OpenCart : Create a Controller

To make a cotorller
class Controller<foldername><filename with out extention> extends Controller{
   public function index(){
    .....
    }
   public function showlist(){
    .....
    } 
} 
The there will be no space in the class name and it should extend the controller class.

This controller can be called by example.com/index?route=foldername/filename
The file name should not include extension  . The method index will call automatically and it should be public .  We can access the method showlist by the link example.com/index?route=foldername/filename/showlist the method showlist should me public .