Jpanel UI main（）方法

Question

我写了一个程序，它是一个带有两个文本字段和两个按钮的登录窗口，此阶段的actionPerformed方法用于测试目的。

我的问题是，我把所有组件放在构造函数中，我不知道如何编写我的main（）方法以使程序运行，我尝试了类似于获取类的引用，设置可见性，但它们都不起作用。

 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.*;
 import javax.swing.JButton;
 import javax.swing.JFrame;
 import javax.swing.JLabel;
 import javax.swing.JPanel;
 import javax.swing.JPasswordField;
 import javax.swing.JTextField;


 public class LoginUI extends JFrame implements ActionListener
 {


JTextField Tusername;
JTextField Tpassword;
JButton Login = new JButton("Login");
JButton register = new JButton("Register");
JLabel passwordLabel = new JLabel("Password");
JLabel userLabel = new JLabel("User");

public String username;
public String password;

public LoginUI()
{

    JFrame frame = new JFrame("Login or register");
    JPanel Panel = new JPanel();
    frame.add(Panel);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    Login.setBounds(10, 80, 80, 25);
    Panel.add(Login);
    Login.addActionListener(this);

    register.setBounds(180, 80, 80, 25);
    Panel.add(register);
    register.addActionListener(this);

    Panel.setLayout(null);

    JLabel userLabel = new JLabel("User");
    userLabel.setBounds(10, 10, 80, 25);
    Panel.add(userLabel);

    Tusername = new JTextField(20);
    Tusername.setBounds(100, 10, 160, 25);
    Panel.add(Tusername);

    JLabel passwordLabel = new JLabel("Password");
    passwordLabel.setBounds(10, 40, 80, 25);
    Panel.add(passwordLabel);

    Tpassword = new JPasswordField(20);
    Tpassword.setBounds(100, 40, 160, 25);
    Panel.add(Tpassword);

}


public void actionPerformed(ActionEvent e)
{
    if (e.getSource() == Login) 
    {
        String username = Tusername.getText(); 
        System.out.println(username);
    }
    else if (e.getSource() == register)
    {
        String password = Tpassword.getText(); 
        System.out.println(password);
    }
}


public static void main(String args[])
{




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