When attempting to minify using the non-default JSmin compressor (the resulting js file seemed rather large and I wanted to see what another compressor could do) I get the following error:
The following minifiers cannot be found or are no longer working: YUI Compressor (JS): JAVA executable path was not found. The default minifier JSMin will be used instead. This message will automatically disappear once the issue is resolved.
I get the same message when trying to use Closure Compiler.