UDAF_v1

public class SomeUDAF extends UDAF {
    static final Log LOG = LogFactory.getLog(UDAFFoldIn.class.getName());

    public static class SomeUDAFEvaluator implements UDAFEvaluator{

        public static class FinalResult{
            //class to stores partial results
        }

        public static class PartialResult{
            //class to store final result
        }

        public void init() {
            //initialize
        }

        public boolean aggregate(DoubleWritable wm, DoubleWritable lambda,
            //aggregate values
            return true;
        }

        public PartialResult evaluatePartial(){
            //return partial result
            return new PartialResult();
        }

        public boolean aggregatePartial(PartialResult other) throws Exception{
            //aggregate partial
            return true;
        }

        public FinalResult evaluate(){
            //return final result
            return new FinalResult();
        }
    }
}