any number of instances of a class can be created. It has its own state, behavior, and identity. Objects are created from a user-defined or predefined template called a class.

6. What are the types of Inheritance in OOPS?

The different types of inheritance in OOPs are as follows:

- Single Inheritance
- Multiple Inheritance
- Multi-level Inheritance
- Multi-path Inheritance
- Hierarchical Inheritance
- Hybrid Inheritance

Suggested Read: C# Interview Questions And Answers - UPDATED 2026

Advanced OOPs Interview Questions and Answers

Given below are the OOPs interview questions for freshers at an advanced level.

1. What are the 7 OOPs concepts?

The four main theoretical principles of object-oriented programming are abstraction, encapsulation, inheritance, and polymorphism.

Java operates with three further OOP concepts: aggregation, association, and composition.

2. What is Structured Programming?

Structured Programming refers to an approach to program development that brings high-quality programs with definitive control flow.

This method highlights an approach that makes it easy to test, maintain, modify, and debug.

Most programming paradigms comprise structured programming with the OOP model.

3. What is encapsulation?

In the OOPs concept, encapsulation is binding together the data and the functions that define, manipulate, and safeguard them from getters and setters under a single unit. One can apply encapsulation using access modifiers (public, private, and protected).

For example, make member variables of a class private and provide public getter and setter methods.

4. What is Polymorphism?

Polymorphism is derived from the Greek word “poly”, which means “many”, and “morph”, implying “form.”

In an object-oriented programming system, polymorphism is the process of representing one form (a property, function, or object) in multiple forms.

It is divided into two types:

Method Overloading (compile time): also known as static binding and early binding.

Method Overriding (run time): also known as dynamic binding and late binding.

5. What is multiple inheritance?

Multiple inheritance is an inheritance type where a class inherits attributes and methods from more than one base class (or a parent class).

It has two class levels: base class and derived class.

 

 

6. What is the meaning of the “IS-A” and “HAS-A” relationship?

The “IS-A” is an inheritance relationship. The classes that inherit from the base classes are known as subclasses or child classes (base object). 

Whereas “HAS-A” is a composite relationship. One object that contains a reference to an instance of another class of a similar class.

Intermediate Oops Interview Questions and Answers

Here are the OOPs practice questions with the answers at an intermediate level for experienced professionals or freshers.

1. What is a constructor?

A constructor is a special method of a class in a program that gets invoked implicitly when we create an object of the class.

It does not have any return type, cannot be overridden in Java, and cannot be inherited by a subclass.

There are two types of Constructors, 

Implicit Constructors: They are internally created in the .NET Framework.

Explicit Constructors: They can declare explicit constructors as we prefer.

2. What is a destructor?

A destructor is a method that cannot be manually invoked in C#. It is automatically invoked when an object is to be destroyed.

The destructor clears allocated memory and frees resources by closing the files and database connections of the object to allocate to other processes.

It does not have a return type in C#, cannot be overloaded, and is public by default.

3. Is it possible for a class to inherit the constructor of its base class?

No, a class cannot inherit the constructor of its base class.

4. What are the types of constructors?

Each type of constructor differs from language to language.

Below are the feasible constructors accordingly:

- Copy constructor
- Default constructor
- Private constructor
- Parameterized constructor
- Static constructor

5. What is an interface?

The interface is an OOPs concept that contains methods but not their definitions. Interfaces, unlike classes, can only contain the signature of a class in C#. They do not contain detailed instructions or actions or any implementation.

Multiple interface inheritance with a single base is possible. You cannot create objects; any class that implements an interface defines the methods for the implementation of the interface.

6. What are access modifiers?

An access specifier is a special type of keyword to specify or define the visibility and scope of entities or a class member in C#.

C# has four access modifiers:

- Internal
- Protected
- Public
- Private

They play a crucial role in encapsulation.

Technical OOPs Interview Questions and Answers

Given below are the OOPs concepts interview questions along with answers at a technical level.

1. What is function overloading?

Function overloading is a process where there is a declaration of multiple functions with different parameters. It is an example of compile-time polymorphism.

2. What is operator overloading?

Operator overloading is a type of polymorphism that changes the function or implements operators to achieve different tasks.

An operator is overloaded to give a user-defined meaning to it.

3. What is the default access specifier in a class definition?

Private is the default access specifier in a class definition in C#.

4. What are virtual methods?

A virtual method, or virtual function, is a method or function that is compulsorily declared with the virtual keyword.

The virtual keyword signifies that this method can be overridden by an inherited class using the override keyword to achieve polymorphism.

5. What are the operators that cannot be overloaded?

Below are certain operators.

