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filter

kotlin-stdlib / kotlin.text / filter
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0) 
inline fun CharSequence.filter(
    predicate: (Char) -> Boolean
): CharSequence

Returns a char sequence containing only those characters from the original char sequence that match the given predicate.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val text = "a1b2c3d4e5"

val textWithOnlyDigits = text.filter { it.isDigit() }

println(textWithOnlyDigits) // 12345
//sampleEnd
}
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0) 
inline fun String.filter(
    predicate: (Char) -> Boolean
): String

Returns a string containing only those characters from the original string that match the given predicate.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val text = "a1b2c3d4e5"

val textWithOnlyDigits = text.filter { it.isDigit() }

println(textWithOnlyDigits) // 12345
//sampleEnd
}

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Licensed under the Apache License, Version 2.0.
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/filter.html