Roman Numerals

/**
 * Created by Nicolo on 24/10/2016.
 */
public class Roman {

    private enum Numerals {
        I(1),
        V(5),
        X(10),
        L(50),
        C(100),
        D(500),
        M(1000);

        private int decimal;

        public int getDecimal() {
            return decimal;
        }

        Numerals(int decimal) {
            this.decimal = decimal;
        }
    }

    private static int romanToDecimal(String romanNumeral) {
        if (romanNumeral.length() <= 1) {
            return getCharValue(romanNumeral);
        }

        int rank = Integer.MIN_VALUE;
        int position = 0;

        for (int i = 0; i < romanNumeral.length(); i++) {
            String c = String.valueOf(romanNumeral.charAt(i));

            int value = getCharValue(c);

            if (value > rank) {
                rank = value;
                position = i;
            }

        }

        if (position == 0) {
            // Start of string, process from second character and on
            return rank + romanToDecimal(romanNumeral.substring(position + 1));
        } else {
            String restOfIt = romanNumeral.substring(0, position);
            if (position == romanNumeral.length() - 1) {
                // End of string, process from start of string to the 2nd last letter
                return rank - romanToDecimal(restOfIt);
            } else {
                // Letters on both sides, subtract the left, add the right
                return rank - romanToDecimal(restOfIt) + romanToDecimal(romanNumeral.substring(position + 1, romanNumeral.length()));
            }
        }
    }

    private static int getCharValue(String roman) {
        try {
            Numerals romanNumeral = Numerals.valueOf(roman.toUpperCase());
            return romanNumeral.getDecimal();
        } catch (IllegalArgumentException e) {
            System.out.println("The letter [" + roman + "] is not a valid roman numeral");
            System.exit(1);
            return 1;
        }
    }

    /**
     *
     */
    public static void main(String[] args) {
        System.out.println(romanToDecimal("MMMMDCCLXXXV"));
    }

}