code: private static void aggregateSingleClusterMemberData(List<ResultCollector> taskResults) {
          for (ResultCollector singleCluster : taskResults) {
              List membersResult = (List) singleCluster.getResult();
              for (Object resultFromNode : membersResult) {
                  System.out.print(((HashMap) resultFromNode).get("ds") + ":");
              }
              System.out.println();
          }
      }
docs: only for partitioned region!