Image capture -- renegade threads

Hello visad-list

I have another question for you regarding offscreen image rendering.

I've set a up a simple class to capture my images, but the process never
completes -- my program never exits.  It seems to me that there must be
some thread buried deep inside VisAD that isn't finishing.

Here's the general outline of my code:

public class ImageMaker{

        public void main( String[] args ){

        private void captureImages(){
                // create DisplayImpl
                // add data to DisplayImpl
                // call thread to capture images
                Thread thread = new ImageCapturer( DisplayImpl disp );
                System.out.println( "All Done!" );

        class ImageCapturer extends Thread{

                // constructor

                // run
                public void run(){
                        // get the image
                        // write it to file
                        System.out.println( "Thread Done!" );

I run the code with
> java ImageMaker
And see...
All Done!
Thread Done!

But the prompt never comes back.  What is still running that won't let my
program exit?

Thanks for the help.