ArrayIndex中带有LoginForm的Java中的绑定异常

Question

该程序使用用户输入文件（users.txt）并获取用户名和密码。 如果用户使用正确的用户名和密码输入表单，则应显示登录成功。

由于某种原因，当我使用users.txt测试程序时，我得到了Arrayindex超出范围的异常。

LoginFrame.java：

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
//package emptyframeviewer;

/**
 *
 * @author ACER
 */

import java.awt.CardLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

/*Business P11.26  Write a program with a graphical interface that implements a login window with text
 fields for the user name and password. When the login is successful, hide the login
 window and open a new window with a welcome message. Follow these rules for
 validating the password:
 1.   The user name is not case sensitive.
 2.   The password is case sensitive.
 3.   The user has three opportunities to enter valid credentials.
 Otherwise, display an error message and terminate the program. When the program
 starts, read the file users.txt . Each line in that file contains a username and password,
 separated by a space. You should make a users.txt file for testing your program.
 Business P11.27     In Exercise P11.26, the password is shown as it is typed. Browse the Swing documentation 
 to find an appropriate component for entering a password. Improve the
 solution of Exercise P11.26 by using this component instead of a text field. Each
 time the user types a letter, show a ■ character.*/
@SuppressWarnings("serial")
public class LoginFrame extends JFrame {
    private static final int FRAME_WIDTH = 300;
    private static final int FRAME_HEIGHT = 200;
    private HashMap<String, String> usernamesAndPasswords;
    private JTextField usernameField;
    private JTextField passwordField;
    private JButton loginButton;
    private JPanel loginPanel;
    private JPanel welcomePanel;
    private JPanel mainPanel;
    private CardLayout cardLayout;

    public LoginFrame() {
        this.createComponents();
        super.setTitle("Login Panel");
        super.setSize(FRAME_WIDTH, FRAME_HEIGHT);
        super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        super.setVisible(true);
    }

    private void createComponents() {
        this.mainPanel = new JPanel(new CardLayout());
        this.createHashMap();
        this.loginPanel = this.createLoginPanel();
        this.welcomePanel = this.createWelcomePanel();
        this.mainPanel.add(this.loginPanel, "LoginPanel");
        this.mainPanel.add(this.welcomePanel, "WelcomePanel");
        this.cardLayout = (CardLayout) this.mainPanel.getLayout();
        this.cardLayout.show(this.mainPanel, "LoginPanel");
        super.add(this.mainPanel);
    }

    private JPanel createLoginPanel() {
        JPanel panel = new JPanel(new GridLayout(3, 2));
        this.loginButton = new JButton("Login");
        final int TEXT_FIELD_SIZE = 10;
        this.usernameField = new JTextField(TEXT_FIELD_SIZE);
        this.passwordField = new JPasswordField(TEXT_FIELD_SIZE);
        this.loginButton.addActionListener(new ActionListener() {
            private int loginAttempts = 3;
            @Override
            public void actionPerformed(ActionEvent arg0) {
                boolean loggedIn = false;
                String inputUsername = usernameField.getText().toLowerCase();
                String inputPassword = passwordField.getText();
                if (this.loginAttempts == 1) {
                    JOptionPane.showMessageDialog(null, "Number of login attemtps exceeded. Exitting...");
                    System.exit(1);
                }
                for (Map.Entry<String, String> validUser : usernamesAndPasswords.entrySet()) {
                    if (inputUsername.equals(validUser.getKey().toLowerCase())) {
                        if (inputPassword.equals(validUser.getValue())) {
                            System.out.println("Login successful!");
                            cardLayout.show(mainPanel, "WelcomePanel");
                            loggedIn = true;
                        }
                    }
                }
                if (!loggedIn) {
                    this.loginAttempts -= 1;
                    String message = String.format("Invalid username/password. %d %s remaining", this.loginAttempts,
                            (this.loginAttempts > 1) ? "attempts" : "attempt");
                    JOptionPane.showMessageDialog(null, message, "LOGIN FAILED", JOptionPane.INFORMATION_MESSAGE);
                }
            }
        });
        panel.add(new JLabel("Username"));
        panel.add(this.usernameField);
        panel.add(new JLabel("Password"));
        panel.add(this.passwordField);
        panel.add(this.loginButton);
        return panel;
    }

    private JPanel createWelcomePanel() {
        JPanel panel = new JPanel(new GridLayout(3, 1));
        panel.add(new JLabel("Welcome"));
        panel.add(new JButton("Change password"));
        JButton logoutBtn = new JButton("Logout");
        logoutBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                System.exit(0);
            }
        });
        panel.add(logoutBtn);
        return panel;
    }

    private void createHashMap() {
        this.usernamesAndPasswords = new HashMap<String, String>();
        try {
            Scanner fileScanner = new Scanner(new File("usersff.txt"));
            while (fileScanner.hasNextLine()) {
                String[] line = fileScanner.nextLine().split(" ");
                this.usernamesAndPasswords.put(line[0], line[1]);
                System.out.println(line[0] + " " + line[1]);
            }
            fileScanner.close();
        } catch (FileNotFoundException e) {
            JOptionPane.showMessageDialog(null,
                    "Error: no users.txt file found. No users/passwords available to read.", "USERS.TXT NOT FOUND!",
                    JOptionPane.ERROR_MESSAGE);
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        JFrame testFrame = new LoginFrame();
    }
}

测试文件：users.txt

John 234 Peter abc

Answer 1

如果这是文件中唯一的内容，请检查文件末尾是否有新行。 您也可以添加小额支票。

基于代码段中唯一值得注意的数组

   String[] line = fileScanner.nextLine().split(" ");
   if(line.length == 2) 
   {
       this.usernamesAndPasswords.put(line[0], line[1]);
       System.out.println(line[0] + " " + line[1]);

    }

有很多可能性...