code: private void postProcess(StringBuilder result, NFRuleSet ruleSet) {
          if (postProcessRules != null) {
              if (postProcessor == null) {
                  int ix = postProcessRules.indexOf(";");
                  if (ix == -1) {
                      ix = postProcessRules.length();
                  }
                  String ppClassName = postProcessRules.substring(0, ix).trim();
                  try {
                      Class<?> cls = Class.forName(ppClassName);
                      postProcessor = (RBNFPostProcessor)cls.newInstance();
                      postProcessor.init(this, postProcessRules);
                  }
                  catch (Exception e) {
                      // if debug, print it out
                      if (DEBUG) System.out.println("could not locate " + ppClassName + ", error " +
                                         e.getClass().getName() + ", " + e.getMessage());
                      postProcessor = null;
                      postProcessRules = null; // don't try again
                      return;
                  }
              }
  
              postProcessor.process(result, ruleSet);
          }
      }
docs: Post-process the rules if we have a post-processor.