Android Academy · Lesson

map, filter, forEach

Transform collections with lambdas.

Collection Operations

Kotlin collections come with powerful built-in operations. Three you will use constantly are map, filter, and forEach.

They let you transform, select, and iterate over data in one clear line, instead of writing manual loops.

map creates a new list by applying a transformation to every item.

Inside the lambda, it refers to the current item. The original list is unchanged.

fun main() {
    val nums = listOf(1, 2, 3)
    val doubled = nums.map { it * 2 }
    println(doubled)
}