Welcome!
Here, I'd like to show how to use Weka API to explore some powerful tools like Classification (Supervised and Unsupervised), some Filters (Discretize, Attribute Selection, so forth), how to do Bagging, Boosting and others powerful meta-classification techniques, all that need to be present in toolbox of any Data Scientist.
** Observe that it's not the Weka API Source Code. If you are seeking for it, visit http://www.cs.waikato.ac.nz/ml/weka/documentation.html.