OOP Introduction

OOP — Object-Oriented Programming

OOP organizes code around objects — bundles of data (fields) and behavior (methods). Java is built for OOP.

Four pillars: Encapsulation, Inheritance, Polymorphism, Abstraction. You will learn each in this course.

Real-life example: A car object has data (color, speed) and behavior (accelerate, brake). You interact with the car, not raw engine wires.

• Encapsulation — hide details, expose safe methods
• Inheritance — reuse code from parent classes
• Polymorphism — one interface, many forms
• Abstraction — show only what matters

Why OOP matters in real projects

Large apps use classes to model users, orders, payments — each class owns its data and rules.

Teams work on different classes without breaking the whole system.

Real-life example: A school has Student, Teacher, Course classes — like departments in a company, each with clear duties.

// Instead of loose variables everywhere:
// String studentName; int studentMarks;

// Group related data in a class:
class Student {
    String name;
    int marks;
}