@Test
  public void materializedValues() throws Exception {
    // #mat-combine-1
    // Materializes to Promise<BoxedUnit>                                     (red)
    final Source<Integer, CompletableFuture<Optional<Integer>>> source = Source.<Integer>maybe();

    // Materializes to BoxedUnit                                              (black)
    final Flow<Integer, Integer, NotUsed> flow1 = Flow.of(Integer.class).take(100);

    // Materializes to Promise<Option<>>                                     (red)
    final Source<Integer, CompletableFuture<Optional<Integer>>> nestedSource =
        source.viaMat(flow1, Keep.left()).named("nestedSource");
    // #mat-combine-1

    // #mat-combine-2
    // Materializes to BoxedUnit                                              (orange)
    final Flow<Integer, ByteString, NotUsed> flow2 =
        Flow.of(Integer.class).map(i -> ByteString.fromString(i.toString()));

    // Materializes to Future<OutgoingConnection>                             (yellow)
    final Flow<ByteString, ByteString, CompletionStage<OutgoingConnection>> flow3 =
        Tcp.get(system).outgoingConnection("localhost", 8080);

    // Materializes to Future<OutgoingConnection>                             (yellow)
    final Flow<Integer, ByteString, CompletionStage<OutgoingConnection>> nestedFlow =
        flow2.viaMat(flow3, Keep.right()).named("nestedFlow");
    // #mat-combine-2

    // #mat-combine-3
    // Materializes to Future<String>                                         (green)
    final Sink<ByteString, CompletionStage<String>> sink =
        Sink.<String, ByteString>fold("", (acc, i) -> acc + i.utf8String());

    // Materializes to Pair<Future<OutgoingConnection>, Future<String>>       (blue)
    final Sink<Integer, Pair<CompletionStage<OutgoingConnection>, CompletionStage<String>>>
        nestedSink = nestedFlow.toMat(sink, Keep.both());
    // #mat-combine-3

    // #mat-combine-4b
    // Materializes to Future<MyClass>                                        (purple)
    final RunnableGraph<CompletionStage<MyClass>> runnableGraph =
        nestedSource.toMat(nestedSink, Combiner::f);
    // #mat-combine-4b
  }
  public void demonstrateACustomMaterializedValue() throws Exception {
    // tests:
    RunnableGraph<CompletionStage<Integer>> flow =
        Source.from(Arrays.asList(1, 2, 3))
            .viaMat(new FirstValue(), Keep.right())
            .to(Sink.ignore());

    CompletionStage<Integer> result = flow.run(mat);

    assertEquals(new Integer(1), result.toCompletableFuture().get(3, TimeUnit.SECONDS));
  }
  @Test
  public void demonstrateMaterializeMultipleTimes() {
    final Source<Tweet, NotUsed> tweetsInMinuteFromNow =
        tweets; // not really in second, just acting as if

    // #tweets-runnable-flow-materialized-twice
    final Sink<Integer, CompletionStage<Integer>> sumSink =
        Sink.<Integer, Integer>fold(0, (acc, elem) -> acc + elem);
    final RunnableGraph<CompletionStage<Integer>> counterRunnableGraph =
        tweetsInMinuteFromNow
            .filter(t -> t.hashtags().contains(AKKA))
            .map(t -> 1)
            .toMat(sumSink, Keep.right());

    // materialize the stream once in the morning
    final CompletionStage<Integer> morningTweetsCount = counterRunnableGraph.run(mat);
    // and once in the evening, reusing the blueprint
    final CompletionStage<Integer> eveningTweetsCount = counterRunnableGraph.run(mat);
    // #tweets-runnable-flow-materialized-twice

  }
  @Test
  public void demonstrateCountOnFiniteStream() {
    // #tweets-fold-count
    final Sink<Integer, CompletionStage<Integer>> sumSink =
        Sink.<Integer, Integer>fold(0, (acc, elem) -> acc + elem);

    final RunnableGraph<CompletionStage<Integer>> counter =
        tweets.map(t -> 1).toMat(sumSink, Keep.right());

    final CompletionStage<Integer> sum = counter.run(mat);

    sum.thenAcceptAsync(
        c -> System.out.println("Total tweets processed: " + c), system.dispatcher());
    // #tweets-fold-count

    new Object() {
      // #tweets-fold-count-oneline
      final CompletionStage<Integer> sum = tweets.map(t -> 1).runWith(sumSink, mat);
      // #tweets-fold-count-oneline
    };
  }
  public static void main(String[] args) {

    Outlet<Integer> outlet = null;

    Outlet<Integer> outlet1 = null;
    Outlet<Integer> outlet2 = null;

    Inlet<Integer> inlet = null;

    Inlet<Integer> inlet1 = null;
    Inlet<Integer> inlet2 = null;

    Flow<Integer, Integer, BoxedUnit> flow = Flow.of(Integer.class);
    Flow<Integer, Integer, BoxedUnit> flow1 = Flow.of(Integer.class);
    Flow<Integer, Integer, BoxedUnit> flow2 = Flow.of(Integer.class);

    Promise<Option<Integer>> promise = null;

    {
      Graph<SourceShape<Integer>, BoxedUnit> graphSource = null;
      Graph<SinkShape<Integer>, BoxedUnit> graphSink = null;
      Graph<FlowShape<Integer, Integer>, BoxedUnit> graphFlow = null;

      // #flow-wrap
      Source<Integer, BoxedUnit> source = Source.fromGraph(graphSource);
      Sink<Integer, BoxedUnit> sink = Sink.fromGraph(graphSink);
      Flow<Integer, Integer, BoxedUnit> aflow = Flow.fromGraph(graphFlow);
      Flow.fromSinkAndSource(Sink.<Integer>head(), Source.single(0));
      Flow.fromSinkAndSourceMat(Sink.<Integer>head(), Source.single(0), Keep.left());
      // #flow-wrap

