Object-Oriented Programming (OOP) is a key part of software development interviews. Companies test how well you understand concepts like encapsulation, inheritance, polymorphism, and abstraction. This list of top 50+ OOPs interview questions and answers for 2025 covers both basic and advanced topics. It is designed to help you explain OOP principles clearly and solve real-world problems.
If you are preparing for a technical interview, going through these OOPs interview questions will sharpen your approach and boost your confidence.
Let’s get started.
Fun Fact: Employees skilled in Object-Oriented Programming earn an average salary of ₹24.7 lakhs per year, with most salaries falling between ₹17.8 lakhs and ₹71.7 lakhs annually.
OOPs Basic Interview Questions
Here are the basic Object Oriented Programming interview questions and answers:
- What are the four main principles of Object-Oriented Programming?
The four main principles of OOP are:
- Encapsulation: Wrapping data and methods within a class while restricting direct access to the data.
- Abstraction: Hiding unnecessary details and exposing only relevant parts of an object.
- Inheritance: Allowing a class (child) to derive properties and behaviour from another class (parent).
- Polymorphism: Enabling a single interface to be used for different types (method overloading and overriding).
- How is OOP different from procedural programming?
OOP organizes code into objects, while procedural programming follows a linear sequence of instructions. OOP focuses on reusability through classes and objects, making code more modular. Procedural programming relies on functions and structured logic but lacks inheritance and polymorphism, leading to more redundant code in complex applications.
- What is a class and how is it different from an object?
A class is a blueprint that defines attributes and behaviours for objects. It acts as a template but does not hold actual data. An object is an instance of a class, meaning it represents a real entity with assigned values. For example, if a class is “Car” with attributes like colour and speed, an object could be “Red Ferrari” with specific values.
- What is encapsulation, and why is it important?
Encapsulation restricts direct access to certain object properties by using access modifiers like private, protected, and public. It improves security and prevents unintended modifications.
For example, in Java:
class BankAccount {
private double balance;
public void deposit(double amount) { balance += amount; }
public double getBalance() { return balance; }
}
Here, balance is private, so it can’t be accessed directly. This prevents unauthorized modifications.
- What is the difference between compile-time and runtime polymorphism?
This is one of OOPs most asked interview questions.
Compile-time polymorphism occurs when the method to be called is determined at compile time (method overloading). Runtime polymorphism happens when the method to be executed is determined at runtime (method overriding).
Object Oriented Concepts Interview Questions
Here is a list of common Object Oriented Programming concepts interview questions and answers:
- What is abstraction? How does it help in OOP?
Abstraction hides unnecessary details while exposing only the relevant features of an object. It reduces complexity by allowing interaction with an object without knowing its inner workings. In Java, abstraction is implemented using abstract classes and interfaces.
- How is inheritance implemented in OOP? Give an example.
Inheritance allows a class to acquire properties and methods from another class. In Java, it is implemented using the extends keyword.
class Vehicle {
String brand = “Ford”;
}
class Car extends Vehicle {
int speed = 120;
}
Here, Car inherits the brand property from Vehicle, making the code reusable and reducing duplication.
- What is method overloading? How is it different from method overriding?
Method overloading allows multiple methods in the same class to have the same name but different parameters. Method overriding occurs when a subclass provides a specific implementation of a method already defined in the parent class. Overloading happens at compile-time, while overriding happens at runtime.
- What is an interface, and how does it differ from an abstract class?
An interface defines a contract that classes must implement. It only contains method declarations (without implementation), whereas an abstract class can have both abstract and concrete methods.
- What is the purpose of constructors in OOP?
You might also come across OOPs concepts interview questions like this one.
A constructor initializes an object when it is created. It is automatically called when an instance of a class is made.
Example:
class Person {
String name;
Person(String n) { name = n; }
}
When Person p = new Person(“John”); is executed, “John” is assigned to name automatically.
Note: Knowing OOPs concepts for interview like encapsulation, inheritance, polymorphism, and abstraction can help you answer questions easily.
