kotlin-stdlib/kotlin.text/replaceFirst

replaceFirst

inline fun CharSequence.replaceFirst(regex: Regex, replacement: String): String(source)

Replaces the first occurrence of the given regular expression regex in this char sequence with the specified replacement expression.

This is a convenience function that is equivalent to regex.replaceFirst(this, replacement). For details about its behaviour and the substitution syntax of replacement expression, refer to Regex.replaceFirst.

Since Kotlin

1.0

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   val text = "The events are on 15-09-2024 and 16-10-2024."
// Regex to match dates in dd-mm-yyyy format
val dateRegex = "(?<day>\\d{2})-(?<month>\\d{2})-(?<year>\\d{4})".toRegex()
// Replacement expression that puts day, month and year values in the ISO 8601 recommended yyyy-mm-dd format
val replacement = "\${year}-\${month}-\${day}"

// Replacing the first occurrence of a date from dd-mm-yyyy to yyyy-mm-dd format
println(text.replaceFirst(dateRegex, replacement)) // The events are on 2024-09-15 and 16-10-2024.

// One can also reference the matched groups by index
println(text.replaceFirst(dateRegex, "$3-$2-$1")) // The events are on 2024-09-15 and 16-10-2024.

// Using a backslash to include the special character '$' as a literal in the result
println(text.replaceFirst(dateRegex, "$3-\\$2-$1")) // The events are on 2024-\$2-15 and 16-10-2024. 
   //sampleEnd
}
expect fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)

Returns a new string with the first occurrence of oldChar replaced with newChar.

Since Kotlin

1.0
expect fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Returns a new string obtained by replacing the first occurrence of the oldValue substring in this string with the specified newValue string.

Since Kotlin

1.0
actual fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)
actual fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Since Kotlin

1.1
actual fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)

Returns a new string with the first occurrence of oldChar replaced with newChar.

Since Kotlin

1.0
actual fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Returns a new string obtained by replacing the first occurrence of the oldValue substring in this string with the specified newValue string.

Since Kotlin

1.0
actual fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)

Returns a new string with the first occurrence of oldChar replaced with newChar.

Since Kotlin

1.3
actual fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Returns a new string obtained by replacing the first occurrence of the oldValue substring in this string with the specified newValue string.

Since Kotlin

1.3
actual fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)

Returns a new string with the first occurrence of oldChar replaced with newChar.

Since Kotlin

1.8
actual fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Returns a new string obtained by replacing the first occurrence of the oldValue substring in this string with the specified newValue string.

Since Kotlin

1.8
actual fun String.replaceFirst(oldChar: Char, newChar: Char, ignoreCase: Boolean = false): String(source)

Returns a new string with the first occurrence of oldChar replaced with newChar.

Since Kotlin

1.8
actual fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: Boolean = false): String(source)

Returns a new string obtained by replacing the first occurrence of the oldValue substring in this string with the specified newValue string.

Since Kotlin

1.8