RFR: 8341982: Simplify JButton/bug4323121.java

[Abhishek Kumar]

On Mon, 14 Oct 2024 13:59:58 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> test/jdk/javax/swing/JButton/bug4323121.java line 58:
>> 
>>> 56:     private static final CountDownLatch mouseEntered = new CountDownLatch(1);
>>> 57: 
>>> 58:     // Thread-safe by using the mouseEntered latch
>> 
>> Comment may be put before `private static final CountDownLatch mouseEntered = new CountDownLatch(1);`
>
> Why?
> 
> This comment is meant for the `modelArmed` flag. The way it's used now is thread-safe because of using `mouseEntered`, specifically a value is written to the flag before `mouseEntered.countDown()` is called, and its value is read after `mouseEntered.await` returns.
> 
> If any of the above is modified, the `modelArmed` flag may become not thread-safe and require some kind of synchronisation.

Ok.. I misunderstood `mouseEntered` flag, thought the comment is for `CountDownLatch` object.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21475#discussion_r1799703931