private String getNodeIndex(JTree tree, TreeNode node) {
	    TreeNode root = (TreeNode) tree.getModel().getRoot();
	    if (node == root) {
	        return "";
	    }
	    TreeNode parent = node.getParent();
	    if (parent == null) {
	        return null;
	    }
	    String parentIndex= getNodeIndex(tree, parent);
	    if (parentIndex == null) {
	        return null;
	    }
	    return parentIndex+":"+parent.getIndex(node);
	}