updating JTree

[Sergio Mergen]

hello all     i have a JTree that represents an object at the top level and it´s associated objects as childs nodes, and so on... the problem i´m facing is when i update the tree to reflect the changes(insertion or deletion) of the set of objects.   sometimes a deletion works in cascade mode, erasing all the references to the object being deleted. How can i update the JTree on situations like this,  where i want to maintain all the expanded nodes as they are, unless of course some changes must took place on these nodes.   I´m handling the update by collapsing the whole tree and then updating it....but, these is not the behavior i, along with future users :) , want from the software... Can you help me out here? the bottom line is: maintain the JTree expanded when updating it thanks                        Sergio