JavaAlgorithms/Maths/RomanNumeralUtil.java

package Maths;

/**
 * Translates numbers into the Roman Numeral System.
 *
 * @see <a href="https://en.wikipedia.org/wiki/Roman_numerals">Roman numerals</a>
 * @author Sokratis Fotkatzikis
 * @version 1.0
 */
public class RomanNumeralUtil {

    private static final int MIN_VALUE = 1;
    private static final int MAX_VALUE = 5999;
    //1000-5999
    private static final String[] RN_M = {"", "M", "MM", "MMM", "MMMM", "MMMMM"};
    //100-900
    private static final String[] RN_C = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
    //10-90
    private static final String[] RN_X = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
    //1-9
    private static final String[] RN_I = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};

    public static String generate(int number) {
        if (number < MIN_VALUE || number > MAX_VALUE) {
            throw new IllegalArgumentException(
                    String.format(
                            "The number must be in the range [%d, %d]",
                            MIN_VALUE,
                            MAX_VALUE
                    )
            );
        }

        return RN_M[number / 1000] +
                RN_C[number % 1000 / 100] +
                RN_X[number % 100 / 10] +
                RN_I[number % 10];
    }
}