Idiomatic Kotlin: Writing Efficient Code

Introduction

The book «Writing Idiomatic Kotlin» (authors Stephen Samuel and Stefan Bocutiu, 2017, 342 pages) is not just another syntax reference, but a deep dive into the culture and style of the Kotlin language. In a world where Kotlin is rapidly replacing Java in Android development and backend projects, the ability to write not just working but idiomatic code becomes a key skill. This book teaches exactly that: how to use the language's features to 100% so that code is concise, safe, and easy to read.

What This Book Is About

The authors do not waste time explaining basic syntax — it is assumed that the reader is already familiar with Kotlin fundamentals. Instead, they focus on best practices and idioms that turn ordinary code into elegant solutions. The book covers a wide range of topics:

• Working with collections: using functions like map, filter, flatMap and others for a declarative style.
• Functional programming: lambdas, higher-order functions, immutability.
• Null safety: how to avoid NullPointerException with safe calls and the Elvis operator.
• Extensions (extension functions) and properties: how to enrich existing classes without inheritance.
• Delegation: lazy initialization, delegated properties, delegates for patterns.
• Sealed classes and when expressions: modeling restricted hierarchies.