Optional additions

Definition

Java 9 added ifPresentOrElse (do one thing if there is a value, another if not), or (try another Optional) and stream (turn an Optional into a stream of zero or one items).

Example code

Handling both cases without an if statement

import java.util.List;
import java.util.Optional;

class Demo {
    public static void main(String[] args) {
        Optional<String> found = Optional.of("Asha");
        Optional<String> missing = Optional.empty();

        found.ifPresentOrElse(n -> System.out.println("Hello " + n), () -> System.out.println("nobody"));
        missing.ifPresentOrElse(n -> System.out.println("Hello " + n), () -> System.out.println("nobody"));

        System.out.println(missing.or(() -> Optional.of("backup")).get());      // try another source

        List<String> names = List.of("Asha", "Ravi").stream()
                .map(n -> n.equals("Ravi") ? Optional.<String>empty() : Optional.of(n))
                .flatMap(Optional::stream)                                       // drops the empty ones
                .toList();
        System.out.println(names);
    }
}

// Output:
// Hello Asha
// nobody
// backup
// [Asha]