Kotlin in Action

Introduction

The book "Kotlin in Action" (original title Kotlin in Action) is one of the first and most authoritative guides to the Kotlin programming language, written directly by the language developers from JetBrains. Dmitry Jemerov and Svetlana Isakova, leading engineers of the Kotlin team, created a practical guide that helps you quickly master the syntax, idioms, and ecosystem of the language. The book was published in 2017, but its content remains relevant today, as it covers the fundamental concepts of Kotlin that have not undergone drastic changes.

What the book is about

"Kotlin in Action" is a structured introduction to the Kotlin language with an emphasis on practical application. The authors consistently guide the reader from basic constructs to advanced features such as coroutines, DSLs, and Java interoperability. The book is divided into three parts:

• Part I: Introduction to Kotlin — installation, basic syntax, functions, classes, data types.
• Part II: Idioms and Advanced Features — lambdas, functional programming, generics, delegation, annotations, reflection.
• Part III: Kotlin in Real Projects — creating DSLs, Java interoperability, testing, multithreading, and coroutines.

Each chapter contains numerous code examples that can be immediately tried out in IntelliJ IDEA or Android Studio. The authors do not just list the language's features but explain why a particular construct works the way it does and how best to apply it in everyday development.

Who this book is for

The book is aimed at developers already familiar with Java or another object-oriented language (C#, C++). It may be challenging for beginners due to the lack of an introduction to basic programming concepts. However, if you have experience with Java, you will quickly get into it. The book will be useful for:

• Android developers looking to switch to Kotlin;
• Java developers who want to learn a modern language for the JVM;
• team leads and architects evaluating Kotlin for new projects;
• students studying programming languages at an advanced level.

What the reader will learn

After reading the book, you will be able to:

• Write concise and safe Kotlin code, avoiding NullPointerException;
• Use functional features: lambdas, higher-order functions, sequences;
• Create type-safe DSLs (e.g., for building HTML or SQL queries);
• Effectively interoperate with Java code using annotations and compatibility mechanisms;
• Apply coroutines for asynchronous programming;
• Understand the inner workings of generics, delegation, and reflection in Kotlin.

Strengths of the book

The main advantage of "Kotlin in Action" is the authority of the authors. Dmitry Jemerov and Svetlana Isakova not only know the language, they created it. Therefore, the explanations are precise, and the examples reflect the best practices accepted in the Kotlin community. The book is written in a lively, accessible language, with complex concepts broken down using simple examples. The chapter on coroutines deserves special mention — at the time of the book's release, it was one of the first detailed publications on the topic. The book also contains many tips on migrating from Java to Kotlin, which is especially valuable for teams working with legacy code.

Who it is recommended for

I recommend this book to everyone who is serious about learning Kotlin and applying it in commercial development. If you are an Android developer and want to write modern applications in Kotlin — this is your choice. If you are a Java programmer looking to broaden your horizons and increase productivity — the book will provide a solid foundation. Even if you are already somewhat familiar with Kotlin, "Kotlin in Action" will help you systematize your knowledge and fill in the gaps. The only caveat: the book