Simple question: How can I initialize a custom entity's variables when it is spawned in the world (by an egg)? I tried the constructor but it overwrites variables read from nbt for some reason. I need to set an integer to something random when it is spawned into the world.

I typically use #onSpawnWithEgg because that gives me access to real world coordinates, but if all you need to do is set a random integer, you can do so in the constructor as diesieben mentioned.

 

Also, if you are spawning the entity, it won't have any NBT to overwrite because it didn't exist yet - can you give us more details / code on what you are doing?