EntityJoinWorldEvent is fired when an Entity joins the world. If this event is canceled, the Entity is not added to the world.

You will need to cast the event in the function header as this class:
crafttweaker.event.EntityJoinWorldEvent
You can, of course, also import the class before and use that name then.

EntityJoinWorld Event implements the following interfaces and are able to call all of their methods/getters/setters as well:

• IEntityEvent
• IEventCancelable

The following information can be retrieved/set during the event:

ZenGetter	Return Type
ZenGetter world	Return Type IWorld