@Override
    public void valueChanged(ListSelectionEvent e) {
      PaletteComponentList sourceList = (PaletteComponentList)e.getSource();
      for (int i = e.getFirstIndex(); i <= e.getLastIndex(); i++) {
        if (sourceList.isSelectedIndex(i)) {
          // selection is being added
          for (PaletteGroupHeader group : myGroupHeaders) {
            if (group.getComponentList() != sourceList) {
              group.getComponentList().clearSelection();
            }
          }
          break;
        }
      }
      notifySelectionChanged(e);
    }
@Override
    public void valueChanged(ListSelectionEvent e)