By Alvin Alexander. Last updated: August 14, 2018
Here’s a quick example of how to use the Kotlin groupBy
syntax on a list, with the result of each example shown in the comments:
val names = listOf("kim", "julia", "jim", "hala")
names.groupBy { it -> it.length } //LinkedHashMap: {3=[kim, jim], 5=[julia], 4=[hala]}
names.groupBy({it}, {it.length}) //LinkedHashMap: {kim=[3], julia=[5], jim=[3], hala=[4]}
As shown in the comments, the result of each groupBy
example is a LinkedHashMap
.
The groupBy
function uses the value returned by the lambda function to group the list’s elements, as shown. While I show a List
here, this syntax works for all Kotlin iterable collections, including Array
and others.