# Object-Oriented Programming (OOP)
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

OOP organizes code around objects (data + behavior) rather than functions. Four pillars: Encapsulation (hide internals), Inheritance (reuse through hierarchy), Polymorphism (same interface, different behavior), Abstraction (simplify complex reality). Languages: Java, C++, Python, C#, Ruby.

## Core Explanation

Encapsulation: private fields, public methods — protects data integrity. Inheritance: `class Dog extends Animal` — code reuse but can create fragile hierarchies. Polymorphism: `animal.speak()` works differently for Dog vs Cat. Composition over inheritance: has-a vs is-a — more flexible. SOLID principles (Robert C. Martin) guide good OOP design.

## Further Reading

- [Object-Oriented Analysis and Design (Booch)](undefined)