Oop(Object-Oriented Programming) in Java

What is Oop?

• Oop(Object-Oriented Programming) is a method of programming where we organize code like real-world things.

• Classes → blueprint
  Objects → real things created from class

• Example:
  Class = Car design
  Object = Actual car

Main Concepts of Oop

1) Polymorphism (Many Forms)

• Same method name, different behavior

• Example: Same method → pay()

But different behavior:

• Credit Card → pay via card

• UPI → pay via mobile

• Net Banking → pay via bank

2) Inheritance (Reuse)

• One class can use properties of another class

• Example: Vehicle System

Parent class → Vehicle
Child classes → Car, Bike

• All vehicles have: Speed, Fuel

• Car & Bike can reuse these properties

3) Abstraction (Hide Details)

• Show only important things, hide internal details

• Example: ATM Machine

We just:

• Insert card

• Enter PIN

• Withdraw money

We don’t know:

• how money is processed

• how server works

✔ Only important things shown
✔ Internal logic hidden

4) Encapsulation (Data Hiding)

• Wrapping data + methods together in one class

• Example: Bank Account

Balance is hidden
Cannot directly change it
Must use methods like: deposit(), withdraw()

• You can’t access balance directly

• Data is safe