public class TestCompletion { public static <T, V> ParallelPipeline<T, V> test(T base, V newStage, T upstream) { if (base != null){ return <selection>new ParallelPipeline<>(base, newStage)</selection>; } else { return new ParallelPipeline<>(upstream, newStage); } } void f() { test(null, null, null); } private static class ParallelPipeline<T, V> { public ParallelPipeline(T p0, V p1) { } } }