This book is a hands-on programming guide for Java developers who want to gain practical, production-ready knowledge of Kotlin. Whether you’re maintaining Java systems or adopting Kotlin for Android, backend, or cross-platform projects, it will help you bridge the gap by building on your existing understanding of Java’s syntax and design principles. You’ll begin by learning why Kotlin was created and how it improves on Java – exploring types, expressions, control flow, and null handling while mapping each concept to familiar Java constructs. Each topic is introduced with clear purpose, showing how Kotlin’s concise syntax, safety features, and expressive APIs lead to cleaner, more maintainable code. As you progress, you’ll master object-oriented and functional programming, extension functions, smart casting, and interoperability with Java. The second half of the book dives into generics, data and sealed classes, coroutines for concurrency, and DSL design – demonstrating when and why to use these features to build scalable, elegant solutions. By the end, you’ll not only write idiomatic Kotlin but also understand the reasoning behind its design, enabling you to craft modern, reliable applications with confidence.