Summary

Update the minimum version needed to run JavaFX to JDK 23.

Problem

In order for JavaFX to be able to use more recent JDK features, we should increase the minimum version of the JDK that can run the latest JavaFX. Additionally, there is an ongoing cost to keeping JavaFX buildable and runnable on older versions of Java, and little reason to continue to do so.

Solution

Use javac --release 23 to generate the class files that make up the JavaFX modules, except for the javafx.swing module where we will use -source 23 -target 23. The javafx.swing module requires the jdk.unsupported.desktop module, which is excluded by --release NN. Using -source 23 -target 23 is functionally equivalent, although it doesn't provide protection against accidentally using APIs that are present in the boot JDK with which we build JavaFX, but are unavailable in JDK 23. Care must be taken not to introduce a dependency on a too-new API by the javafx.swing module. As that module is unlikely to evolve, this is not much of a concern.

Specification

The class files in all JavaFX modules will be version 67.0 class files, meaning that they will only run on JDK 23 or newer.

The following will be added to the JavaFX 25 release notes:

### JavaFX 25 Requires JDK 23 or Later

JavaFX 25 is compiled with `--release 23` and thus requires JDK 23 or later in order to run.
If you attempt to run with an older JDK, the Java launcher will exit with an error message
indicating that the `javafx.base` module cannot be read.

See JDK-8359387(https://bugs.openjdk.org/browse/JDK-8359387) for more information.