Several hundred classes in the `java.desktop` module used to rely on default constructors as part of their public API. However, many were lacking a default constructor, so they were added to those classes in JDK-8250852.

In that regard, a `BasicSliderUI` default constructor was added in JDK16, missing the fact that there was already another pre-existing constructor `BasicSliderUI(JSlider b)` in it, so there was no need of another constructor.

So, it was deprecated in JDK23 and is now being removed in JDK25.