How to "export" a Map as a websites parameter on java EE

I have recently begun working with Tomcat and Java EE, and there is a function that can be used in .jsp files:

Map map = request.getParameterMap();

The request.getParameterMap() function takes a parameter such as this one

a=b&c=d&a=zzz&empty=&empty=&1=22

and puts it into a Map. Now I am wondering, is there a way to convert a Map that you already have to this sort of parameter to be appended on a url? Perhaps something like:

String parameter = map.getUrlParameter;

or do I have to write a function that does this manually?