Java 如何将数组中的所有字符或字符串替换为；X"；由用户输入？

“X”表示已占用，但我的代码似乎不正确，因为在我的输出中，它没有划掉或替换，而唯一划掉的是[A]，在它之后，它不能划掉用户将输入的任何内容。解决办法是什么？我希望这是一个清楚的解释

目标：模拟一个工作的机场售票终端，用户可以选择什么级别和座位号

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问题：它不能删除多个用户输入。它不能是任何字母，而不是添加了[A]

代码以替换为X

package machineproblem;

import java.util.Scanner;


public class Test3 {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String[][] classes ={{"A","B","C"},{"D","E","F"}};

        String userclass, userletter = null;

        do {



            System.out.println("/-----------------------------/");
            System.out.print("First Class: ");

        for (int i = 0; i <= classes.length; i++) 
        {

            System.out.print("[" + " " + classes [0][i] + " " + "]");

        }

        System.out.println(" ");
        System.out.println("-------------------------------");
        System.out.print("Economy Class: ");

        for (int x = 0; x <= classes.length; x++) 
        {
            System.out.print("[" + " " + classes [1][x] + " " + "]"); 
        }

        System.out.println(" ");
        System.out.println("/-----------------------------/");

        System.out.println(" ");
        System.out.print("What class would you like? F/E: ");
        userclass = input.nextLine();

        if (userclass.equalsIgnoreCase("F")) 
        {
            for (int i = 0; i <= classes.length; i++) 
            {
            System.out.print("[" + " " + classes [0][i] + " " + "]"); 
            }
            System.out.println("\n");
            System.out.println("Please choose one of the class of your choice: ");
            userletter = input.nextLine();
            System.out.println("Thank you! Your seat is now reserved. Please take your ticket number.");
        }
        else if (userclass.equalsIgnoreCase("E")) 
        {
            for (int x = 0; x <= classes.length; x++) 
            {
            System.out.print("[" + " " + classes [1][x] + " " + "]"); 
            }
            System.out.println("\n");
            System.out.println("Please choose one of the class of your choice: ");
            userletter = input.nextLine();
            System.out.println("Thank you! Your seat is now reserved. Please take your ticket number.");
        }
        else
        {
            System.out.println("Invalid choice! Try again: ");
        }

        for (int i = 0; i < userclass.length(); i++)
        { 
        classes[i][i] = classes[i][i].replaceAll((userletter), "X");
        }


        } while (true);

    }

}

---

for（int i=0；i）您仍然缺少一个用例，一旦预订了票，就不应该再预订了。
for (int i = 0; i <= classes.length; i++)
{
    if(classes [0][i].equals(userletter))
    {
        classes[0][i] = "X";
        break;
    }
}

for (int i = 0; i <= classes.length; i++)
{
    if(classes [1][i].equals(userletter))
    {
        classes[1][i] = "X";
        break;
    }
}

for (int i = 0; i < userclass.length(); i++)
{
    classes[i][i] = classes[i][i].replaceAll((userletter), "X");
}

package machineproblem;

import java.util.Scanner;


public class Test3 {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String[][] classes ={{"A","B","C"},{"D","E","F"}};

        String userclass, userletter = null;

        do {



            System.out.println("/-----------------------------/");
            System.out.print("First Class: ");

            for (int i = 0; i <= classes.length; i++)
            {

                System.out.print("[" + " " + classes [0][i] + " " + "]");

            }

            System.out.println(" ");
            System.out.println("-------------------------------");
            System.out.print("Economy Class: ");

            for (int x = 0; x <= classes.length; x++)
            {
                System.out.print("[" + " " + classes [1][x] + " " + "]");
            }

            System.out.println(" ");
            System.out.println("/-----------------------------/");

            System.out.println(" ");
            System.out.print("What class would you like? F/E: ");
            userclass = input.nextLine();

            if (userclass.equalsIgnoreCase("F"))
            {
                for (int i = 0; i <= classes.length; i++)
                {
                    System.out.print("[" + " " + classes [0][i] + " " + "]");
                }
                System.out.println("\n");
                System.out.println("Please choose one of the class of your choice: ");
                userletter = input.nextLine();

                for (int i = 0; i <= classes.length; i++)
                {
                    if(classes [0][i].equals(userletter))
                    {
                        classes[0][i] = "X";
                        break;
                    }
                }

                System.out.println("Thank you! Your seat is now reserved. Please take your ticket number.");
            }
            else if (userclass.equalsIgnoreCase("E"))
            {
                for (int x = 0; x <= classes.length; x++)
                {
                    System.out.print("[" + " " + classes [1][x] + " " + "]");
                }
                System.out.println("\n");
                System.out.println("Please choose one of the class of your choice: ");
                userletter = input.nextLine();
                for (int i = 0; i <= classes.length; i++)
                {
                    if(classes [1][i].equals(userletter))
                    {
                        classes[1][i] = "X";
                        break;
                    }
                }
                System.out.println("Thank you! Your seat is now reserved. Please take your ticket number.");
            }
            else
            {
                System.out.println("Invalid choice! Try again: ");
            }


        } while (true);

    }

}