The "open" program is specific to OS X and lets you basically drag and drop a file with the -a command onto an application. This way it overrides the per-user OBJ open-with settings.

Create, view, and modify Java archive files on the command line Learn how to do basic CRUD operations on JAR, WAR, and EAR files using the command line.

The next time you need to examine command line arguments and things get a little complex, whip out your trusty open source Java toolkit, and use Command Line Interface (CLI).