@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("Encoding: ");
    sb.append(encoding);
    sb.append(", p: ");
    sb.append(p);
    sb.append(", estimatedCardinality: ");
    sb.append(estimateNumDistinctValues());
    return sb.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