A small word of caution: I'd strongly recommend against using a huge java heap size. Java GC is stop the world, and a huge java heap size can lead to hour long gc sessions. It's much better to store data in a memory mapped file that is off heap, and access accordingly. Still very fast.
Good advice. Even with G1GC it's hard to run heaps that large. However, not to be overly pedantic, Java GC has many different algorithms and many avoid STW collection for as long as possible and do concurrent collection until it's no longer possible. I don't think it's fair to just call it stop the world.
Azul C4 will collect with stop the world due to GC no longer than 40ms. You might want to think beyond Oracle/OpenJDK (altough openjdk with Shendoah GC will be interesting in the future) if you are dealing with this kind of heap sizes.
