import java.util.ArrayList; import java.util.Optional; import java.util.stream.Stream; public class Main { Stream<String> m1() { return new ArrayList<String>().stream().map(s -> s + s); } Optional<String> m2() { return m1().filter(s -> s.indexOf('s') == 123).findFirst(); } void m3() { String target = m2().orElse(null); } }