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Kotlin Programming Cookbook

You're reading from   Kotlin Programming Cookbook Explore more than 100 recipes that show how to build robust mobile and web applications with Kotlin, Spring Boot, and Android

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Product type Paperback
Published in Jan 2018
Publisher
ISBN-13 9781788472142
Length 434 pages
Edition 1st Edition
Languages
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Authors (2):
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Aanand Shekhar Roy Aanand Shekhar Roy
Author Profile Icon Aanand Shekhar Roy
Aanand Shekhar Roy
Rashi Karanpuria Rashi Karanpuria
Author Profile Icon Rashi Karanpuria
Rashi Karanpuria
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Toc

Table of Contents (16) Chapters Close

Preface 1. Installation and Working with Environment FREE CHAPTER 2. Control Flow 3. Classes and Objects 4. Functions 5. Object-Oriented Programming 6. Collections Framework 7. Handling File Operations in Kotlin 8. Anko Commons and Extension Function 9. Anko Layouts 10. Databases and Dependency Injection 11. Networking and Concurrency 12. Lambdas and Delegates 13. Testing 14. Web Services with Kotlin 15. Other Books You May Enjoy

How to flatten an array or map


In the previous few recipes of this chapter, we learned how to create multidimension arrays. In this recipe, we will see how we can convert them to a 1D list, or flatten it.

Getting ready

I'll be using IntelliJ IDEA for writing and running Kotlin code; you are free to use any IDE that can do the same task.

How to do it…

We will be using the .flatten method of the kotlin.stdlib library. It takes in an array or collection and returns a single list of all elements from all collections/arrays in the given collection/array.

For example, with an array of arrays:

[[1,2,3],[1,2,3],[1,2,3]] -> [1,2,3,1,2,3,1,2,3]

fun main(args: Array<String>) {
    val a= arrayOf(arrayOf(1,2,3),arrayOf(1,2,3),arrayOf(1,2,3))
    a.flatten().forEach { print(" ${it} ") }
}

//Output:  1 2 3 1 2 3 1 2 3

For example, with a list of lists:

[[1,2,3],[1,2,3],[1,2,3]] -> [1,2,3,1,2,3,1,2,3]

fun main(args: Array<String>) {
    val a= listOf(listOf(1,2,3),listOf(1,2,3),listOf(1,2,3))...
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