### Question:
OptionalDouble { public double orElse(double other) { return optional.orElse(other); } private  OptionalDouble(); private  OptionalDouble(double value); static OptionalDouble empty(); static OptionalDouble of(double value); static OptionalDouble ofNullable(Double value); Optional<Double> boxed(); OptionalDouble filter(@NonNull DoublePredicate predicate); double getAsDouble(); void ifPresent(DoubleConsumer consumer); boolean isPresent(); Optional<T> map(@NonNull DoubleFunction<T> mapper); double orElse(double other);  }### Answer:
@Test public void testOrElse() { assertThat(OptionalDouble.empty().orElse(2.0)).isEqualTo(2.0); assertThat(OptionalDouble.of(1.0).orElse(2.0)).isEqualTo(1.0); }