I was installing some piece of software. As I ran ant build it asked if it was okay to download some libraries from the web. Sure! Couple of minutes later I see this on my screen:
-install-junit:
[copy] Copying 1 file to /opt/ant/lib
[echo] *** junit-3.8.1.jar has been installed to /opt/ant/lib.
[echo] *** You must restart the build to continue.
Lucky I noticed it. Then again maybe I missed some copying to /opt/java/jre/lib/ext/ :)