Refactoring Kotlin Code: Improving Architecture, Performance, and Readability

The book "Refactoring Kotlin Code" is a practical guide for developers who want to learn how to improve existing Kotlin code. Unlike abstract theoretical manuals, this book offers specific techniques, examples, and patterns that can be applied in real projects.

What is this book about?

The book covers the full refactoring cycle: from identifying code smells to implementing improvements and testing changes. You will learn how to:

• identify and eliminate common problems in Kotlin code (long functions, duplication, complex conditions);
• apply classic and Kotlin-specific refactoring techniques (inline functions, sealed classes, coroutines);
• improve project architecture without changing external behavior;
• enhance code performance and readability;
• work with tests and ensure change safety.

Who is this book for?

• Junior developers — will master the basics of refactoring and learn to write higher-quality code from the start of their careers.
• Middle and Senior developers — will deepen their knowledge and learn advanced techniques and approaches for working with legacy projects.
• Tech Leads and Architects — will gain tools for evaluating and improving the codebase within a team.

What will you learn?

• How to properly separate responsibilities between classes and functions.
• How to use Kotlin features (extension functions, data classes, lambdas) to simplify code.
• How to perform refactoring under time constraints and strict deadlines.
• How to integrate refactoring into the CI/CD process and avoid regressions.
• How to work with inheritance, composition, and API design.

The book contains over 50 real code examples, error analyses, and step-by-step instructions. Each chapter concludes with practical exercises to reinforce the material.

"Refactoring Kotlin Code" is not just a textbook, but a desk reference for anyone who writes in Kotlin. Whether you are working on an Android application, a Spring Boot backend, or a multiplatform project, this book will help make your code cleaner, faster, and more reliable.