How to check to see if a string is a decimal number in Scala

You also may consider something like this:

import scala.util.control.Exception.allCatch

def isLongNumber(s: String): Boolean = (allCatch opt s.toLong).isDefined
// or
def isDoubleNumber(s: String): Boolean = (allCatch opt s.toDouble).isDefined

Try this:

def isAllDigits(x: String) = x forall Character.isDigit

forall takes a function (in this case Character.isDigit) that takes an argument that is of the type of the elements of the collection and returns a Boolean; it returns true if the function returns true for all elements in the collection, and false otherwise.

Do you want to know if the string is an integer? Then .toInt it and catch the exception. Do you instead want to know if the string is all digits? Then ask one of:

s.forall(_.isDigit)
s matches """\d+"""