生成一个完整的实现登录功能的界面代码，包含有登录、注册、忘记密码等功能，当用户输入正确的用户名和密码后可以成功登录并跳转到一个新的空页面，并可设置图片背景，用Java语言写

以下是一个简单的Java Swing界面代码，实现了登录、注册、忘记密码等功能，同时可以设置图片背景：

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

public class LoginFrame extends JFrame {
    private JTextField usernameField;
    private JPasswordField passwordField;
    private JButton loginButton;
    private JButton registerButton;
    private JButton forgetButton;
    private JLabel backgroundImageLabel;

    public LoginFrame() {
        setTitle("登录");
        setSize(500, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        // 背景图片
        ImageIcon backgroundImage = new ImageIcon("background.jpg");
        Image image = backgroundImage.getImage();
        Image scaledImage = image.getScaledInstance(500, 300, Image.SCALE_SMOOTH);
        backgroundImage = new ImageIcon(scaledImage);
        backgroundImageLabel = new JLabel(backgroundImage);
        backgroundImageLabel.setBounds(0, 0, 500, 300);
        add(backgroundImageLabel);

        // 用户名
        JLabel usernameLabel = new JLabel("用户名：");
        usernameLabel.setBounds(100, 50, 100, 30);
        backgroundImageLabel.add(usernameLabel);
        usernameField = new JTextField();
        usernameField.setBounds(200, 50, 200, 30);
        backgroundImageLabel.add(usernameField);

        // 密码
        JLabel passwordLabel = new JLabel("密码：");
        passwordLabel.setBounds(100, 100, 100, 30);
        backgroundImageLabel.add(passwordLabel);
        passwordField = new JPasswordField();
        passwordField.setBounds(200, 100, 200, 30);
        backgroundImageLabel.add(passwordField);

        // 登录按钮
        loginButton = new JButton("登录");
        loginButton.setBounds(100, 150, 80, 30);
        backgroundImageLabel.add(loginButton);
        loginButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                String password = String.valueOf(passwordField.getPassword());
                if (checkUser(username, password)) {
                    // 登录成功，跳转到新页面
                    dispose(); // 关闭当前窗口
                    JFrame frame = new JFrame();
                    frame.setTitle("新页面");
                    frame.setSize(500, 300);
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setResizable(false);
                    // 新页面背景图片
                    ImageIcon backgroundImage = new ImageIcon("background2.jpg");
                    Image image = backgroundImage.getImage();
                    Image scaledImage = image.getScaledInstance(500, 300, Image.SCALE_SMOOTH);
                    backgroundImage = new ImageIcon(scaledImage);
                    JLabel backgroundImageLabel = new JLabel(backgroundImage);
                    backgroundImageLabel.setBounds(0, 0, 500, 300);
                    frame.add(backgroundImageLabel);
                    frame.setVisible(true);
                } else {
                    // 登录失败
                    JOptionPane.showMessageDialog(LoginFrame.this, "用户名或密码错误！", "错误", JOptionPane.ERROR_MESSAGE);
                }
            }
        });

        // 注册按钮
        registerButton = new JButton("注册");
        registerButton.setBounds(200, 150, 80, 30);
        backgroundImageLabel.add(registerButton);
        registerButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // 打开注册窗口
                RegisterFrame registerFrame = new RegisterFrame();
                registerFrame.setVisible(true);
            }
        });

        // 忘记密码按钮
        forgetButton = new JButton("忘记密码");
        forgetButton.setBounds(300, 150, 100, 30);
        backgroundImageLabel.add(forgetButton);
        forgetButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // 打开忘记密码窗口
                ForgetFrame forgetFrame = new ForgetFrame();
                forgetFrame.setVisible(true);
            }
        });
    }

    // 检查用户名和密码是否正确
    private boolean checkUser(String username, String password) {
        // TODO: 实现用户名和密码的验证逻辑
        return true;
    }

    public static void main(String[] args) {
        LoginFrame loginFrame = new LoginFrame();
        loginFrame.setVisible(true);
    }
}

