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Discussion on: Proper API for Java List

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michelemauro profile image
michelemauro

The original Java improvement project was Apache Commons Collections, and then of course Google Guava; both however never went as far as trying to redesign the Collections classes.

Have you checked out any of the many functional programming libraries out there? for example, Vavr and its List interface.

Or, going up in abstraction, Arrow-kt's NonEmptyList or even Scala's Seq.

You may find there some good new ideas, and a validation of your approach.

I wasn't able to find any JSR on the topic, so if you build up something interesting, there may be space for that.

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siy profile image
Sergiy Yevtushenko Author

As for JSR: there is another idea I'm considering to submit to JCP. The idea is to implement support for variadic templates for Java. While working on Reactive Toolbox Core I've found that in many places such a functionality would significantly simplify code.

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Sergiy Yevtushenko Author

Thanks for the suggestion.

In my practice I've used Apache Commons and Guava. I've also looked into several other collections implementations, in particular Efficient Immutable/Persistent Collections for Java, GS Collections (now Eclipse Collections) and The Capsule Hash Trie Collections Library. Last one lacks List, but contains efficient implementations of Set and Map.

Also, I did read several articles which compare different implementations. One of them shows that GS Collections significantly more efficient in regard to memory and performance than Scala implementation. Sorry, have no link on that article handy.

Unfortunately most of mentioned above implementations do not try to rethink Java Collections interfaces completely.

The idea is to prepare API convenient for everyday use, rather than based on any theoretical considerations or paradigms.

Most inspiration for the API above I've obtained from Kotlin and some extension functions written by my colleagues for one of the projects I've recently worked on. As far as I can tell, this API covers vast majority of use cases I see in code.

One note: I think that java.util.List (as well as other collections) API stopped changing because of addition of stream() method. Streams are really powerful and convenient, so most (if not all) use cases can be covered with them. There are two drawbacks though:

  • bridge to Streams caused stall in JCF API evolution (recent addition of factory methods basically changes nothing in List/Set/Map API's)
  • there is some extra verbosity which pollutes code with unnecessary noise (.stream()...collect()).
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michelemauro profile image
michelemauro

Cool, didn't know about the Capsule library. Oh, and the Scala library is not optimized for primitive type efficiency like the GS one, so the benchmark result is not surprising 😁

Is your idea about introducing a better API, a more explicit (and probably better) performance footprint, or are you aiming at both with one stone?

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siy profile image
Sergiy Yevtushenko Author

I've decided to start with API and implement it in very simple and straightforward way. Later I'm going to write better performing implementation while keeping API intact. Trying to do both things together is not the best approach since changes in API will be much harder to adopt and maintain.