private static int[] allArabianRomanNumbers = new int[]{1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};

private static String[] allRomanNumbers = new String[]{"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

//Value must be > 0

public static String integerToRoman(int num) {

if (num <= 0) {

return "";

}

StringBuilder builder = new StringBuilder();

for (int a = 0; a < allArabianRomanNumbers.length; a++) {

int times = num / allArabianRomanNumbers[a];

for (int b = 0; b < times; b++) {

builder.append(allRomanNumbers[a]);

}

num -= times * allArabianRomanNumbers[a];

}

return builder.toString();

}

public static void main(String[] args) {

System.out.println(IntegerToRoman.integerToRoman(2131));

}