Merge remote-tracking branch 'akka/master' into scalatest310

akka-docs/src/test/java/jdocs/stream/operators/source/FromCompletionStage.java

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+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.source;
+
+// #sourceFromCompletionStage
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.CompletableFuture;
+
+import akka.NotUsed;
+import akka.Done;
+import akka.actor.typed.ActorSystem;
+import akka.stream.javadsl.*;
+
+// #sourceFromCompletionStage
+
+class FromCompletionStage {
+
+  public static void sourceFromCompletionStage() {
+    // Use one ActorSystem per application
+    ActorSystem system = null;
+
+    // #sourceFromCompletionStage
+    CompletionStage<Integer> stage = CompletableFuture.completedFuture(10);
+
+    Source<Integer, NotUsed> source = Source.completionStage(stage);
+
+    Sink<Integer, CompletionStage<Done>> sink = Sink.foreach(i -> System.out.println(i.toString()));
+
+    source.runWith(sink, system); // 10
+    // #sourceFromCompletionStage
+  }
+}

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

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+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.sourceorflow;
+
+import akka.NotUsed;
+import akka.actor.ActorSystem;
+import akka.stream.javadsl.Source;
+
+import java.util.Arrays;
+
+public class FlatMapMerge {
+  private static ActorSystem system = null;
+
+  // #flatmap-merge
+  // e.g. could be a query to a database
+  private Source<String, NotUsed> lookupCustomerEvents(String customerId) {
+    return Source.from(Arrays.asList(customerId + "-evt-1", customerId + "-evt-2"));
+  }
+  // #flatmap-merge
+
+  void example() {
+    // #flatmap-merge
+    Source.from(Arrays.asList("customer-1", "customer-2"))
+        .flatMapMerge(10, this::lookupCustomerEvents)
+        .runForeach(System.out::println, system);
+    // prints - events from different customers could interleave
+    // customer-1-evt-1
+    // customer-2-evt-1
+    // customer-1-evt-2
+    // customer-2-evt-2
+    // #flatmap-merge
+  }
+}

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

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+/*
+ * Copyright (C) 2009-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.sourceorflow;
+
+import akka.NotUsed;
+import akka.actor.typed.ActorSystem;
+import akka.stream.javadsl.Source;
+
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+public class Sliding {
+
+  private final ActorSystem<Void> system = null;
+
+  public void slidingExample1() {
+    // #sliding-1
+    Source<Integer, NotUsed> source = Source.range(1, 4);
+    source.sliding(2, 1).runForeach(n -> System.out.println(n), system);
+    // prints:
+    // [1, 2]
+    // [2, 3]
+    // [3, 4]
+    // #sliding-1
+  }
+
+  public void slidingExample2() {
+    // #sliding-2
+    Source<Integer, NotUsed> source = Source.range(1, 4);
+    source.sliding(3, 2).runForeach(n -> System.out.println(n), system);
+    // prints:
+    // Vector(1, 2, 3)
+    // [1, 2, 3]
+    // [3, 4] - shorter because stream ended before we got 3 elements
+    // #sliding-2
+  }
+
+  public void slidingExample3() {
+    // #moving-average
+    Source<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 3, 10, 2, 3, 4, 2, 10, 11));
+    Source<Float, NotUsed> movingAverage =
+        numbers
+            .sliding(5, 1)
+            .map(window -> ((float) window.stream().mapToInt(i -> i).sum()) / window.size());
+    movingAverage.runForeach(n -> System.out.println(n), system);
+    // prints
+    // 3.8 = average of 1, 3, 10, 2, 3
+    // 4.4 = average of 3, 10, 2, 3, 4
+    // 4.2 = average of 10, 2, 3, 4, 2
+    // 4.2 = average of 2, 3, 4, 2, 10
+    // 6.0 = average of 3, 4, 2, 10, 11
+    // #moving-average
+  }
+}