Kotlin List none()
Syntax & Examples

Syntax of List.none()

There are 2 variations for the syntax of List.none() extension function. They are:

1.
fun <T> Iterable<T>.none(): Boolean

This extension function returns true if the collection has no elements.

2.
fun <T> Iterable<T>.none(predicate: (T) -> Boolean): Boolean

This extension function returns true if no elements match the given predicate.


✐ Examples

1 Example

In this example,

  • We create a list of integers named list containing elements 1, 2, 3, 4, 5.
  • We check if the list has no elements using the none() function.
  • The result, which is a Boolean value indicating if the list has no elements, is stored in noneResult.
  • The value of noneResult is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf(1, 2, 3, 4, 5)
    val noneResult = list.none()
    println(noneResult)
}

Output

false

2 Example

In this example,

  • We create a list of characters named list containing elements 'a', 'e', 'i', 'o', 'u'.
  • We check if none of the elements are uppercase letters using the none() function with a predicate.
  • The result, which is a Boolean value indicating if none of the elements match the predicate, is stored in noneResult.
  • The value of noneResult is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf('a', 'e', 'i', 'o', 'u')
    val noneResult = list.none { it.isUpperCase() }
    println(noneResult)
}

Output

true

3 Example

In this example,

  • We create a list of strings named list containing elements "apple", "banana", "cherry".
  • We check if none of the strings have a length greater than 6 characters using the none() function with a predicate.
  • The result, which is a Boolean value indicating if none of the elements match the predicate, is stored in noneResult.
  • The value of noneResult is printed to standard output using println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list = listOf("apple", "banana", "cherry")
    val noneResult = list.none { it.length > 6 }
    println(noneResult)
}

Output

true

Summary

In this Kotlin tutorial, we learned about none() extension function of List: the syntax and few working examples with output and detailed explanation for each example.