public boolean isPalindrome(String s) {
        if (s.length() == 0) {
            return true;
        }
        s = s.toLowerCase();
        int start = 0;
        int end = s.length() - 1;
        while (start <= end) {
            while (start < s.length() && !isCharNum(s.charAt(start))) {
                start++;
            }
            while (end >= 0 && !isCharNum(s.charAt(end))) {
                end--;
            }
            if (start <= end) {
                if (s.charAt(start) == s.charAt(end)) {
                    start++;
                    end--;
                } else {
                    return false;
                }
            } else {
                return true;
            }
        }
        return true;

    }