Valid Palindrome

 1 public class Solution {
 2     /**
 3      * @param s A string
 4      * @return Whether the string is a valid palindrome
 5      */
 6     public static boolean isPalindrome(String s) {
 7         if (s == null || s.isEmpty()){
 8             return true;
 9         }
10         int left = 0;
11         int right = s.length() - 1;
12         while (left < right){
13             if (!Character.isLetterOrDigit(s.charAt(left))){
14                 ++left;
15                 continue;
16             }
17             if (!Character.isLetterOrDigit(s.charAt(right))){
18                 --right;
19                 continue;
20             }
21             if (Character.toLowerCase(s.charAt(left)) == Character.toLowerCase(s.charAt(right))){
22                 ++left;
23                 --right;
24             } else {
25                 return false;
26             }
27         }
28         return true;
29     }
30 }