parquet-column/src/main/java/org/apache/parquet/column/statistics/Statistics.java
public void mergeStatistics(Statistics stats) {
    if (stats.isEmpty()) return;

    // Merge stats only if they have the same type
    if (type.equals(stats.type)) {
      incrementNumNulls(stats.getNumNulls());
      if (stats.hasNonNullValue()) {
        mergeStatisticsMinMax(stats);
        markAsNotEmpty();
      }
    } else {
      throw StatisticsClassException.create(this, stats);
    }
  }
public void mergeStatistics(Statistics stats) {
    if (stats.isEmpty()) return;

    // Merge stats only if they have the same type
    if (type.equals(stats.type)) {
      incrementNumNulls(stats.getNumNulls());
      if (stats.hasNonNullValue()) {
        mergeStatisticsMinMax(stats);
        markAsNotEmpty();
      }
    } else {
      throw StatisticsClassException.create(this, stats);
    }
  }
Method to merge this statistics object with the object passed
as parameter. Merging keeps the smallest of min values, largest of max
values and combines the number of null counts.
@param stats Statistics object to merge with