Java Problem

package com.gmail.adrianrod2205;

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.Color;
import javax.swing.JToolBar;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import java.awt.ScrollPane;
import javax.swing.AbstractAction;
import java.awt.event.ActionEvent;
import javax.swing.Action;

public class mainFrame extends JFrame {

    private JPanel contentPane;
    private final Action action = new SwingAction();

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    mainFrame frame = new mainFrame();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public mainFrame() {
        setBackground(Color.WHITE);
        setTitle("Grafischer Akzeptor");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 800, 600);

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);

        JMenu mnDatei = new JMenu("Datei");
        menuBar.add(mnDatei);

        JMenuItem mntmExportieren = new JMenuItem("Exportieren");
        mnDatei.add(mntmExportieren);

        JMenuItem mntmLaden = new JMenuItem("Laden");
        mnDatei.add(mntmLaden);

        JMenu mnAkzeptor = new JMenu("Akzeptor");
        menuBar.add(mnAkzeptor);

        JMenu mnZustnde = new JMenu("Zust\u00E4nde");
        mnAkzeptor.add(mnZustnde);

        JMenuItem mntmHinzufgen = new JMenuItem("Hinzuf\u00FCgen");
        mntmHinzufgen.setAction(action);
        mnZustnde.add(mntmHinzufgen);

        contentPane = new JPanel();
        contentPane.setBackground(Color.WHITE);
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);
    }

    private class SwingAction extends AbstractAction {
        public SwingAction() {
            putValue(NAME, "Hinzuf\u00FCgen");
            putValue(SHORT_DESCRIPTION, "F\u00FCgt einen Zustand hinzu");
        }

        public void actionPerformed(ActionEvent e) {
            Akzeptor.createZustand();
        }
    }
}