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Unresolved : Release in which this issue/RFE will be addressed. Resolved: Release in which this issue/RFE has been resolved. Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.
ThreadGroup has been significantly degraded in Java 19, see release note JDK-8286768. In addition, its class description has an API note to make it a bit clearer that the API is legacy and should be rare for new code to use it directly.
19-06-2022
JDK-8252885 is draft JEP with a proposal for addressing the issues with ThreadGroup without causing significant disruption. The proposal amounts to addressing its main issues and can be thought of as "pushing ThreadGroup aside" so that thread creation, starting, or termination does not need bookkeeping overhead. The proposal does not preclude deprecating or removing ThreadGroup in the future.