@Override
    public ObjectInspector getResultObjectInspector() {
      return ObjectInspectorFactory.getStandardListObjectInspector(
              PrimitiveObjectInspectorFactory.writableDoubleObjectInspector);
    }
A state class to store intermediate aggregation results.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFPercentileCont.java