Yes, my mistake, thanks for pointing out, upvoting. I meant asking memory allocator, not kernel.

I meant that Java usually already has that memory allocated, JVM is a memory allocator of its own. It operates within its own heap. One can do that within Rust of course (or easier in Zig, as it welcomes passing an allocator around), it's just built-in in JVM already. Drawback is that it's more complex to release that memory back from the JVM process, so Java apps (not AOT-compiled) usually consume more RAM.