I have never done development related to Embed System. How can I give you advise, it is out of my abality.

xixi. The most comon useage of java is the development of Web app with implementing some business logic. it belong to top level of App.
Maybe you don't agree. but I consider it is more simple than Device Diver development.

Come on , guys,we r not young anymore, Choose the easy one, can't put all ot improve your coding skill, just for money, what we need is to enjoy life.
take care of you life, ignore the coding skill. haha

About linux, I am still new comer and continue to learn it. just be the level of how to use it.