Optional

Definition

Optional is a box that holds a value or is empty. It makes "there may be no result" visible in the method signature, so callers must decide what to do instead of hitting a NullPointerException.

Example code

Finding a user that may not exist

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

record User(String name, String email) { }

class Demo {
    static Optional<User> findByName(List<User> users, String name) {
        return users.stream().filter(u -> u.name().equals(name)).findFirst();
    }

    public static void main(String[] args) {
        List<User> users = List.of(new User("Asha", "asha@example.com"));

        String email = findByName(users, "Asha")
                .map(User::email)
                .orElse("unknown");
        System.out.println(email);

        String missing = findByName(users, "Nobody")
                .map(User::email)
                .orElse("unknown");               // no NullPointerException, just a default
        System.out.println(missing);
    }
}

// Output:
// asha@example.com
// unknown