Leetcode 125. Valid Palindrome

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.

"race a car" is not a palindrome.

alphanumeric means the number and alpha, so please pay attention to the alpha:

public static boolean isPalindrome(String s) {            if(s.length()==0)                return true;                        s = s.toUpperCase();            int low1 = 'A', high1 = 'Z';            int low2 = '0', high2 = '9';            int low = 0, high = s.length()-1;                        while(low < high){                if((s.charAt(low)<low1||s.charAt(low)>high1)                    && (s.charAt(low)<low2||s.charAt(low)>high2)){                        low++;                        continue;                    }                                    if((s.charAt(high)<low1||s.charAt(high)>high1)                    && (s.charAt(high)<low2||s.charAt(high)>high2)){                        high--;                        continue;                    }                if(s.charAt(low) == s.charAt(high)){                    low++;                    high--;                }else                    return false;            }            return true;        }