OOPs Interview Questions and Answers in 2025

Introduction

Object-oriented programming (OOPs) is a fundamental paradigm in modern software development, shaping the way developers design and structure their code. If you're getting ready for a tech interview, make sure to read OOPs interview questions and OOPs concepts. Mastering OOPs concepts is crucial for anyone looking to excel in the field of programming. 

Object-oriented programming has always been a favourite topic to be asked in interviews, So we have compiled a list of some crucial questions that are asked on the subject of OOPs. After going through these questions, your preparation for placement will reach its zenith.

Let us begin!

Basic OOPs Interview Questions and Answers

1 What do you mean by OOPs?

Ans - OOPs stand for object-oriented programming. As the name suggests, this is a pattern of programming that emphasizes more on objects and classes rather than functions. It is not a programming language but a paradigm used by almost all new generations of programming languages like Java, C++, etc.

2 Name some of the programming languages which use the concept of OOPs?

Ans - Nowadays, almost all programming languages use object-oriented concepts.

Some of them are mentioned below.

1. C++
2. Java
3. Python
4. C#
5. Ruby

3 What is the need for Object-oriented programming?

Ans - As we evolve, our problems also become more complex and the code. To solve this problem of writing complex codes, we need object-oriented programming. It allows reusability of code which shortens the code to a greater extent. The primary importance of OOPs is to bind together the data and the functions that operate on them with the help of its essential features. 

4 What are the essential features of OOPs?

Ans - There are four main pillars of object-oriented programming

1. Encapsulation
2. Polymorphism
3. Inheritance
4. Data Abstraction

Encapsulation

Encapsulation name suggests, It is the wrapping up of data and methods (functions) that manipulates them in a single unit. It is one of the essential features of OOPs and is achieved with the help of access modifiers.

Polymorphism

Polymorphism in OOPs refers to the objects created that can take many forms in different instances. The Word polymorphism has been made from "poly," which means many, and "morphs," which means forms. It can also be understood as function overloading, as in it, any object or method gets to act differently on different instances.

Inheritance 

The capability of a class to derive properties and characteristics from another class is called Inheritance. It is an actual world entity that gets implemented in OOPs.

There are three different modes of Inheritance.

1. Public mode
2. Protected mode
3. Private mode

These modes of Inheritance are used in OOPs according to the requirements.

Inheritance can be further divided into six types

1. Single Inheritance
2. Multiple Inheritance
3. Multilevel Inheritance
4. Hierarchical Inheritance
5. Hybrid Inheritance
6. Multipath Inheritance

Data abstraction

Data abstraction is the concept of object-oriented programming which shows only the necessary attributes of a code and hides all the unnecessary things. It helps in avoiding code duplication and thus increases reusability.

5 Discuss the advantages and disadvantages of OOPs?

Following are some of the advantages of OOPs

6 What are classes and objects in OOPs?

Ans - A class in object-oriented programming is a user-defined data type that contains a type's variables and methods(functions). A class object can only access these data variables and member functions.

An object in object-oriented programming is nothing but an instance of a class used in accessing the data members and member functions of a class.

7 What are the differences between OOPs and structural programming?

Ans - 

8. What are the differences between class and object?

Ans - 

Must Read Characteristics of OOPS

9. What are the differences between class and structure?

Ans - 

10. Do class and object acquire any memory?

Ans - 

When we build a class, no memory is allocated to it as it is just a blueprint. But when an object of the class is created, memory is allocated accordingly. 

We saw some of the fundamental questions the Interviewer can ask in an interview. In the next blog, we will look for some advanced questions on OOPs. Let us now summarize what we learned in this article.

11. Explain the four pillars of OOPs.

Ans - The four pillars of Object-Oriented Programming (OOPs) are:

1. Encapsulation: Bundling data (attributes) and methods (functions) that operate on that data within a single unit called a class. This promotes data protection and information hiding.
2. Abstraction: Focusing on the essential details of an object while hiding its underlying implementation. This allows users to interact with objects without worrying about the complexities of their internal workings.
3. Inheritance: Creating new classes (subclasses) that inherit properties and behaviors from existing classes (superclasses). This promotes code reusability and simplifies the creation of class hierarchies.
4. Polymorphism: The ability of objects of different classes to respond to the same method call in different ways. This allows for flexible and dynamic behavior in programs.

