Replace a character at a specific index in a Kotlin string

This article explores different ways to replace the character at a specific index in a Kotlin string.

Strings are immutable in Kotlin. That means their values cannot be changed once created. To replace the character in a string, you will need to create a new string with the replaced character.

1. Using `substring()` function

The idea is to use the substring() function to partition the string into two halves consisting of substring before and after the character to be replaced. Once you have isolated the character to be replaced, you can use the + operator to build the final string.

fun main() {

var string = "Kotlin 1.3"

val char = '_'

val index = 6

string = string.substring(0, index) + char + string.substring(index + 1)

println(string) // Kotlin_1.3

}

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2. Using `StringBuilder` instance

You can also use the StringBuilder class to efficiently replace the character at a specific index in a string in Kotlin.

fun main() {

var string = "Kotlin 1.3"

val char = '_'

val index = 6

val sb = StringBuilder(string).also { it.setCharAt(index, char) }

string = sb.toString()

println(string) // Kotlin_1.3

}

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3. Using Character array

Another plausible way to replace the character at the specified index in a string is using a character array. The trick is to convert the given string to a character array using its toCharArray() function and then replace the character at the given index. Finally, convert the character array back to the string with the String constructor.

fun main() {

var string = "Kotlin 1.3"

val char = '_'

val index = 6

val chars = string.toCharArray()

chars[index] = char

string = String(chars)

println(string) // Kotlin_1.3

}

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That’s all about replacing a character at a specific index in a Kotlin string.

Replace a character at a specific index in a Kotlin string

1. Using substring() function

2. Using StringBuilder instance

3. Using Character array

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1. Using `substring()` function

2. Using `StringBuilder` instance