/** DOC hywang Comment method "createToolbar". */
 protected void createToolbar() {
   super.createToolbar();
   getLayoutManager().setSpacing(0);
   add = new AddButton();
   setTooltips(add, "Add variable");
   remove = new RemoveButton();
   setTooltips(remove, "Remove selected variable(s)");
   remove.setEnabled(false);
   move_up = new MoveUpButton();
   setTooltips(move_up, "Move up selected variable(s)");
   move_up.setEnabled(false);
   move_down = new MoveDownButton();
   setTooltips(move_down, "Move down selected variable(s)");
   move_down.setEnabled(false);
   this.add(add);
   this.add(remove);
   this.add(move_up);
   this.add(move_down);
   this.add(min_size);
 }
 @Override
 public void toolBarButtonPressed(MouseEvent me) {
   super.toolBarButtonPressed(me);
   moveUp();
 }