On Sun, 14 Dec 2025 at 14:06, Gary Gregory <[email protected]> wrote: > > On Fri, Dec 12, 2025 at 7:17 AM Paul King <[email protected]> wrote: > > > > Okay, there doesn't seem to be a lot of interest, but I went ahead and > > created the PR anyway: > > > > https://github.com/apache/commons-collections/pull/665 > > > > If the decision is to close the PR, at least future users wanting such > > functionality might find the discussion and find something useful in > > the PR for their own codebases. > > Hi All: > > The feature request and PR look good (after review) and fit in this > component's scope IMO. > > I plan on merging it unless there are valid technical objections.
My concern is that this offers very little gain for a the extra maintenance needed. Also, there are lots of other similar methods in 3rd party libraries such as Eclipse Collections. We don't have the resources to emulate them, nor should we do so. Given that it is not diifficult for users to create their own inverses, I am not convinced we should include it. I think we should only consider new features which are genuinely useful AND are not trivial for end users to implement correctly. > Gary > > > > > Cheers, Paul. > > > > On Fri, Dec 12, 2025 at 8:54 PM Paul King <[email protected]> wrote: > > > > > > On Fri, Dec 12, 2025 at 8:39 PM sebb <[email protected]> wrote: > > > > > > > > On Thu, 11 Dec 2025 at 23:49, Paul King <[email protected]> > > > > wrote: > > > > > > > > > > True, I guess an analysis of the above suggested searches could > > > > > reveal, in some cases, the sizes of the data and why the dozens or > > > > > hundreds of cases mentioned above chose to use the flip/inver** > > > > > methods instead of double storing the datasets. I would think small > > > > > immutable datasets could be suitable for double storing. For large > > > > > datasets, the storage requirements might be problematic. For mutable > > > > > sets, the double manipulations for a putAll (as one example) can > > > > > become messy. > > > > > > > > AFAICT, Eclipse Collections flip creates a new Map with the keys and > > > > values reversed. > > > > So no saving in storage. > > > > > > Certainly that would be true for cases where both the normal and the > > > inverse maps were always both needed and were created and used in a > > > short time span. In the scenarios I am using multimaps, the normal > > > data is more long-lived, and the inverse is only needed occasionally > > > when the user asks for certain "query" operations. > > > > > > > > Cheers, Paul. > > > > > > > > > > On Fri, Dec 12, 2025 at 8:19 AM sebb <[email protected]> wrote: > > > > > > > > > > > > On Thu, 11 Dec 2025 at 20:57, Paul King <[email protected]> > > > > > > wrote: > > > > > > > > > > > > > > Well, I can just give you one user (multiple instances in the > > > > > > > codebase) that I know of which is why I brought it up. I don't > > > > > > > know > > > > > > > anyone else using Commons Collections in their projects. Many > > > > > > > projects > > > > > > > I am involved in use Groovy which has some nicer workarounds than > > > > > > > the > > > > > > > stream variant I mentioned earlier. So, it's less critical for > > > > > > > me, but > > > > > > > I thought Java users would appreciate the simpler form. > > > > > > > > > > > > > > Asking ChatGPT about Eclipse Collections flip() usage and > > > > > > > inverse() > > > > > > > and invertFrom() for Guava points to Minecraft and Eclipse Xtext > > > > > > > as > > > > > > > quick examples of usage. It goes on to say: > > > > > > > > > > > > > > > How to find more examples yourself > > > > > > > > > > > > > > > > Use GitHub code search (or grep over downloaded repos) with > > > > > > > > queries like: > > > > > > > > > > > > > > > > Multimaps.invertFrom( > > > > > > > > invertFrom( + Multimap > > > > > > > > flip() + org.eclipse.collections (or search for Multimap.flip()) > > > > > > > > > > > > > > > > Those queries will turn up dozens — often hundreds — of usages > > > > > > > > across OSS. > > > > > > > > > > > > > > > > > > > However, if you know that you will need the inverse, it's not > > > > > > difficult to build that in parallel. > > > > > > > > > > > > Are there any occasions where the inverse has to be built later from > > > > > > an existing Multimap? > > > > > > > > > > > > > Cheers, Paul. > > > > > > > > > > > > > > > > > > > > > On Fri, Dec 12, 2025 at 1:23 AM Elliotte Rusty Harold > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > On Thu, Dec 11, 2025 at 3:06 PM Gilles Sadowski > > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > > > Hello. > > > > > > > > > > > > > > > > > Isn't it a "chicken-and-egg" question? > > > > > > > > > Isn't the purpose of a "common" library to implement > > > > > > > > > well-defined and > > > > > > > > > generally useful functionality, in the hope that it'll incite > > > > > > > > > code reuse? > > > > > > > > > Until said functionality is implemented, it obviously cannot > > > > > > > > > be used... > > > > > > > > > > > > > > > > No, it isn't. The use case comes first. If you can point to > > > > > > > > three > > > > > > > > existing projects that have had to implement this functionality > > > > > > > > already, and that would be willing to replace their existing > > > > > > > > code with > > > > > > > > a common library, then you have a case for implementing it here. > > > > > > > > Absent that, it is unlikely it will be adopted broadly enough > > > > > > > > to be > > > > > > > > worth the effort. > > > > > > > > > > > > > > > > -- > > > > > > > > Elliotte Rusty Harold > > > > > > > > [email protected] > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > > > > To unsubscribe, e-mail: [email protected] > > > > > > > > For additional commands, e-mail: [email protected] > > > > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > > > To unsubscribe, e-mail: [email protected] > > > > > > > For additional commands, e-mail: [email protected] > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > > To unsubscribe, e-mail: [email protected] > > > > > > For additional commands, e-mail: [email protected] > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > To unsubscribe, e-mail: [email protected] > > > > > For additional commands, e-mail: [email protected] > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > To unsubscribe, e-mail: [email protected] > > > > For additional commands, e-mail: [email protected] > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: [email protected] > > For additional commands, e-mail: [email protected] > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
