private boolean isValid(@Nullable JTree tree) {
    if (!validator.isValidThread()) {
      LOG.error("TreeUI should be accessed only from EDT");
      return false;
    }
    if (tree != null && tree == getTree()) return true;
    LOG.warn(new IllegalStateException(tree != null ? "unexpected tree" : "undefined tree"));
    return false;
  }
private boolean isValid(@Nullable JTree tree)