JTreeのノードを折り畳み不可に設定する

tree.addTreeWillExpandListener(new TreeWillExpandListener() {
  @Override public void treeWillExpand(TreeExpansionEvent e)
      throws ExpandVetoException {
    // throw new ExpandVetoException(e, "Tree expansion cancelled");
  }

  @Override public void treeWillCollapse(TreeExpansionEvent e)
      throws ExpandVetoException {
    throw new ExpandVetoException(e, "Tree collapse cancelled");
  }
});