Java - ¿Cómo se hace para que admita sólo HH:mm:ss?

/*
* NuevoJFrame.java
*
* Created on 11 de septiembre de 2007, 23:28
*/

/**
*
* @author Admin
*/

public class NuevoJFrame extends javax.swing.JFrame {

/** Creates new form NuevoJFrame */
public NuevoJFrame() {
//La siguiente línea es la que falla... (No encuentra la clase MaskFormatter...)
MaskFormatter maskN = new MaskFormatter("**********"); //Permite introducir caracteres y numeros.COn ? solo caracteres y con # solo numeros.
jFormattedTextField1 = new javax.swing.JFormattedTextField(maskN);
initComponents();
}

/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
private void initComponents() {
jFormattedTextField1 = new javax.swing.JFormattedTextField();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jFormattedTextField1.setText("jFormattedTextField1");

org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
.add(layout.createSequentialGroup()
.add(109, 109, 109)
.add(jFormattedTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
.addContainerGap(165, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
.add(layout.createSequentialGroup()
.add(120, 120, 120)
.add(jFormattedTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
.addContainerGap(159, Short.MAX_VALUE))
);
pack();
}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NuevoJFrame().setVisible(true);
}
});
}

// Declaración de variables - no modificar
private javax.swing.JFormattedTextField jFormattedTextField1;
// Fin de declaración de variables

}

Has importado la clase ??

import javax.swing.text.MaskFormatter;

Saludos