Split a string on whitespace in Kotlin

This article explores different ways to split a string on whitespace in Kotlin. The whitespace characters consist of ' ', '\t', '\n', '\r', 'f', etc.

We can use the split() function to split a char sequence around matches of a regular expression. To split on whitespace characters, we can use the regex '\s' that denotes a whitespace character.

fun main()

{

val str = "A B"

val words = str.split("\\s".toRegex()).toTypedArray()

println(words.contentToString()) // [A, B]

}

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Note that we have called the toTypedArray() function, since the split() function returns a list. Here’s an equivalent version using POSIX character class \p{Space}.

fun main()

{

val str = "A B"

val words = str.split("\\p{Space}".toRegex()).toTypedArray()

println(words.contentToString()) // [A, B]

}

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If you need to group the adjacent whitespaces as a single delimiter, use the greedy quantifier '\s+' where + represents one or more times.

fun main()

{

val str = "A B"

val words = str.split("\\s+".toRegex()).toTypedArray()

println(words.contentToString()) // [A, B]

}

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All the above solutions don’t remove the leading or trailing spaces from a String. To handle it, we can trim the string before calling the split() function.

fun main()

{

val str = " A B"

val words = str.trim().split("\\s+".toRegex()).toTypedArray()

println(words.contentToString()) // [A, B]

}

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If the regular expression is frequently called, better compile the regular expression to get a performance boost:

import java.util.regex.Pattern

private val WHITESPACE = Pattern.compile("\\s+")

fun main()

{

val str = " A B"

val words = WHITESPACE.split(str.trim())

println(words.contentToString()) // [A, B]

}

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That’s all about splitting a string on whitespace in Kotlin.

Split a string on whitespace in Kotlin

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