code: private static CacheEntry getOrCreateCacheEntry(final NodeInterface startNode, final NodeInterface endNode) {
  
  		final String cacheKey = cacheKey(startNode, endNode);
  		CacheEntry entry      = cache.get(cacheKey);
  
  		if (entry == null) {
  
  			entry = new CacheEntry();
  			entry.key = cacheKey;
  
  			cache.put(cacheKey, entry);
  		}
  
  		return entry;
  	}
docs: ----- private methods -----