Recently someone mentioned to me that you can run PHP on Java using a package called Quarcus. Its supposed to help performance. There are specific examples of this making a huge difference to Drupal.

I installed Resin and followed the instructions to get Drupal running. Painless.
http://wiki.caucho.com/Quercus:_Drupal
https://wiki.terracotta.org/confluence/display/wiki/Drupal

Now to play with it...