code: public Enumeration getInitParameterNames() {
          final LinkedList<String> keys = new LinkedList<String>(_parameters.keySet());
          return new Enumeration() {
  
              public boolean hasMoreElements() {
                  return keys.isEmpty();
              }
  
              public Object nextElement() {
                  return keys.pop();
              }
          };
      }
docs: Returns the names of the filter's initialization parameters
  as an <code>Enumeration</code> of <code>String</code> objects,
  or an empty <code>Enumeration</code> if the filter has
  no initialization parameters.
  @return an <code>Enumeration</code> of <code>String</code>
  objects containing the names of the filter's
  initialization parameters