As far as java vs R. Java is very common, and has a large number of libraries for building things like servers, and interfaces. It is probably faster computation wise as well. However if computation speed is not a major concern, and you are doing mostly statistic works, then switching to something you are not familiar with is probably not a good idea. Use the right tool depending on what you want. There is a reason so many statistics people use R / python, and not c.