long getSizeOfStoreFile(TableName tn, StoreFileReference storeFileName) {
    String regionName = storeFileName.getRegionName();
    return storeFileName.getFamilyToFilesMapping().entries().stream().collect(
      Collectors.summingLong((e) -> getSizeOfStoreFile(tn, regionName, e.getKey(), e.getValue())));
  }
Computes the size of the store files for a single region.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/FileArchiverNotifierImpl.java