Hi. I'm currently using BeanShell in a project that runs a lot of concurrent threads. I've found that there were a few performance bottlenecks calling Class.forName
I fixed one typo in some caching code, and shuffled things around a little bit to make things a little more efficient. This cleared up some deadlocks resulting in a 4x speedup in my application (Due to the way I'm using BeanShell; I doubt it would have as much of an affect in normal scenarios).
Attached is a diff file from the current subversion snapshot if you're interested in merging the changes.