These principles work together to create well-structured, maintainable, and reusable code. Encapsulation protects data integrity, abstraction simplifies object interaction, inheritance promotes code reuse, and polymorphism enables flexible method behavior.

12. Describe the use cases for inheritance.

Ans - Inheritance is beneficial when you have a set of existing functionalities (parent class) that can be reused as a foundation for creating new classes (child classes) with specialized features. Here are some common use cases:

• Creating Class Hierarchies: Inheritance allows you to establish relationships between classes, where child classes inherit general attributes and methods from a parent class, and then add their own specific functionalities. For example, an Animal class can be a parent class for Dog and Cat child classes, inheriting common attributes like name and methods like eat(), while also having specific methods like bark() for dogs and purr() for cats.
• Code Reusability: By inheriting common functionalities, you avoid duplicating code and streamline development.
• Extending Functionality: Child classes can add new methods or override inherited methods to provide specialized behavior.

There are different types of inheritance to suit various needs:

• Single Inheritance: A child class inherits from one parent class.
• Multilevel Inheritance: A child class inherits from a parent class, which itself inherits from another parent class, creating a chain of inheritance.
• Hierarchical Inheritance: Multiple child classes inherit from a single parent class.

13. Differentiate between method overloading and overriding.

Ans - 

Method Overloading: Occurs within the same class when you define multiple methods with the same name but different numbers or types of parameters. The compiler determines which overloaded method to call based on the arguments provided at runtime.

Method Overriding: Involves redefining a method inherited from a parent class within a child class. The child class method has the same name, return type, and sometimes parameter list (though covariant parameter types are allowed) as the parent class method. Overriding allows for customizing inherited behavior in child classes.

Here's an example:

• Java

Java

class Shape {
  public void area() {
    System.out.println("Area calculation for generic shape");
  }
}

class Square extends Shape {
  @Override // Not mandatory, but good practice to indicate overriding
  public void area(int side) { // Overloaded method with parameter
    System.out.println("Area of square: " + side * side);
  }
}

You can also try this code with Online Java Compiler

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In this example, the Shape class has a general area() method. The Square class inherits this method but overrides it with a new area(int side) method specific to calculating the area of a square.

14. Explain the benefits of encapsulation.

Ans - Encapsulation offers several advantages:

• Data Protection: By encapsulating data (attributes) within a class and making them private, you control access to that data. Public methods within the class act as gatekeepers, ensuring data is modified only through authorized channels.
• Information Hiding: Encapsulation hides the internal implementation details of a class, exposing only essential functionalities through public methods. This simplifies code interaction and reduces the risk of unintended modifications.
• Modularity: Encapsulation promotes modularity by grouping related data and methods within a single unit (class). This makes code easier to understand, maintain, and reuse.
• Improved Maintainability: Changes made within a class are less likely to impact other parts of the codebase if data access is controlled through proper encapsulation.

15. Describe a scenario where polymorphism is useful.

Ans - Polymorphism allows objects of different classes to respond to the same method call in different ways. Suppose we have a scenario i.e., animal sounds with polymorphism. Imagine you're building a program for a zoo website that displays information and plays sounds for different animals. Here's how polymorphism can be useful:

• Base Class Animal: Create a base class Animal with attributes like name and type (e.g., mammal, bird). It can also have a generic makeSound() method that might print a message like "Animal sound".
• Subclasses for Specific Animals: Create subclasses like Dog, Cat, and Bird that inherit from Animal. Each subclass can override the makeSound() method to provide its specific sound (e.g., Dog.makeSound() prints "Woof!", Cat.makeSound() prints "Meow!").
• Polymorphic Array: Create an array of type Animal and add instances of Dog, Cat, and Bird to it. This allows you to treat all objects as animals initially.
• Looping and Polymorphic Behavior: Loop through the animal array and call the makeSound() method on each object. Here's the magic of polymorphism: even though the variable holding each object is of type Animal, the actual makeSound() method called will be the overridden version specific to the object's subclass (Dog, Cat, or Bird), resulting in the appropriate animal sound being played.