Top OOPs Interview Questions for Freshers: Your Ultimate Guide 2025

Top OOPs interview questions for freshers – Object-Oriented Programming (OOP) has revolutionized the way developers approach software design and coding. For freshers aspiring to start their careers in software development, understanding OOP concepts is essential. Interviewers frequently ask questions to evaluate a candidate’s knowledge of OOP principles and their practical application.

In this guide, we’ll cover the top OOPs interview questions for freshers, along with clear examples and explanations for each OOP pillar: encapsulation, inheritance, polymorphism, and abstraction.

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1. What is Object-Oriented Programming (OOP)?

Object-Oriented Programming is a paradigm that structures programs using objects and classes. It emphasizes reusability, modularity, and the organization of code for better maintainability.

Key features of OOP include:

• Encapsulation
• Inheritance
• Polymorphism
• Abstraction

2. What are the four pillars of OOP? Explain each with an example.

Encapsulation

Encapsulation involves wrapping data (variables) and methods (functions) that operate on the data into a single unit called a class. It restricts direct access to some components and ensures data security.

Example of Encapsulation:

class BankAccount {
    private double balance; // Encapsulated data

    // Public method to access private data
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public double getBalance() {
        return balance;
    }
}

In this example, the balance variable is private, and only the deposit and getBalance methods control access to it.

Inheritance

Inheritance allows a class (child) to inherit properties and methods from another class (parent). This promotes code reusability and establishes relationships between classes.

Example of Inheritance:

class Vehicle {
    String fuelType;

    public void startEngine() {
        System.out.println("Engine started");
    }
}

class Car extends Vehicle {
    int numberOfDoors;

    public void showCarDetails() {
        System.out.println("Fuel: " + fuelType + ", Doors: " + numberOfDoors);
    }
}

Here, the Car class inherits the fuelType property and startEngine method from the Vehicle class.

Polymorphism

Polymorphism means “many forms” and allows objects to behave differently based on the context. It can be achieved through method overloading and overriding.

Example of Polymorphism:
Method Overloading:

class Calculator {
    public int add(int a, int b) {
        return a + b;
    }

    public double add(double a, double b) {
        return a + b;
    }
}

Method Overriding:

class Animal {
    public void sound() {
        System.out.println("Animal makes a sound");
    }
}

class Dog extends Animal {
    @Override
    public void sound() {
        System.out.println("Dog barks");
    }
}

In method overriding, the Dog class provides its own implementation of the sound method from the Animal class.

Abstraction

Abstraction focuses on hiding implementation details while exposing only the necessary features of an object. It is achieved through abstract classes or interfaces.

Example of Abstraction:

abstract class Shape {
    abstract void draw(); // Abstract method
}

class Circle extends Shape {
    void draw() {
        System.out.println("Drawing a Circle");
    }
}

class Rectangle extends Shape {
    void draw() {
        System.out.println("Drawing a Rectangle");
    }
}

In this example, the Shape class provides a blueprint for its subclasses, Circle and Rectangle, to implement the draw method.

3. What is the difference between a Class and an Object?

• Class: A blueprint for creating objects. It defines properties and methods.
• Object: An instance of a class that holds specific values for the properties defined in the class.

Example:

class Person {
    String name;
    int age;
}

Person person1 = new Person(); // Object creation
person1.name = "John";
person1.age = 25;

4. Why is OOP important in software development?

OOP is essential for building scalable, reusable, and maintainable applications. Its principles make it easier to manage complexity in large codebases and enable developers to implement real-world scenarios in code.

5. What is the difference between Abstract Class and Interface?

• Abstract Class: Can contain both abstract methods and concrete methods.
• Interface: Only contains abstract methods (default in older versions of Java).

Example of Interface:

interface Animal {
    void eat();
}

class Dog implements Animal {
    public void eat() {
        System.out.println("Dog eats bones");
    }
}

6. What are some real-world applications of OOP?

• Banking Systems: Encapsulation is used to secure sensitive information like account details.
• E-commerce Websites: Polymorphism allows various payment methods to be implemented.
• Gaming: Inheritance helps define common properties like score and health for different game characters.

7. Commonly Asked OOP Questions

Here are some additional top OOPs interview questions for freshers:

• What is the difference between constructor and destructor?
• Explain the concept of static methods in OOP.
• How does multiple inheritance differ in Java and C++?

Conclusion

These top OOPs interview questions for freshers are crucial for anyone preparing for technical interviews. By understanding these concepts and practicing the examples, you’ll gain the confidence needed to excel. Remember, clarity in basics can make a lasting impression on interviewers.

If you’re preparing for an interview, bookmark this page for quick reference. All the best for your coding journey!

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