RomanNumerals Scala

gistfile1.scala

import org.scalatest.FlatSpec

class RomanNumerals private(val number: Int) {

  private val keyNumbers = List(50, 10, 5, 1)
  private val pairs = Map(1 -> "I", 5 -> "V", 10 -> "X", 50 -> "L")

  def roman() = {
    val romanHolder = new StringBuilder
    var left = number

    for (keyNumber <- keyNumbers) {
      appendCharacter(romanHolder, left, pairs(keyNumber), keyNumber)
      left = left % keyNumber
    }

    val result = romanHolder.toString()
      .replace("VIIII", "IX")
      .replace("IIII", "IV")
      .replace("XXXX", "XL")

    result
  }

  private def appendCharacter(result: StringBuilder, number: Int, character: String, characterNumber: Int) {
    for (i <- 1 to number / characterNumber) {
      result.append(character)
    }
  }

}

object RomanNumerals {
  def apply(number: Int) = new RomanNumerals(number)
}

class RomanNumeralsSpec extends FlatSpec {

  "Number 1" should "I" in {
    assert("I" === RomanNumerals(1).roman)
  }

  "Number 2" should "II" in {
    assert("II" === RomanNumerals(2).roman)
  }

  "Number 4" should "IV" in {
    assert("IV" === RomanNumerals(4).roman)
  }

  "Number 5" should "V" in {
    assert("V" === RomanNumerals(5).roman)
  }

  "Number 6" should "VI" in {
    assert("VI" === RomanNumerals(6).roman)
  }

  "Number 9" should "IX" in {
    assert("IX" === RomanNumerals(9).roman)
  }

  "Number 10" should "X" in {
    assert("X" === RomanNumerals(10).roman)
  }

  "Number 11" should "XI" in {
    assert("XI" === RomanNumerals(11).roman)
  }

  "Number 14" should "XIV" in {
    assert("XIV" === RomanNumerals(14).roman)
  }

  "Number 15" should "XV" in {
    assert("XV" === RomanNumerals(15).roman)
  }

  "Number 19" should "XIX" in {
    assert("XIX" === RomanNumerals(19).roman)
  }

  "Number 20" should "XX" in {
    assert("XX" === RomanNumerals(20).roman)
  }

  "Number 40" should "XL" in {
    assert("XL" === RomanNumerals(40).roman)
  }

  "Number 50" should "L" in {
    assert("L" === RomanNumerals(50).roman)
  }
}