Valid Palindrome

public class Solution {    public boolean isPalindrome(String s) {        if (s == null) {throw new IllegalArgumentException("aa");}if (s.length() == 0) {return true;}s = s.toLowerCase();char dl = '0', dh = '9';char cl = 'a', ch = 'z';int i = 0, j = s.length() - 1;while (i < j) {if (!((s.charAt(i)>= dl && s.charAt(i) <= dh) ||(s.charAt(i)>= cl && s.charAt(i) <= ch))) {i++;continue;}if (!((s.charAt(j)>= dl && s.charAt(j) <= dh) ||(s.charAt(j)>= cl && s.charAt(j) <= ch))) {j--;continue;}if (s.charAt(i) == s.charAt(j)) {i++;j--;} else {return false;}}return true;    }}