Book Image

Learn Kotlin Programming - Second Edition

By : Stephen Samuel, Stefan Bocutiu
Book Image

Learn Kotlin Programming - Second Edition

By: Stephen Samuel, Stefan Bocutiu

Overview of this book

Kotlin is a general-purpose programming language used for developing cross-platform applications. Complete with a comprehensive introduction and projects covering the full set of Kotlin programming features, this book will take you through the fundamentals of Kotlin and get you up to speed in no time. Learn Kotlin Programming covers the installation, tools, and how to write basic programs in Kotlin. You'll learn how to implement object-oriented programming in Kotlin and easily reuse your program or parts of it. The book explains DSL construction, serialization, null safety aspects, and type parameterization to help you build robust apps. You'll learn how to destructure expressions and write your own. You'll then get to grips with building scalable apps by exploring advanced topics such as testing, concurrency, microservices, coroutines, and Kotlin DSL builders. Furthermore, you'll be introduced to the kotlinx.serialization framework, which is used to persist objects in JSON, Protobuf, and other formats. By the end of this book, you'll be well versed with all the new features in Kotlin and will be able to build robust applications skillfully.
Table of Contents (21 chapters)
Free Chapter
1
Section 1: Fundamental Concepts in Kotlin
5
Section 2: Practical Concepts in Kotlin
15
Section 3: Advanced Concepts in Kotlin

Kotlin from Java

Just as Java can be used seamlessly in Kotlin, Kotlin can just as easily be used from your Java programs. The following sections will cover some ways in which Kotlin code can be reused in other projects written in Java.

Top-level functions

The JVM does not support top-level functions. Therefore, to make them work with Java, the Kotlin compiler creates a Java class with the name of the 'kt' file with the first letter being capitalized. The functions are then defined as Java methods on this class, which must be instantiated before use.

For example, consider the following top-level function:

    package com.packt.chapter4 
    fun cube(n: Int): Int = n * n * n 

For this, the Kotlin compiler will generate...