java - 为什么我的程序中存储的值总是被删除

Question

好吧，我正在尝试完成数据结构的简单项目，但总是有一些错误不断出现在我的程序中。我已经修复了其中一些，但有一个让我想放弃。也许你们可以帮我找到解决方案？

这是我的代码(LogInSystem 类):

    // NMQ

    import java.util.ArrayList;
    import java.util.Scanner;
    import java.util.Vector;

public class LogInSystem {
    private static final int MAX_SEATS = 10;

    Vector<String> username = new Vector<String>();
    ArrayList<String> password = new ArrayList<String>();

    int p;
    String Username, Password, rUsername, rPassword;

    private Scanner input = new Scanner(System.in);


    public LogInSystem() {
        loginScreen();
    }
    private void loginScreen() {
        boolean done = false;

        do {
            printMainMenu();
            int choice = getMainMenuChoice();

            switch (choice) {
            case 1: // Log In
                logIn();
                break;

            case 2: // To Register
                register();
                break;

            case 3: // Exit
                done = true;
                break;
            }

        } while (!done);
    }

    //Registration

    private void register() {
        System.out.println("Input a Username");
        Username = input.next();
        System.out.println("Input a Password");
        Password = input.next();
        System.out.println("... Registered!");

    }

    //Log In

    private void logIn() {
        p = 0;
        System.out.println("Input a Username");
        rUsername = input.next();
        System.out.println("Input a Password");
        rPassword = input.next();

        // If the log in is successful it will got to the next menu

        if(rUsername.equals(Username)&& rPassword.equals(Password))
        {
            System.out.println("... Logging In");
            boolean done = false;

            String[] seats = new String[MAX_SEATS]; // the item list
            initializeItems(seats);
         // Printing of 2nd menu
            do {
                printMainMenu2();
                int choice = getMainMenuChoice2(); // choice off of the main menu

                switch (choice) {
                case 1: // Adding Seat
                    addSeat(seats);
                    break;
                case 2: // Viewing Seat List
                    viewSeatList(seats);
                    break;
                case 3: // Exit
                    done = true;
                    break;
                }

            } while (!done);
        }

        else
            System.out.println("Invalid log in, please try again.");

    }
    private int getMainMenuChoice() {
        int choice; // choice entered
        boolean valid = false; // is choice valid?

        do {
            System.out.print(">>>>> ");
            choice = cineplexError.readInt();

            if (1 <= choice && choice <= 4) {
                valid = true;
            } else {
                System.out.println("Invalid choice.");
            }
        } while (!valid);

        return choice;
    }
    private void printMainMenu() {
        System.out.println("\nMain Menu\n");
        System.out.println("Press 1 to Log In");
        System.out.println("Press 2 to Register");
        System.out.println("Press 3 to Exit");
        System.out.println();
    }
    public static void main(String[] args) {
        new LogInSystem();
    }

    int getMainMenuChoice2() {
        int choice; // choice entered
        boolean valid = false; // is choice valid?

        do {
            System.out.print(">>>>> ");
            choice = cineplexError.readInt();

            if (1 <= choice && choice <= 4) {
                valid = true;
            } else {
                System.out.println("Invalid choice.");
            }
        } while (!valid);

        return choice;
    }
    void printMainMenu2() {
        System.out.println("\nMain Menu\n");
        System.out.println("Press 1 to Reserve a Seat");
        System.out.println("Press 2 to View the Seat List");
        System.out.println("Press 3 to Exit Buying");
        System.out.println();
    }
    void initializeItems(String[] seats) {
        for (int i = 0; i < seats.length; i++) {
            seats[i] = "";
        }
    }
    void addSeat(String[] seats) {
           int seatIndex = findEmptySeatList(seats); // index of first empty item list
            if (seatIndex == seats.length) {
                System.out.println("Seat is already occupied. Sorry.");
            } 

            else {
                String seat = getSeatName(); // seat's name
                seats[seatIndex] = seat;
                System.out.println(seat + " is on seat list #"
                        + (seatIndex + 1));
            }
        }
    int findEmptySeatList(String[] seat) {
        for (int i = 0; i < seat.length; i++) {
            if (isEmpty(seat, i)) {
                return i;
            }
        }

        return seat.length;
    }
    boolean isEmpty(String[] seats, int seatIndex) {
        return seats[seatIndex].equals("");
    }
    String getSeatName() {
        System.out.print("Enter the name of reservator: ");
        return cineplexError.readString();
    }
    void viewSeatList(String[] seats) {
        System.out.println("\nSeat List\n");
        for (int i = 0; i < seats.length; i++) {
            System.out.println((i + 1) + ". " + seats[i]);
        }
    }
}

这是另一个类(cineplexError):

// NMQ

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

public class cineplexError {
    private  static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    private  static String integerReprompt = "Invalid integer. Try again: ";
    private  static String doubleReprompt = "Invalid double. Try again: ";
    private  static String charReprompt = "Invalid character. Try again: ";

    public static String readString() {
        String s = null;
        try {
            s = in.readLine();
        } catch (IOException ex) {}
        return s;
    }

    public static char readChar() {
        char c = 0;
        String s = null;
        try {
            s = in.readLine();
        } catch (IOException ex) {}
                if (s.length() == 1) {
                    c = s.charAt(0);
//                  valid = true;
                } else {
                    System.out.print(charReprompt);
                }
        return c;
    }

    public static int readInt() {
        int i = 0;

            boolean valid = false;

            try {
                    i = Integer.parseInt(in.readLine());
            } catch (IOException ex) {
                System.out.print(integerReprompt);
                }
                    valid = true;



        return i;
    }

    public static double readDouble() {
        double d = 0.0;

        boolean valid = true;

        try {
                    d = Double.parseDouble(in.readLine());
        } catch (IOException ex) {}
                    valid = true;
                    valid = false;
                    System.out.print(doubleReprompt);


        return d;
    }

    public void pause() {
            System.out.print("Press enter to continue...");
            try {
            in.readLine();
            } catch (IOException ex) {}
        }

    public static void setIntegerReprompt(String prompt) {
        integerReprompt = prompt;
    }

    public void setDoubleReprompt(String prompt) {
        doubleReprompt = prompt;
    }

    public void setCharReprompt(String prompt) {
        charReprompt = prompt;
    }

 }

<小时/>

程序中的错误是，每当我预订座位并注销并重新登录时，当我查看座位列表时，预订者的姓名或预订座位的人的姓名都会被删除。我应该放置一个控制语句来永久存储该值吗？你能帮我吗？谢谢。

Answer 1

Line 73:   String[] seats = new String[MAX_SEATS]; // the item list
Line 74:   initializeItems(seats);

每次调用 logIn 时，您都会将席位列表重新初始化为所有空字符串。该初始化应该在构造函数中完成。因此，将第 73 行(String[] 席位的声明)移至该类的实例变量，并将第 74 行移至构造函数中。