The MutableTreeNode has the attribute userObject where you can store anything that describes the object represented by the node.
you should write your custom TreeNode (by implementing the appropriate interface (be aware that you have to implement all the listener methods as well) or extending DefaultMutableTreeNode (event/listener are handled in this case but the class is quite complex)). and moreover a custom TreeModel that handles the data (= the nodes). changes made to the data is displayed at once in the JTree and vice versa. see the swing tutorial on TreeModels.
it might sound more difficult than it is, just give it a shot.
cheers