直接双指针

import java.util.*;
public class Solution {
    public boolean judge (String str) {
        // write code here
        int n = str.length();
        if(n == 0 || n == 1)
            return true;
        int left = 0, right = n-1;
        while(left < right){
            if(str.charAt(left) != str.charAt(right))
                return false;
            left++;
            right--;
        }
        return true;
    }
}