Weka is a collection of machine learning algorithms for data mining tasks. The algorithms can either be applied directly to a dataset or called from your own Java code. Weka contains tools for data pre-processing, classification, regression, clustering, association rules, and visualization. It is also well-suited for developing new machine learning schemes.

The classes which can be used for combining the predictions of heterogeneous ensemble are listed below:

  • weka.classifiers.meta.Vote
  • weka.classifiers.meta.MultiScheme
  • weka.classifiers.meta.Stacking
  • weka.classifiers.meta.StackingC
  • weka.classifiers.meta.Grading

Source: Weka FAQ