Book Image

Kotlin Quick Start Guide

By : Marko Devcic
Book Image

Kotlin Quick Start Guide

By: Marko Devcic

Overview of this book

Kotlin is a general purpose, object-oriented language that primarily targets the JVM and Android. Intended as a better alternative to Java, its main goals are high interoperability with Java and increased developer productivity. Kotlin is still a new language and this book will help you to learn the core Kotlin features and get you ready for developing applications with Kotlin. This book covers Kotlin features in detail and explains them with practical code examples.You will learn how to set up the environment and take your frst steps with Kotlin and its syntax. We will cover the basics of the language, including functions, variables, and basic data types. With the basics covered, the next chapters show how functions are first-class citizens in Kotlin and deal with the object-oriented side of Kotlin. You will move on to more advanced features of Kotlin. You will explore Kotlin's Standard Library and learn how to work with the Collections API. The book finishes by putting Kotlin in to practice, showing how to build a desktop app. By the end of this book, you will be confident enough to use Kotlin for your next project.
Table of Contents (15 chapters)
Title Page
Copyright and Credits
Packt Upsell


Java uses packages to organize classes. Kotlin also has packages and they work in the same way. The biggest difference from Java is that declaring a package is optional. In Kotlin you can have a file or a class without a package.

Package declaration has to be at the top of the file. If you want to use other types that are declared in the same package, then you can access them directly. If they are declared in another package, then you have to import them first. The following example shows a package and import declarations. It shows how a package is declared on the top, uses an import from the Java standard library and declares a function on a file level:

package quickstartguide.kotlin.chapter2

import java.lang.Math.PI

fun circumference(radius: Double): Double {
return 2 * PI * radius

Unlike Java, where you import classes, Kotlin allows importing of any kind of declarations.

If you were to import the circumference function from the preceding example, it would look like this: