原题链接：

校验回文字符串，题目较为简单：

/** * Created by clearbug on 2018/2/26. */public class Solution {    public static void main(String[] args) {        Solution s = new Solution();        System.out.println(s.isPalindrome("0P"));        System.out.println(s.isPalindrome("ab"));        System.out.println(s.isPalindrome("aba"));        System.out.println(s.isPalindrome("A man, a plan, a canal: Panama"));        System.out.println(s.isPalindrome("race a car"));    }    public boolean isPalindrome(String s) {        if (s == null) {            return false;        }        if (s.length() < 2) {            return true;        }        s = s.toLowerCase();        char[] sCharArr = s.toCharArray();        for (int i = 0, j = sCharArr.length - 1; i < j; i++, j--) {            while (i < j && !(sCharArr[i] >= 'a' && sCharArr[i] <= 'z') && !(sCharArr[i] >= '0' && sCharArr[i] <= '9')) {                i++;            }            while (i < j &&!(sCharArr[j] >= 'a' && sCharArr[j] <= 'z') && !(sCharArr[j] >= '0' && sCharArr[j] <= '9')) {                j--;            }            if (sCharArr[i] != sCharArr[j]) {                return false;            }        }        return true;    }}