如何让使用递归的回文程序在java中忽略字符串所有地方的特殊字符？

Question

我的回文程序有一点逻辑错误，当我在字符串的前面或后面插入特殊字符时，我得到一个指示，表明该字符串不是回文。我正在编写回文，以便在考虑字符串时忽略所有特殊字符。例如，@bob将被认为不是回文，而b@ob将被认为是回文。我该如何编辑我的代码，使特殊字符被忽略，而不管位置在哪里？所有这些都是通过递归完成的。

'''

import java.util.Scanner;

公共类递归练习{

//the recursive function that checks to see whether the 
//string is a palindrone or not
public static boolean checkPalindrome(String str, int firstChar, int lastChar) {
    //if only one character exists
    if (firstChar == lastChar) 
        return true;
    
    //checks to see if the first and last characters match
    if ((str.charAt(firstChar)) != (str.charAt(lastChar))) 
        
        return false;
    
    //checks to see if it has characters
    if (!isChar(str))
        return true;
    
    
    //checks the middle strings with multiple characters
    //on whether or not they are a palindrome with recursive method
    if (firstChar < lastChar + 1)
        return checkPalindrome(str, firstChar + 1, lastChar - 1 );
                return true;
    
}
   //method that actually determines what a palindrome is
public static boolean isAPalindrome(String str) {
    
    int n = str.length();
    //if string is not 0 or 1 then it's a palindrome
    if(n == 0 || n == 1) 
        return false;
    return checkPalindrome(str, 0, n - 1);
    
}

//method that checks for characters
public static boolean isChar(String str) {
    
    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (!Character.isLetter(c) && !Character.isDigit(c))
            return false;
    }
    return true;
}

//tests out recursive methods
public static void main(String args[]) {
    
    Scanner scanner = new Scanner(System.in);
    System.out.println("Enter a string to see if it's a palindrome:");
    
    String str = scanner.nextLine(); //input from the user
    
    
    //checks to see if it's a palindrome and puts them all
    //to be lower case to ignore the case issue
    if(isAPalindrome(str.toLowerCase()))
        System.out.println(str+" is a palindrome");
    
    else
        System.out.println(str+" is not a palindrome");
    
    scanner.close();
}

}

'''

Answer 1

这一个对我来说太糟糕了！！我现在正在学校讨论这个问题，我正在网上寻求帮助。没有运气！！我对检查一个单词是否为回文没有任何问题，但当谈到句子时，我很纠结。因此，我必须找到一种方法来消除字符串中的空格，同时保持原始字符串的完整性。我尝试了很多方法，但这是它对我有效的唯一方法，并通过了电子书的所有测试。希望这有帮助！！！

import java.util.Scanner;

public class LabProgram {
    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        String userText;
        String backText = "";
        String userTextNoSpace = "";
        int i;

        userText = scnr.nextLine();

        if (userText.contains(" ")) {
            userTextNoSpace = userText.replace(" ", "");
            for (i = userTextNoSpace.length() - 1; i >= 0; --i) {
                backText += userTextNoSpace.charAt(i);
            }
        } else {
            for (i = userText.length() - 1; i >= 0; --i) {
                backText += userText.charAt(i);
            }
        }
        if (backText.equalsIgnoreCase(userTextNoSpace) || backText.equalsIgnoreCase(userText)) {
            System.out.println( userText + " is a palindrome");
        } else {
            System.out.println(userText + " is not a palindrome");
        }

    }
}