// 注册窗口
class RegisterFrame extends JFrame {
    public RegisterFrame() {
        setTitle("注册");
        setSize(300, 200);
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setResizable(false);

        JPanel panel = new JPanel();
        panel.setLayout(null);
        add(panel);

        // 用户名
        JLabel usernameLabel = new JLabel("用户名：");
        usernameLabel.setBounds(30, 30, 60, 30);
        panel.add(usernameLabel);
        JTextField usernameField = new JTextField();
        usernameField.setBounds(100, 30, 150, 30);
        panel.add(usernameField);

        // 密码
        JLabel passwordLabel = new JLabel("密码：");
        passwordLabel.setBounds(30, 70, 60, 30);
        panel.add(passwordLabel);
        JPasswordField passwordField = new JPasswordField();
        passwordField.setBounds(100, 70, 150, 30);
        panel.add(passwordField);

        // 确认密码
        JLabel confirmPasswordLabel = new JLabel("确认密码：");
        confirmPasswordLabel.setBounds(10, 110, 80, 30);
        panel.add(confirmPasswordLabel);
        JPasswordField confirmPasswordField = new JPasswordField();
        confirmPasswordField.setBounds(100, 110, 150, 30);
        panel.add(confirmPasswordField);

        // 提交按钮
        JButton submitButton = new JButton("提交");
        submitButton.setBounds(100, 150, 80, 30);
        panel.add(submitButton);
        submitButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                String password = String.valueOf(passwordField.getPassword());
                String confirmPassword = String.valueOf(confirmPasswordField.getPassword());
                if (username.isEmpty() || password.isEmpty() || confirmPassword.isEmpty()) {
                    JOptionPane.showMessageDialog(RegisterFrame.this, "请填写完整！", "错误", JOptionPane.ERROR_MESSAGE);
                } else if (!password.equals(confirmPassword)) {
                    JOptionPane.showMessageDialog(RegisterFrame.this, "两次输入的密码不一致！", "错误", JOptionPane.ERROR_MESSAGE);
                } else {
                    // TODO: 实现注册逻辑
                    JOptionPane.showMessageDialog(RegisterFrame.this, "注册成功！", "提示", JOptionPane.INFORMATION_MESSAGE);
                    dispose(); // 关闭当前窗口
                }
            }
        });
    }
}

// 忘记密码窗口
class ForgetFrame extends JFrame {
    public ForgetFrame() {
        setTitle("忘记密码");
        setSize(300, 150);
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setResizable(false);

        JPanel panel = new JPanel();
        panel.setLayout(null);
        add(panel);

        // 用户名
        JLabel usernameLabel = new JLabel("用户名：");
        usernameLabel.setBounds(30, 30, 60, 30);
        panel.add(usernameLabel);
        JTextField usernameField = new JTextField();
        usernameField.setBounds(100, 30, 150, 30);
        panel.add(usernameField);

        // 提交按钮
        JButton submitButton = new JButton("提交");
        submitButton.setBounds(100, 80, 80, 30);
        panel.add(submitButton);
        submitButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                if (username.isEmpty()) {
                    JOptionPane.showMessageDialog(ForgetFrame.this, "请填写用户名！", "错误", JOptionPane.ERROR_MESSAGE);
                } else {
                    // TODO: 实现忘记密码逻辑
                    JOptionPane.showMessageDialog(ForgetFrame.this, "我们已经将重置密码的链接发送到您的邮箱，请查收！", "提示", JOptionPane.INFORMATION_MESSAGE);
                    dispose(); // 关闭当前窗口
                }
            }
        });
    }
}

需要注意的是，这里只是一个简单的示例代码，实际应用中还需要进行更严格的输入验证和安全保护，以确保用户信息不被非法获取或篡改。