Anyone used the YUI Compressor (if so, how does it work?)

I tried using the command prompt in Windows Vista Ultimate (x64), and it says java is an "unrecognized command".

Any idea how I could get this to work?

We use YUICompressor via a set of Ant tasks provided by YUIAnt, all executed from Eclipse which has built in Ant support, to compress the JavaScript we use in Revolution when building the distributions. But you’ll just need to get the Java executable in your path environment variable in order to execute the jar directly from the command line.

EDIT: Seems the /Java folder wasn’t added under Vista’s Environmental Variables. Fixed + restarted it, and it worked as expected.

Yes, you are missing Java itself. Wherever it is installed on your system, you need the path where the java executable resides (java.exe) on your filesystem, typically something like this on Windows systems:

So something like this would work assuming the above is the location of your JRE...

You’ll have to consult YUICompressor folk for more assistance with how to use the jar.