Uses of Interface
org.bukkit.entity.Projectile

Packages that use Projectile 
Package Description
org.bukkit.entity
Interfaces for non-voxel objects that can exist in a world, including all players, monsters, projectiles, etc.
org.bukkit.event.entity
Events relating to entities, excluding some directly referencing some more specific entity types.
org.bukkit.projectiles
Classes to represent the source of a projectile