Refactoring Kotlin Code: Improving Architecture and Performance

The book "Refactoring Kotlin Code" is a practical guide for developers who want to take their Kotlin skills to the next level. Unlike academic textbooks, this book focuses on real-world tasks: how to make code not just functional, but maintainable, scalable, and performant.

What is this book about?

You will learn how to systematically improve existing code without breaking functionality. Each chapter is dedicated to specific problems and their solutions:

• Refactoring Basics — when and why to refactor, how to avoid common mistakes.
• Clean Code in Kotlin — naming, function and class structure, working with null-safety.
• Performance Optimization — inline functions, lazy evaluation, working with collections and coroutines.
• Patterns and Anti-patterns — how to apply GoF patterns in Kotlin and which pitfalls to avoid.
• Working with Legacy Code — strategies for gradually improving large projects.
• Testing and Refactoring — how tests help safely change code.

Who is this book for?

• Java developers transitioning to Kotlin who want to write idiomatic code.
• Android developers who want to improve the architecture of their applications.
• Backend developers using Kotlin (Ktor, Spring Boot) striving for cleanliness and performance.
• Tech leads and architects responsible for codebase quality.

What will you learn?

• How to identify code smells in Kotlin projects.
• How to use automated tools (Detekt, Ktlint) to maintain quality.
• How to refactor coroutines and Flow without losing readability.
• How to turn spaghetti code into a modular, testable architecture.

The book is rich with code examples that can be immediately applied in practice. Each section contains step-by-step instructions: from "bad" code to "good" code with an explanation of each change. You will learn to see not only that the code works, but also how good it is from a long-term maintenance perspective.

Why should you read this book? Because refactoring is not a luxury, but a necessity. In a world where projects live for years, the ability to safely and effectively improve code becomes a key developer skill. This book will save you hours of debugging and rewriting, and your colleagues will thank you for clean, understandable code.

Perfect for self-study and as a desktop reference for daily work. Start improving your code today!