// Lists are up to date. Do the rest of the book-keeping
// Neue Einträge in die nodeMap einfügen
for (DefaultMutableTreeNode treeNode : addList) {
DataObject obj = (DataObject) treeNode.getUserObject();
obj.addObserver(this);
DataObject oldVal = nodeMap.put(treeNode, obj);
if (oldVal != null) {
oldVal.removeObserver(this);
}