Probably a mix of Z systems, that stuff goes back 20-odd years, and even then older code can still run on new Z systems which is something IBM brags about.
Mainframes aren’t old they’re just niche technology, and that includes enterprise Java software.
Uh, Java is specifically supported by IBM in the Power and Z ISA, and they have both their own distribution, and guides for writing Java programs for mainframes in particular.
This shouldn’t be a surprise, because after Cobol, Java is the most enterprise language that has ever enterprised.
Reddit is becoming such a shit hole anyway, the site barely functions on mobile browser now, half the time it has API errors or fails to load.
Alternative roots are an interesting concept, but really people just need good alternatives recursives.
Man this reminds me of the lockers we had in middle school that used dial locks, cheap masterlock jobbies that despite having notches between the major numbers, just being within 2 of the actual number would register.
Plus it felt like they’d slip internally so if you dialed too quickly (because class starts in 3 minutes at the other end of the building) you’d have to start all over.