Top 25 Java OOP Interview Questions and Answers

Master Java OOP concepts with these top 25 object-oriented programming interview questions. Learn about classes, objects, inheritance, polymorphism, encapsulation, abstraction, interfaces, and design principles.

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

OOP is a programming paradigm based on the concept of “objects,” which can contain data in the form of fields (attributes) and code in the form of methods. It allows structuring programs so that properties and behaviors are bundled together.

Java follows the OOP paradigm and supports key principles like encapsulation, inheritance, polymorphism, and abstraction. This approach promotes code reusability, scalability, and easier maintenance.

2. What are the four main principles of OOP?

The four core principles of object-oriented programming are:

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

Each principle contributes to better software design by providing a way to organize code effectively and ensure flexibility and maintainability.

3. What is a class in Java?