On Sat, 11 May 2024 17:37:08 GMT, Alexander Scherbatiy <alex...@openjdk.org>
wrote:
>> @AlexanderScherbatiy did you see the comment in the CSR about sealed classes
>> ?
>> I had originally suggested in this PR (search for a comment from a while
>> ago) and I don't know if you saw it there either.
>
> @prrace
>
> I have updated the fix to make the `OutputBin` class sealed and
> `CustomOutputBin` class final.
> The `OutputBin` class permits internal `sun.print.CustomOutputBin` class.
> The `OutputBin` javadoc that `Implementation- or site-defined names for an
> output bin kind attribute may also be created by defining a subclass of class
> {@code OutputBin}.` is removed.
> If it is an applicable change I will update the CSR as well.
> > @AlexanderScherbatiy did you see the comment in the CSR about sealed
> > classes ?
> > I had originally suggested in this PR (search for a comment from a while
> > ago) and I don't know if you saw it there either.
>
> @prrace There are two things which are not clear for me.
>
> The first one is that a user can extend `OutputBin` class and provide its own
> implementation. Should it be possible to the user provide output bins other
> than supported ones?
>
> The another question relates to `CustomOutputBin` class which is used to
> provide a list of supported output bins and which is not public. To make
> `OutputBin` class sealed it needs to add `CustomOutputBin` class to
> `OutputBin` class permits list:
>
> ```
> public sealed class OutputBin extends EnumSyntax implements
> PrintRequestAttribute, PrintJobAttribute
> permits sun.print.CustomOutputBin {
> }
>
> public final class CustomOutputBin extends OutputBin {
> }
> ```
>
> Is it good to use a non public class in the public class permits list?
>
> I made docs for the jdk with sealed `OutputBin` class. It has the `sealed`
> keyword in the javadoc but mentions nothing about internal `CustomOutputBin`
> class.
> `images/docs/api/java.desktop/javax/print/attribute/standard/OutputBin.html`:
>
> ```
> public sealed class OutputBin
> extends EnumSyntax
> implements PrintRequestAttribute, PrintJobAttribute
> ```
javadoc knows to not list the permitted class unless it is exported as public
API, so it is fine.
"Users" should not need to to sub-class OutputBin, the JDK implementation will
do this when it finds a printer. If we ever find a use-case that really demands
it, the class can be unsealed.
"sealing" is like "final" in this regard. You can remove it, but typically you
can't add it later.
I wish we'd had sealing 20 years ago ..
-------------
PR Comment: https://git.openjdk.org/jdk/pull/16166#issuecomment-2105980495
