java 8 optional if present throw exception 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: stream optional if present anymatch

List<String> filteredList = listOfOptionals.stream()
  .filter(Optional::isPresent)
  .map(Optional::get)
  .collect(Collectors.toList());