code: private double getFileAge(File file) {
          final Date d = new Date();
          final long modified = file.lastModified();
          final double time = (d.getTime() - modified) / 1000.0 / 60.0;
          LOGGER.debug("Lock file age is {} minutes", time);
          return time;
      }
docs: Returns the age of the file in minutes.
  
  @param file the file to calculate the age
  @return the age of the file