Remove non-alphanumeric characters from a string in Kotlin

This article explores different ways to remove non-alphanumeric characters from a string in Kotlin.

It is not possible to modify the contents of a string once it is created. This is because strings are immutable in Kotlin. To remove all non-alphanumeric characters from the string, you have to create a new string. This post provides an overview of several methods to accomplish this:

1. Using `Regex.replace()` function

You can use the regular expression [^a-zA-Z0-9] to identify non-alphanumeric characters in a string and replace them with an empty string. Use the regular expression [^a-zA-Z0-9 _] to allow spaces and underscore character.

fun main() {

val s = "Test@@String#123"

val regex = Regex("[^A-Za-z0-9]")

val result = regex.replace(s, "")

println(result) // TestString123

}

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The word characters in ASCII are [a-zA-Z0-9_]. The regular expression \w and \W checks for the word and non-word character, respectively. Therefore, you can use the regular expression [^\w]* or [\W]* to identify non-alphanumeric characters in a string.

fun main() {

val s = "Test@@String#123"

val regex = Regex("[^\\w]")

val result = regex.replace(s, "")

println(result) // TestString123

}

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2. Using `String.replace()` function

Alternatively, you can use the replace() function of the String class.

fun main() {

val s = "Test@@String#123"

val result = s.replace(("[^\\w]").toRegex(), "")

println(result) // TestString123

}

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3. Using `filter()` function

The filter() function returns all elements of the specified string that satisfies a certain predicate. To filter only alphanumeric characters, you can pass the isLetterOrDigit() to the filter() function, as demonstrated below:

fun main() {

val s = "Test@@String#123"

val result = s.filter { it.isLetterOrDigit() }

println(result) // TestString123

}

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That’s all about removing non-alphanumeric characters from a string in Kotlin.

Remove non-alphanumeric characters from a string in Kotlin

1. Using Regex.replace() function

2. Using String.replace() function

3. Using filter() function

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1. Using `Regex.replace()` function

2. Using `String.replace()` function

3. Using `filter()` function