Java Optional: How to handle null with classes

Question

I am trying with Optionals and I am pretty sure my solution is not good. I put a little sample below.

class Person {
    String name;    // can be null
    Integer age;    // can be null
}

class DB {
    // returns an Optional
    public static Optional<Person> getPerson() {
        //irrelevant code here
    }
}



public static void main() {
    Person p = DB.getPerson().orElse(null);

    // did I get a Person?
    if (p != null) {
        // both information of a Person available?
        if (p.name != null && p.age != null) {
            dosomthing (p.name, p.age);
        }
    }
}

Any idea how to improve this? I see HERE no benefit in using Optionals. But I am not in charge of getPerson.

If you just call getPerson() without the orElse, you'll receive an Optional<Person>. Then you can check things like p.isPresent() instead of p != null. Although the example feels a little contrived — byxor
– byxor, Commented Dec 17, 2020 at 10:38
If a Person's name and age cannot be null, can't you just make them non-nullable? If that's not possible, you could have dosomthing do the checks before running any operation. — sp00m
– sp00m, Commented Dec 17, 2020 at 10:38
Are you sure that you didn't mean to make getName() and getAge() return Optional, as they are the things you indicate can be null? — tgdavies
– tgdavies, Commented Dec 17, 2020 at 10:39
If you are not in charge of getPerson, you can't really improve this... Ideally no person should have no name or age. getPerson should return an empty optional in such cases. — Sweeper
– Sweeper, Commented Dec 17, 2020 at 10:40

Youcef LAIDANI · Accepted Answer · 2020-12-17 10:48:54Z

1

So what about using Optional like this;

DB.getPerson()
        .filter(p -> p.name != null && p.age != null)
        .ifPresent(p -> dosomthing(p.name, p.age));

I assume you are using Optional::ofNullable in getPerson()

edited Dec 17, 2020 at 10:48

answered Dec 17, 2020 at 10:39

Youcef LAIDANI

60.3k21 gold badges111 silver badges178 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

marstran Over a year ago

No need to do .filter(Objects::nonNull). An Optional cannot contain null. It would just be empty.

Collectives™ on Stack Overflow

Java Optional: How to handle null with classes

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related