=doc: take and takeWhile (#28078)

* Switch java examples to pass in actorsystem instead of materializer

akka-docs/src/test/java/jdocs/stream/operators/SourceOrFlow.java

@@ -6,7 +6,6 @@ package jdocs.stream.operators;
 
 import akka.actor.ActorSystem;
 import akka.japi.pf.PFBuilder;
-import akka.stream.Materializer;
 import akka.stream.javadsl.Flow;
 
 import akka.NotUsed;
@@ -45,7 +44,6 @@ import java.util.Arrays;
 import java.util.Comparator;
 
 class SourceOrFlow {
-  private static Materializer materializer = null;
   private static ActorSystem system = null;
 
   void logExample() {
@@ -62,11 +60,10 @@ class SourceOrFlow {
   }
 
   void zipWithIndexExample() {
-    Materializer materializer = null;
     // #zip-with-index
     Source.from(Arrays.asList("apple", "orange", "banana"))
         .zipWithIndex()
-        .runWith(Sink.foreach(System.out::print), materializer);
+        .runWith(Sink.foreach(System.out::print), system);
     // this will print ('apple', 0), ('orange', 1), ('banana', 2)
     // #zip-with-index
   }
@@ -75,7 +72,7 @@ class SourceOrFlow {
     // #zip
     Source<String, NotUsed> sourceFruits = Source.from(Arrays.asList("apple", "orange", "banana"));
     Source<String, NotUsed> sourceFirstLetters = Source.from(Arrays.asList("A", "O", "B"));
-    sourceFruits.zip(sourceFirstLetters).runWith(Sink.foreach(System.out::print), materializer);
+    sourceFruits.zip(sourceFirstLetters).runWith(Sink.foreach(System.out::print), system);
     // this will print ('apple', 'A'), ('orange', 'O'), ('banana', 'B')
 
     // #zip
@@ -89,7 +86,7 @@ class SourceOrFlow {
         .zipWith(
             sourceFruits,
             (Function2<String, String, String>) (countStr, fruitName) -> countStr + " " + fruitName)
-        .runWith(Sink.foreach(System.out::print), materializer);
+        .runWith(Sink.foreach(System.out::print), system);
     // this will print 'one apple', 'two orange', 'three banana'
 
     // #zip-with
@@ -99,7 +96,7 @@ class SourceOrFlow {
     // #prepend
     Source<String, NotUsed> ladies = Source.from(Arrays.asList("Emma", "Emily"));
     Source<String, NotUsed> gentlemen = Source.from(Arrays.asList("Liam", "William"));
-    gentlemen.prepend(ladies).runWith(Sink.foreach(System.out::print), materializer);
+    gentlemen.prepend(ladies).runWith(Sink.foreach(System.out::print), system);
     // this will print "Emma", "Emily", "Liam", "William"
 
     // #prepend
@@ -109,7 +106,7 @@ class SourceOrFlow {
     // #concat
     Source<Integer, NotUsed> sourceA = Source.from(Arrays.asList(1, 2, 3, 4));
     Source<Integer, NotUsed> sourceB = Source.from(Arrays.asList(10, 20, 30, 40));
-    sourceA.concat(sourceB).runWith(Sink.foreach(System.out::print), materializer);
+    sourceA.concat(sourceB).runWith(Sink.foreach(System.out::print), system);
     // prints 1, 2, 3, 4, 10, 20, 30, 40
 
     // #concat
@@ -119,7 +116,7 @@ class SourceOrFlow {
     // #interleave
     Source<Integer, NotUsed> sourceA = Source.from(Arrays.asList(1, 2, 3, 4));
     Source<Integer, NotUsed> sourceB = Source.from(Arrays.asList(10, 20, 30, 40));
-    sourceA.interleave(sourceB, 2).runWith(Sink.foreach(System.out::print), materializer);
+    sourceA.interleave(sourceB, 2).runWith(Sink.foreach(System.out::print), system);
     // prints 1, 2, 10, 20, 3, 4, 30, 40
 
