Kotlin Tip #38: Use groupBy to Organize Collections by Criteria — 100 Kotlin Tips in 100 Days
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Tip #37: Transforming Collections with map and flatMap
In Kotlin, managing collections is a fundamental aspect of daily programming, often leading to the need for efficient organization and retrieval of data based on specific characteristics.
The groupBy function segregates a collection into a map, where each key represents a unique criterion, and the corresponding value is a list of elements that match this criterion. This grouping mechanism allows for a tidy and intuitive way to organize data, making subsequent operations on grouped data more straightforward.
Consider a scenario where you have a list of books, and you wish to group them by their genre. The Book class might look something like this:
data class Book(val title: String, val author: String, val genre: String)You can group the books by genre as follows:
This code snippet organizes the books into a map where the keys are genres, and the values are lists of books belonging to those genres. It then prints out the titles of books grouped by their genre, making it easy to see the organization at a glance.
By grouping collection elements based on specified criteria, developers can write more expressive, efficient, and cleaner code. Whether for organizing data or preparing it for further processing, groupBy is a versatile function that showcases the elegance of Kotlin in simplifying complex tasks.
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