The Grinder load testing framework. The Grinder is a load testing
framework that makes it easy to run a distributed test using many load
injector machines. Test scripts are written in Jython or Clojure. HTTP
scripts can be recorded easily from a browser session.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window grinder-3.11.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.