Kotlin – Get First Element of List

Kotlin List.first()

The Kotlin List.first() function is used to get the first element of this List.

Syntax

The syntax of List.first() function is

fun <T> List<T>.first(): T

Examples

In the following example, we take a list of strings, and get the first element using List.first() function.

Kotlin Program

fun main(args: Array<String>) {
    var list = listOf("apple", "banana", "cherry", "avocado")
    var result = list.first()
    println(result)
}

Output

apple

In the following example, we take a list of numbers, and get the first element using List.first() function.

Kotlin Program

fun main(args: Array<String>) {
    var list = listOf(2, 4, 6, 8)
    var result = list.first()
    println("First Element : " + result)
}

Output

First Element : 2

If the array is empty, then List.first() returns NoSuchElementException.

In the following example, we take an empty list of integers, and try to get the first element using List.first() function.

Kotlin Program

fun main(args: Array<String>) {
    var list = listOf<Int>()
    var result = list.first()
    println("First Element : " + result)
}

Output

Exception in thread "main" java.util.NoSuchElementException: List is empty.
	at kotlin.collections.CollectionsKt___CollectionsKt.first(_Collections.kt:212)
	at MainKt.main(Main.kt:3)

Conclusion

In this Kotlin Tutorial, we learned how to get the first element of this List, using Kotlin List.first() function.