### Question:
Maybe { public abstract boolean isPresent(); private  Maybe(); static Maybe<T, E> of(T value); static Maybe<T, E> except(E exception); abstract Maybe<T2, E> map(Function<? super T, ? extends T2> function); abstract Maybe<T2, E> flatMap(Function<? super T, Maybe<T2, E>> function); abstract boolean isPresent(); abstract Maybe<T, E> ifPresent(Consumer<? super T> consumer); abstract T orElse(
      CheckedFunction<? super E, ? extends T, X> function); final T orElseThrow(); final T orElseThrow(Function<? super E, ? extends E> exceptionWrapper); final Stream<T> catching(
      CheckedConsumer<? super E, ? extends X> handler); static Predicate<Maybe<T, E>> byValue(
      Predicate<? super T> condition); static Maybe<T, E> maybe(
      CheckedSupplier<? extends T, ? extends E> supplier); static Stream<Maybe<T, E>> maybeStream(
      CheckedSupplier<? extends Stream<? extends T>, E> supplier); static Function<F, Maybe<T, E>> maybe(
      CheckedFunction<? super F, ? extends T, E> function); static Function<F, Stream<Maybe<T, E>>> maybeStream(
      CheckedFunction<? super F, ? extends Stream<? extends T>, E> function); static BiFunction<A, B, Maybe<T, E>> maybe(
      CheckedBiFunction<? super A, ? super B, ? extends T, ? extends E> function); static BiFunction<A, B, Stream<Maybe<T, E>>> maybeStream(
      CheckedBiFunction<? super A, ? super B, ? extends Stream<? extends T>, ? extends E> function); static Maybe<T, E> maybe(
      CheckedSupplier<? extends T, ? extends E> supplier, Class<E> exceptionType); static Stream<Maybe<T, E>> maybeStream(
      CheckedSupplier<? extends Stream<? extends T>, ? extends E> supplier,
      Class<E> exceptionType); static Function<F, Maybe<T, E>> maybe(
      CheckedFunction<? super F, ? extends T, ? extends E> function, Class<E> exceptionType); static Function<F, Stream<Maybe<T, E>>> maybeStream(
      CheckedFunction<? super F, ? extends Stream<? extends T>, ? extends E> function,
      Class<E> exceptionType); static BiFunction<A, B, Maybe<T, E>> maybe(
      CheckedBiFunction<? super A, ? super B, ? extends T, ? extends E> function,
      Class<E> exceptionType); static BiFunction<A, B, Stream<Maybe<T, E>>> maybeStream(
      CheckedBiFunction<? super A, ? super B, ? extends Stream<? extends T>, ? extends E> function,
      Class<E> exceptionType); static CompletionStage<Maybe<T, E>> catchException(
      Class<E> exceptionType, CompletionStage<? extends T> stage);  }### Answer:
@Test public void testIsPresent() { assertThat(Maybe.of(1).isPresent()).isTrue(); assertThat(Maybe.except(new Exception()).isPresent()).isFalse(); }