src/main/java/org/efaps/ui/wicket/models/objects/UIForm.java
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);
    }
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);
    }
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