> users usually reboot because some poorly written piece of software
You can have that in Java - in any runtime environment, if your java processes keep consuming too much memory - swapping starts, on linux you will have the OOM killer, in the end the thing will reboot.
Also operating systems can have bugs, hardware has bugs, nobody is perfect.
> Also keeping RAM running all the time would eat electricity and generate heat.
In a server room you wouldn't turn out the lights, ever.
You can have that in Java - in any runtime environment, if your java processes keep consuming too much memory - swapping starts, on linux you will have the OOM killer, in the end the thing will reboot. Also operating systems can have bugs, hardware has bugs, nobody is perfect.
> Also keeping RAM running all the time would eat electricity and generate heat.
In a server room you wouldn't turn out the lights, ever.