public void valueChanged(ListSelectionEvent e) {
        if (e.getValueIsAdjusting() == false) {

            if (list.getSelectedIndex() == -1) {
            //No selection, disable fire button.
                fireButton.setEnabled(false);

            } else {
            //Selection, enable the fire button.
                fireButton.setEnabled(true);
            }
        }
    }