How To Submit
Download the starter files from the submit server. Then in Eclipse, right-click on your project root, choose Import, then Archive, then find the starter files you downloaded. Then import everything from the archive.
You can submit from Eclipse using the submit plugin. (You can also submit from the command-line using the same .submit file; grab the submit.jar from the public directory on GRACE.)
Your code will be run from the public static void main(String[]) method of the Main class in the default package. It will read in its input from stdin and write its output to stdout.
You can see exactly how your code will be tested by examining the public tests.