OOPs Interview Questions for Freshers
Let’s go through some common Object Oriented Programming interview questions and answers for freshers:
- What is an object in OOP, and how is it created?
An object is an instance of a class. It represents real-world entities and contains both data (attributes) and behaviour (methods). Objects are created using the new keyword in most OOP languages.
Example in Java:
class Car {
String brand = “Toyota”;
}
public class Main {
public static void main(String[] args) {
Car myCar = new Car(); // Object creation
System.out.println(myCar.brand);
}
}
Here, myCar is an object of the Car class.
- What are access specifiers? Explain with examples.
Access specifiers define the visibility of class members.
- Public: Accessible from anywhere.
- Private: Accessible only within the same class.
- Protected: Accessible within the same package and subclasses.
- Default (no modifier in Java): Accessible within the same package.
Example in Java:
class Example {
private int privateVar = 10;
public int publicVar = 20;
}
public class Main {
public static void main(String[] args) {
Example obj = new Example();
// System.out.println(obj.privateVar); // Error: private access
System.out.println(obj.publicVar); // Works
}
}
- Can a constructor be private? If yes, when would you use it?
Yes, a constructor can be private. It is used in singleton classes, where only one instance of a class is allowed.
Example of Singleton Pattern:
class Singleton {
private static Singleton instance;
private Singleton() {} // Private constructor
public static Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
}
Here, Singleton prevents direct object creation from outside the class.
- What happens when you create an object without defining a constructor?
If no constructor is defined, a default constructor is automatically created by the compiler. This default constructor initializes variables with default values (0 for integers, null for objects, etc.).
- What is the difference between deep copy and shallow copy in OOP?
This is one of the most-asked OOPs concepts interview questions for freshers.
A shallow copy creates a new object but copies references to the original object’s fields. A deep copy creates a new object and duplicates all fields, including referenced objects.
Example in Java:
class ShallowCopy {
int x = 10;
}
class Main {
public static void main(String[] args) {
ShallowCopy obj1 = new ShallowCopy();
ShallowCopy obj2 = obj1; // Shallow copy
obj2.x = 20;
System.out.println(obj1.x); // Output: 20 (same reference)
}
}
For a deep copy, a new object is created with independent data.
OOPs Top Interview Questions for Experienced
These are the top interview questions for Object Oriented Programming for experienced candidates:
- What is multiple inheritance? How is it handled in Java?
Multiple inheritance allows a class to inherit from multiple classes. Java does not support multiple inheritance using classes due to the diamond problem, but it supports it through interfaces.
Example in Java using Interfaces:
interface A { void methodA(); }
interface B { void methodB(); }
class C implements A, B {
public void methodA() { System.out.println(“A”); }
public void methodB() { System.out.println(“B”); }
}
Here, C implements both A and B, avoiding conflicts.
- How do design patterns relate to OOP? Can you name a few?
Design patterns are reusable solutions for common software design problems in OOP. Some common ones include:
- Singleton: Restricts a class to a single instance.
- Factory Pattern: Creates objects without specifying the exact class.
- Observer Pattern: Allows multiple objects to listen for changes in another object.
- Decorator Pattern: Adds behaviour dynamically to objects.
- What is the SOLID principle in OOP? Explain with an example.
The SOLID principles are guidelines for writing maintainable and scalable code:
- S – Single Responsibility Principle (SRP)
- O – Open/Closed Principle (OCP)
- L – Liskov Substitution Principle (LSP)
- I – Interface Segregation Principle (ISP)
- D – Dependency Inversion Principle (DIP)
Example of SRP:
class ReportGenerator {
void generateReport() { System.out.println(“Generating report”); }
}
Here, ReportGenerator only handles report generation, following SRP.
- How does dependency injection work in OOP-based applications?
Dependency Injection (DI) is a technique where objects receive their dependencies from an external source rather than creating them internally.
Example in Java:
class Service {
void serve() { System.out.println(“Service called”); }
}
class Client {
Service service;
Client(Service service) { this.service = service; }
void doTask() { service.serve(); }
}
Here, Client does not create Service; it gets it from outside. This improves flexibility and testability.
