How can I get all currently running nodes from the master in rosjava?

edit

Is there a simple way to retrieve all currently running nodes from the ros master in rosjava? In order to obtain all topics in the system the following works:

MasterClient masterClient = new MasterClient(this.node.getMasterUri());
Response<SystemState> systemState = masterClient.getSystemState(defaultNodeName);
List<TopicSystemState> topicSystemStateList = systemState.getResult().getTopics();

Is there something similar to obtain all running nodes? The only way I found is to indirectly retrieve them via TopicSystemState.getPublishers() and TopicSystemState.getSubscribers() - but this would ignore nodes which do not subscribe or publish anything.

Regards scr