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
Dedication
Packt Upsell
Contributors
Preface
Index

Enum classes


Enumeration types are used to define a set of named constants. Kotlin, same as Java has an enumeration type, the enum class. Let's say that you want to define a type that represents all months in a year. Yes, you could create a normal class with one property, month name, which is of String type. But, then you would have to guard against invalid month name assignments and throw exceptions in such cases. The class would be error-prone and users of your class wouldn't be happy. This is a perfect use case for the enum class, and here is how you would define an enum type to represent all the months of the year:

enum class Month {
JANUARY,
FEBRUARY,
MARCH,
APRIL,
MAY,
JUNE,
JULY,
AUGUST,
SEPTEMBER,
OCTOBER,
NOVEMBER,
DECEMBER
}

Now you can't have invalid months, and if you want to assign a month type to a variable, you can only choose from the constants we have defined:

val march = Month.MARCH

Enum classes, both in Kotlin and in Java, are full-blown classes, so they can have members,...