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<div class="moz-cite-prefix">On 1/16/2025 11:26 PM, Rafael
Winterhalter wrote:<br>
</div>
<blockquote type="cite" cite="mid:CA+DM0A=B8hwo6-yrRq_uwMm=TV+HVj5470n-zE6K-aA89XCWoQ@mail.gmail.com">
<div dir="ltr">
<div>Would it even be possible to change the return types of
Set.of(...) and Map.of(...) without breaking binary
compatibility?</div>
</div>
</blockquote>
<p><br>
</p>
<p>In short, no.</p>
<p>The methods in question are *static* methods. Switching to
covariant overrides with more precise return types works for
subclasses because of bridge methods.</p>
<p>In a bit more detail, in a covariant override a single method in
the source code gets translated into multiply methods in the class
file. References to methods in the class file use the argument
types and return type so if an old class file refers to the
previously declared source-level return type, there is the bridge
method present to be linked to (for binary compatibility) and then
executed.<br>
</p>
<p>-Joe<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CA+DM0A=B8hwo6-yrRq_uwMm=TV+HVj5470n-zE6K-aA89XCWoQ@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>I also think that the randomization of Set.of(...) and
Map.of(...) is a good property as it uncovers bugs early if
one relies on iteration order. This especially since those
methods are often used in tests where production code would
use a proper HashSet which cannot guarantee iteration order
for good reasons. Exactly here I think the new interfaces are
a good addition as it uncovers such misconceptions. If code
relies on insertion order, providing a Set.of(...) does no
longer compile, what is a good thing.<br>
</div>
<div><br>
</div>
<div>To me, adding SequencedSet.of(...) and SequencedMap.of(...)
sounds like the right approach, with implementations similar
to that of Set.of(...) and Map.of(...). As for megamorphism, I
think the chance of encounter at a call site is similar, as
Set12 and SetN from the Set interface are typically combined
with HashMap. As for a possible SequencedSet12 and
SequencedSetN, I think they would normally be seen with
LinkedHashSet.</div>
<div><br>
</div>
<div>Best regards, Rafael<br>
</div>
</div>
<br>
<div class="gmail_quote gmail_quote_container">
<div dir="ltr" class="gmail_attr">Am Fr., 17. Jan. 2025 um
00:36 Uhr schrieb David Alayachew <<a href="mailto:davidalayachew@gmail.com" moz-do-not-send="true" class="moz-txt-link-freetext">davidalayachew@gmail.com</a>>:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<p dir="ltr">I should also add, the documentation went out of
their way to specify that iteration order is unspecified.</p>
<p dir="ltr">Also, I see Rémi's comment, but that's even more
unconvincing to me.</p>
<p dir="ltr">Map.of has an upper limit of 10 entries, and
Map.ofEntries has an upper limit of that Java max file size
limit thing. You all know what I am talking about.</p>
<p dir="ltr">Point is, both of these static factories were
meant to be used on a small number of entries. If it truly
has just been not done until now, then the bug database will
confirm that easily.</p>
<p dir="ltr">When I get back, I can check myself.</p>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 16, 2025,
6:25 PM David Alayachew <<a href="mailto:davidalayachew@gmail.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">davidalayachew@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<p dir="ltr">I guess let me ask the obvious question.</p>
<p dir="ltr">Chesterton's fence -- why wasn't this done
before? I refuse to believe that this idea wasn't
thought up years ago, which leads me to believe there
was a reason that it hasn't been done.</p>
<p dir="ltr">Is there any way we can look this up in the
bug database or something?</p>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 16, 2025,
2:28 PM Jens Lideström <<a href="mailto:jens@lidestrom.se" rel="noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">jens@lidestrom.se</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Having
the result Map.of and Set.of preserve the insertion
order would <br>
often be convenient.<br>
<br>
More often than not programs iterate over the contents
of a maps and <br>
sets at some point. For example to present the values
in a GUI, for <br>
serialisation, or even for error printouts. In all
those cases having a <br>
fixed iteration order is much better than having a
random iteration <br>
order.<br>
<br>
Often it is even a subtle bug to have a random
iteration order. For <br>
example, I ran in to a situation where jdeps printed a
error message <br>
containing a list of modules. But the list was in a
different order on <br>
each run of the program! It took me a while to figure
out that it was <br>
actually the same list. A possible explanation is that
jdeps is <br>
implemented using Map.of or Set.of.<br>
<br>
Because of this I think I would be better if the most
commonly used <br>
standard collection factories produced collections
with a fixed <br>
iteration order.<br>
<br>
Guavas ImmutableMap and ImmutableSet also preserve
insertion order.<br>
<br>
Regards,<br>
Jens Lideström<br>
<br>
<br>
On 2025-01-16 08:44, Remi Forax wrote:<br>
<br>
> -------------------------<br>
> <br>
>> From: "Rafael Winterhalter" <<a href="mailto:rafael.wth@gmail.com" rel="noreferrer noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">rafael.wth@gmail.com</a>><br>
>> To: "core-libs-dev" <<a href="mailto:core-libs-dev@openjdk.java.net" rel="noreferrer noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">core-libs-dev@openjdk.java.net</a>><br>
>> Sent: Thursday, January 16, 2025 8:13:17 AM<br>
>> Subject: Factory methods for SequencedSet and
SequencedMap<br>
> <br>
>> Hello,<br>
> <br>
> Hello,<br>
> <br>
>> I am happily taking SequencedSet and
SequencedMap into use, but one <br>
>> inconvenience I encounter is the lack of
factory methods for the two.<br>
>> In code where many (initial) collections have
zero or one element (for <br>
>> later aggregation), I now write
Set.of()/Set.of(one) and <br>
>> Map.of()/Map.of(key, value), as it makes the
code shorter and more <br>
>> readable. Those collections are of course
implicitly sequenced, but <br>
>> now I must make the variable type of the
surrounding monad Set and <br>
>> Map, and simply assume that a LinkedHashSet
or LinkedHashMap is used <br>
>> when a collection of more than one element is
set, without requiring <br>
>> the interface type. This does not require any
type casting, as I rely <br>
>> on the iteration order only, but the code
loses some of its <br>
>> expressiveness.<br>
>> I did not find any discussion around
introducing factories for <br>
>> SequencedSet.of(...) and
SequencedMap.of(...), similar to those that <br>
>> exist in the Set and Map interfaces. Was this
ever considered, and if <br>
>> not, could it be?<br>
> <br>
> Thanks for re-starting that discussion, it was
talked a bit, but not as <br>
> it should be.<br>
> <br>
> So the issue is that currently we do not have any
compact, unmodifiable <br>
> and ordered Set/Map implementation,<br>
> one use case is when you have data that comes
from a JSON object as a <br>
> Map and you want to keep the inserted order, if
by example the JSON is <br>
> a config file editable by a human, an other
example is in unit tests <br>
> where you want to help the dev to read the output
of the test so the <br>
> code that creates a Set/Map and what is outputed
by the test should be <br>
> in the same order.<br>
> Currently there is no good solution for those use
cases because <br>
> Set|Map.copyOf() does not keep the ordering.<br>
> <br>
> I see two solutions, either we add a new <br>
> SequenceSet|SequenceMap.of/copyOf, or we change
the impleemntation of <br>
> Set|Map.of()/copyOf().<br>
> Python had gone for the latter solution, which
has the advantage a <br>
> being simple from the user POV, but from an
algorithm expert POV, a Set <br>
> and a SequencedSet are different concepts we may
want to emphasis ?<br>
> <br>
>> Best regards, Rafael<br>
> <br>
> regards,<br>
> Rémi<br>
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