使用java实现一个登录页demo

以下是Java实现的登录页Demo代码示例：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class LoginDemo extends JFrame implements ActionListener {
    private JLabel usernameLabel, passwordLabel;
    private JTextField usernameField;
    private JPasswordField passwordField;
    private JButton loginButton, cancelButton;

    public LoginDemo() {
        super("Login Demo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 150);
        setLocationRelativeTo(null);

        usernameLabel = new JLabel("Username:");
        passwordLabel = new JLabel("Password:");
        usernameField = new JTextField(10);
        passwordField = new JPasswordField(10);
        loginButton = new JButton("Login");
        cancelButton = new JButton("Cancel");

        JPanel mainPanel = new JPanel(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 0;
        c.insets = new Insets(5, 5, 5, 5);
        mainPanel.add(usernameLabel, c);
        c.gridx = 1;
        mainPanel.add(usernameField, c);
        c.gridx = 0;
        c.gridy = 1;
        mainPanel.add(passwordLabel, c);
        c.gridx = 1;
        mainPanel.add(passwordField, c);
        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 2;
        c.anchor = GridBagConstraints.CENTER;
        JPanel buttonPanel = new JPanel();
        buttonPanel.add(loginButton);
        buttonPanel.add(cancelButton);
        mainPanel.add(buttonPanel, c);

        add(mainPanel);
        setVisible(true);

        loginButton.addActionListener(this);
        cancelButton.addActionListener(this);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == loginButton) {
            String username = usernameField.getText();
            String password = new String(passwordField.getPassword());

            if (username.equals("admin") && password.equals("admin")) {
                JOptionPane.showMessageDialog(null, "Login successful!");
                dispose();
            } else {
                JOptionPane.showMessageDialog(null, "Invalid username or password!");
                usernameField.setText("");
                passwordField.setText("");
            }
        } else if (e.getSource() == cancelButton) {
            dispose();
        }
    }

    public static void main(String[] args) {
        new LoginDemo();
    }
}

该Demo使用了Swing库来创建和显示登录页面。其中，使用了GridBagLayout布局管理器来实现页面布局。登陆按钮和取消按钮分别添加了事件监听器，点击登陆按钮时根据输入的用户名和密码判断是否登录成功，登录成功则弹出提示框，否则清空输入框。点击取消按钮则关闭窗口。