I have a dragon whistle item, i want the whistle to use it for specific tasks such as circling the player coming to the player, following the player while flying etc. I have coded the flight AI now I need an Item, A dragon whistle to trigger them, so i tried putting commands with an ENUM. but when I use it on addInformation() the game crashes with a nullPointerException

 

ItemDragonWhistle: https://pastebin.com/YQ2MMzEF

EntityTameableDragon: https://pastebin.com/wBYHLk26

StatCollector: https://pastebin.com/Bud1QeZ8

Well obviously commands is null. Yes, an Enum can be null in java.

Also you can't store the field in the Item like this. Items are singletons, meaning that when you change this field for your item it will be changed for all of them. You must use capabilities or NBT.