Docs: mergeLatest (#28586)

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 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;
+
+public class MergeLatest {
+
+  private static final ActorSystem<Void> system = null;
+
+  public static void example() {
+    // #mergeLatest
+    Source<Integer, NotUsed> prices = Source.from(Arrays.asList(100, 101, 99, 103));
+    Source<Integer, NotUsed> quantities = Source.from(Arrays.asList(1, 3, 4, 2));
+
+    prices
+        .mergeLatest(quantities, true)
+        .map(priceAndQuantity -> priceAndQuantity.get(0) * priceAndQuantity.get(1))
+        .runForeach(System.out::println, system);
+
+    // prints something like:
+    // 100
+    // 101
+    // 303
+    // 297
+    // 396
+    // 412
+    // 206
+    // #mergeLatest
+  }
+}