[Chore]: Consider dropping JDK 11 support

[ascopes]

Brief description

As of this morning, I have seen that v6 of Junit has been released, requiring a minimum version of JDK17.

At this point, the following projects have dropped support for JDK11:

• Apache Maven (via Maven v4.0.0)
• Junit
• AssertJ (via their v4.0.0 pre-release)
• Spring Framework, Spring Boot
• Eclipse Compiler for Java
• Micronaut
• Quarkus

At this point, I think it is worth starting to consider removing Java 11 support. This will provide a few benefits to this project as well:

• Fewer JDKs to test with.
• Sealed types support.
• Record support.
• java.nio.file.Path API improvements.
• Access to Virtual Thread APIs (via preview options).

Aims and goals

• Consider whether it is time to remove Java 11 support.
• If removing support, this needs to be a new major version.

[ascopes]

For now, the choice is to keep JDK 11 support until 2026 before re-assessing, unless further issues arise that force us to update the baseline.

[ascopes]

Had another think about this. Since I wrote this comment, Checkstyle has upgraded to Java 17-minimum builds, and Jackson has also migrated to Java-17-minimum builds as well.

Oracle has ended free JDK 11 support, additionally. I think v4 is going to be the right time to make this change, so will be including this in that change.