Java OOPs Interview Questions and Answers

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

OOP is a programming paradigm that uses objects to organize code. It involves concepts like encapsulation, inheritance, and polymorphism.

Ques 2. Explain the concept of encapsulation in Java.

Encapsulation is the bundling of data and methods that operate on the data into a single unit known as a class. It helps in hiding the implementation details and restricting access to the internal state of an object.

Example:

class BankAccount {
  private double balance;
  // other methods and fields
}

Ques 3. What is the difference between abstraction and encapsulation?

Abstraction involves hiding the complex reality while encapsulation involves bundling the data and the methods that operate on the data into a single unit.

Ques 4. How does inheritance work in Java?

Inheritance allows a class to inherit properties and behaviors from another class. It promotes code reusability and establishes a relationship between a superclass and a subclass.

Example:

class Animal {
 /* properties and methods */
 }
class Dog extends Animal { /* additional methods and properties */ }

Ques 5. Explain polymorphism in Java.

Polymorphism allows objects of different types to be treated as objects of a common type. It can be achieved through method overloading and method overriding.

Example:

void drawShape(Shape s) {
 /* method implementation */
 }