Another round of improvements to ForkJoin framework. The main change is an overhaul to core control that better avoids creating or restarting more threads than needed. You'll probably see better overall performance too. Also, exceptions stemming from user errors are now more informative.

see mail on core-libs-dev mailing list:
  http://mail.openjdk.java.net/pipermail/core-libs-dev/2011-February/005949.html