private DefaultMutableTreeNode getSelectedNode( )
{
	TreePath
		selectionPath = dataTr.getSelectionPath();
	if ( selectionPath == null )
		return(null);
	DefaultMutableTreeNode
		selectedNd = (DefaultMutableTreeNode)selectionPath.getLastPathComponent();
	if ( !dataRootNd.isNodeDescendant(selectedNd) )
		return(null);
	return(selectedNd);
}