Switch to Java 21 for compilation

[koppor]

Before this PR

palantir-java-format relied on Java 11 for compilation.

Gradle update does not work. See #977.

After this PR

palantir-java-format relias on Java 21 for compilation, but sticks with Gradle 7.6.2.

This enables working on Java 21 related tickets.

Possible downsides?

Java 21 might be a too strong requirement for some "legacy" code. One could release 3.0.0 and say, hey, 2.x supports up to Java 20, 3.x supports 21+.

[changelog-app]

Generate changelog in changelog/@unreleased

What do the change types mean?

• feature: A new feature of the service.
• improvement: An incremental improvement in the functionality or operation of the service.
• fix: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way.
• break: Has the potential to break consumers of this service's API, inclusive of both Palantir services
  and external consumers of the service's API (e.g. customer-written software or integrations).
• deprecation: Advertises the intention to remove service functionality without any change to the
  operation of the service itself.
• manualTask: Requires the possibility of manual intervention (running a script, eyeballing configuration,
  performing database surgery, ...) at the time of upgrade for it to succeed.
• migration: A fully automatic upgrade migration task with no engineer input required.

Note: only one type should be chosen.

How are new versions calculated?

• ❗The break and manual task changelog types will result in a major release!
• 🐛 The fix changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease.
• ✨ All others will result in a minor version release.

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Switch to Java 21 for compilation

Check the box to generate changelog(s)

• Generate changelog entry

[koppor]

This damn error prone is not compatible with Java 21. And I don't know how to remove it from the build configuration.

[koppor]

I have following error now:

error: exporting a package from system module jdk.compiler is not allowed with --release

It is not possible to remove --release in gradle 7.x. - cf. gradle/gradle#22449.

stackoverflow also wasn't of help. Cf. https://stackoverflow.com/q/70477692/873282

Thus closing this.