Precisely. Is it good that this can happen? No, Java must be more like Scala and push immutability as sane default. Is it a bug? No. Is it possible to "fix"

Precisely. Is it good that this can happen? No, Java must be more like Scala and push immutability as sane default. Is it a bug? No. Is it possible to "fix" the language and the VM at this stage? Yes, but that would be a new language and new VM. So, that's not going to happen.