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Learn Kotlin Programming

Learn Kotlin Programming

By : Stephen Samuel, Stefan Bocutiu
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Learn Kotlin Programming

Learn Kotlin Programming

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)
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1
Section 1: Fundamental Concepts in Kotlin
5
Section 2: Practical Concepts in Kotlin
15
Section 3: Advanced Concepts in Kotlin

Kotlin for scripting

Kotlin can also be run as a script. If bash or Perl is not for you, now you have an alternative.

Say you want to delete all files that are older than N given days. The following code example does just that:

    import java.io.File 
    val purgeTime = System.currentTimeMillis() - args[1].toLong() * 24  * 60 * 60 * 1000 
    val folders = File(args[0]).listFiles { file -> file.isFile } 
    folders ?.filter { 
      file -> file.lastModified() < purgeTime } 
    ?.forEach { 
      file -> println("Deleting ${file.absolutePath}") 
      file.delete() 
    } 

Create a file named delete.kts with the preceding content. Note the predefined variable args, which contains all the incoming parameters passed when it is invoked. You might wonder what the ? character is doing there. If you are familiar with the C# language and you know about nullable...

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