if (selection.isEmpty()) return canOperateOnEmptySelection();  if (selection.size() > 1 && !canOperateOnMultiSelection()) return false;
	public boolean canOperateOn(IStructuredSelection selection){		for  (Iterator iter= selection.iterator(); iter.hasNext(); ) {			Object obj= iter.next();			if (!fActivationType.isInstance(obj) || !shouldAcceptElement(obj))				return false;		}		return true;	}