How to catch an exception from a SwingWorker

[Luigi Plinge]

Below is a code exerpt from a JPanel I've made. The ActionListener launches a Runnable class, which works OK.

2 questions:

1) Am I using SwingWorker correctly here? (first time )

2) How do I catch any exception thown by the Runnable launched by the SwingWorker in the doInBackground method? I've had exceptions ocurring but there is no feedback.

Thanks

    class LaunchButtonListener implements ActionListener{
        Class target;

        public LaunchButtonListener(Class c) {
            target = c;
        }

        public void actionPerformed(ActionEvent e) {

            if (Runnable.class.isAssignableFrom(target)) {
                try {
                    Runnable r = (Runnable) target.newInstance();
                    LaunchWorker lw = new LaunchWorker(r);
                    lw.execute();

                } catch (Exception ex) {
                    System.out.println("Error launching " + target);
                }
            } else {
                System.out.println("Target class not Runnable");
            }

        }
    }

    class LaunchWorker extends SwingWorker<Void, Void> {

        private Runnable r;
        private long startTime, endTime;

        public LaunchWorker(Runnable r) {
            this.r = r;
        }

        @Override
        protected Void doInBackground() throws Exception {
            startTime = System.nanoTime();
            r.run();
            return null;
        }

        @Override
        protected void done() {
            // Note: error of approx 0.032 s in this benchmark, after 4 warm-up runs
            endTime = System.nanoTime();
            System.out.printf("Class " + r.getClass().getName() + ": time = %f s (-~0.032 s)%n",
                    (endTime - startTime) / 1000000000d);
        }

    }

[Luigi Plinge]

No-one knows?