Basically, every single credit card sized security chip (including actual credit cards, of course) is a small processor running Java applets. Pretty much everyone has one or more in their wallet. I'd assume those were actual Java CPUs directly executing bytecode?
Not sure: https://en.wikipedia.org/wiki/Java_processor doesn't seem to mention any in current use. I am ignorant of the actual correct answer: I had simply presumed it is simpler to write the virtual machine using a commercial ISA than to develop a custom ISA.
Java Card bytecode run by the Java Card Virtual Machine is a functional subset of Java 2 bytecode run by a standard Java Virtual Machine but with a different encoding to optimize for size.
Patriot Scientific's Ignite processor family https://www.cpushack.com/2013/03/02/chuck-moore-part-2-from-...
ARM Jazelle technology https://developer.arm.com/documentation/ddi0222/b/introducti...
https://www.eetimes.com/nazomi-offers-plug-in-java-accelerat...
It's all dot-com era stuff and Sun Microsystems also created a Java OS that could run directly on hardware without a host operating system.
That's about it
If you think of an SOC, the chip in your phone, more and more of the real estate is being dedicated to specialized compute (AI accelerators, GPUs, etc. vs general purpose compute (CPU).
At the enterprise scale, one of the big arguments NVIDIA has been making, beyond their value in the AI market, has been the value of moving massive, resource intense workloads from CPU to more specialized GPU acceleration. In return for the investment to move their workload, customers can get a massive increase in performance per watt/dollar.
There are some other factors at play in that example, and it may not always be true that the transistors/mm^2 is always lower, but I think it illustrates the overall point.