import java.util.*;

public class RomanNumeral {
    /*
     * Description:
     *
     * In this program, you are to create a Roman Numeral class to handle Roman
     * numeral operations. The class is supposed to convert numerical input to
     * Roman numerals, and vice versa.
     */
    private static String[] romanNumerals = { "M", "CM", "D", "CD", "C", "XC",
            "L", "XL", "X", "IX", "V", "IV", "I" };
    private static int[] numbers = { 1000, 900, 500, 400, 100, 90, 50, 40, 10,
            9, 5, 4, 1 };
    private static String resultString = "";
    private static int resultInt = 0;

    public static String numberToRomanNumeral(int input) {
        String result = "";
        for (int i = 0; i < numbers.length; i++) {
            if (input - numbers[i] >= 0) {
                input -= numbers[i];
                result += "" + romanNumerals[i];
            }
        }
        return result;
    }

    public static int romanNumeralToNumber(String input) {
        int result = 0;
        for (int i = 0; i < romanNumerals.length; i++) {
            while (input.startsWith(romanNumerals[i])) {
                result += numbers[i];
                input = input.substring(romanNumerals[i].length());
            }
        }
        return result;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out
                .println("Enter 1 to have a Roman numeral converted to a number"
                        + " or 2 to have a number converted into a Roman Numeral.");
        String choice = scanner.nextLine();
        int choiceInteger = 0;
        try {
            choiceInteger = Integer.parseInt(choice);
        } catch (NumberFormatException e) {
            System.out.println("You didn't enter a valid option.");
            System.exit(1);
        }

        switch (choiceInteger) {
        case 1: {
            System.out
                    .println("Enter the Roman Numeral to be converted into an integer");
            String input = scanner.nextLine().toUpperCase();
            if (input.matches("[MCDXLVI]*")) {
                resultInt = RomanNumeral.romanNumeralToNumber(input);
                System.out.println(input + " is " + resultInt);
                break;
            }
            else
                System.out.println("You didn't enter a Roman Numeral.  Try again.");
                System.exit(1);
        }
        case 2: {
            System.out
                    .println("Enter the number to be converted into a Roman numeral");
            String input = scanner.nextLine();
            int inputInt = 0;
            try {
                inputInt = Integer.parseInt(input);
            } catch (NumberFormatException e) {
                System.out.println("You didn't enter an integer!");
                System.exit(1);
            }
            resultString = RomanNumeral.numberToRomanNumeral(inputInt);
            System.out.println(inputInt + " is " + resultString);
            break;
        }
        }
    }

}