code: public void updateClassElements(final UIClassification _uiclass)
          throws EFapsException
      {
          // remove previous added classification forms
          final Iterator<Element> iter2 = this.elements.iterator();
          final Map<UUID, String> uuid2InstanceKey = new HashMap<>();
          while (iter2.hasNext()) {
              final IFormElement element = iter2.next().getElement();
              if (element instanceof UIFieldForm) {
                  final String instanceKey = ((UIFieldForm) element).getInstanceKey();
                  final TargetMode mode = ((UIFieldForm) element).getMode();
                  if (instanceKey != null && !TargetMode.CREATE.equals(mode)) {
                      final UUID classUUID = ((UIFieldForm) element).getClassificationUUID();
                      uuid2InstanceKey.put(classUUID, instanceKey);
                  }
                  iter2.remove();
              }
          }
          addClassElements(_uiclass, uuid2InstanceKey);
      }
docs: Method that removes all classifcations and afterwards adds the
  classification forms as elements to the form by walking down the tree.
  
  @param _uiclass the classification to be added
  @throws EFapsException on error