MixedTreeModel model = new MixedTreeModel();
DefaultMutableTreeNode tree = new DefaultMutableTreeNode();
tree.add(new DefaultMutableTreeNode());
tree.add(new DefaultMutableTreeNode());
UITreeData data = new UITreeData();
data.setValue(tree);
UITreeNode node = new UITreeNode();
model.beginBuildNode(node);
model.beginBuildNodeData(data);
model.beginBuildNode(node);