JTable: Detect cell data change

In Netbeans, I used the GUI Builder to insert a JTable into my application.

I have just one class (CustomerDB) so far which is:

package CustomerDB;

import [...];

public class CustomerDB extends javax.swing.JFrame {

    CellEditorListener ChangeNotification = new CellEditorListener() {
        public void editingCanceled(ChangeEvent e) {
            System.out.println("The user canceled editing.");
        }

        public void editingStopped(ChangeEvent e) {
            System.out.println("The user stopped editing successfully.");
        }
    };

    public CustomerDB() {
        customerTable = new javax.swing.JTable();
        customerTable.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "ID", "Name", "Address", "Phone"
            }
        ) {
            Class[] types = new Class [] {
                java.lang.String.class, java.lang.String.class, java.lang.String.class, java.lang.String.class
            };

            public Class getColumnClass(int columnIndex) {
                return types [columnIndex];
            }
        });
        customerTable.getDefaultEditor(String.class).addCellEditorListener(ChangeNotification);
    } 

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new CustomerDB().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify
    [...]
    pr