Object-Oriented Programming: Beginner to Pro

A complete, 20-chapter, language-agnostic guide to Object-Oriented Programming — from what a class and object are, through encapsulation, inheritance, and polymorphism, all the way to SOLID principles, the classic design patterns, and UML. Explained with universal, language-neutral examples applicable to Java, C++, C#, Python, PHP, and more.

Introduction to OOP

What is Object-Oriented Programming?Procedural vs. Object-Oriented Programming

Classes and Objects

Classes as Blueprints Objects as Instances

Encapsulation

What is Encapsulation?Getters, Setters, and Controlled Access

Abstraction

What is Abstraction?Abstraction vs. Encapsulation

Inheritance

What is Inheritance?Types of Inheritance

Polymorphism

What is Polymorphism?Compile-Time vs. Runtime Polymorphism

Constructors and Destructors

Constructors: Initializing Objects Destructors and Resource Cleanup

Access Modifiers and Visibility

Public, Private, and Protected Why Visibility Matters: The Principle of Least Privilege

Static Members and Class-Level State

Static Properties and Methods

Interfaces

What are Interfaces?Interfaces vs. Abstract Classes

Abstract Classes

Understanding Abstract Classes

Composition vs. Inheritance

"Has-a" vs. "Is-a" Relationships Why 'Favor Composition Over Inheritance'?

Method Overloading and Overriding

Method Overriding Method Overloading

Operator Overloading

Operator Overloading Explained

The SOLID Principles

S — Single Responsibility, O — Open/Closed L — Liskov Substitution, I — Interface Segregation, D — Dependency Inversion

Creational Design Patterns

Singleton and Factory Patterns Builder and Prototype Patterns

Structural Design Patterns

Adapter and Decorator Patterns Facade and Composite Patterns

Behavioral Design Patterns

Strategy and Observer Patterns Command and Iterator Patterns

UML and Class Diagrams

Reading UML Class Diagrams

OOP Best Practices, Anti-Patterns & Wrap-Up

Common OOP Anti-Patterns to Avoid A Pro-Level OOP Design Checklist

OOP Tutorial 2026: Object-Oriented Programming Beginner to Pro | DevNotes