Code Error Java?
public class Main {
public static void main(String[] args) {


    GUI gui = new GUI();
    
    }
    
   public static int fak (int n) {
        if (n == 0) {
            return 1;
        }
        return n * fak(n - 1);
    }
    
}

import javax.swing.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;


import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;


public class GUI extends JFrame {
    JButton button = new JButton("Berechnen");
    JLabel label = new JLabel("Bitte geben Sie die Zahl ein: ");
    JTextField textfield = new JTextField(2);
    JOptionPane popup = new JOptionPane();
    JPanel panel = new JPanel();
    
    public GUI () {
        setSize(300, 300);
        setTitle("Fakultätsrechner");
        setLayout(new FlowLayout());
        setVisible(true);
        
        panel.add(textfield);
        panel.add(label);
        panel.add(button);
        add(panel);
        
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);


        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    String input = textfield.getText();
                    int number = Integer.parseInt(input);
                    int result = Main.fak(number);
                    JOptionPane.showMessageDialog(null, "Die Fakultät von " + number + " ist " + result);
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Bitte geben Sie eine gültige Ganzzahl ein.");
                }
            }
        });
        
    }





}

Error: java.lang.ClassNotFoundException: Main

Aber wieso findet er denn die Main-Klasse nicht? Verstehe ich nicht.

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