Initial data commit

Task/Flatten-a-list/Java/flatten-a-list-3.java

@@ -0,0 +1,17 @@
+import java.util.List;
+import java.util.stream.Stream;
+import java.util.stream.Collectors;
+
+public final class FlattenUtil {
+
+	public static Stream<Object> flattenToStream(List<?> list) {
+		return list.stream().flatMap(item ->
+			item instanceof List<?> ?
+			flattenToStream((List<?>)item) :
+			Stream.of(item));
+	}
+
+	public static List<Object> flatten(List<?> list) {
+		return flattenToStream(list).collect(Collectors.toList());
+	}
+}