Get the index of a pattern in a string using regex with Kotlin

Question

I want to search a string for a specific pattern with kotlin.

Do the regular expression classes provide the positions (indexes within the string) of the pattern within the string?

The MatchResult object has the range property: "The range of indices in the original string where match was captured.". Also, MatchGroup has a range property, too. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 5, 2019 at 18:24

Wiktor Stribiżew · Accepted Answer · 2019-12-05 23:01:42Z

8

The MatchResult object has the range property:

The range of indices in the original string where match was captured.

Also, MatchGroup has a range property, too.

A short demo showing the range of the first match of a whole word long:

val strs = listOf("Long days become shorter","winter lasts longer")
val pattern = """(?i)\blong\b""".toRegex()
strs.forEach { str ->
    val found = pattern.find(str)
    if (found != null) {
      val m = found?.value
      val idx = found?.range
      println("'$m' found at indexes $idx in '$str'")
    }
}
// => 'Long' found at indexes 0..3 in 'long days become shorter'

answered Dec 5, 2019 at 23:01

Wiktor Stribiżew

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