Currency generateCurrency() {
    return pickInstance(Currency.getAvailableCurrencies(), Currency.getInstance(Locale.US));
  }

  @Empty
  <T> Optional<T> generateJavaOptional() {
    return Optional.empty();
  }

  @Generates
  <T> Optional<T> generateJavaOptional(T value) {
    return Optional.of(value);
  }

  @Generates
  OptionalInt generateOptionalInt() {
    return OptionalInt.of(generateInt());
  }