Kotlin List filterNotTo()
Syntax & Examples

Syntax of List.filterNotTo()

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

fun <T, C : MutableCollection<in T>> Iterable<T>.filterNotTo( destination: C, predicate: (T) -> Boolean ): C

This filterNotTo() extension function of List appends all elements not matching the given predicate to the given destination.

✐ Examples

1 Example

In this example,

We create a list named list1 containing integers.
We create an empty mutable list named result to store elements not matching the predicate.
We use the filterNotTo function on list1 with a predicate that filters out even numbers and appends the remaining numbers to result.
Finally, we print the value of result to standard output using the println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf(1, 2, 3, 4, 5)
    val result = mutableListOf<Int>()
    list1.filterNotTo(result) { it % 2 == 0 }
    println(result)
}

Output

[1, 3, 5]

2 Example

In this example,

We create a list named list2 containing strings.
We create an empty mutable list named result to store strings not starting with 'a'.
We use the filterNotTo function on list2 with a predicate that filters out strings starting with 'a' and appends the remaining strings to result.
Finally, we print the value of result to standard output using the println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list2 = listOf("apple", "banana", "cherry")
    val result = mutableListOf<String>()
    list2.filterNotTo(result) { it.startsWith('a') }
    println(result)
}

Output

[banana, cherry]

3 Example

In this example,

We create a list named list3 containing characters.
We create an empty mutable list named result to store characters not equal to 'a' or 'e'.
We use the filterNotTo function on list3 with a predicate that filters out 'a' and 'e' characters and appends the remaining characters to result.
Finally, we print the value of result to standard output using the println statement.

Kotlin Program

fun main(args: Array<String>) {
    val list3 = listOf('a', 'b', 'c', 'd', 'e')
    val result = mutableListOf<Char>()
    list3.filterNotTo(result) { it == 'a' || it == 'e' }
    println(result)
}

Output

[b, c, d]

Summary

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