code: @Override
  	public void run() {
  		final long stamp = lock.writeLock();
  		try {
  			Iterator<ErrorCounter> i = errorCounters.values().iterator();
  			while (i.hasNext()) {
  				if (i.next().isEmpty()) {
  					i.remove();
  				}
  			}
  		} finally {
  			lock.unlockWrite(stamp);
  		}		
  	}
docs: --- CLEANUP COUNTERS ---