public boolean find(int key) {
    Tree234Node node = root;
    while (node != null) {
      if (key < node.key1) {
        node = node.child1;
      } else if (key == node.key1) {
        return true;
      } else if ((node.keys == 1) || (key < node.key2)) {
        node = node.child2;
      } else if (key == node.key2) {
        return true;
      } else if ((node.keys == 2) || (key < node.key3)) {
        node = node.child3;
      } else if (key == node.key3) {
        return true;
      } else {
        node = node.child4;
      }
    }
    return false;
  }