添加最少的字符让字符串变成回文串（2）

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;


public class Main {
    private static String getPalindrome(String str, String strlps) {
        if (str == null || str.equals("")) {
            return "";
        }

        char[] chas = str.toCharArray();
        char[] lps = strlps.toCharArray();
        int strLen = chas.length;
        int lpsLen = lps.length;
        int resLen = 2 * strLen - lpsLen;
        char[] res = new char[resLen];
        int chasl = 0;
        int chasr = strLen - 1;
        int lpsIdx = 0;
        int resIdx = 0;

        while (chasl <= chasr) {
            if (chas[chasl] != lps[lpsIdx]) {
                res[resIdx] = chas[chasl];
                res[resLen - resIdx - 1] = chas[chasl++];
            } else if (chas[chasr] != lps[lpsIdx]) {
                res[resIdx] = chas[chasr];
                res[resLen - resIdx - 1] = chas[chasr--];
            } else {
                res[resIdx] = lps[lpsIdx];
                res[resLen - resIdx - 1] = lps[lpsIdx];
                chasl++;
                chasr--;
                lpsIdx++;
            }
            resIdx++;
        }

        return new String(res);
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String str = br.readLine();
        String strlps = br.readLine();
        System.out.println(getPalindrome(str, strlps));
    }
}