Roman numerals kata

kata.java

import org.junit.Test;

import java.util.Collections;
import java.util.TreeMap;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class FizzBuzzTest {
    // doc:
    // https://github.com/pedrovgs/RomanNumerals-Kata
    // http://blog.8thlight.com/uncle-bob/2013/05/27/TheTransformationPriorityPremise.html

    // TDD cycle
    // 1. write a red test
    // 2. make it green (as simple as possible)
    // 3. refactor
    // 4. start with 1. again

    // examples
    //    I 	1
    //    IV    4
    //    V 	5
    //    VI 	6
    //    IX 	9
    //    X 	10
    //    XI 	11
    //    L 	50
    //    C 	100
    //    D 	500
    //    CM 	900
    //    M 	1000
    //    MC    1100

    //   XXXII  32

    @Test
    public void romanNumeral_for1_IisReturned() {
        String romanNumber = arabicToRoman(1);

        assertThat(romanNumber, is("I"));
    }

    @Test
    public void romanNumeral_for2_isReturned() {
        String romanNumber = arabicToRoman(2);

        assertThat(romanNumber, is("II"));
    }

    @Test
    public void romanNumeral_for3_isReturned() {
        String romanNumber = arabicToRoman(3);

        assertThat(romanNumber, is("III"));
    }

    @Test
    public void romanNumeral_for4_IVisReturned() {
        String romanNumber = arabicToRoman(4);

        assertThat(romanNumber, is("IV"));
    }

    @Test
    public void romanNumeral_for5_VisReturned() {
        String romanNumber = arabicToRoman(5);

        assertThat(romanNumber, is("V"));
    }

    @Test
    public void romanNumeral_for6_VIisReturned() {
        String romanNumber = arabicToRoman(6);

        assertThat(romanNumber, is("VI"));
    }

    @Test
    public void romanNumeral_for7_VIIisReturned() {
        String romanNumber = arabicToRoman(7);

        assertThat(romanNumber, is("VII"));
    }

    @Test
    public void romanNumeral_for8_VIIIisReturned() {
        String romanNumber = arabicToRoman(8);

        assertThat(romanNumber, is("VIII"));
    }

    @Test
    public void romanNumeral_for9_IXisReturned() {
        String romanNumber = arabicToRoman(9);

        assertThat(romanNumber, is("IX"));
    }

    @Test
    public void romanNumeral_for10_XisReturned() {
        String romanNumber = arabicToRoman(10);

        assertThat(romanNumber, is("X"));
    }


    @Test
    public void romanNumeral_for11_XIisReturned() {
        String romanNumber = arabicToRoman(11);

        assertThat(romanNumber, is("XI"));
    }

    @Test
    public void romanNumeral_for12_XIIisReturned() {
        String romanNumber = arabicToRoman(12);

        assertThat(romanNumber, is("XII"));
    }

    @Test
    public void romanNumeral_for14_XIVisReturned() {
        String romanNumber = arabicToRoman(14);

        assertThat(romanNumber, is("XIV"));
    }

    @Test
    public void romanNumeral_for20_XXisReturned() {
        String romanNumber = arabicToRoman(20);

        assertThat(romanNumber, is("XX"));
    }

    @Test
    public void romanNumeral_for30_XXXisReturned() {
        String romanNumber = arabicToRoman(30);

        assertThat(romanNumber, is("XXX"));
    }

    @Test
    public void romanNumeral_for40_XLisReturned() {
        String romanNumber = arabicToRoman(40);

        assertThat(romanNumber, is("XL"));
    }

    @Test
    public void romanNumeral_for49_XLIXisReturned() {
        String romanNumber = arabicToRoman(49);

        assertThat(romanNumber, is("XLIX"));
    }

    @Test
    public void romanNumeral_for50_LisReturned() {
        String romanNumber = arabicToRoman(50);

        assertThat(romanNumber, is("L"));
    }

    @Test
    public void romanNumeral_for88_LXXXVIIIisReturned() {
        String romanNumber = arabicToRoman(88);

        assertThat(romanNumber, is("LXXXVIII"));
    }

    @Test
    public void romanNumeral_for99_XCIXisReturned() {
        String romanNumber = arabicToRoman(99);

        assertThat(romanNumber, is("XCIX"));
    }

    @Test
    public void romanNumeral_for100_CisReturned() {
        String romanNumber = arabicToRoman(100);

        assertThat(romanNumber, is("C"));
    }

    @Test
    public void romanNumeral_for499_CDXCIXisReturned() {
        String romanNumber = arabicToRoman(499);

        assertThat(romanNumber, is("CDXCIX"));
    }

    @Test
    public void romanNumeral_for500_DisReturned() {
        String romanNumber = arabicToRoman(500);

        assertThat(romanNumber, is("D"));
    }

    @Test
    public void romanNumeral_for999_CMXCIXisReturned() {
        String romanNumber = arabicToRoman(999);

        assertThat(romanNumber, is("CMXCIX"));
    }

    @Test
    public void romanNumeral_for1000_MisReturned() {
        String romanNumber = arabicToRoman(1000);

        assertThat(romanNumber, is("M"));
    }

    @Test
    public void romanNumeral_for3479_MMMCDLXXIXisReturned() {
        String romanNumber = arabicToRoman(3479);

        assertThat(romanNumber, is("MMMCDLXXIX"));
    }

    public String arabicToRoman(Integer arabicNumber) {
        return arabicToRomanRecursive(arabicNumber);
    }

    private String arabicToRomanRecursive(Integer arabicNumber) {
        TreeMap<Integer, String> specialNumbers = specialNumbers();
        String romanNumeral = "";

        int index = 0;
        while (index < specialNumbers.size()) {
            Integer specialNumber = (Integer) specialNumbers.keySet().toArray()[index];
            if (arabicNumber >= specialNumber) {
                romanNumeral += arabicToRomanRecursive(arabicNumber - specialNumber);

                arabicNumber -= specialNumber;
                index = 0;
            } else {
                index++;
            }
        }

        for (int i = 0; i < arabicNumber; i++) {
            romanNumeral += "I";
        }

        return romanNumeral;
    }

    private TreeMap<Integer, String> specialNumbers() {
        TreeMap<Integer, String> specialNumbers = new TreeMap<Integer, String>(Collections.reverseOrder());
        specialNumbers.put(4, "IV");
        specialNumbers.put(5, "V");
        specialNumbers.put(9, "IX");
        specialNumbers.put(10, "X");
        specialNumbers.put(40, "XL");
        specialNumbers.put(50, "L");
        specialNumbers.put(90, "XC");
        specialNumbers.put(100, "C");
        specialNumbers.put(400, "CD");
        specialNumbers.put(500, "D");
        specialNumbers.put(900, "CM");
        specialNumbers.put(1000, "M");

        return specialNumbers;
    }


    /*
    public String arabicToRoman(Integer arabicNumber) {
        TreeMap<Integer, String> specialNumbers = specialNumbers();
        String romanNumeral = "";

        int index = 0;
        while (index < specialNumbers.size()) {
            Integer specialNumber = (Integer) specialNumbers.keySet().toArray()[index];
            if (arabicNumber >= specialNumber) {
                romanNumeral += specialNumbers.get(specialNumber);
                arabicNumber -= specialNumber;
                index = 0;
            } else {
                index++;
            }
        }

        for (int i = 0; i < arabicNumber; i++) {
            romanNumeral += "I";
        }

        return romanNumeral;
    }
     */
}