JEP proposed to target JDK 12: 325: Switch Expressions (Preview)

mark.reinhold at mark.reinhold at
Tue Aug 28 21:16:29 UTC 2018

2018/8/27 16:46:55 -0700, Roman Kennke <roman at>:
>> 2018/8/17 10:44:29 -0700, mark.reinhold at
>>> The following JEP is proposed to target JDK 12:
>>>  325: Switch Expressions (Preview)
>>> Feedback on this proposal is more than welcome, as are reasoned
>>> objections.  If no such objections are raised by 23:00 UTC on Friday,
>>> 24 August, or if they’re raised and then satisfactorily answered, then
>>> per the JEP 2.0 process proposal [1] I’ll target this JEP to JDK 12.
>> The few objections raised here are not new, having already been raised
>> and answered over on the amber-dev and amber-spec-experts lists.  I’ve
>> therefore targeted this JEP to JDK 12.
> I am not following amber-dev nor amber-spec-experts. I found the
> objections raised here very reasonable, in particular the objection to
> not include a controversial feature as 'preview' which would then
> manifest itself by people using it.

That a few people don’t like a feature does not make it “controversial.”

Aside from that, the very point of a preview language feature is to
invite further feedback without completely committing to the current
design, so of course people will use it (we hope!).  They’re highly
unlikely to use it in production, however, since preview features must
be enabled explicitly, on the command line, at both compile time and
run time [1].  We’re thus free to revise this design, based on new
information, before it’s etched into the stone of the language.

Yet ...

>                                     I can't see that those objections
> have been 'satisfactorily answered'. If they have been satisfactorily
> answered on any of the amber-* mailing lists, maybe it would be worth to
> repeat that here for those of use who don't follow those lists.

This is a fair point.  We can’t expect everyone to follow the progress
of every JEP in complete detail, so if objections to targeting a JEP
are raised then it’s reasonable to ask its owner to summarize previous
relevant discussions and answers in response -- which, in this case,
Brian has now done.

>                                                                 I'd find
> an answer satisfactory if those who raised it agree and state here that
> they're ok.

Here I must disagree.

If someone makes a suggestion during the development of a JEP, and that
suggestion is reasonably rejected at that time, then if they really,
really want to they can re-raise that suggestion as an objection when
the JEP is proposed to target a specific release.  To require that the
objection be answered to their satisfaction, however, would open the
door to design by consensus, which I doubt anyone actually wants.

In such a case it is reasonable to ask if Committers who didn’t raise
the objection are satisfied with the answers as summarized by the JEP’s
owner.  (Even then, however, complete consensus is not a criterion for

So -- are you satisfied with Brian’s response?

- Mark


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