code: private static void releaseReferences() {
  		synchronized(versionedEcodDBs) {
  			Iterator<Entry<String, SoftReference<EcodDatabase>>> it = versionedEcodDBs.entrySet().iterator();
  			while(it.hasNext()) {
  				Entry<String, SoftReference<EcodDatabase>> entry = it.next();
  				SoftReference<EcodDatabase> ref = entry.getValue();
  				if(ref.get() == null) {
  					logger.debug("Removed version {} from EcodFactory to save memory.",entry.getKey());
  					it.remove();
  				}
  			}
  		}
  	}
docs: removes SoftReferences which have already been garbage collected