I also use C++ for large numerical simulations and R for modeling, analysis and graphics.
Although I have to confess that I really hate C++. With challenging simulations there’s little choice since a small difference in performance can make a big difference in simulation run time. But everything in harder in C++.
In my opinion Java (or JVM languages) are the best choice for Web applications. Although Python may come in second. I’m still waiting to feel that Python love, however.