RFR: 8302899: Executors.newSingleThreadExecutor can use Cleaner to shutdown executor

[Roger Riggs]

On Mon, 20 Feb 2023 18:34:17 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> Executors.newSingleThreadExecutor returns a delegating ExecutorService that has finalizer to shutdown the underlying TPE when the wrapper is finalizable. It goes back to JDK 6 and JDK-6399443. This is the last non-empty finalizer in java.base. Removing it will likely lead to bug reports/complaints as the current behavior goes back to 2006. So the proposal is to just replace it with a Cleaner, trivially done in this case. As part of the changes, I've replaced the existing test with a more modern test that exercises more scenarios.

LGTM

src/java.base/share/classes/java/util/concurrent/Executors.java line 192:

> 190:      * @throws NullPointerException if threadFactory is null
> 191:      */
> 192: 

Extra blank line.

-------------

Marked as reviewed by rriggs (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12675