chunked

Learn chunking with chunked.

chunked

chunked splits a collection into consecutive, non-overlapping chunks. Unlike windowed, chunks do not slide.

Example: listOf(1, 2, 3, 4, 5).chunked(2) returns [[1, 2], [3, 4], [5]]. The last chunk may be smaller. With chunked(2) { it.sum() } you can transform each chunk into a value. It is ideal for paging and grouping.

chunked transform

Passing a lambda to chunked transforms each chunk. The result is a list; no intermediate List is built.

Example: listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.joinToString("") }. This returns ["123", "456"]. joinToString turns each chunk into a string. This pattern is useful for grouping numbers into strings.

Exercise Group sums with chunked

In main assign the result of listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.sum() } to a variable and print it with println.

Show example solution

fun main() {
    val sums = listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.sum() }
    println(sums)
}

Test yourself

Complete the chunked call

val chunks = listOf(1, 2, 3, 4, 5).____(2)

Show answer

val chunks = listOf(1, 2, 3, 4, 5).chunked(2)

What does listOf(1, 2, 3, 4, 5).chunked(2) return?
- [1, 2, 3, 4, 5]
- [[1, 2], [2, 3], [3, 4], [4, 5]]
- [[1, 2], [3, 4], [5]]
- [[1, 2, 3, 4, 5]]
Show answer

[[1, 2], [3, 4], [5]] — chunked yields consecutive chunks; the last may be smaller.
Match the chunked parts

chunked(2)

Chunk size
[[1, 2], [3, 4], [5]]

Result
chunked { }

Transform
last chunk smaller

Trait

Next lesson: zip and unzip

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