Hi! I'm new here and it'd be nice to say something on start. I've got a little problem with hashmap. I want to make assist-system on my Minecraft server and I'm stuck right now. I have one HashMap: public static HashMap<Entity, HashMap<UUID,Integer>> test = new HashMap<>(); I want to save entity (e.g. zombie) into this hashmap and next add player (as UUID code) with total damage that he/she gives to enemy. And... that's a problem. I'm stucked here. At entity's death I'm going to say all players who attacked enemy how much damage they had given. For example: Fight with Zombie: Zombie is attacked by 3 players. On fight player one gave 110 damage points to enemy. On fight player two gave 60 damage points to enemy. On fight player three gave 25 damage points to enemy. Final attack (when zombie's dead) - player one. After enemy's death for players display messages about who killed zombie, how much damage gave and other informations about assists (for player who killed only assist, for other players - other players-in-fight statistics). I know I can't explain this very good, but I'm stuck at hashmap and I don't know what's next... Please, any proposes below. Thanks.