I want to reduce the spawn rate of certain mobs (creepers and skeletons). I use the CreatueSpawnEvent and then check in a forach loop if the entity about to spawn is an instanceof any of the entities in my list. If yes, I generated a random number between 0 and 1 and if the number is bigger than 0.5, I cancel the event. This should reduce spawns of the mobs specified by 50%. And as far as I can tell it's working just fine. Is this the correct way or is there a better approach?