This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
If I'm not mistaken, you seem to have some code from an implementation of QuickSort. Swap would look something like this:
The split() method is dividing the array into two partitions. The elements in one partition are all greater than the elements in the other partition. The return value of split() is the location where the partitions meet.