0125. Valid Palindrome

class Solution {
    public static boolean isPalindrome(String s) {
        ArrayList<Character> arr = new ArrayList<>();
        for (int i = 0; i < s.length(); i++) {
            char now = s.charAt(i);
            if (Character.isLowerCase(now)) {
                arr.add(now);
            }
            else if (Character.isLetter(now)) {
                arr.add(Character.toLowerCase(now));
            }
            else if (Character.isDigit(now)) {
                arr.add(now);
            }
        }
        for (int i = 0, j = arr.size() - 1; i < j; i++,j--) {
            if (arr.get(i) != arr.get(j)) {
                return false;
            }
        }
        return true;
    }
}