Kotlin String replace()

Kotlin String replace() Tutorial

The String.replace() function in Kotlin is used to create a new string by replacing occurrences of a specified character or substring with another character or substring. It provides two overloaded versions to accommodate both character and string replacements. The resulting string is returned, leaving the original string unchanged.

Syntax

The syntax of the replace() function for character replacement is as follows:

fun String.replace(
    oldChar: Char,
    newChar: Char,
    ignoreCase: Boolean = false
): String

And for string replacement:

fun String.replace(
    oldValue: String,
    newValue: String,
    ignoreCase: Boolean = false
): String

The oldChar or oldValue parameter represents the character or substring to be replaced, newChar or newValue represents the replacement character or substring, and ignoreCase is an optional parameter to perform case-insensitive replacements.

Examples for String replace() function

1. Replace a Character in String using replace()

In this example, we’ll use replace() to replace occurrences of a specified character with another character in a given string.

1. Take a string value in originalString.
2. Call replace() function on originalString with the values of oldChar and newChar as arguments. The function returns a new string with occurrences of oldChar replaced by newChar.
3. You may print the original and resulting strings to the console output.

Kotlin Program

fun main() {
    val originalString = "Hello, World!"

    // Using replace() to replace occurrences of 'o' with '0'
    val resultString = originalString.replace('o', '0')

    // Printing the original and resulting strings
    println("Original String:\n$originalString\n")
    println("Result String:\n$resultString")
}

Output

Original String:
Hello, World!

Result String:
Hell0, W0rld!

2. Replace a Substring in String using replace()

In this example, we’ll use replace() to replace occurrences of a specified substring with another substring in a given string.

1. Take a string value in originalString.
2. Call replace() function on originalString with the values of oldValue and newValue as arguments. The function returns a new string with occurrences of oldValue replaced by newValue.
3. You may print the original and resulting strings to the console output.

Kotlin Program

fun main() {
    val originalString = "Kotlin is fun!"

    // Using replace() to replace occurrences of 'is' with 'rocks'
    val resultString = originalString.replace("is", "rocks")

    // Printing the original and resulting strings
    println("Original String:\n$originalString\n")
    println("Result String:\n$resultString")
}

Output

Original String:
Kotlin is fun!

Result String:
Kotlin rocks fun!

Summary

In this tutorial, we’ve covered the replace() function in Kotlin strings, its syntax, and how to use it to create new strings by replacing occurrences of a specified character or substring with another character or substring. This function is handy for string manipulation and substitution in various scenarios.