@Test
  public void demonstrateUpdate() {
    probe = new JavaTestKit(system);

    // #update
    final Cluster node = Cluster.get(system);
    final ActorRef replicator = DistributedData.get(system).replicator();

    final Key<PNCounter> counter1Key = PNCounterKey.create("counter1");
    final Key<GSet<String>> set1Key = GSetKey.create("set1");
    final Key<ORSet<String>> set2Key = ORSetKey.create("set2");
    final Key<Flag> activeFlagKey = FlagKey.create("active");

    replicator.tell(
        new Replicator.Update<PNCounter>(
            counter1Key,
            PNCounter.create(),
            Replicator.writeLocal(),
            curr -> curr.increment(node, 1)),
        self());

    final WriteConsistency writeTo3 = new WriteTo(3, Duration.create(1, SECONDS));
    replicator.tell(
        new Replicator.Update<GSet<String>>(
            set1Key, GSet.create(), writeTo3, curr -> curr.add("hello")),
        self());

    final WriteConsistency writeMajority = new WriteMajority(Duration.create(5, SECONDS));
    replicator.tell(
        new Replicator.Update<ORSet<String>>(
            set2Key, ORSet.create(), writeMajority, curr -> curr.add(node, "hello")),
        self());

    final WriteConsistency writeAll = new WriteAll(Duration.create(5, SECONDS));
    replicator.tell(
        new Replicator.Update<Flag>(
            activeFlagKey, Flag.create(), writeAll, curr -> curr.switchOn()),
        self());
    // #update

    probe.expectMsgClass(UpdateSuccess.class);
    // #update-response1
    receive(
        ReceiveBuilder.match(
                UpdateSuccess.class,
                a -> a.key().equals(counter1Key),
                a -> {
                  // ok
                })
            .build());
    // #update-response1

    // #update-response2
    receive(
        ReceiveBuilder.match(
                UpdateSuccess.class,
                a -> a.key().equals(set1Key),
                a -> {
                  // ok
                })
            .match(
                UpdateTimeout.class,
                a -> a.key().equals(set1Key),
                a -> {
                  // write to 3 nodes failed within 1.second
                })
            .build());
    // #update-response2
  }
  @SuppressWarnings({"unused", "unchecked"})
  @Test
  public void demonstrateGet() {
    probe = new JavaTestKit(system);

    // #get
    final ActorRef replicator = DistributedData.get(system).replicator();
    final Key<PNCounter> counter1Key = PNCounterKey.create("counter1");
    final Key<GSet<String>> set1Key = GSetKey.create("set1");
    final Key<ORSet<String>> set2Key = ORSetKey.create("set2");
    final Key<Flag> activeFlagKey = FlagKey.create("active");

    replicator.tell(new Replicator.Get<PNCounter>(counter1Key, Replicator.readLocal()), self());

    final ReadConsistency readFrom3 = new ReadFrom(3, Duration.create(1, SECONDS));
    replicator.tell(new Replicator.Get<GSet<String>>(set1Key, readFrom3), self());

    final ReadConsistency readMajority = new ReadMajority(Duration.create(5, SECONDS));
    replicator.tell(new Replicator.Get<ORSet<String>>(set2Key, readMajority), self());

    final ReadConsistency readAll = new ReadAll(Duration.create(5, SECONDS));
    replicator.tell(new Replicator.Get<Flag>(activeFlagKey, readAll), self());
    // #get

    // #get-response1
    receive(
        ReceiveBuilder.match(
                GetSuccess.class,
                a -> a.key().equals(counter1Key),
                a -> {
                  GetSuccess<PNCounter> g = a;
                  BigInteger value = g.dataValue().getValue();
                })
            .match(
                NotFound.class,
                a -> a.key().equals(counter1Key),
                a -> {
                  // key counter1 does not exist
                })
            .build());
    // #get-response1

    // #get-response2
    receive(
        ReceiveBuilder.match(
                GetSuccess.class,
                a -> a.key().equals(set1Key),
                a -> {
                  GetSuccess<GSet<String>> g = a;
                  Set<String> value = g.dataValue().getElements();
                })
            .match(
                GetFailure.class,
                a -> a.key().equals(set1Key),
                a -> {
                  // read from 3 nodes failed within 1.second
                })
            .match(
                NotFound.class,
                a -> a.key().equals(set1Key),
                a -> {
                  // key set1 does not exist
                })
            .build());
    // #get-response2

  }