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Example of replaceFirst() function in Kotlin

Learn about the replaceFirst() function in Kotlin, and demonstrate the example of the replaceFirst() function.
Submitted by IncludeHelp, on March 25, 2022

replaceFirst() Function

The replaceFirst() function returns a new string with the first occurrence of oldChar (string to be replaced) replaced with newChar (string to replace with).

Syntax:

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

Kotlin program to demonstrate the example of replaceFirst() function

// Example of replaceFirst() function
fun main()
{
	// Demonstrating the replaceFirst() function
	val pattern = Regex("Hi")

	// Replace all "Hi" with "Hello"
	println(pattern.replaceFirst("Hi, there.", "Hello"))
	println(pattern.replaceFirst("Hi Alex! Please say Hi to Boss.", "Hello"))
	println(pattern.replaceFirst("IncludeHelp", "Okay"))
	println()
}

Output:

Hello, there.
Hello Alex! Please say Hi to Boss.
IncludeHelp