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How to Make Your Reviewer Cry Using Java Optional

Majid Abarghooei on December 25, 2020

I think code review is one of the best sources of inspiration. I see it as an opportunity to learn new things from other software developers sendin...

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Joshua Baker • Dec 27 '20

This line could be made simpler:

System.out.println("The number is: " + number.orElseGet(() -> alternativeNumber()));

is equivalent to

System.out.println("The number is: " + number.orElseGet(alternativeNumber));

Gonçalo Martins • Jan 14 '21 • Edited

Not like you described, but like this

System.out.println("The number is: " + number.orElseGet(NameOfTheClass::alternativeNumber));

With method reference.

If the method was not static and was an instance one, then it would be like this

System.out.println("The number is: " + number.orElseGet(this::alternativeNumber));

Majid Abarghooei • Dec 28 '20

Hi Joshua. I don't think so; It faces a compile error.

Clavin June • Dec 25 '20

Java Optional is a life-safer! Even I created a blog post for it too. But still its map function can't call another function that throws an exception except you catch it.

Majid Abarghooei • Dec 25 '20

Actually, this issue is related to all of the lambda expressions. Take a look at this article:
baeldung.com/java-lambda-exceptions

Andreas Stensig • Dec 27 '20

Good article. Though I will add a legitimate use for orElse(null) that I encounter a lot: when transitioning from code that operates on Optional types to code that does not (and which accepts null refences). Sadly this is something that happens a lot when you try and use Optional, because a lot of frameworks cannot handle that gracefully - sad and infuriating as it is.

Majid Abarghooei • Dec 27 '20

Yes, Andreas, you're right. Unfortunately, accepting null references is a bad practice that I usually face. In that case, especially when you're dealing with a framework, I think it's inevitable.

Alessandro Aiezza • Dec 27 '20

This is good, but I would have loved to see another common pitfall I see a lot of. And that is accepting an Optional as a constructor or method parameter.

Majid Abarghooei • Dec 27 '20

Thanks for your comment. Exactly, you're right. I see it a lot. I tried to cover that in the first section ("What is Optional?"), where I referred to Optional's Javadoc.