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

Overriding rules

You decided your new class has to redefine one of the methods inherited from one of the parent classes. This is known as overriding; I have already used it in Chapter 2, Kotlin Basics. If you have already programmed in Java, you will find Kotlin a more explicit language. In Java, every method is virtual by default; therefore, each method can be overridden by any derived class. In Kotlin, you have to tag the function as being opened to redefine it. To do so, you need to add the open keyword as a prefix to the method definition, and when you redefine the method, you specifically have to mark it using the override keyword:

    abstract class SingleEngineAirplane protected constructor() { 
      abstract fun fly() 
    } 
 
    class CesnaAirplane : SingleEngineAirplane() { 
     override fun fly() { 
       println("Flying a cesna") 
     } 
   } 

You can...