@Override
      public void actionPerformed(ActionEvent e) {
        JCheckBox toUncheck = null;
        if (myStartTracing.isSelected() && myEndTracing.isSelected()) {
          Object source = e.getSource();
          if (myStartTracing.equals(source)) {
            toUncheck = myEndTracing;
          }
          else if (myEndTracing.equals(source)) {
            toUncheck = myStartTracing;
          }
          if (toUncheck != null) {
            toUncheck.setSelected(false);
          }
        }
      }
@Override
      public void actionPerformed(ActionEvent e)