A .class is no most cases a compiled Java application or applet. How you use it depends on whether it's an application or an applet.
If it's an applet, it's made for embedding in html documents. You better look for the creator's documentation of it, or a page that uses it, if you want to find out what parameters you need to get it to work.
If it's an application, you need a JVM (Java Virtual Machine). If you're on a Mac, the MJR (Macintosh Java Runtime) is with all probability already installed. If you're on Windows, you better go to Sun's webpage and download J2SE. Then when that is set up, you run it from the command line using J2SE.
Last edited by liorean; 11-29-2004 at 06:13 PM..