Embedded Systems Programming using Java
I always use C programming language to program many embedded modules and microcontrollers. I have wroked on Atmel's PIC's STM controllers and programming them using C works fine always. Apart from this if you are planning to make UI interface for your embedded design and you are in windows, you can do it with C++/C# in visual studio or if you are in linux you can do it using gtk/glade which can be done in C. So if you want to design firmware or want to write drivers, you can use C. No need of java. I have never heard someone using java to make driver or firmware

So I think C is enough to start with any embedded design.