Java OOP Concepts

Object-Oriented Programming (OOP)

• OOP is a programming paradigm that focuses on using objects to represent and manipulate data.
• In OOP, data is encapsulated within objects, which are defined by their properties (attributes) and behaviors (methods).

Objects

• Objects are instances of a class, created from a class in languages like Java.
• They have states and behaviors.
• Objects correspond to real-world entities, can be physical or logical, and take up space in memory.
• Examples of objects include a dog, chair, tree, etc.

Classes

• Classes are like object constructors for creating objects.
• A collection of objects is said to be a class.
• Classes are logical quantities that don't consume space in memory.
• A class is also called a template of an object.
• Classes have members, including fields, methods, and constructors.

Class Declaration

• A class declaration consists of:
  • Modifiers (public or default access)
  • Class name (initial letter)
  • Superclass (a class can only extend one parent)
  • Interfaces (a class can implement more than one interface)
  • Body (surrounded by braces, { })

Java OOP Concepts

Abstraction

• Abstraction is using simple things to represent complexity.
• It allows programmers to create reusable tools by breaking down complex systems into smaller components.

Encapsulation

• Encapsulation is the practice of keeping fields within a class private.
• It provides access to those fields via public methods, creating a protective barrier that keeps data and code safe.

Inheritance

• Inheritance is a special feature of OOP in Java.
• It lets programmers create new classes that share some attributes of existing classes.

Polymorphism

• Polymorphism allows programmers to use the same word to mean different things in different contexts.
• It has two forms: method overloading and method overriding.