code: public DirectoryPollerBuilder setPollingInterval(long interval, TimeUnit timeUnit) {
          if (interval < 0) {
              throw new IllegalArgumentException("Argument 'interval' is negative: " + interval);
          }
          pollingIntervalInMillis = timeUnit.toMillis(interval);
          return this;
      }
docs: Set the interval between each poll cycle. Optional parameter.
  Default value is 1000 milliseconds.
  
  @param interval - the interval between two poll-cycles.
  @param timeUnit - the unit of the interval. Example: TimeUnit.MINUTES
  @return {@link DirectoryPollerBuilder}
  @throws IllegalArgumentException if <code>interval</code> is negative.