- What are the benefits and drawbacks of using OOP in large-scale applications?
Benefits:
- Modularity: Code is organized into reusable objects.
- Scalability: New features can be added without changing existing code.
- Maintainability: Encapsulation and abstraction make debugging easier.
Drawbacks:
- Increased Complexity: Too many classes can complicate a simple task.
- Performance Overhead: Object creation and garbage collection may slow execution.
- Memory Usage: OOP requires more memory than procedural programming.
OOP is ideal for large projects but should be used wisely to avoid unnecessary complexity.
Also Read - Top 15+ Inheritance in Java Interview Questions With Answers
OOPs Interview Questions for 5 Years Experienced
If you have around 5 years of experience, you might come across these Object Oriented Programming interview questions:
- What is the role of metaclasses in Python OOP?
Metaclasses define the behaviour of classes in Python. While a class defines how objects behave, a metaclass defines how a class behaves. By default, Python classes use type as their metaclass.
Example of a Metaclass:
class Meta(type):
def __new__(cls, name, bases, dct):
print(f”Creating class: {name}”)
return super().__new__(cls, name, bases, dct)
class MyClass(metaclass=Meta):
pass
When MyClass is created, the metaclass Meta modifies its behaviour before the class exists.
- How do you handle circular dependencies in OOP design?
Circular dependencies occur when two or more classes depend on each other, leading to import errors or execution issues.
Solutions:
- Use Dependency Injection: Pass objects as arguments instead of directly importing them.
- Use Forward Declarations: In languages like C++, declare a class before defining it.
- Break into Smaller Modules: Avoid tightly coupled classes.
Also Read - Top 25+ Python OOPs Interview Question (2025)
OOPs Interview Questions for 10 Years Experienced
These Object Oriented interview questions are commonly-asked for professionals with 10 years of experience:
- How does OOP support scalability in software architecture?
OOP supports scalability by promoting modularity, maintainability, and code reusability. Large systems are built using classes and objects that can be extended without modifying existing code.
Key aspects:
- Encapsulation: Isolates changes to specific components.
- Inheritance & Polymorphism: Allows adding new behaviours without modifying old code.
- Design Patterns: Scalable architectures use patterns like Factory, Singleton, and Observer to manage complexity.
- What are mixins, and how do they improve code reusability?
Mixins are lightweight classes used to add functionality to other classes without affecting their inheritance hierarchy. Unlike traditional inheritance, mixins do not create deep hierarchies.
Also Read - Top 20 C++ OOPs Interview Questions and Answers
Advanced OOPs Interview Questions
Here are some advanced interview questions about OOPs along with answers:
- How does method resolution order (MRO) work in Python?
MRO determines the order in which base classes are searched for methods when called in a subclass. Python uses the C3 linearization (or C3 MRO) algorithm.
Example:
class A: pass
class B(A): pass
class C(A): pass
class D(B, C): pass
print(D.mro()) # Output: [D, B, C, A, object]
Python follows the depth-first, left-to-right rule while ensuring consistency.
- What is duck typing in OOP, and where is it used?
This is one of the most important OOP questions for interviews.
Duck typing allows objects to be used based on their behaviour rather than their type. In Python, if an object implements the required methods, it can be used regardless of its class. Duck typing is commonly used in dynamic languages like Python for flexible code.
Note: Advanced OOPs interview questions often include topics like design patterns, SOLID principles, multiple inheritance, and memory management.
Also Read - Top 20 OOPs ABAP Interview Questions and Answers
OOPs Technical Interview Questions
Let’s cover come important technical OOP Programming interview questions and answers:
- How does garbage collection work in OOP-based languages like Java or Python?
Garbage collection (GC) automatically frees memory by reclaiming unused objects.
- Java: Uses JVM Garbage Collector (Mark-Sweep, G1, ZGC) to clean up unreachable objects.
- Python: Uses reference counting and cycle detection (GC module).
