OOP organizes software around objects rather than functions. Java uses OOP to create reusable, secure and scalable applications.

Core OOP Concepts in Java

• Class
• Object
• Encapsulation
• Abstraction
• Polymorphism
• Inheritance
• Dynamic Binding
• Message Passing

Definition List

• Class: A user-defined blueprint containing variables and methods used to create objects.
• Object: An instance of a class that occupies memory and accesses class members.
• Encapsulation: Wrapping data and methods into a single unit while restricting direct access.
• Abstraction: Hiding implementation details and showing only essential features.
• Polymorphism: The ability of a method or object to take multiple forms.
• Inheritance: A mechanism where one class acquires properties of another class.
• Dynamic Binding: Method to execute is determined at runtime.
• Message Passing: Communication between objects through method calls.

Class in Java

A class is a blueprint for creating objects. It contains variables and methods but does not consume memory until objects are created.

• Defines object properties and behavior
• Supports code reusability
• Does not consume memory until objects are created

Object in Java

An object is an instance of a class. Memory is allocated only when an object is created. Each object can have different values for the same class properties.

Encapsulation in Java

Encapsulation wraps data and methods into a single unit. It protects data from unauthorized access through getters and setters.

• Data hiding from external access
• Better security and maintainability
• Controlled access using getters and setters

Abstraction in Java

Abstraction shows only essential features and hides implementation details. Like a car driver who knows the pedals but not the engine internals.

• Reduces complexity
• Improves security
• Simplifies program usage

Polymorphism

Polymorphism means many forms. The same method behaves differently based on context.

• Compile-Time Polymorphism: Achieved through method overloading.
• Runtime Polymorphism: Achieved through method overriding.

Inheritance in Java

Inheritance allows a class to acquire properties and behaviors of another class. Promotes code reuse and reduces redundancy.

• Base Class (Superclass): The class whose properties are inherited.
• Derived Class (Subclass): The class that inherits from the superclass.

Dynamic Binding in Java

Also called Late Binding. The method to execute is determined at runtime, not compile time.

Animal animal = new Dog();
animal.speak(); // Dog's method runs at runtime

Message Passing in Java

Objects communicate by invoking methods on each other. Each method call is a message passed between objects.

FAQ

1. What is a class in Java?

A blueprint that defines object properties and behaviors.

2. What is the difference between a class and an object?

A class is a template. An object is an instance that occupies memory.

3. Why are OOP concepts important in Java?

They improve reusability, security, maintainability and scalability.