CollideEntityEvent get hitted entity

As by title, when listening to CollideEntityEvent (fired when, for example, an arrow or a snowball hits an entity) how can i see wich entity has been hitted? For example, i throw a snowball to an item frame, how in the event can i check if the hitted entity is in fact an item frame?

You would use getEntities, and check their EntityTypes.

The javadocs are your friend.