Roman Numeral Calculator Kata

RomanNumeralCalculator.java

import com.sun.xml.internal.xsom.impl.scd.Iterators;

import java.util.ArrayList;
import java.util.HashMap;

public class RomanNumeralCalculator {

    ArrayList<String> numeralOrder = new ArrayList<String>() {{
        add("I");
        add("V");
        add("X");
        add("L");
        add("C");
        add("D");
        add("M");
    }};

    HashMap<String, String> calculator = new HashMap<String, String>(){{
        put("IIIII", "V");
        put("VV", "X");
        put("XXXXX", "L");
        put("LL", "C");
        put("CCCCC", "D");
        put("DD", "M");
    }};

    public String add(String numeral1, String numeral2) {
        String combinedString = combineString(numeral1, numeral2);
        String simplifiedString = replaceRepeats(combinedString);

        return simplifiedString;
    }

    private String combineString(String numeral1, String numeral2) {
        String combinedString = numeral1 + numeral2;

        if (shouldSwap(numeral1, numeral2)) {
            combinedString = numeral2 + numeral1;
        }

        return combinedString;
    }

    private boolean shouldSwap(String numeral1, String numeral2) {
        int maxIndexOfNumeralOne = getMaxIndexOfRomanNumeral(numeral1);
        int maxIndexOfNumeralTwo = getMaxIndexOfRomanNumeral(numeral2);
//        int minIndexOfNumeralTwo = getMinIndexOfRomanNumeral(numeral2);

//        if (minIndexOfNumeralTwo >= maxIndexOfNumeralOne) {
//            return true;
//        }

        return maxIndexOfNumeralOne < maxIndexOfNumeralTwo;
    }

    private int getMaxIndexOfRomanNumeral(String romanNumeral) {
        int maxIndexOfRomanNumeral = -1;
        for (int i = 0; i < romanNumeral.length(); i++) {
            if (numeralOrder.indexOf(romanNumeral.substring(i, i + 1)) > maxIndexOfRomanNumeral) {
                maxIndexOfRomanNumeral = numeralOrder.indexOf(romanNumeral.substring(i, i + 1));
            }
        }
        return maxIndexOfRomanNumeral;
    }

    private int getMinIndexOfRomanNumeral(String romanNumeral) {
        int minIndexOfRomanNumeral = 100;
        for (int i = 0; i < romanNumeral.length(); i++) {
            if (numeralOrder.indexOf(romanNumeral.substring(i, i + 1)) < minIndexOfRomanNumeral) {
                minIndexOfRomanNumeral = numeralOrder.indexOf(romanNumeral.substring(i, i + 1));
            }
        }
        return minIndexOfRomanNumeral;
    }

    private String replaceRepeats(String combinedString) {
        for (HashMap.Entry<String, String> entry : calculator.entrySet()) {
            combinedString = combinedString.replaceAll(entry.getKey(), entry.getValue());
        }

        return combinedString;
    }
}

RomanNumeralCalculatorTest.java

import static org.junit.Assert.assertEquals;

import org.junit.Ignore;
import org.junit.Test;

public class RomanNumeralCalculatorTest {

  RomanNumeralCalculator calculator = new RomanNumeralCalculator();

  @Test
  public void onePlusOneIsTwo() {
    String actualResult = calculator.add("I", "I");
    String expectedResult = "II";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void onePlusTwoIsThree() {
    String actualResult = calculator.add("I", "II");
    String expectedResult = "III";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void twoPlusThreeEqualsFive() {
    String actualResult = calculator.add("III", "II");
    String expectedResult = "V";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void onePlusFiveEqualsSix() {
    String actualResult = calculator.add("I", "V");
    String expectedResult = "VI";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void onePlusSixEqualsSeven() {
    String actualResult = calculator.add("I", "VI");
    String expectedResult = "VII";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void fivePlusFiveEqualsTen() {
    String actualResult = calculator.add("V", "V");
    String expectedResult = "X";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void twentyPlusThirtyEqualsFifty() {
    String actualResult = calculator.add("XX", "XXX");
    String expectedResult = "L";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void fiftyPlusFiftyEqualsOneHundred() {
    String actualResult = calculator.add("L", "L");
    String expectedResult = "C";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void tenPlusFiftyEqualsSixty() {
    String actualResult = calculator.add("X", "L");
    String expectedResult = "LX";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void oneHundredPlusFiveHundreddEqualsSixHundred() {
    String actualResult = calculator.add("C", "D");
    String expectedResult = "DC";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void oneHundredPlusOneThousandEqualsElevenHundred() {
    String actualResult = calculator.add("C", "M");
    String expectedResult = "MC";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void twoHundredPlusThreeHundredEqualsFiveHundred() {
    String actualResult = calculator.add("CC", "CCC");
    String expectedResult = "D";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void fiveHundredPlusFiveHundredEqualsOneThousand() {
    String actualResult = calculator.add("D", "D");
    String expectedResult = "M";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void fourPlusFiveEqualsNine() {
    String actualResult = calculator.add("IV", "V");
    String expectedResult = "IX";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void fortyPlusFiftyEqualsNinety() {
    String actualResult = calculator.add("XL", "L");
    String expectedResult = "XC";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void twoPlusFortyEqualsFortyTwo() {
    String actualResult = calculator.add("II", "XL");
    String expectedResult = "XLII";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void twentyPlusFourHundredEqualsForHundredTwenty() {
    String actualResult = calculator.add("XX", "CD");
    String expectedResult = "CDXX";

    assertEquals(expectedResult, actualResult);
  }

  @Test
  public void eighteenPlusTwentyEqualsThirtyEight() {
    String actualResult = calculator.add("XVIII", "XX");
    String expectedResult = "XXXVIII";

    assertEquals(expectedResult, actualResult);
  }
}