Please review the API documentation. APIs are divided into categories like Volume, LUN, disk, and aggregate. For example you should find AggrList, DiskList, etc. The API documentation will inform you about the parameters. API documentation can be downloaded from http://developer.netapp.com.
The classes in the Java bindings map by name to the API names that are listed in the documentation that Rick pointed you to. For example, if you look at the APIs listed in the lun category, you'll find the lun-list-info API, which gets information on LUNs. You invoke this API using the LunListInfoRequest class in the Java bindings.