ServletRequest.getParameterMap() returns Map and ServletRequest.getParameter() returns String?

Question

Can someone explain to me why ServletRequest.getParameterMap() returns type

Map 

ServletRequest

Answer 1

It returns all parameter values for controls with the same name.

For example:

 Audi
 Ford
 Opel

or

    Audi
    Ford
    Opel

Any checked/selected values will come in as:

String[] cars = request.getParameterValues("cars");

It's also useful for multiple selections in tables:

        

    

        
Delete?
        
Foo
    
    

            

            
${item.foo}
        
    

in combination with

itemDAO.delete(request.getParameterValues("delete"));