Replace all occurrences of a substring (or a char) in Kotlin

This article explores different ways to replace all occurrences of a substring (or a character) from a string in Kotlin.

The standard solution to replace all occurrences of a “substring” with another string is using the built-in function replace(). Here’s how the code would look like:

fun main() {

var str = "ABCABD"

val target = "AB"

str = str.replace(target, "")

println(str) // CD

}

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We can also use the replace() function to replace all occurrences of a “character” in the string with another character, as shown below:

fun main() {

var str = "A|B|C|D|E"

val target = '|'

str = str.replace(target, ',')

println(str) // A,B,C,D,E

}

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The replace() function is overloaded to accept a Regex. The overloaded version replaces each substring that matches the given regular expression with the specified replacement. It can be used as follows:

fun main() {

var str = "A|B|C|D|E"

val regex = "[^\\p{Alpha}+]"

str = str.replace(regex.toRegex(), ", ")

println(str) // A, B, C, D, E

}

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There is another alternative to accomplish this – using the replaceAll() function of the Matcher class to replace each matching substring with the replacement.

import java.util.regex.Matcher

import java.util.regex.Pattern

fun replace(str: String?, target: String?, replacement: String?): String {

return Pattern.compile(target, Pattern.LITERAL).matcher(str)

.replaceAll(Matcher.quoteReplacement(replacement))

}

fun main() {

var str = "ABCABD"

val target = "AB"

val replacement = ""

str = replace(str, target, replacement)

println(str) // CD

}

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We can also “extract” the substring that needs to be removed/replaced, and call the replace() method on the original string by passing the substring and the replacement.

fun replace(word: String, replacement: String): String {

// the beginning index, inclusive.

val beginIndex = word.indexOf('(') + 1

// the ending index, exclusive.

val endIndex = word.lastIndexOf(')')

// get substring that needs to be replaced

val target = word.substring(beginIndex, endIndex)

// replace the target with the replacement

return word.replace(target, replacement)

}

fun main() {

val word = "Java (SE Development Kit) 8"

println(replace(word, "SDK")) // Java (SDK) 8

}

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That’s all about replacing all occurrences of a substring (or a character) from a string in Kotlin.

Replace all occurrences of a substring (or a char) in Kotlin

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