How to migrate from Java 8 `Optional` to Kotlin's ...

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[Dave Leeds]

How to migrate from Java 8 Optional to Kotlin's null-safety features.
https://typealias.com/guides/java-optionals-and-kotlin-nulls/

[artem_zin]

There might still be one case when you’d use an Optional in Kotlin

Second case is when API you’re working with doesn’t support null values, like RxJava 2

Plus you can add that Kotlin nullable saves an allocation in compare to Optional in exchange to != null checks added by compiler (although Optional needs to be dereferenced, so Kotlin nullable should win overall)

Other than that — really good migration guide 👍

[raulraja]

In case anyone is interested in a safe Option type in Kotlin there is also http://kategory.io/docs/datatypes/option/

[raulraja]

contains no unsafe APIs and monad comprehension among other features

[artem_zin]

Or a more minimalistic one <https://github.com/gojuno/koptional>

[Dave Leeds]

@artem_zin and @raulraja - Thanks for your comments! I haven't looked at Kategory's Option or koptional, so I'm going to go check 'em out. Do you all mind if I incorporate your feedback into the article?

[artem_zin]

@Dave Leeds sure, go ahead 🙂

[raulraja]

@artem_zin please and thank you for your article!

[raulraja]

It's already is helpful to people wondering about the differences. I learnt new stuff reading it.

[artem_zin]

I guess you meant djleeds 😄

[Oleksii]

By the way, it is possible to define all the Optional methods on nullable as extension methods.

Then change Option<Type> to Type? and fix all the compile errors with alt+enter.

Then inline these extension methods.

You are done with the migration.

I'm not 100% sure it will work with all Optional's methods, but it worked on my previous project very well.

[raulraja]

@artem_zin yeah sorry I ment to mention @Dave Leeds xD

[Dave Leeds]

@Oleksii That's a clever idea! I'll have to give that a try.