Design of OS in java

HI,
Can operating system is design in pure java language.

If not than what are the problems are occured.

If yes than why at present any OS is not written in java.

I think a special type of OS is written in java like "Java Programming
Language", java is very good and popular lan. So if os is written in
java than os is also popular os.

you can develop operating systems in java.The strength
of the operating system lies in its capability for
handling different software, hardware Configuration
used for that OS. So any programming language which
can do this can be used to implement the OS.

But people preferred C because it can be very
effective with memory managment.

JOS (Java operating system) is a current ongoing
project. check the link
http://sourceforge.net/projects/jos/