Help to solve UDAF errors!

[Abhishek Bhattacharya]

Hi,

I have implemented a simple UDAF for top-n-percent as follows:
import java.util.ArrayList;
import java.util.Collections;

import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;

public class UDAFTopNPercent extends UDAF{

    public static class Result {
        ArrayList<Double> list;
        double min;
    }

    public class TopNPercentEvaluator implements UDAFEvaluator {

        private Result res;
        private int rowIndex;
        private int percent;

        public TopNPercentEvaluator() {
            super();
            res = new Result();
            init();
            rowIndex = 0;
        }
        @Override
        public void init() {
            res.list = new ArrayList<Double>();
            res.min = Double.MAX_VALUE;
        }

        public boolean iterate(Double rowVal, int pct) {
            ArrayList<Double> resList = res.list;
            rowIndex++;
            resList.add(rowVal);
            percent = pct;
            return true;
        }

        public ArrayList<Double> terminatePartial() {
            ArrayList<Double> resList = res.list;
            Collections.sort(resList);
            return resList;
        }

        public boolean merge(ArrayList<Double> otherList) {
            ArrayList<Double> resList = res.list;
            resList.addAll(otherList);
            return true;
        }

        public ArrayList<Double> terminate() {
            ArrayList<Double> resList = res.list;
            double num_rows = (double)percent/100.0*rowIndex;
            Collections.sort(resList);
            int lastIdx = resList.size()- (int) num_rows;
            if(lastIdx <= 0) {
                return resList;
            }
            for(int i=0; i<lastIdx; i++) {
                resList.remove(i);
            }
            return resList;
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

    }

}

But throws some error such as first few lines are:
FAILED: Hive Internal Error:
java.lang.ClassCastException(org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableFloatObjectInspector
cannot be cast to
org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector)
java.lang.ClassCastException:
org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableFloatObjectInspector
cannot be cast to
org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector
        at
org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorConverters.getConverter(ObjectInspectorConverters.java:116)
        at
org.apache.hadoop.hive.ql.udf.generic.GenericUDFUtils$ConversionHelper.<init>(GenericUDFUtils.java:300)
        at
org.apache.hadoop.hive.ql.udf.generic.GenericUDAFBridge$GenericUDAFBridgeEvaluator.init(GenericUDAFBridge.java:129)

Please help me to debug this!
Is it throwing from returning ArrayList<Double> in terminate()?
How should I return a List from UDAF?

Thanks,
Abhishek