Roman to Integer

private static int romanToInt(String s) {
        s = s.toUpperCase();
        int arabicNum = 0;
        HashMap<Character, Integer> romanNums = new HashMap<Character, Integer>();
        romanNums.put('M', 1000);
        romanNums.put('D', 500);
        romanNums.put('C', 100);
        romanNums.put('L', 50);
        romanNums.put('X', 10);
        romanNums.put('V', 5);
        romanNums.put('I', 1);

        for(int i = 0; i < s.length(); i++) {
            if(i != s.length() - 1 && romanNums.get(s.charAt(i)) < romanNums.get(s.charAt(i + 1))) {
                arabicNum -= romanNums.get(s.charAt(i));
            } else {
                arabicNum += romanNums.get(s.charAt(i));
            }
        }

        return arabicNum;
    }