code: protected static boolean isSingleDataSet(File[] subDirs)
      {
          boolean onlyNumericDirs = true;
  
          for (File sd : subDirs)
          {
              if (!isNumeric(sd.getName()))
                  onlyNumericDirs = false;
          }
  
          return onlyNumericDirs;
      }
docs: Determines if a list of sub-directories should be treated as a single data set. This implementation returns
  {@code true} if all of the sub-directories have numeric names. In this case, the numeric directories are most
  likely used by the cache implementation to group files in a single data set. The numeric directory names do not
  provide meaningful grouping to the user.
  
  @param subDirs List of sub-directories to test.
  
  @return {@code true} if the directories should be treated as a single data set.