<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div><br></div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"Viktor Klang" <viktor.klang@oracle.com><br><b>To: </b>"Remi Forax" <forax@univ-mlv.fr>, "Brian Goetz" <brian.goetz@oracle.com><br><b>Cc: </b>"amber-spec-experts" <amber-spec-experts@openjdk.java.net><br><b>Sent: </b>Saturday, January 17, 2026 5:00:41 PM<br><b>Subject: </b>Re: Data Oriented Programming, Beyond Records<br></blockquote></div><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><p>Just a quick note regarding the following, given my experience in
this area:</p>
<div class="moz-cite-prefix">On 2026-01-17 11:36, Remi Forax wrote:<br>
</div>
<blockquote cite="mid:1085557496.17567763.1768646213005.JavaMail.zimbra@univ-eiffel.fr">A
de-constructor becomes an instance method that must return a
carrier class/carrier interface, a type that has the information
to be destructured and the structure has to match the one defined
by the type.</blockquote>
</blockquote><div><br></div><div>Hello Viktor,</div><div>thanks to bring back that point,</div><div><br data-mce-bogus="1"></div><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;">
This simply <b>does not work</b> as a deconstructor cannot be an
instance-method just like a constructor cannot be an instance
method: It strictly belongs to the type itself (not the hierarchy)
and</blockquote><div><br data-mce-bogus="1"></div><div>It can work as you said for a concrete type, but for an abstract type, you need to go from the abstract definition to the concrete one,</div><div>if you do not want to re-invent the wheel here, the deconstructor has to be an abstract instance method.</div><div><br data-mce-bogus="1"></div><div>For example, with a non-public named implementation</div><div><br data-mce-bogus="1"></div><div>interface Pair<F, S>(F first, S second) {</div><div> public <F,S> Pair<F,S> of(F first, S second) {</div><div> record Impl<F, S>(F first, S second) implements Pair<F, S>{ }</div><div> return new Impl<>(first, second);</div><div> }</div><div>}</div><div><br data-mce-bogus="1"></div><div>inside Pair, there is no concrete field first and second, so you need a way to extract them from the implementation.</div><div><br data-mce-bogus="1"></div><div>This can be implemented either using accessors (first() and second()) but you have a problem if you want your implementation to be mutable and synchronized on a lock (because the instance can be changed in between the call to first() and the call to second()) or you can have one abstract method, the deconstructor.</div><div><br data-mce-bogus="1"></div><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"> it doesn't play well with implementing multiple interfaces (name
clashing), and interacts poorly with overload resolution (instead of
choosing most-specific, you need to select a specific point in the
hierarchy to call the method).
</blockquote><div><br></div><div>It depends on the compiler translation, but if you limit yourself to one destructor per class (the dual of the canonical constructor), the deconstructor can be desugared to one instance method that takes nothing and return java.lang.Object, so no name clash and no problem of overloading (because overloading is not allowed, you have to use '_' at use site).</div><div><br data-mce-bogus="1"></div><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><pre class="moz-signature">--
Cheers,
√</pre></blockquote><div><br></div><div>regards,</div><div>Rémi</div><div><br data-mce-bogus="1"></div><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><pre class="moz-signature">
Viktor Klang
Software Architect, Java Platform Group
Oracle</pre><br></blockquote></div></div></body></html>