RFR: 8286663: Resolve IDE warnings in WTrayIconPeer and SystemTray [v2]

[Alexey Ivanov]

On Tue, 24 May 2022 00:03:54 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> I'm sure I've used this pattern
>> return icons.toArray(EMPTY_TRAY_ARRAY);
>> in code that runs often and may be performance sensitive, so I don't see anything weird about it.
>> OTOH I am not sure this code is anything that needs super-optimising .. we seem to have gone down that discussion route because it was the justification for the change.
>> 
>> BTW the shiplev article, which I skimmed must be suggesting that the array initialisation must be faster if it is on the array it allocates itself because of the APIs used .. but as he also notes things can change.
>> 
>> Anyway this is mildly interesting discussion but no one will ever, ever be able to measure a difference when it used here since it is probably 0.0001 % of the work ...
>
> It also has a functional implication, in the old code  the "size" on a Vector is called outside of the lock. So the resulted array after "icons.toArray" can be bigger than the number of icons. This is similar to this:
> https://github.com/openjdk/jdk/blob/739769c8fc4b496f08a92225a12d07414537b6c0/src/java.desktop/share/classes/javax/sound/midi/Sequence.java#L281
> I think that race can even be triggered by the new test.

I remember IDEs used to suggest using correctly sized arrays in the calls to `toArray`. Now they suggest using zero-sized array.

My idea was to resolve the warning raised by the IDE to reduce the number of yellow highlights on the file outline.

I agree the performance gain if any is negligible in this case: we don't expect many icons, probably no more than 3.

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PR: https://git.openjdk.java.net/jdk/pull/8850