LinuxQuestions.org - Java, code compiles and supposedly runs fine in windows, but not linux

I get this error:
Exception in thread "main" java.lang.NoClassDefFoundError: //MenuBalloon/class

when I run this code that I downloaded from a website, it is part of a book and it says it works in windows and unix. It compiles fine. I also wrote my own program based on it that is completely different and also compiles fine.

http://www.shu.ac.uk/java/3rdEdition...enuBalloon.txt
is the books code

my code is:
import java.awt.*;
import java.util.*;
import java.awt.event.*;
public class Assign10 extends Frame implements ActionListener, WindowListener
{

private MenuItem New, Open, Delete;
private MenuItem Undo, Redo, Cut, Copy, Paste;
private String TheString = new String("Select a menu item");

public static void main(String[] args)
{
Frame f = new Assign10();
f.setSize(300, 300);
f.setVisible(true);
}

public Assign10()
{
setTitle("MenuThingy :-D");

MenuBar menuBar = new MenuBar();

Menu fileMenu = new Menu("File");
Menu editMenu = new Menu("Edit");

New = new MenuItem("New");
fileMenu.add(New);
New.addActionListener(this);

Open = new MenuItem("Open");
fileMenu.add(Open);
Open.addActionListener(this);

Delete = new MenuItem("Delete");
fileMenu.add(Delete);
Delete.addActionListener(this);

Undo = new MenuItem("Undo");
editMenu.add(Undo);
Undo.addActionListener(this);

Redo = new MenuItem("Redo");
editMenu.add(Redo);
Redo.addActionListener(this);

editMenu.addSeparator();

Cut = new MenuItem("Cut");
editMenu.add(Cut);
Cut.addActionListener(this);

Copy = new MenuItem("Copy");
editMenu.add(Copy);
Copy.addActionListener(this);

Paste = new MenuItem("Paste");
editMenu.add(Paste);
Paste.addActionListener(this);

menuBar.add(fileMenu);
menuBar.add(editMenu);
setMenuBar(menuBar);
addWindowListener(this);
}

public void actionPerformed(ActionEvent event)
{
if (event.getSource() == New)
{
TheString = new String("You Selected New");
}
if (event.getSource() == Open)
{
TheString = new String("You Selected Open");
}
if (event.getSource() == Delete)
{
TheString = new String("You Selected Delete");
}
// MenuItem Undo, Redo, Cut, Copy, Paste;
if (event.getSource() == Undo)
{
TheString = new String("You Selected Undo");
}
if (event.getSource() == Redo)
{
TheString = new String("You Selected Redo");
}
if (event.getSource() == Cut)
{
TheString = new String("You Selected Cut");
}
if (event.getSource() == Copy)
{
TheString = new String("You Selected Copy");
}
if (event.getSource() == Paste)
{
TheString = new String("You Selected Paste");
}
repaint();
}

public void paint (Graphics g)
{
g.drawString(TheString,20,20);
}

public void windowClosing(WindowEvent e)
{
System.exit(0);
}

public void windowIconified(WindowEvent e)
{
}
public void windowOpened(WindowEvent e)
{
}
public void windowClosed(WindowEvent e)
{
}
public void windowDeiconified(WindowEvent e)
{
}
public void windowActivated(WindowEvent e)
{
}
public void windowDeactivated(WindowEvent e)
{
}
}

i compile with javac ./filename.java