Lexical ordering Roman Numbers in King Titles

Roman.scala

package algo

class Roman(kings: Array[String]) {

  val basicLetters = Map(
    'I' -> 1,
    'V' -> 5,
    'X' -> 10,
    'L' -> 50,
    'C' -> 100,
    'D' -> 500,
    'M' -> 1000)

  def sortLetters(): Array[String] = {
    kings.
      map { x => x.split(" ") }.
      sortWith { (x, y) => sortByLexical(x(1), y(1)) }.
      map { z => z.mkString(" ") }
  }

  def sortByLexical(s1: String, s2: String) = {
    computeNumericVal(s1) < computeNumericVal(s2)
  }

  def sortTest(str: Array[String]): Unit = {
    println("[Kings in Order]")
    for (s: String <- str) {
      print("=> ")
      println(s)
    }
  }

  def computeNumericVal(roman: String): Int = {
    var acc = 0
    var previousSymbol: Char = roman(0)

    for (currentSymbol: Char <- roman) {
      if (basicLetters(currentSymbol) > basicLetters(previousSymbol)) {
        acc = (basicLetters(currentSymbol) - (basicLetters(previousSymbol) * 2)) + acc
      } else {
        acc += basicLetters(currentSymbol)
      }
      previousSymbol = currentSymbol
    }
    acc
  }

}

RomanDemo.scala

package algo

object RomanDemo {

  def main(args: Array[String]) {

    val letters = Array("Luis X", "Luis III", "Luis L", "Luis VII", "Luis XIX")

    val roman = new Roman(letters)

    val sortedLetters = roman.sortLetters()

    roman.sortTest(sortedLetters)

  }

}

I made revisions at Roman class to compute numeric values on the fly.