import lombok.AccessLevel;
import lombok.experimental.FieldDefaults;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
final class OddsHelper {

  static String COMMA = ",";

  static List<Integer> getOdds(String numbers) throws EmptyDataException {
    return getNumbers(numbers).stream()
        .filter(number -> !isEven(number))
        .collect(Collectors.toList());
  }

  static List<Integer> getEven(String numbers) throws EmptyDataException {
    return getNumbers(numbers).stream()
        .filter(OddsHelper::isEven)
        .collect(Collectors.toList());
  }

  private static List<Integer> getNumbers(String numbers) throws EmptyDataException {
    return Arrays.stream(Optional.ofNullable(numbers)
        .filter(val -> !val.isEmpty())
        .orElseThrow(EmptyDataException::new)
        .split(COMMA))
        .map(Integer::parseInt)
        .collect(Collectors.toList());
  }

  private static boolean isEven(int number) {
    return number % 2 == 0;
  }
}