Example in Python:
import gc
gc.collect() # Manually trigger garbage collection
In Java, GC runs in the background and cannot be forced, but it can be suggested using:
System.gc();
- What is the difference between a static method and an instance method?
- Instance Method: Requires an instance and can access instance variables.
- Static Method: Does not require an instance and cannot access instance variables.
OOPs Scenario Based Interview Questions
Here are some scenario-based OOPs interview questions with real-time examples:
- If you had to design a car rental system using OOP, how would you structure the classes?
To design a car rental system, I would use a modular approach with the following classes:
- Car (attributes: carID, model, brand, rentalPrice, availability).
- Customer (attributes: customerID, name, licenseNumber).
- Rental (attributes: rentalID, customer, car, rentalStart, rentalEnd).
- Payment (attributes: paymentID, amount, paymentStatus).
Each class would have methods to handle operations like booking a car, updating availability, processing payments, and returning a car.
- If a class has too many responsibilities, how would you refactor it?
If a class has multiple responsibilities, I would apply the Single Responsibility Principle (SRP) by breaking it into smaller, focused classes.
Example:
Before (Violating SRP)
class ReportManager {
void generateReport() { /* Generates report */ }
void saveToDatabase() { /* Saves report */ }
void sendEmail() { /* Sends report */ }
}
After (Following SRP)
class ReportGenerator { void generateReport() { /* Logic */ } }
class ReportSaver { void saveToDatabase() { /* Logic */ } }
class ReportSender { void sendEmail() { /* Logic */ } }
Now each class has a clear responsibility, making it easier to maintain and test.
Tricky OOPs Interview Questions
Here is a list of tricky OOPs interview questions and answers:
- Can you override a private method in Java? Why or why not?
No, private methods cannot be overridden in Java because they are not accessible outside their class. Overriding works only with inherited methods, but private methods are not inherited by child classes.
- Can a constructor call another constructor of the same class? Explain with an example.
Yes, a constructor can call another constructor of the same class using this(). This is called constructor chaining and helps avoid redundant code.
Example in Java:
class Car {
String model;
Car() {
this(“Default Model”); // Calling parameterized constructor
}
Car(String model) {
this.model = model;
}
}
In this example, the no-argument constructor calls the parameterized constructor.
Note: Tricky OOPs interview questions often test concepts like method overriding, diamond problem, multiple inheritance, and dynamic binding.
OOPs Polymorphism Interview Questions
You might also come across Polymorphism interview questions about OOPs like these:
- How does method overriding achieve runtime polymorphism?
Method overriding allows a subclass to provide a specific implementation of a method already defined in its parent class. The method that gets executed is determined at runtime based on the object type.
Example in Java:
class Parent {
void show() { System.out.println(“Parent”); }
}
class Child extends Parent {
void show() { System.out.println(“Child”); }
}
public class Main {
public static void main(String[] args) {
Parent obj = new Child(); // Runtime polymorphism
obj.show(); // Calls Child’s show() method
}
}
- Can polymorphism be achieved without inheritance? If yes, how?
Yes, polymorphism can be achieved using interfaces or duck typing.
Example in Python (Duck Typing):
class Dog:
def speak(self): return “Bark”
class Cat:
def speak(self): return “Meow”
def animal_sound(animal):
print(animal.speak())
animal_sound(Dog()) # Output: Bark
animal_sound(Cat()) # Output: Meow
Here, animal_sound() works with any object that has a speak() method, achieving polymorphism without inheritance.
SystemVerilog OOPs Interview Questions
Here are common SystemVerilog interview questions for Object Oriented Programming:
- How is OOP implemented in SystemVerilog?
SystemVerilog uses classes, objects, inheritance, and polymorphism for OOP implementation. It allows dynamic memory allocation and supports constrained random verification.
- How does SystemVerilog handle dynamic objects and memory allocation?
Objects in SystemVerilog are dynamically allocated using the new keyword.
Example:
class Packet;
int id;
function new(int i);
id = i;
endfunction
endclass
Packet pkt1 = new(5); // Dynamically allocated object
Garbage collection is manual, and unused objects must be set to null to free memory.
