public static Collection<UUID> nodeIds(@Nullable Collection<? extends ClusterNode> nodes){
  if (nodes == null || nodes.isEmpty())   return Collections.emptyList();
  return F.viewReadOnly(nodes,node2id());
}

public static Collection < UUID > nodeIds ( @ Nullable Collection < ? extends ClusterNode > nodes ) { if ( nodes == null || nodes . isEmpty ( ) ) return Collections . emptyList ( ) ; return F . viewReadOnly ( nodes , node2id ( ) ) ; }
convenient utility method that returns collection of node ids for a given collection of grid nodes . < p > note that this method doesn ' t create a new collection but simply iterates over the input one .
