code: public SC registerFilter(Class<? extends Filter> filterClass, String urlPattern) {
          __throwIfInitialized();
  
          List<Class<? extends Filter>> filterList = filterMap.get(urlPattern);
  
          if (filterList == null) {
              filterList = new LinkedList<>();
              filterMap.put(urlPattern, filterList);
          }
  
          if (!filterList.contains(filterClass)) {
              filterList.add(filterClass);
          }
  
          return (SC) this;
      }
docs: Registers a filter.
  
  @param filterClass class to be registered.
  @param urlPattern url pattern to be associated with given class.
  @return this