      Graph<BidiShape<Integer, Integer, Integer, Integer>, BoxedUnit> bidiGraph = null;

      // #bidi-wrap
      BidiFlow<Integer, Integer, Integer, Integer, BoxedUnit> bidiFlow =
          BidiFlow.fromGraph(bidiGraph);
      BidiFlow.fromFlows(flow1, flow2);
      BidiFlow.fromFlowsMat(flow1, flow2, Keep.both());
      // #bidi-wrap

    }

    {
      // #graph-create
      GraphDSL.create(
          builder -> {
            // ...
            return ClosedShape.getInstance();
          });

      GraphDSL.create(
          builder -> {
            // ...
            return new FlowShape<>(inlet, outlet);
          });
      // #graph-create
    }

    {
      // #graph-create-2
      GraphDSL.create(
          builder -> {
            // ...
            return SourceShape.of(outlet);
          });

      GraphDSL.create(
          builder -> {
            // ...
            return SinkShape.of(inlet);
          });

      GraphDSL.create(
          builder -> {
            // ...
            return FlowShape.of(inlet, outlet);
          });

      GraphDSL.create(
          builder -> {
            // ...
            return BidiShape.of(inlet1, outlet1, inlet2, outlet2);
          });
      // #graph-create-2
    }

    {
      // #graph-builder
      GraphDSL.create(
          builder -> {
            builder.from(outlet).toInlet(inlet);
            builder.from(outlet).via(builder.add(flow)).toInlet(inlet);
            builder.from(builder.add(Source.single(0))).to(builder.add(Sink.head()));
            // ...
            return ClosedShape.getInstance();
          });
      // #graph-builder
    }

    // #source-creators
    Source<Integer, Promise<Option<Integer>>> src = Source.<Integer>maybe();
    // Complete the promise with an empty option to emulate the old lazyEmpty
    promise.trySuccess(scala.Option.empty());

    final Source<String, Cancellable> ticks =
        Source.tick(
            FiniteDuration.create(0, TimeUnit.MILLISECONDS),
            FiniteDuration.create(200, TimeUnit.MILLISECONDS),
            "tick");

    final Source<Integer, BoxedUnit> pubSource =
        Source.fromPublisher(TestPublisher.<Integer>manualProbe(true, sys));

    final Source<Integer, BoxedUnit> futSource = Source.fromFuture(Futures.successful(42));

    final Source<Integer, Subscriber<Integer>> subSource = Source.<Integer>asSubscriber();
    // #source-creators

    // #sink-creators
    final Sink<Integer, BoxedUnit> subSink =
        Sink.fromSubscriber(TestSubscriber.<Integer>manualProbe(sys));
    // #sink-creators

    // #sink-as-publisher
    final Sink<Integer, Publisher<Integer>> pubSink = Sink.<Integer>asPublisher(false);

    final Sink<Integer, Publisher<Integer>> pubSinkFanout = Sink.<Integer>asPublisher(true);
    // #sink-as-publisher

    // #empty-flow
    Flow<Integer, Integer, BoxedUnit> emptyFlow = Flow.<Integer>create();
    // or
    Flow<Integer, Integer, BoxedUnit> emptyFlow2 = Flow.of(Integer.class);
    // #empty-flow

    // #flatMapConcat
    Flow.<Source<Integer, BoxedUnit>>create()
        .<Integer, BoxedUnit>flatMapConcat(
            new Function<Source<Integer, BoxedUnit>, Source<Integer, BoxedUnit>>() {
              @Override
              public Source<Integer, BoxedUnit> apply(Source<Integer, BoxedUnit> param)
                  throws Exception {
                return param;
              }
            });
    // #flatMapConcat

    Uri uri = null;
    // #raw-query
    final akka.japi.Option<String> theRawQueryString = uri.rawQueryString();
    // #raw-query

    // #query-param
    final akka.japi.Option<String> aQueryParam = uri.query().get("a");
    // #query-param

    // #file-source-sink
    final Source<ByteString, Future<Long>> fileSrc = FileIO.fromFile(new File("."));

    final Source<ByteString, Future<Long>> otherFileSrc = FileIO.fromFile(new File("."), 1024);

    final Sink<ByteString, Future<Long>> fileSink = FileIO.toFile(new File("."));
    // #file-source-sink

    // #input-output-stream-source-sink
    final Source<ByteString, Future<java.lang.Long>> inputStreamSrc =
        StreamConverters.fromInputStream(
            new Creator<InputStream>() {
              public InputStream create() {
                return new SomeInputStream();
              }
            });

    final Source<ByteString, Future<java.lang.Long>> otherInputStreamSrc =
        StreamConverters.fromInputStream(
            new Creator<InputStream>() {
              public InputStream create() {
                return new SomeInputStream();
              }
            },
            1024);

    final Sink<ByteString, Future<java.lang.Long>> outputStreamSink =
        StreamConverters.fromOutputStream(
            new Creator<OutputStream>() {
              public OutputStream create() {
                return new SomeOutputStream();
              }
            });
    // #input-output-stream-source-sink

    // #output-input-stream-source-sink
    final FiniteDuration timeout = FiniteDuration.Zero();

    final Source<ByteString, OutputStream> outputStreamSrc = StreamConverters.asOutputStream();

    final Source<ByteString, OutputStream> otherOutputStreamSrc =
        StreamConverters.asOutputStream(timeout);

    final Sink<ByteString, InputStream> someInputStreamSink = StreamConverters.asInputStream();

    final Sink<ByteString, InputStream> someOtherInputStreamSink =
        StreamConverters.asInputStream(timeout);
    // #output-input-stream-source-sink

  }