Servlet init method

Question on servlet init method
O'Reilly book says that init method should pass along an object that implements ServletConfig interface.
Not inis is typically like this
public init (ServletConfig config),
Now servlet makes a call to init method, so which object does the servlet use to call init method.
I may be little confused here, but can enyone explain.

The important point is, you (servlet) never call the init method.
The servlet engine (container) calls the init method right after it creates the servlet object. The API guarantees that the init method will be finished before the first request is sent to the servlet. Your init method should grab all of the init parameters and handle any other initialization.
The destroy() method is similar, you never call it. The servlet engine calls destroy when it is about to remove a servlet object. This is where you have a final chance to clean up.
Bill

------------------
author of: