Kotlin List windowed()
Syntax & Examples

Syntax of List.windowed()

There are 2 variations for the syntax of List.windowed() extension function. They are:

1.
fun <T> Iterable<T>.windowed( size: Int, step: Int = 1, partialWindows: Boolean = false ): List<List<T>>

This extension function returns a list of snapshots of the window of the given size sliding along this collection with the given step, where each snapshot is a list.

2.
fun <T, R> Iterable<T>.windowed( size: Int, step: Int = 1, partialWindows: Boolean = false, transform: (List<T>) -> R ): List<R>

This extension function returns a list of results of applying the given transform function to an each list representing a view over the window of the given size sliding along this collection with the given step.


✐ Examples

1 Example

In this example,

  • We create a list named list containing integers from 1 to 5.
  • We use the windowed(3) function to obtain snapshots of the window of size 3 sliding along the list.
  • Each snapshot is represented as a list within the windows list.
  • Finally, we print the windows list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf(1, 2, 3, 4, 5);
    val windows = list.windowed(3);
    println(windows);
}

Output

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

2 Example

In this example,

  • We create a list named list containing characters 'a' to 'e'.
  • We use the windowed(2) function to obtain snapshots of the window of size 2 sliding along the list.
  • Each snapshot is represented as a list within the windows list.
  • Finally, we print the windows list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf('a', 'b', 'c', 'd', 'e');
    val windows = list.windowed(2);
    println(windows);
}

Output

[[a, b], [b, c], [c, d], [d, e]]

3 Example

In this example,

  • We create a list named list containing strings "apple" to "elderberry".
  • We use the windowed(4) function to obtain snapshots of the window of size 4 sliding along the list.
  • Each snapshot is represented as a list within the windows list.
  • Finally, we print the windows list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf("apple", "banana", "cherry", "date", "elderberry");
    val windows = list.windowed(4);
    println(windows);
}

Output

[[apple, banana, cherry, date], [banana, cherry, date, elderberry]]

Summary

In this Kotlin tutorial, we learned about windowed() extension function of List: the syntax and few working examples with output and detailed explanation for each example.