Kotlin List onEach()
Syntax & Examples

Syntax of List.onEach()

The syntax of List.onEach() extension function is:

fun <T, C : Iterable<T>> C.onEach(action: (T) -> Unit): C

This onEach() extension function of List performs the given action on each element and returns the collection itself afterwards.

✐ Examples

1 Example

In this example,

We create a list named list containing the integers [1, 2, 3, 4, 5].
We apply the onEach function to the list, which prints each element to the console.
The onEach function returns the original list.
Finally, we print the original list to standard output using the println function.

Kotlin Program

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

Output

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

2 Example

In this example,

We create a list named list containing the characters ['a', 'b', 'c', 'd', 'e'].
We apply the onEach function to the list, which prints the uppercase of each character to the console.
The onEach function returns the original list.
Finally, we print the original list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf('a', 'b', 'c', 'd', 'e');
    list.onEach { print(it.toUpperCase()) };
}

Output

ABCDE

3 Example

In this example,

We create a list named list containing the strings ['apple', 'banana', 'orange', 'grape'].
We apply the onEach function to the list, which prints the uppercase of each string to the console.
The onEach function returns the original list.
Finally, we print the original list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf("apple", "banana", "orange", "grape");
    list.onEach { println(it.toUpperCase()) };
}

Output

APPLE
BANANA
ORANGE
GRAPE

Summary

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