Tiago, The Java file would be in a jar (an ear uses the jar format) within a jar (the code itself would be in a jar file.) I'm not sure whether you can do this, but I suspect not. I'll be keeping an eye on this thread to see if someone else knows.
When you deploy the ear, it is unzipped/jar'd. Then you have loose jars for your libraries. At this point, it is definitely possible to run a Java program - main method.
An EAR file is meant for deployment on an appserver. It typically contains jar files that describe EJBs and/or web warchives (WAR files). The standard Java runtime will not execute an EAR file similar to a Jar file so you cannot pass it on the command line to the java executable. You may drop it into an application server like JBoss or WebSphere, assuming it is properly constructed and includes all of the relevant deployment XML files. What you are probably looking for is a solution like One Jar which allows you to nest jar files in one another. Hope that helps some