Introduction to Design Patterns in Java – Gang of Four Guide

Learn what design patterns are, why they matter, and how they help Java developers write clean, modular, and testable code. Covers all 23 GoF patterns categorized into creational, structural, and behavioral types.

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💡 What Are Design Patterns?

Design patterns are standard, reusable solutions to common problems in software design.

A group of four authors — known as the Gang of Four (GoF) — documented 23 patterns in their famous book:
Design Patterns: Elements of Reusable Object-Oriented Software.


✅ Benefits of Using Design Patterns

  • 📦 Write modular, clean, and maintainable code
  • 🔁 Promote code reuse and flexibility
  • 🧱 Follow industry-standard practices
  • 🧠 Improve communication with developers (patterns = common language)
  • 🧪 Make code easier to test and refactor
  • 💼 Frequently asked in job interviews

📚 What You’ll Learn in This Series

We will explore 3 main categories of Design Patterns:

1. Creational Patterns

These deal with object creation mechanisms, trying to create objects in a manner suitable to the situation.

  • Singleton
  • Factory Method
  • Abstract Factory
  • Builder
  • Prototype

2. Structural Patterns

These deal with object composition — how classes and objects are composed to form larger structures.

  • Adapter
  • Bridge
  • Composite
  • Decorator
  • Facade
  • Flyweight
  • Proxy

3. Behavioral Patterns

These focus on communication between objects.

  • Strategy
  • Observer
  • Command
  • Iterator
  • Mediator
  • Memento
  • State
  • Template Method
  • Visitor
  • Chain of Responsibility

🔍 Pre-Requisite: SOLID Principles

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

Part of a Series

This tutorial is part of our Design Patterns Java . Explore the full guide for related topics, explanations, and best practices.

View all tutorials in this series →