code: public void setDefault(final UUID _selectCmdUUID)
      {
          final UIMenuItem menuItem = getProvider().getRoots().next();
          menuItem.setHeader(true);
          boolean hasDefault = false;
          for (final UIMenuItem childItem : menuItem.getChildren()) {
              if (_selectCmdUUID == null && childItem.isDefaultSelected()
                              || _selectCmdUUID != null && _selectCmdUUID.equals(childItem.getCommandUUID())) {
                  hasDefault = true;
                  childItem.setSelected(true);
              }
          }
          if (!hasDefault) {
              menuItem.setSelected(true);
          }
          expand(menuItem);
          expandChildren(menuItem);
      }
docs: Set the default selected item.
  
  @param _selectCmdUUID UUID of the selected Command