[LintCode] Length of Last Word

public int lengthOfLastWord(String s) {
        // Write your code here
        if(s == null || s.length() == 0)
            return 0;
        for(int i = s.length()-1; i >=0; i--) {
            if(s.charAt(i) != ' ') {
                int res = 0;
                while(i >=0 && s.charAt(i) != ' ' ){
                    res++;
                    i--;
                }
                return res;
            }
        }
        return 0;
    }