How do I use WEKA's classes in my own code?

It's not that hard to use WEKA classes in your own code, the following articles give a good overview of how to do that:

Further resources:
  • Check out the chapter Using the API in the Weka manual (snapshots later than 09/08/2009 and releases >3.6.1 and >3.7.0).
  • The Weka Examples collection is a an ANT project that is available through snapshots and releases later than 09/08/2009, containing a lot of example classes.

Note: WEKA is open-source software under the GNU General Public License, which means that your code has to be licensed under the GPL as well.