Introduction to Design Patterns in Java – Gang of Four Guide

Illustration for Introduction to Design Patterns in Java – Gang of Four Guide
By Last updated:

💡 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