public String toStringExtended() {
    if (encoding.equals(EncodingType.DENSE)) {
      return toString() + ", " + denseRegister.toExtendedString();
    } else if (encoding.equals(EncodingType.SPARSE)) {
      return toString() + ", " + sparseRegister.toExtendedString();
    }

    return toString();
  }
Converts sparse to dense hll register.
@param sparseRegister
         - sparse register to be converted
@return converted dense register
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HyperLogLog.java