leetcode--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.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

public class Solution {
    public boolean isPalindrome(String s) {
        boolean isPalindrome = true;
		s = s.toLowerCase();
		int length = s.length();
		int left = 0, right= length - 1;
		while(left <= right){
			if((s.charAt(left) < 97 || s.charAt(left) > 122) && (s.charAt(left) < 48 || s.charAt(left) > 57))
				++left;
			else if((s.charAt(right) < 97 || s.charAt(right) > 122) && (s.charAt(right) < 48 || s.charAt(right) > 57))
				--right;
			else{
				isPalindrome &= (s.charAt(left) == s.charAt(right));
				if(!isPalindrome)
					break;
				++left;
				--right;
			}
		}
		return isPalindrome;    
    }
}