Also Read - Top 35+ System Verilog Interview Questions and Answers
Top OOPs Interview Questions MCQ
Interview questions about OOPs are often asked in MCQ format during assessments. Here are some common ones you might come across:
- Which OOP principle ensures that only relevant details of an object are exposed?
a) Encapsulation
b) Inheritance
c) Polymorphism
d) Abstraction
Answer: d) Abstraction
- What keyword is used to define a subclass in Java?
a) extends
b) implements
c) inherits
d) derive
Answer: a) extends
- Which of the following is NOT a characteristic of OOP?
a) Procedural approach
b) Encapsulation
c) Abstraction
d) Inheritance
Answer: a) Procedural approach
- In Python, what is used to indicate that a method belongs to the class rather than an instance?
a) @classmethod
b) @staticmethod
c) @property
d) None of the above
Answer: a) @classmethod
- What type of inheritance is not directly supported in Java?
a) Single inheritance
b) Multiple inheritance
c) Multilevel inheritance
d) Hierarchical inheritance
Answer: b) Multiple inheritance
- Which of the following statements about polymorphism is true?
a) It allows a class to have multiple constructors.
b) It enables a single function name to work with different types.
c) It restricts method overriding.
d) It forces the use of abstract classes.
Answer: b) It enables a single function name to work with different types.
- What is the main advantage of using interfaces in Java?
a) They allow multiple inheritance
b) They provide a way to store objects in memory
c) They prevent object creation
d) They eliminate the need for constructors
Answer: a) They allow multiple inheritance
- What is the default access specifier for class members in Java?
a) Private
b) Public
c) Protected
d) Default (package-private)
Answer: d) Default (package-private)
Company-Specific OOPs Interview Questions
Here is a list of commonly-asked company-specific OOPs interview questions.
TCS OOPs Interview Questions
Common OOPs TCS interview questions often include:
- What four principles does OOPs adhere to?
- Explain OOPs Concepts.
- What is the difference between abstraction and encapsulation with a real-world example?
- How is memory management handled in Java?
Amazon OOPs Interview Questions
These interview questions for Object Oriented Programming are asked at Amazon:
- What are the advantages of OOPS
- How would you design an inventory system using OOP principles?
- What are the advantages of using interfaces in OOP?
- How would you optimize an OOP-based e-commerce platform for high performance?
Capgemini OOPs Interview Questions
Here are some common Object Oriented interview questions asked at Capgemini:
- Explain concepts of OOPs with real time example?
- How does OOP improve code maintainability in large-scale applications?
- What is dynamic method dispatch in Java?
- What are the key differences between abstract classes and interfaces?
Microsoft OOPs Interview Questions
These are commonly-asked Object Oriented interview questions at Microsoft:
- How do you handle versioning in an OOP-based API design?
- What are delegates in C#? How are they used?
- How do SOLID principles influence software architecture in OOP?
Also Read - Top 30+ C# OOPs Interview Questions and Answers
Tips to Answer OOPs Interview Questions
Follow these tips when answering OOPs interview questions to increase your chances of getting hired:
- Be Confident: Speak clearly and explain concepts like inheritance or polymorphism as if teaching someone new.
- Use Real Examples: Support answers with real-world examples (e.g., use a “Car” class for encapsulation).
- Write Code When Asked: Keep syntax correct and simple—avoid unnecessary complexity.
- Know Common Pitfalls: Be prepared for tricky concepts like multiple inheritance and method resolution order (MRO).
- Review OOPs Cheat Sheet for Interview: It will helps you to recall key principles quickly.
- Explain Why, Not Just What: Don’t just define; explain why concepts matter in real applications.
- Stay Calm: If unsure, break down the question logically. Many OOPs interview questions test thought processes, not just answers.
Wrapping Up
So, these are the top OOPs interview questions and answers to help you prepare for technical interviews. Understanding these concepts will boost your confidence and improve your problem-solving skills. Looking for oops jobs in India? Hirist is the perfect platform for professionals with OOPs skills. Find top opportunities and apply today!
