自分でswingでメモ帳のインタフェースを書きました

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JSeparator;
import javax.swing.JSplitPane;

public class MainFrame extends JFrame implements ActionListener {

	private static final long serialVersionUID = 295941050339534223L;
	
	private static final String FILE_MENU = "  (F)";
	private static final String EDIT_MENU = "  (E)";
	private static final String OUTLOOK_MENU = "  (O)";
	private static final String VIEW_MENU = "  (V)";
	private static final String HELP_MENU = "  (H)";
	
	Container contentPane;
	JPanel menuPanel,filePanel,editPanel,outLookPanel,viewPanel,helpPanel;
	JMenuBar menuBar;
	JMenu fileMenu,editMenu,outLookMenu,viewMenu,helpMenu;
	JMenuItem newFile,open,save,anotherSave,pageSetup,print,quit;
	JMenuItem undo,cut,copy,paste,del,find,findNext,replace,turnto,selectAll,datetime;
	JMenuItem auto,font,status,helptheme,aboutNotepad;
	
	public void actionPerformed(ActionEvent e) {

	}
	
	public void showContent(){
		
		//fileMenu
		newFile = new JMenuItem("  (N)      Ctrl+N  ");
		open = new JMenuItem("  (O)...   Ctrl+O  ");
		save = new JMenuItem("  (S)      Ctrl+S  ");
		anotherSave = new JMenuItem("   (A)...       ");
		pageSetup = new JMenuItem("    (U)...");
		print = new JMenuItem("  (P)...   Ctrl+P  ");
		quit = new JMenuItem("  (X)");
		
		//editMenu
		undo = new JMenuItem("  (U)      Ctrl+Z");
		cut = new JMenuItem("  (T)      Ctrl+X");
		copy = new JMenuItem("  (C)      Ctrl+C");
		paste = new JMenuItem("  (P)      Ctrl+V");
		del = new JMenuItem("  (L)      DEL");
		find = new JMenuItem("  (F)...   Ctrl+F");
		findNext = new JMenuItem("     (N)   F3");
		replace = new JMenuItem("  (R)...   Ctrl+H");
		turnto = new JMenuItem("  (G)...   Ctrl+G");
		selectAll = new JMenuItem("  (A)...   Ctrl+A");
		datetime = new JMenuItem("  /  (D)     F5");
		
		//outLookMenu
		auto = new JMenuItem("    (W)   ");
		font = new JMenuItem("  (F)...");
		
		//viewMenu
		status = new JMenuItem("   (S)  ");
		status.setEnabled(false);
		
		//helpMenu
		helptheme = new JMenuItem("    (H)  ");
		aboutNotepad = new JMenuItem("     (A)  ");
		
		fileMenu = new JMenu(FILE_MENU);
		fileMenu.add(newFile);
		fileMenu.add(open);
		fileMenu.add(save);
		fileMenu.add(anotherSave);
		fileMenu.add(new JSeparator());
		fileMenu.add(pageSetup);
		fileMenu.add(print);
		fileMenu.add(new JSeparator());
		fileMenu.add(quit);
		
		editMenu = new JMenu(EDIT_MENU);
		editMenu.add(undo);
		editMenu.add(new JSeparator());
		editMenu.add(cut);
		editMenu.add(copy);
		editMenu.add(paste);
		editMenu.add(del);
		editMenu.add(new JSeparator());
		editMenu.add(find);
		editMenu.add(findNext);
		editMenu.add(replace);
		editMenu.add(turnto);
		editMenu.add(new JSeparator());
		editMenu.add(selectAll);
		editMenu.add(datetime);
		
		outLookMenu = new JMenu(OUTLOOK_MENU);
		outLookMenu.add(auto);
		outLookMenu.add(font);
		
		viewMenu = new JMenu(VIEW_MENU);
		viewMenu.add(status);
		
		helpMenu = new JMenu(HELP_MENU);
		helpMenu.add(helptheme);
		helpMenu.add(new JSeparator());
		helpMenu.add(aboutNotepad);
		
		menuBar = new JMenuBar();
		menuBar.add(fileMenu);
		menuBar.add(editMenu);
		menuBar.add(outLookMenu);
		menuBar.add(viewMenu);
		menuBar.add(helpMenu);
		
		contentPane.add(menuBar,BorderLayout.NORTH);
	}
	
	public void init(){
		contentPane =  getContentPane(); 
		setContentPane(contentPane); 
		setTitle("    -    "); 
	}
	
	public void showFrame(){
		addWindowListener(new WindowAdapter(){
			@Override
			public void windowClosing(WindowEvent e) {
				super.windowClosing(e);
                dispose(); 
                System.exit(0); 
			}
		});
        setSize(700, 525);
        setVisible(true); 
	}
	
	
	public void showAll(){
		init();
		showContent();
		showFrame();
	}
	
	public static void main(String[] args) {
		MainFrame frame = new MainFrame();
		frame.showAll();
	}

}