How to extract nth URL from string using regex? - regex

Question

I wanted to extract second URL using regex, I cant use any other thing, So far I have managed to extract all URLs from the string using a regex but its just giving out the first URL.
fun main() {
var text = "hello world https://www.google.com hello world https://www.stackoverflow.com hello world https://www.test.com"
var regex = """((http|ftp|https):\/\/([\w_-]+(?:(?:\.[\w_-]+)+))([\w.,#?^=%&:\/~+#-]*[\w#?^=%&\/~+#-])?)"""
println(performRegex(text, regex))
}
private fun performRegex(text: String?, regex: String?): String? {
val regexPattern = Regex("""$regex""")
return regexPattern.find(text.toString())?.value
}
Current Output: https://www.google.com
Expected Output: https://www.stackoverflow.com

Answer 1

You can use
private fun performRegex(text: String?, regex: String?): String? {
val regexPattern = Regex("""$regex""")
val matchList = regexPattern.findAll(text.toString()).map{it.value}.toList()
return if (matchList.size >= 2) matchList[1] else null
}
fun main(args: Array<String>) {
var text = "hello world https://www.google.com hello world https://www.stackoverflow.com hello world https://w...content-available-to-author-only...t.com"
var regex = """(?:https?|ftp)://\S+"""
println(performRegex(text, regex))
}
See the online Kotlin demo.
The regex is (?:https?|ftp)://\S+, it matches http://, https:// or ftp:// and then any one or more non-whitespace chars.
The val matchList = regexPattern.findAll(text.toString()).map{it.value}.toList() part finds all matches and maps the results to a list of strings.
The return if (matchList.size >= 2) matchList[1] else null part returns the second match found if the match list size is two or more, else, it returns null.