- Member Access or Dot Operator (.)
- Pointer to Member Operator (.*)
- sizeof operator
- Scope Resolution Operator (::)
- Ternary Operator (? :)

6. What are the advantages of OOPs?

The major advantages include,

- Code reusability via inheritance
- Data Security via Encapsulation
- Simple User Interface via Abstraction
- Structured class approach with objects to maintain code with easy detection of errors.
- Maintainability of objects
- Modifiability in an OO program
- Simple Structure 

7. Explain the multicast delegate.

A multicast delegate is a variable that has references from multiple functions. All the functions to which the multicast delegate is referenced are going to be invoked when the multicast delegate is invoked.

The two steps to create a multicast delegate involve;

+ or += to subscribe to the method or function with the delegate.
+= or -= to unsubscribe the method or function with the delegate.

Paradigms of programming apart from OOPs

Since we have had an understanding of OOP (object-oriented programming), now let’s look at some other important paradigms of programming.

Imperative programming—

This is a new type of programming paradigm that usually tells you about a task that is accomplished by specifying a very clear and well-structured sequence of instructions. This majorly includes writing code that directly changes the program's working. This also controls flow mechanisms such as loops and conditionals.

Declarative programming—

A type of programming paradigm that tells what the program should achieve, instead of just outlining the exact steps to achieve it. It tries to define the intended result or logic while leaving the details of execution to the underlying system or interpreter. 

Functional programming—

A declarative paradigm that focuses on performing computations by evaluating mathematical functions and avoiding changes in the working and mutable data.

 It relies on "pure functions," which consistently return the same output for the same input and do not cause any side effects. Some of its core principles are recursion, immutability, and the use of higher-order functions.

 

Difference between Structured Programming and Object-Oriented Programming

Object-oriented programming (OOP) and structured programming are two programming paradigms that have their own specific differences when it comes to software design and organization.

Structured programming is a foundational programming approach that tries to tell a very clear and organized code through the use of certain well-defined components. This method allows developers to create their own user-defined functions and aims to eliminate the problems caused by unconditional jumps (like goto statements), which in turn makes way for promoting a more logical and predictable program flow.

On the other hand, object-oriented programming (OOP) is a programming paradigm that organizes code by combining data and the functions that operate on that data into certain coordinated units called objects. It also supports certain key principles such as encapsulation, abstraction, inheritance, and polymorphism.

Along with this, it has certain built-in data-hiding mechanisms through which it is able to improve the security by limiting certain unauthorized access to internal object states. This approach makes use of real-world entities and explains who performs a task, rather than simply what needs to be done.

Advantages and Disadvantages of OOPs

Even though OOPs has several advantages, such as a well-maintained and organized code structure, there are also certain disadvantages that are associated with it.

 Here, we have tried to discuss some of the important advantages and disadvantages of OOPs.

Reutilization—

Various classes and objects can be reused in different segments of a program, along with various other programs, which indeed play a very important role in helping you complete your work and, at the same time, save a lot of your time and effort. 

Efficient handling of difficult problems—

OOPs, no doubt, plays a very essential role in breaking down various difficult problems into easier and smaller objects, which indeed makes the process very smooth and efficient.

Encapsulation—

Various data are packed together within an object, which in a way secures the data from certain illegal access. 

Now, since we know about the important advantages of OOPs, let's discuss some of the disadvantages associated with it.

Potential Performance Overhead:

Object-oriented programming can introduce performance overhead due to the management of objects and method resolution. These factors can often result in slower execution compared to more straightforward and procedural programming approaches, especially when it comes to certain performance-critical applications.

Limited Applicability Across All Domains:

Even though OOPs is highly effective for many types of software development, it is not always the best fit for every problem.

Certain tasks are better addressed using other paradigms, such as functional or logic programming. Applying OOP in such scenarios can lead to unnecessarily complicated and less efficient solutions.

Increased Difficulty and Steeper Learning Curve:

OOP mainly includes abstract concepts such as classes, objects, inheritance, polymorphism, and encapsulation, which at times can become quite difficult for beginners to understand. 

Conclusion

OOPs has a good call in business and with software publishers that demand skills to develop software as per their requirements. A career with OOPs knowledge is promising, as using the methodologies of OOPs is frequent.

The OOPs interview questions and answers preparation course will bridge success to your next OOPs work.

A candidate must be subjectively prepared and go in hand with OOPs concepts for the interview to crack the tricky OOPs interview questions.

 To explore certification programs in your field, chat with our experts, and find the certification that fits your career requirements.

Data Science Master Program
Java Certification Training
Full Stack Developer Master Program