Adding a JMenuBar

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.io.FileNotFoundException;

import javax.swing.*;

public class JavaAssignmentPanel {

    public static JMenuBar setupMenu() { // method modifiers where mising here

        JMenuBar menuBar = new JMenuBar(); // menubar
        JMenu menu1 = new JMenu("Menu"); // menu
        menuBar.add(menu1); // add menu to gui
        JMenuItem menuItem1 = new JMenuItem("Item 1", KeyEvent.VK_1); // create
                                                                        // drop
                                                                        // down
                                                                        // menu
        menu1.add(menuItem1); // adds drop down menu to gui

        // execute code when selected
        menuItem1.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {

                // panel.showText("Example1 text - normally read from file");
            }
        });

        return menuBar;
    }

    public static void main(String[] args) throws FileNotFoundException {

        window window = new window();

    }

    private static class window extends JFrame {

        public window() throws FileNotFoundException {

            JPanel leftScrollPane = new JPanel();
            JPanel rightPane = new JPanel();
            JSplitPane splitPane;

            this.setVisible(true);
            this.setSize(400, 400);
            this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            splitPane = new JSplitPane();
            splitPane.setOrientation(JSplitPane.HORIZONTAL_SPLIT);
            splitPane.setDividerSize(10);
            splitPane.setDividerLocation(100);
            splitPane.setLeftComponent(leftScrollPane);
            splitPane.setRightComponent(rightPane);
            splitPane.setOneTouchExpandable(true);
            splitPane.setDividerLocation(200);

            Dimension minimumSize = new Dimension(100, 50);

            leftScrollPane.setSize(400, 400);

            this.setJMenuBar(setupMenu());
            splitPane.setPreferredSize(new Dimension(400, 200));
            splitPane.setLeftComponent(leftScrollPane);
            splitPane.setRightComponent(rightPane);
            this.add(splitPane);
            this.setSize(1280, 720);
        }
    }
}