all'oggetto JTree registri i listener appropriati...
addTreeExpansionListener(TreeExpansionListener)
addTreeSelectionListener(TreeSelectionListener)
addTreeWillExpandListener(TreeWillExpandListener)


di questi listener implementi i metodi
>>TreeExpansionListener
treeCollapsed(TreeExpansionEvent evt)
treeExpanded(TreeExpansionEvent evt)
>>TreeSelectionListener
valueChanged(TreeSelectionEvent evt)
>>TreeWillExpandListener
treeWillCollapse(TreeExpansionEvent evt)
treeWillExpand(TreeExpansionEvent evt)