MPJTaskCalculator is a framework for executing predefined sets of independent parallel tasks in Java with MPJ (without having to write any MPI commands). Check it out if you need to efficiently execute large nubmers of independent Java tasks on a cluster. I initially developed it for use in OpenSHA, where it is used for many large earthquake-related simulations (e.g. UCERF3-ETAS aftershock simulations), but have since split it into its own repository so that it can be used by other groups.