Integer To Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

The idea is keep substracting value in the following table if the number is greater than the value.

   I  1  
   IV 4
   V  5  
   IX 9
   X  10
   XL 40
   L  50
   XC 90
   C  100
   CD 400
   D  500
   CM 900
   M  1000

public enum romanChar {
        I(1), IV(4), V(5), IX(9), X(10), XL(40), L(50), XC(90), C(100), CD(400), D(500), CM(900), M(1000);
        int weight;
        romanChar(int weight) {
            this.weight = weight;
        }
    }

public String intToRoman(int num) {
        if (num<=0||num>3999) {
            return "";
        }

        StringBuilder result = new StringBuilder();
        romanChar[] romans = romanChar.values();
        for (int i=romans.length-1; i>=0; i--) {
            while (num>=romans[i].weight) {
                result.append(romans[i]);
                num = num - romans[i].weight;
            }
        }
        return result.toString();
    }