#3018 - Enabling -Xlint and dealing with the situation that occurs

akka-docs/rst/java/code/docs/future/FutureDocTestBase.java

@@ -564,7 +564,7 @@ public class FutureDocTestBase {
         return "foo";
       }
     }, ec);
-    Future<String> result = Futures.firstCompletedOf(Arrays.asList(future, delayed), ec);
+    Future<String> result = Futures.firstCompletedOf(Arrays.<Future<String>>asList(future, delayed), ec);
     //#after
     Await.result(result, Duration.create(2, SECONDS));
   }