根据您的要求，下面是一个简化基于Java的示例程序，该程序实现了展示个人信息、注册用户、登录功能及使用对话框提示错误信息。它使用了Swing库来创建，使用了一个简化版的“数据库”，实际上只是一个内存中的HashMap来存储用户信息，以简化演示。

：实际应用中您需要连接真实的，而不是使用HashMap，以及涉及加密存储密码、错误处理等安全和健壮性考虑，里仅为示例。

import javax.swingimport java.awt.*;
import java.awt.event.ActionEvent;
import java.event.ActionListener;
import java.util.HashMap;
import java.util.Map;

// Assume we have a User class to store user information
class User    String username;
    String password;
    String fullName;
    String classNumber;
    String studentID;

    public User(String username, String password, String fullName, String classNumber, String studentID) {
        this.username = username;
        this.password = password;
        this.fullName = fullName;
        this.classNumber = classNumber;
        this.studentID = studentID;
    }
}

public class SimpleApp extends JFrame {
    // "Database" of users
 private Map<String, User> users = new HashMap<>();

    // Constructor
    public SimpleApp() {
        createUserInterface();
    }

    // Create GUI
    private void createUserInterface() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(, 200);
        setLocationRelativeTo(null);

        // Registration button
        JButton btnRegister = new JButton("Register");
        btnRegister.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
               User();
            }
        });

        // Login button
        JButton btnLogin = new JButton("Login");
        btnLogin.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                loginUser();
            }
        });

 // Layout
        setLayout(new FlowLayout());
        add(btnRegister);
        add(btnLogin);
    }

    // user function
    private void registerUser() {
        JTextField usernameField = new JTextField(5);
        JTextField passwordField = new JTextField(5);
        JTextField fullNameField = new JTextField(5);
        JTextField classField = new JTextField(5);
        JTextField studentIDField = new JTextField(5        JPanel panel = new JPanel(new GridLayout(0, ));
        panel.add(new JLabel("Username:"));
        panel.add(usernameField);
        panel.add(new JLabel("Password:"));
        panel.add(passwordField);
        panel.add(new JLabel("Full Name:"));
        panel.add(fullNameField);
        panel.add(new JLabel("Class Number:"));
        panel.add(classField);
        panel.add(new JLabel("Student ID:"));
        panel.add(studentIDField);

        int result = JOptionPane.showConfirmDialog(null,, 
            "Register", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE        if (result == JOptionPane.OK_OPTION) {
            // This is where you would normally check for valid input and handle errors
            User = new User(usernameField.getText(), passwordField.getText(), 
                fullNameField.getText(), classNumberField.getText(), studentIDField.getText());
            users.put(newUser.username, newUser);
 JOptionPane.showMessageDialog(this, "User " + newUser.username + " registered successfully!");
        }
    }

    // Login user function
    private void loginUser() {
        JTextField usernameField = new JTextField(5);
        JTextField passwordField = new JTextField(5);

        JPanel panel = new JPanel(new GridLayout(0, 2));
        panel.add JLabel("Username:"));
        panel.add(usernameField);
        panel.add(new JLabel("Password:"));
        panel.add(passwordField);

        int result = JOptionPane.showConfirmDialog, panel, 
            "Login", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
        if (result == JOptionPane.OK_OPTION) {
            User user = users.get(usernameField.getText());
            if (user == null) {
                JOptionPane.showMessageDialog(this, " does not exist.");
            } else if (!user.password.equals(passwordField.getText())) {
                JOptionPane.showMessageDialog(this, "Password is incorrect.");
            } else {
                JOptionPane(this, "Login successful. Welcome, " + user.fullName + "!");
                // Here you would navigate to the calculator screen or another part of the application
            }
        }
    }

    public static void main(String[] args) {
 SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new SimpleApp().setVisible(true);
            }
        });
    }
}

请注意，您际上需要在实际的Java环境中运行此代码，其中括正确处理多线程GUI更新（invokeLater