How do you download android os for java?
Android OS is typically pre-installed in various Android
devices, which includes smartphones, tablets, cameras,
smartwatches, consoles, and so on. Updates to the OS happen
periodically, and you can check on your own by going under
Settings>About Phone>System Updates.
Developers have served up all versions of Android on the web,
but to install them on a device (especially a non-Android device),
it has to be one that has development out there to port the OS, and
you'd have to be comfortable enough to do this on your own.