match expression

object Bob {

  def response(statement: String): String = {
    val input = statement.trim()
    if (input.isEmpty) return "Fine. Be that way!"
    
    val isShout =
      input.exists(_.isLetter) && input.toUpperCase() == input
    val isQuestion = input.endsWith("?")

    (isQuestion, isShout) match {
      case (true, true) => "Calm down, I know what I'm doing!"
      case (_, true)    => "Whoa, chill out!"
      case (true, _)    => "Sure."
      case _            => "Whatever."
    }
  }
}

In this approach you use a match to test if there is a question or a shout. The match returns the right response for a question, shout, shouted question, or for not being a shout or question. Being a question and/or a shout is pattern-matched on a tuple made of the isQuestion and isShout values.

The String trim() method is applied to the input to eliminate any whitespace at either end of the input. If the string has no characters left, it returns the response for saying nothing.

The first half of setting isShout uses the exists and isLetter methods to look for at least one English alphabetic character.

This is because the second half of the condition tests that the uppercased input is the same as the input. If the input were only "123" it would equal itself uppercased, but without letters it would not be a shout.

A question is determined by use of the endsWith method to see if the input ends with a question mark.

If the input statement is neither a question nor a shout, the underscore wildcard is used to match to anything else. It is like default in a switch statement in other languages.