Currently, they are two option existing:
- they are running a custom piece of software that support a jvm
- they are running a minimum version of a linux , just what’s enough to run the jvm, everything else is disabled / removed.
It’s booting that fast because it has only the piece of code needed to run a minimal jvm, and everything else is disabled in opposition of the raspberry pi who has a complete kernel, with a lot of modules, a desktop environment, etc, … to load.
solved How do BluRay players or washing machine run Java programs? [closed]