Trouble updating a JtextArea from a JTable ListSelectionListener..

Question

Hi, I'm having trouble updating a JtextArea from a JTable ListSelectionListener, it is working for another JTextArea but I have created JNMTextArea which extends JTextArea and I am getting no data passed to it.
Any help is really greatly appreciated. Im a relative newbie to Java.
Here is the class declaration for JNMTextArea
public class JNMTextArea extends JTextArea
     //Constructor
     public JNMTextArea(String text){
          super(text);
          setLineWrap(true);
          setEditable(false);
     //Constructor
     public JNMTextArea()
          this(new String());
     //This sets the data in setText, works ok.
     void displayPacket(Packet p){
          //Function works fine
          //Need to pass this data to the JNMTextArea!!!
          setText(buffer.toString());
          setCaretPosition(0);
Here is where I use JNMTextArea, Im
class JNMGui extends JFrame implements ActionListener, WindowListener{
     public static JNMTextArea txtPktContent;
     //Constructor
          JNMGui(){
               buildGUI();
     private void buildGUI(){
     mainWindow = new JFrame("Monitor");
     tblPacket = new JTable(tblPacketM);
     tblPacket.setToolTipText("Packet Panel");
     tblPacket.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
     if (ALLOW_ROW_SELECTION) {
          ListSelectionModel rowSM = tblPacket.getSelectionModel();
          rowSM.addListSelectionListener(new ListSelectionListener() {                     public void valueChanged(ListSelectionEvent e) {
                    if (e.getValueIsAdjusting())
                         return;
                    ListSelectionModel lsm =      (ListSelectionModel)e.getSource();
                    if (lsm.isSelectionEmpty()) {
                         System.out.println("No rows are selected.");
                    else {
                         int selectedRow = lsm.getMinSelectionIndex();
                         selectedRow++;
                         String str;// = "";
                         //Unsure if I need to create this here!
                         txtPktContent = new JNMTextArea();
                         //This works perfectly
                         txtPktType.append ( "Packet No: " + Integer.toString(selectedRow) + "\n\n");
                         Packet pkt = new Packet();
                         pkt = (Packet) CaptureEngine.packets.elementAt(selectedRow);
                         if(pkt.datalink!=null && pkt.datalink instanceof EthernetPacket){
                              str = "Ethernet ";
                              //THis works txtPktType is another JTextArea!!          
                              txtPktType.append ( s );
                              //This is not working
                              //I realise displayPacket return type is void but how do get
                              //the setText it created to append to the JNMTextArea??               
                              txtPktContent.displayPacket(pkt);
          //Adding to ScrollPane
          tblPane = new JScrollPane(tblPacket);
          txtPktTypePane = new JScrollPane ( txtPktType );
          txtPktTypePane.setToolTipText("Packet Type");
          txtPktContentPane = new JScrollPane ( txtPktContent );
          txtPktContentPane.setToolTipText("Packet Payload");
          panel.add( tblPane, BorderLayout.CENTER );
//End Class JNMGui

Answer 1

void displayPacket(Packet p){
          //Function works fine
          //Need to pass this data to the JNMTextArea!!!
          setText(buffer.toString());
          setCaretPosition(0);
This seems really odd. Notice that you pass in "p" but use "buffer". Where is "buffer" defined?