Object-Oriented Programming (OOP) is a paradigm that structures software around objects, which combine data and behavior, making systems more modular and reusable. Its four foundational pillars are **Encapsulation** (bundling data and methods within classes, e.g., a `BankAccount` with private balance and deposit/withdraw methods), **Abstraction** (hiding complex details while exposing essential functionality, e.g., a `Car` class with a `drive()` method), **Inheritance** (allowing classes to derive properties and behaviors from parent classes, e.g., `Dog` inheriting from `Animal`), and **Polymorphism** (enabling methods to behave differently depending on the object, e.g., `draw()` implemented uniquely in `Circle`, `Square`, and `Triangle`). Together, these pillars make OOP a powerful approach for building flexible, scalable, and maintainable software systems.

1. WELCOME TO COM 123
OBJECT ORIENTED PROGRAMMING
WITH JAVA
By
Bilyaminu ABUBAKAR

2. LECTURE 1

3. Course Introduction

4. Agenda
1- Course Syllabus
2- Introduction to Course

5. Course Syllabus

6. Introduction To
Object-oriented Programming
Object-oriented programming (OOP) is a model organized around
objects rather than "actions" and data rather than logic.
Historically, a program has been viewed as a logical procedure
that takes input data, processes it, and produces output data.
The programming challenge was seen as how to write the logic, not how to
define the data. Object-oriented programming takes the view that what we
really care about are the objects we want to manipulate rather than the logic
requiredtomanipulatethem.

7. Definition:
Object-Oriented Programming is methodology or Concept to
Design a Program using Object and Class.
Why Object come first because it’s an
Object-Oriented not Class-Oriented…

9. General Picture of OOP

10. Object
Any entity that has state and behaviour is known as
an object. For example: chair, pen, table, keyboard,
bike etc.
It can be physical and logical.

11. Class
Collection of objects is called class. It is a logical
entity.

12. Inheritance
When one object acquires all the properties and behaviours of
parent object i.e. known as inheritance. It provides code
reusability. It is used to achieve runtime polymorphism.

13. Polymorphism
When one task is performed by different ways i.e. known as
polymorphism
In java, we use method overloading and method overriding to
achieve polymorphism.

14. Abstraction
Hiding internal details and showing functionality is known as
abstraction. For example: phone call, we don't know the
internal processing.
In java, we use abstract class and interface to achieve
abstraction.

15. Encapsulation
Binding (or wrapping) code and data together into a single unit
is known as encapsulation. For example: capsule, it is wrapped
with different medicines.
A java class is the example of encapsulation. Java bean is the
fully encapsulated class because all the data members are
private here.

16. Benefits of Inheritance
• One of the key benefits of inheritance is to minimize the amount of
duplicate code in an application by sharing common code amongst
several subclasses
• Inheritance can also make application code more flexible to change
because classes that inherit from a common super class can be used
interchangeably. If the return type of a method is super class
• Reusability - facility to use public methods of base class without
rewriting the same.
• Extensibility - extending the base class logic as per business logic of the
derived class