     // #interleave
@@ -129,7 +126,7 @@ class SourceOrFlow {
     // #merge
     Source<Integer, NotUsed> sourceA = Source.from(Arrays.asList(1, 2, 3, 4));
     Source<Integer, NotUsed> sourceB = Source.from(Arrays.asList(10, 20, 30, 40));
-    sourceA.merge(sourceB).runWith(Sink.foreach(System.out::print), materializer);
+    sourceA.merge(sourceB).runWith(Sink.foreach(System.out::print), system);
     // merging is not deterministic, can for example print 1, 2, 3, 4, 10, 20, 30, 40
 
     // #merge
@@ -141,13 +138,13 @@ class SourceOrFlow {
     Source<Integer, NotUsed> sourceB = Source.from(Arrays.asList(2, 4, 6, 8));
     sourceA
         .mergeSorted(sourceB, Comparator.<Integer>naturalOrder())
-        .runWith(Sink.foreach(System.out::print), materializer);
+        .runWith(Sink.foreach(System.out::print), system);
     // prints 1, 2, 3, 4, 5, 6, 7, 8
 
     Source<Integer, NotUsed> sourceC = Source.from(Arrays.asList(20, 1, 1, 1));
     sourceA
         .mergeSorted(sourceC, Comparator.<Integer>naturalOrder())
-        .runWith(Sink.foreach(System.out::print), materializer);
+        .runWith(Sink.foreach(System.out::print), system);
     // prints 1, 3, 5, 7, 20, 1, 1, 1
     // #merge-sorted
   }
@@ -158,10 +155,10 @@ class SourceOrFlow {
     Source<String, NotUsed> source2 = Source.from(Arrays.asList("Second source"));
     Source<String, NotUsed> emptySource = Source.empty();
 
-    source1.orElse(source2).runWith(Sink.foreach(System.out::print), materializer);
+    source1.orElse(source2).runWith(Sink.foreach(System.out::print), system);
     // this will print "First source"
 
-    emptySource.orElse(source2).runWith(Sink.foreach(System.out::print), materializer);
+    emptySource.orElse(source2).runWith(Sink.foreach(System.out::print), system);
     // this will print "Second source"
 
     // #or-else
@@ -179,7 +176,7 @@ class SourceOrFlow {
   void scanExample() {
     // #scan
     Source<Integer, NotUsed> source = Source.range(1, 5);
-    source.scan(0, (acc, x) -> acc + x).runForeach(System.out::println, materializer);
+    source.scan(0, (acc, x) -> acc + x).runForeach(System.out::println, system);
     // 0  (= 0)
     // 1  (= 0 + 1)
     // 3  (= 0 + 1 + 2)
@@ -259,7 +256,7 @@ class SourceOrFlow {
     // #grouped
     Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7))
         .grouped(3)
-        .runForeach(System.out::println, materializer);
+        .runForeach(System.out::println, system);
     // [1, 2, 3]
     // [4, 5, 6]
     // [7]
@@ -267,7 +264,7 @@ class SourceOrFlow {
     Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7))
         .grouped(3)
         .map(g -> g.stream().reduce(0, Integer::sum))
-        .runForeach(System.out::println, materializer);
+        .runForeach(System.out::println, system);
     // 6   (= 1 + 2 + 3)
     // 15  (= 4 + 5 + 6)
     // 7   (= 7)
@@ -309,4 +306,25 @@ class SourceOrFlow {
     // Prints: Histogram(99, 51)
     // #fold
   }
+
+  void takeExample() {
+    // #take
+    Source.from(Arrays.asList(1, 2, 3, 4, 5)).take(3).runForeach(System.out::println, system);
+    // this will print:
+    // 1
+    // 2
+    // 3
+    // #take
+  }
+
+  void takeWhileExample() {
+    // #take-while
+    Source.from(Arrays.asList(1, 2, 3, 4, 5))
+        .takeWhile(i -> i < 3)
+        .runForeach(System.out::println, system);
+    // this will print:
+    // 1
+    // 2
+    // #take-while
+  }
 }