if (model.getTreeView() == null) return; model.showTreeView(!model.getTreeView().isDisplay());
TreeView treeView = model.createTreeView(); model.showTreeView(!treeView.isDisplay());
    public void actionPerformed(ActionEvent e)    {     	if (model.getTreeView() == null) return;        model.showTreeView(!model.getTreeView().isDisplay());    }