Jeka implementation moving from Java 8 to Java 21

[djeang]

Current Java Version Compatibility

So far, Jeka has been implemented using Java 8. This brings several advantages:

• No limitation in JDK versions: Jeka can run on any Java version ≥ 8.
• Flexible configuration: The configuration code can share the same JDK as the project being built, regardless of that project's Java version.
• Library-friendly: Jeka can be easily used as a library, regardless of the Java version of the hosting project.

However, the Jeka team would prefer to move to a more modern Java version. Since this is an open-source project, attracting contributors is important — and using an up-to-date Java version can help with that. Therefore, we are considering moving quickly to Java 21.

The latest version of Jeka has been prepared for this change by allowing a specific Java version to be set for the project being built. This ensures that projects targeting a Java version older than 21 can still be built gracefully.

Would this transition be a problem for any of you?
Please let us know if relying on Java 21 would prevent you from using or contributing to Jeka.