If I am not wrong then the HttpJspBase class is implemented by the Vendor specific(Tomcat)---right?
So Tomcat's adds a line jspInit() inside the init() of HttpJspBase class.
Yes. The vendor specific class' init method calls the jspInit method (see the
soruce code of org.apache.jasper.runtime.HttpJspBase).
Then why the book writes ServletConfig sConfig = getServletConfig();page:344
The statement is not on page 344 in my book. Anyways, did you check the syntax of jspInit method in HttpJspBase interface?? The jspInit method doesn't take any parameters...