Java sun.misc.Unsafe isn't part of the standard language and is being gradually deprecated / phased out. A lot of libraries are phasing it out. Here's one that I use in one of my projects where it was removed in the past month:
https://github.com/ben-manes/caffeine/releases/tag/v3.0.0…
It's not super pervasive.
https://openjdk.java.net/jeps/193 is a major example of how it's being phased out and is what replaced it in that library.
Java was pretty careful to always consider Unsafe non-standard and strongly discouraged using it. It's also not available in all implementations / environments, etc.