Swing 报错NoClassDefFoundError

问题遇到的现象和发生背景

运行Controller报错NoClassDefFoundError

问题相关代码，请勿粘贴截图

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

public class Controller{
    public static void main(String[] args) {
        Con win=new Con("开始");
    }
}
class Con extends JFrame implements ActionListener {
    public User user;
    public   UserService service;
    JButton button;
    JTextField input;
        Con(String s) {
            super(s);
            addWindowFocusListener(new WindowAdapter() {
                public void windowClosin(WindowEvent e) {
                    dispose();
                }
            });

            user=new User("翠花","1");
            service=new UserService(user);
            button=new JButton("测试");
            setLayout(new FlowLayout());
            add(button);
            input=new JTextField("0",10);
            add(input);
            button.addActionListener(this);
            setBounds(100,100,150,150);
            setVisible(true);
            validate();
        }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource()==button){
            input.setText(service.getUser().getPassword()+service.getUser().getUsername());
        }
    }
}

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

windows系统保留的系统关键字Con

把Con改名为WindowButton问题就解决了