Book Image

Functional Kotlin

Book Image

Functional Kotlin

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. Kotlin supports many of the popular and advanced functional features of functional languages. This book will cover the A-Z of functional programming in Kotlin. This book bridges the language gap for Kotlin developers by showing you how to create and consume functional constructs in Kotlin. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambdas, pattern matching, immutability, and help you develop a deep understanding of the concepts and practices of functional programming. If you want learn to address problems using Recursion, Koltin has support for it as well. You’ll also learn how to use the funKtionale library to perform currying and lazy programming and more. Finally, you’ll learn functional design patterns and techniques that will make you a better programmer.By the end of the book, you will be more confident in your functional programming skills and will be able to apply them while programming in Kotlin.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Preface
Index

Collector and Stream.collect – collecting Streams


We can perform numerous operations with Stream, but we may come into a situation where we need to repack the elements from the Stream into a data structure. The Stream.collect() method helps us achieve the same. It's one of the terminal methods of the Streams API. It allows you to perform mutable foldoperations (repackaging elements to some data structures and applying some additional logic, concatenating them, and many more) on data elements held in a Stream instance.

The collect() method takes a Collector interface implementation as a parameter, for the strategy (whether to repackage them to a data structure, concatenate them, or anything else) of collecting.

So, do we need to write our own implementation of the Collector interface for repackaging the Stream into a List/Set values? Of course not, the Streams API provides you with some of the predefined Collector implementations for some of the most common use cases.

The Collectors class holds...