@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 }