JAVA-20496 Non-article code: rawtypes and sandbox packages (#13886)

* JAVA-14232 Dissolving core-java module completed

core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/flatmap/map/Java8MapAndFlatMapUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.streams.flatmap.map;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static java.util.Arrays.asList;
+import static org.junit.Assert.assertEquals;
+
+public class Java8MapAndFlatMapUnitTest {
+
+    @Test
+    public void givenStream_whenCalledMap_thenProduceList() {
+        List<String> myList = Stream.of("a", "b")
+            .map(String::toUpperCase)
+            .collect(Collectors.toList());
+        assertEquals(asList("A", "B"), myList);
+    }
+
+    @Test
+    public void givenStream_whenCalledFlatMap_thenProduceFlattenedList() throws Exception {
+        List<List<String>> list = Arrays.asList(Arrays.asList("a"), Arrays.asList("b"));
+        System.out.println(list);
+
+        System.out.println(list.stream()
+            .flatMap(Collection::stream)
+            .collect(Collectors.toList()));
+    }
+
+    @Test
+    public void givenOptional_whenCalledMap_thenProduceOptional() {
+        Optional<String> s = Optional.of("test");
+        assertEquals(Optional.of("TEST"), s.map(String::toUpperCase));
+    }
+
+    @Test
+    public void givenOptional_whenCalledFlatMap_thenProduceFlattenedOptional() {
+        assertEquals(Optional.of(Optional.of("STRING")), Optional.of("string")
+            .map(s -> Optional.of("STRING")));
+
+        assertEquals(Optional.of("STRING"), Optional.of("string")
+            .flatMap(s -> Optional.of("STRING")));
+    }
+
+}