Adds mapAsync(Unordered) operator samples (#29600)

akka-docs/src/test/java/jdocs/stream/operators/sourceorflow/MapAsyncs.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.sourceorflow;
+
+import akka.NotUsed;
+import akka.actor.ActorSystem;
+import akka.pattern.Patterns;
+import akka.stream.javadsl.Sink;
+import akka.stream.javadsl.Source;
+
+import java.time.Duration;
+import java.util.Random;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.stream.Stream;
+
+public class MapAsyncs {
+
+  private final Random random = new Random();
+
+  // #mapasync-strict-order
+  // #mapasync-concurrent
+  // #mapasyncunordered
+
+  private final Source<Event, NotUsed> events =
+      Source.fromIterator(() -> Stream.iterate(1, i -> i + 1).iterator())
+          .throttle(1, Duration.ofMillis(50))
+          .map(Event::new);
+  // #mapasync-strict-order
+  // #mapasync-concurrent
+  // #mapasyncunordered
+
+  private final ActorSystem system = ActorSystem.create("mapAsync-operator-examples");
+
+  public MapAsyncs() {}
+
+  // #mapasync-strict-order
+  // #mapasync-concurrent
+  // #mapasyncunordered
+
+  public CompletionStage<Integer> eventHandler(Event in) throws InterruptedException {
+    System.out.println("Processing event number " + in + "...");
+    // ...
+    // #mapasync-strict-order
+    // #mapasync-concurrent
+    // #mapasyncunordered
+    CompletionStage<Integer> cs;
+    if (random.nextInt(5) == 0) {
+      cs =
+          Patterns.after(
+              Duration.ofMillis(500),
+              system,
+              () -> CompletableFuture.completedFuture(in.sequenceNumber));
+    } else {
+      cs = CompletableFuture.completedFuture(in.sequenceNumber);
+    }
+    return cs.thenApply(
+        i -> {
+          System.out.println("Completed processing " + i.intValue());
+          return i;
+        });
+    // #mapasync-strict-order
+    // #mapasync-concurrent
+    // #mapasyncunordered
+  }
+  // #mapasync-strict-order
+  // #mapasync-concurrent
+  // #mapasyncunordered
+
+  private void runStrictOrder() {
+    // #mapasync-strict-order
+
+    events
+        .mapAsync(1, this::eventHandler)
+        .map(in -> "`mapSync` emitted event number " + in.intValue())
+        .runWith(Sink.foreach(str -> System.out.println(str)), system);
+    // #mapasync-strict-order
+  }
+
+  private void run() {
+    // #mapasync-concurrent
+
+    events
+        .mapAsync(10, this::eventHandler)
+        .map(in -> "`mapSync` emitted event number " + in.intValue())
+        .runWith(Sink.foreach(str -> System.out.println(str)), system);
+    // #mapasync-concurrent
+  }
+
+  private void runUnordered() {
+    // #mapasyncunordered
+
+    events
+        .mapAsyncUnordered(10, this::eventHandler)
+        .map(in -> "`mapSync` emitted event number " + in.intValue())
+        .runWith(Sink.foreach(str -> System.out.println(str)), system);
+    // #mapasyncunordered
+  }
+
+  public static void main(String[] args) {
+    new MapAsyncs().run();
+  }
+
+  static class Event {
+    public final int sequenceNumber;
+
+    public Event(int sequenceNumber) {
+      this.sequenceNumber = sequenceNumber;
+    }
+
+    @Override
+    public String toString() {
+      return "Event(" + sequenceNumber + ')';
+    }
+  }
+}