A quick demo of opportunities for chaining from optionals, through nested classes, and onto streams from the result

optional_chaining.java

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

public class Scratch {

    public static void main(String[] args) {
        Optional<Schmoochies> schmoochies = Optional.of(new Schmoochies());

        List<Integer> output = schmoochies
            .flatMap(Schmoochies::getManoochies)
            .map(Manoochies::getMaNumber)
            .orElse(Collections.singletonList(0))
            .stream()
            .map(n -> n + 4)
            .collect(Collectors.toList());

        if (output.get(0) == 9) {
            System.out.println("YAY");
        }
    }
}

class Schmoochies {
    Optional<Manoochies> getManoochies() {
        return Optional.of(new Manoochies());
    }
}

class Manoochies {
    public List<Integer> getMaNumber() {
        return Collections.singletonList(5);
    }
}