Altering a Panel during runtime, repaint etc not working!

Question

Hello all,
I have had a look around this forum for similar problems and all suggestions seem to say use repaint(), revalidate() or validate() to get a JPanel to update, however none of these seem to work for me.
Basically I have a program with multiple panels, one of which is affectedd by JFileChooser, when a new directory is selected the panel alters to show certain files in that directory...all the data alters correctly but the panel will not refresh.
void changeDirectory(String dir){
          currentDirectory = formatDir(dir);
          thumbPanel = new JScrollPane(new thumbnailWindow());
          add(thumbPanel, BorderLayout.CENTER);
          thumbPanel.validate();
          setVisible(true);
     }this is a small snippet of my code and the bit that is giving me the problem,
thumbPanel already exists and is shown in my main program, when the directory is changed the data is altered, so i then want thumbpanel to refrence a new thumbpanel and over write the previous one.
I have already tried to remove the panel first then re add, aswell as repaint, validate, and revalidate. I know this is going to be something fundamental but I don't have a clue what to do now.
All help, comments and criticism is welcomed,
Regards,
Chris.

Answer 1

/* your current code */
void changeDirectory(String dir){
  currentDirectory = formatDir(dir);
  thumbPanel = new JScrollPane(new thumbnailWindow());
  add(thumbPanel, BorderLayout.CENTER);
  thumbPanel.validate();
  setVisible(true);
/* correct code */
void changeDirectory(String dir){
  currentDirectory = formatDir(dir);
  thumbPanel.setViewportView(new thumbnailWindow());
}