Validating JTextfield in an Applet

Question

I am doing a simple assignment for a Java class I am taking. The assignment consists of doing the Tower of Hanoi with just symbols showing the moves of the disks. I have been successful in writing the recursive statement and init() but I am having trouble validating the JTextfield in the applet. I want to validate the entry is only between 1 and 9. Nothing else and no letters. Here is my code at the present time. If anyone could help I would appreciate it.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class HWProblem6_37Hanoi extends JApplet implements ActionListener
/** Initialization method that will be called after the applet is loaded
into the browser.*/
JLabel directions;
JTextField userInput;
//attach JTextArea to a JScrollPane so user can scroll results
JTextArea outputArea = new JTextArea(10, 30);
//Set up applet's GUI
public void init()
//obtain content pane and set its layout to FlowLayout
Container container=getContentPane();
container.setLayout( new FlowLayout() );
JScrollPane scroller = new JScrollPane(outputArea);
//create directions label and attach it to content pane
directions = new JLabel("Enter a Integer Between 1 and 9: ");
container.add( directions );
//create numberField and attach it to content pane
userInput = new JTextField(10);
container.add( userInput );
//register this applet as userInput ActionListener
userInput.addActionListener( this );
container.add (scroller);
public void actionPerformed(ActionEvent event)
//Initialize variables
int number = 0;
while (number == 0)
number = Integer.parseInt(userInput.getText());
if ((number<1) || (number >9))
userInput.setText(" ");
number =0;
showStatus("Error: Invalid Input");
else
showStatus("Valid Input");
tower(number,1,2,3);
public void tower(int n, int needle1/*source*/, int needle2/*destination*/, int needle3/*free space*/)
if (n >0)
tower(n-1, needle1, needle3, needle2);
outputArea.append(needle1 + " -> " + needle3 + "\n");
tower(n-1, needle2, needle1, needle3);
}

Answer 1

How to Use Formatted Text Fields
http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html