RFR: 8349373: Support JavaFX preview features [v2]

[Michael Strauß]

On Tue, 4 Feb 2025 18:18:31 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   move enum field to top
>
> modules/javafx.base/src/main/java/com/sun/javafx/PreviewFeature.java line 37:
> 
>> 35:  * has opted into preview features.
>> 36:  */
>> 37: public enum PreviewFeature {
> 
> Why enum?
> Maybe use a regular class with a public constructor should do it.
> What do you think?

The idea is to make it easy and obvious to use from preview code:

PreviewFeature.MY_PREVIEW_FEATURE.checkEnabled();

In addition to that, any IDE can easily list all uses of an enum constant, which gives you an overview where APIs of a particular feature are located. After all, enums are just regular classes with singleton instances.

By the way, preview features can't be individually enabled or disabled. The point of checking on a enum constant is to generate an appropriate error message (including the name of the feature) in case the user didn't enable preview features.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1359#discussion_r1941783408