I'd wager Unsafe in Java is far more rare per million lines of code written than unsafe blocks in Rust. Been coding in Java since ~1997. Unsafe just doesn't come up in 99.999% of Java projects.

Now JNI on the other hand, that made up maybe 0.5% back in the day. Not anymore where FFI is the predominant native linkage (but still comparatively quite rare).

(Cue the one weird guy coming out of the woodwork who claims that all of his Java projects in the last 10 years have used Unsafe to great effect.)