What is the Fork/Join framework (JSR 166y)?
A new feature in Java 7, the fork/join framework allows developers to take advantage of multiple processors by distributing tasks to worker threads in a thread pool. Unlike other Executor Services, fork/join uses a unique work-stealing algorithm that allows worker threads that aren't busy to do the tasks assigned to threads that currently are busy.
The basic framework for fork/join code is as follows:
if (my portion of the work is small enough) do the work directly else split my work into two pieces invoke the two pieces and wait for the results
You'll need to wrap this code as a ForkJoinTask subclass, usually as a RecursiveTask or a RecursiveAction.
DevX article on fork/join framework