don't if(map.containsKey(x)){map.get(x);}

save a lookup, and use the fact that get returns a null entry on a
failed lookup.
Especially important with complex objects, which are moderatly expensive
to hash.

TileBuildcraft was slightly more tricky, as updatePacket and
descriptionPacket are final, so could only be written once.

saves hashing a hashmap and hashing an array on every liquid render.