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

Inheritance


Inheritance is one of the main aspects of object-oriented programming. Basically, it allows classes (subclasses) to inherit members from base types (superclasses). They usually have their own functions and properties, which are not found in the base type. With inheritance, you can achieve code reuse, build class hierarchies, or extend base types with additional functionality.

Let's take a look at an example. We have the old User class we used in this chapter, and let's say we also need to have a class that represents administrator users, which will have the same properties as the base User class plus one additional property, role. We can say this would be a good use of inheritance, so let's create the AdminUser class, which extends the base User class:

open class User(var firstName: String,
var lastName: String,
var birthYear: String)

class AdminUser(firstName: String,
                lastName: String,
                birthYear: String,
var role: String): User(firstName, lastName...