Swing tree折叠展开事件

tree.addTreeWillExpandListener(new TreeWillExpandListener()   { 
        public   void   treeWillCollapse(TreeExpansionEvent event)   {//折叠 
                  } 
  
        public   void   treeWillExpand(TreeExpansionEvent event)   {//打开 
                             
                  } 
  } );