Trusted final fields Was: Updated document on data classes and sealed types

Remi Forax forax at
Thu Mar 7 22:51:29 UTC 2019

As you may know, there are two kinds of final field in Java,
you have final fields and trusted final fields, the former are classical final fields the later are final fields that can no be changed by reflection thus are considered as "real" final field by JITs
(see for more).

So should record fields always be trusted ?


----- Mail original -----
> De: "Brian Goetz" <brian.goetz at>
> À: "amber-spec-experts" <amber-spec-experts at>
> Envoyé: Vendredi 1 Mars 2019 21:14:31
> Objet: Updated document on data classes and sealed types

> I've updated the document on data classes here:
> (older versions of the document are retained in the same directory for
> historical comparison.)
> While the previous version was mostly about tradeoffs, this version
> takes a much more opinionated interpretation of the feature, offering
> more examples of use cases of where it is intended to be used (and not
> used).  Many of the "under consideration" flexibilities (extension,
> mutability, additional fields) have collapsed to their more restrictive
> form; while some people will be disappointed because it doesn't solve
> the worst of their boilerplate problems, our conclusion is: records are
> a powerful feature, but they're not necessarily the delivery vehicle for
> easing all the (often self-inflicted) pain of JavaBeans.  We can
> continue to explore relief for these situations too as separate
> features, but trying to be all things to all classes has delayed the
> records train long enough, and I'm convince they're separate problems
> that want separate solutions.  Time to let the records train roll.
> I've also combined the information on sealed types in this document, as
> the two are so tightly related.
> Comments welcome.

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