Ant's java task supports an option that allows you to
choose to fork and specify your JVM. A number of our
branches are tied to 1.4, and we build all our branches
on the same machine, so in order to get multiple VM's
to work, we use the java task's fork, bootclasspath,
and jvm options to choose which JVM to run with.
Checkstyle does not support these options, and runs
with whatever VM ant starts with. I'm forced to use
the command line version because of this - the java
task should support these options to help people moving
from 1.4 to 1.5.