RFR: 8189354: ArrayIndexOutOfBoundsException when listening to selection changes on TreeTableView

[Kevin Rushforth]

On Sat, 24 Apr 2021 04:11:28 GMT, mstr2 <github.com+43553916+mstr2 at openjdk.org> wrote:

> This PR fixes the implementation of `ControlUtils.reducingChange`, which incorrectly computed adjacent removed indices, thus resulting in incorrect removal notifications.
> 
> Since there were no unit tests for this method, I also added a bunch of tests.
> 
> After applying this fix, I can no longer reproduce [JDK-8189354](https://bugs.openjdk.java.net/browse/JDK-8189354) and [JDK-8189228](https://bugs.openjdk.java.net/browse/JDK-8189228).

I'll leave it to Ajit to review (I can be a second reviewer if needed). I noted one part of the change that needs to be reverted.

Also, if you could explain the logic changes a bit, that would be helpful.

modules/javafx.controls/src/main/java/javafx/scene/control/ControlUtils.java line 41:

> 39: 
> 40: class ControlUtils {
> 41:     private ControlUtils() { }

The private constructor needs to be restored, since it is the pattern we use for static helper classes that should not be instantiated.

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PR: https://git.openjdk.java.net/jfx/pull/480