Kotlin List map()
Syntax & Examples

Syntax of List.map()

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

fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R>

This map() extension function of List returns a list containing the results of applying the given transform function to each element in the original collection.


✐ Examples

1 Example

In this example,

  • We create a list of integers named list containing elements 1, 2, 3, 4, 5.
  • We use the map() function to multiply each element by 2.
  • The transformed list, result, is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf(1, 2, 3, 4, 5)
    val result = list.map { it * 2 }
    println("Mapped list: \$result")
}

Output

Mapped list: [2, 4, 6, 8, 10]

2 Example

In this example,

  • We create a list of characters named list containing elements 'a', 'b', 'c'.
  • We use the map() function to convert each character to uppercase.
  • The transformed list, result, is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf('a', 'b', 'c')
    val result = list.map { it.toUpperCase() }
    println("Mapped list: \$result")
}

Output

Mapped list: [A, B, C]

3 Example

In this example,

  • We create a list of strings named list containing elements "apple", "banana", "cherry".
  • We use the map() function to get the length of each string.
  • The transformed list, result, is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf("apple", "banana", "cherry")
    val result = list.map { it.length }
    println("Mapped list: \$result")
}

Output

Mapped list: [5, 6, 6]

Summary

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