Design Patterns in Java

The book "Design Patterns in Java" is a practical guide to applying 23 classic GoF (Gang of Four) patterns in modern Java development. The author, an experienced Java architect with 15 years of experience, breaks down each pattern step by step: from theoretical foundations to real-world usage scenarios.

What this book is about

The book covers all three groups of design patterns:

• Creational patterns (Singleton, Factory Method, Abstract Factory, Builder, Prototype) — managing the object creation process.
• Structural patterns (Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy) — organizing relationships between classes and objects.
• Behavioral patterns (Chain of Responsibility, Command, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, Visitor) — distributing responsibilities and algorithms among objects.

Who this book is for

This edition will be useful for:

• Junior developers who want to level up and write not just working code, but high-quality, maintainable code.
• Middle developers looking to systematize their knowledge and master advanced design techniques.
• Senior developers and architects seeking new approaches to solving typical problems and refactoring legacy code.
• Students studying object-oriented programming and preparing for technical interviews.

What you will learn

• What problems each pattern solves and when to apply it.
• How to implement patterns in Java 17+ using modern language features (records, sealed classes, pattern matching).
• How to combine patterns to solve complex architectural problems.
• How to avoid anti-patterns and common design mistakes.
• How to refactor code using patterns.

Book features

• Each pattern is accompanied by a UML diagram and complete Java code.
• Real-world examples from practice: working with databases, web services, GUI applications.
• Comparative analysis of similar patterns (e.g., Strategy vs State, Factory Method vs Abstract Factory).
• Practical exercises to reinforce the material.

The book is written in simple and clear language, with an emphasis on practice. You will not just memorize patterns, but learn to see opportunities for their application in everyday work. This is a must-read for every Java developer striving for professional growth.