java入门 想问一下现在的代码是判断一个单词是否回文，要怎么把它改成判断带标点的字符串是否回文，题上要求见图片，好像还有判断是否为字母的要求

import java.util.Scanner;
public class TestPalindrome {
public static void main(String[] args) {
System.out.print("Enter a String: ");
Scanner in = new Scanner(System.in);
String inStr = in.next(); // read string
String lowStr = inStr.toLowerCase(); // convert to lowercase
int fIdx = 0, bIdx = inStr.length() - 1; // forward & backward indexes
char fChar, bChar; // forward & backward characters
while(fIdx < bIdx) {
fChar = lowStr.charAt(fIdx);
bChar = lowStr.charAt(bIdx);
if(fChar != bChar) {
System.out.println(""" + inStr + "" is not a palindrome");
return;
}
else { // match, change index
fIdx++;
bIdx--;
}
}
System.out.println(""" + inStr + "" is a palindrome");
}
}