How to use

stream

method

in

java.util.Optional

  /** @return Nodes of type host, in any state, that have no children with allocation */
  static Set<Node> candidates(NodeList nodes) {
    Map<String, Node> hostsByHostname = nodes.nodeType(NodeType.host)
        .asList().stream()
        .collect(Collectors.toMap(Node::hostname, Function.identity()));

    nodes.asList().stream()
        .filter(node -> node.allocation().isPresent())
        .flatMap(node -> node.parentHostname().stream())
        .distinct()
        .forEach(hostsByHostname::remove);

    return Set.copyOf(hostsByHostname.values());
  }
}