Using Regex check whether string is numeric

kotlin regex usage

fun main() {
   val str = "12345"
    var numeric = false
     numeric =  str.matches("-?\\d+(\\.\\d+)?".toRegex())
     
    if (numeric)
        println("$str is a number")
    else
        println("$str is not a number")
}

In the matches() method,

    -? allows zero or more - for negative numbers in the string.
    \\d+ checks the string must have at least 1 or more numbers (\\d).
    (\\.\\d+)? allows zero or more of the given pattern (\\.\\d+) in which
        \\. checks if the string contains . (decimal points) or not
        If yes, it should be followed by at least one or more number \\d+.