feat: added another stream gatherer example

Author: claudioaltamura

README.md

@@ -5,4 +5,5 @@ Java 23 feature examples
   * maven-javadoc-plugin version 3.10.1 not working
 * Module Import Declaration
 * Primitive Types in Patterns, instanceof, and switch (Preview)
-* Stream Gatherer (Preview)
+* Stream Gatherer (Preview)
+* Flexible Constructor Bodies

src/main/java/de/claudioaltamura/java23/streamgatherer/StreamGathererExample.java

@@ -3,6 +3,7 @@
 import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Gatherer;
+import java.util.stream.Gatherers;
 
 public class StreamGathererExample {
 
@@ -21,4 +22,10 @@ public List<Integer> toLengths(List<String> words) {
                 .toList();
     }
 
+    public List<List<String>> groupsOfThree(List<String> words) {
+        return words.stream()
+                .gather(Gatherers.windowFixed(3))
+                .toList();
+    }
+
 }

src/test/java/de/claudioaltamura/java23/streamgatherer/StreamGathererExampleTest.java

@@ -17,4 +17,14 @@ void toLengths() {
 
         assertThat(result).containsAll(List.of(4,2,1,4));
     }
+
+    @Test
+    void testeGroupOfThree() {
+        final var streamGathererExample = new StreamGathererExample();
+
+        final List<List<String>> result = streamGathererExample.groupsOfThree(List.of("Hello", "beautiful", "world", "You", "are", "nice"));
+
+        assertThat(result).hasSize(2);
+        assertThat(result.getFirst()).contains("Hello", "beautiful", "world");
+    }
 }