Trouble in implementing a progress monitor?

Question

I need a lot of calculation when I click start button, so, I made a thread using SwingWorker class, this thread is responsible for the calculation. I need a progress monitor to display the progress of the calculation, so, do I need another thread to do it? How can I do it? Any suggestion is great appreciated.
The following is the schetch of my class.
// this class do the calculation
// these stuff is within my button listener
MyClass my = new MyClass(...);
my.go();
// stuff in go() method of MyClass is :
final SwingWorker worker = new SwingWorker() {
void construct(){
// Do calculation
void finished(){}
How to add another thread to do progress monitor stuff?

Answer 1

I assume your concern is about updating JProgressBar's value property from your SwingWorker's thread. Since you're using SwingWorker I assume you know the whole "Swing is not Thread-Safe" drill. If only Sun would specify a few more methods to be thread-safe, like JProgressBar's setValue! After all, isn't the raison d'etre of a progress bar to show how another thread is doing? Oh well, why not use my code, below. You don't need another thread, you only need to access Swing from the EDT, hence my calls to InvokeLater. And in case the progress updates come fast and furious, my code coalesces those events. Enjoy -- Nax.
class Updater implements Runnable {
     public Updater(JProgressBar jpb) {
          this.jpb = jpb;
     public void run() {
          int v;
          synchronized(this) {
               queued = false;
               v = val;
          jpb.setValue(v);
     public void update(int v) {
          boolean go = false;
          synchronized(this) {
               val = v;
               if (!queued) {
                    queued = true;
                    go = true;
          if (go)
               SwingUtilities.invokeLater(this);
     private boolean queued;
     private int val;
     private final JProgressBar jpb;