见http://www.eclipse.org/recommenders/manual/#d0e32
Call Completion
The Call Completion engine, for example, provides you with recommendations of likely methods to call whenever you trigger code completion on an object, be it a variable, field, or constant.The call completion engine bases its recommendations on
what other developers in a similar situation have called on an object of the given type.
Override Completion
The Override Completion engine provides you with recommendations which methods you are most likely to override when triggering code completion in the body of class.