docs: public long cleanup() {
  		int garbageSize = 0;
  		if (isCachingEnabled()) {
  			System.out.println(new LogEntry(Level.VERBOSE, "Identifying expired objects"));
  			ArrayList<K> garbage = getExpiredObjects();
  			garbageSize = garbage.size();
  			System.out.println(new LogEntry("cache cleanup: expired objects: " + garbageSize));
  			for (K key : garbage) {
  				clear(key);
  			}
  		}
  		return garbageSize;
  	}