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

[Viktor Klang]

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.

test/jdk/java/util/concurrent/Executors/AutoShutdown.java line 133:

> 131:         while (!terminated) {
> 132:             System.gc();
> 133:             terminated = executor.awaitTermination(100, TimeUnit.MILLISECONDS);

@AlanBateman Perhaps worth having some upper limit as to how long it will wait until failing the test?

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