optional orelse throw code example

Example 1: optional throw if present

Optional.of(usuarios.findByEmail(usuario.getEmail())).ifPresent(param -> {
      throw new IllegalArgumentException("Only Strings allowed in path parameters.")
    });

Example 2: orElseThrow

private static <T> HttpMessageWriter<T> findWriter(
    BodyInserter.Context context, ResolvableType elementType, @Nullable MediaType mediaType) {
  return context.messageWriters().stream()
      .filter(messageWriter -> messageWriter.canWrite(elementType, mediaType))
      .findFirst()
      .map(BodyInserters::<T>cast)
      .orElseThrow(() -> new IllegalStateException(
          "No HttpMessageWriter for \"" + mediaType + "\" and \"" + elementType + "\""));
}