OOP in Java (Object-Oriented Programming) is a programming approach where you design programs using objects and classes instead of just functions and logic.
- Class
- Object
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
Class:
A class is a blueprint or template used to create objects.
It defines variables (data) and methods (behavior).
Example:
“Car” is a class — it defines properties like color, speed, and behavior like drive.
Object:
An object is an instance of a class.
It represents a real-world entity and contains data + behavior.
Key Points:
- Object occupies memory
- Used to access class members
- Can create multiple objects from one class
Example :
Class → Car
Object → My car
Explanation:
Properties → color, model, speed
Behaviors → drive, brake
So, a specific car (like your red car) is an object.
Encapsulation:
Encapsulation is the process of wrapping data (variables) and methods into a single unit (class) and restricting direct access to the data.
Example:
Bank account: You cannot directly access balance; you use deposit/withdraw methods.
Inheritance:
Inheritance is a concept where one class (child) acquires properties and methods of another class (parent).
Parent class (Superclass) → common features
Child class (Subclass) → inherits + can add new features
Example:
Dog inherits from Animal → Dog can eat (common) and also bark (its own).
Polymorphism:
Polymorphism means “many forms” — the same method or function can behave differently in different situations.
Example:
A person speaks:
Teacher → teaches
Student → learns
Same action “speak”, different behavior.
Abstraction:
Abstraction means hiding internal implementation details and showing only the essential features to the user.
Example:
ATM machine: You withdraw money without knowing internal banking process.
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