Summary - Collection stdlib
- Kotlin course
- Advanced
- Lesson 60/83
- 5 min
Combine windowed, chunked and zip to write a data pipeline.
Summary - Collections stdlib
In this group you saw advanced collections stdlib methods: sliding windows with windowed, splitting with chunked, merging/splitting with zip/unzip, running accumulation with scan, and flattening with flatMap/flatten.
This lesson includes a small task that combines three of them: you will split a list with chunked and sum each chunk with sum. This pattern brings together the power of the collections stdlib.
Practice Summary: chunk 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.
Starter code
// in main split the list 1..6 with chunked(3)
// sum each chunk and printSample solution
fun main() {
val sums = listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.sum() }
println(sums)
}Expected output
[6, 15]
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which method shows running intermediate results in a list?
- reduce
- fold
- scan Correct answer
- forEach
Explanation: scan collects each intermediate result in a list.
2 Match the stdlib methods
| Term | Meaning |
|---|---|
windowed(2) |
Sliding window |
chunked(2) |
Consecutive chunk |
zip(other) |
Parallel merge |
flatMap { } |
Transform and flatten |
3 Complete the chunked call
val sums = listOf(1, 2, 3, 4).____(2) { it.sum() }val sums = listOf(1, 2, 3, 4).chunked(2) { it.sum() }Explanation: chunked(2) yields consecutive pairs.