O'Reilly's On Java service published an article devoted to Trove: Enhance Collection Performance with this Treasure Trove. One factual quibble: the author reports that Map.keySet(), Map.valueSet(), and Map.entrySet() all trigger creation of Map.Entry instances that Trove otherwise avoids. In fact, this is only true of Map.entrySet(), whose API requires that the implementation return instances of Map.Entry. So, use Map.keySet() and Map.valueSet() without fear.