### Question:
ServiceLoaderExt { public Optional<S> findFirst() { return serviceLoader.stream() .map(ServiceLoader.Provider::get) .findFirst(); } private  ServiceLoaderExt(ServiceLoader<S> serviceLoader); static ServiceLoaderExt<S> load(Class<S> service, ClassLoader loader); static ServiceLoaderExt<S> load(Class<S> service); static ServiceLoaderExt<S> loadInstalled(Class<S> service); static ServiceLoaderExt<S> load(ModuleLayer layer, Class<S> service); Optional<S> findFirst(); void reload(); void forEach(Consumer<? super S> action); Spliterator<S> spliterator(); Iterator<S> iterator(); Stream<ServiceLoader.Provider<S>> stream();  }### Answer:
@Test public void findFirst() { assertThat(sampleServiceServiceLoader.findFirst()) .containsInstanceOf(SampleServiceImpl.class); }