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

Function types

Functions are first-class citizens in Kotlin. You can define function types and store them in variables. Functions can return other functions and accept functions as arguments.

Defining function types

Let's take a look at an example of how to define a function type and initialize the variable with a lambda:

val multiplier: (Int, Int) -> Int = { a, b -> a * b }

This function type has two parameters of type Int and returns an Int. The function type syntax always starts with parentheses, where you declare function parameters, then the arrow, and after the arrow, a return type.

Here's how you'd declare a function type that has no parameters and no return type:

val print: () -> Unit = { println("Kotlin") }

Of course, type inference works on function types, so the preceding example could have been written like this:

val print2 = { println("Kotlin") }

Function types can also be nullable; notice how we need to wrap the whole function type inside another set of parentheses and then...