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> Is also a matter of performance (no wonder Java code is that slow)

Surely these would be trivially inlined?

All public non-final methods in Java are virtual, so it is not _that_ trivial. You would have to check all subclasses that might get passed as an argument and check that again whenever new classes are loaded into the JVM.

JVMs are quite smart about this sort of thing, and a nonfinal method can still be inlined, even though the JVM has to safely undo that optimization if a class is loaded. I'm not sure where I learned this originally, but Aleksey Shipilev has a post on method dispatch that should explain it. https://shipilev.net/blog/2015/black-magic-method-dispatch/

It's exactly what the JVM does, it's called Class Hierarchy Analysis (CHA). The VM checks if a method is actually overridden or not.

When a new class is loaded, the analysis checks which codes are no longer valid and mark them for deoptimization.

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