Java tutorial
import java.util.Arrays; import java.util.List; import java.util.Optional; public class Main { public static void main(String[] args) { List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5); Optional<Integer> sum = numbers.stream().reduce(Integer::sum); if (sum.isPresent()) { System.out.println(sum.get()); } else { System.out.println("noValue "); } } }