new DefaultTreeSelectionModel();
treeSelectionModel.setSelectionMode(
TreeSelectionModel.SINGLE_TREE_SELECTION);
prefTree.setSelectionModel(treeSelectionModel);
prefTree.addTreeSelectionListener(
new TreeSelectionListener() {
public void valueChanged(TreeSelectionEvent e) {
TreePath path = e.getNewLeadSelectionPath();
DefaultMutableTreeNode node =
(DefaultMutableTreeNode) path.getLastPathComponent();
setDisplayedPrefPanel((JComponent) node.getUserObject());