what are the prerequisites to join in device drivers course

I'm a graduate from the stream of electrical...i'm interested in embedded systems....what are the prerequisites i should have to build a career in this field??i'm about to join in the device drivers course the next week....i read in an article,it says that" good knowledge in c++ and java is required for embedded software developement"..is it true???what else should i learn to have a good foundation...do i need to do any certification courses to get a job????
please let me know asap...thanks in advance