code: public static DocumentFactory getInstance() {
        if (CONFIGURED_INSTANCE == null) {
           synchronized (DocumentFactory.class) {
              if (CONFIGURED_INSTANCE == null) {
                 CONFIGURED_INSTANCE = new DocumentFactory();
              }
           }
        }
        return CONFIGURED_INSTANCE;
     }
docs: Gets instance of the document factory configured using configuration settings.
  
  @return A document factory whose preprocessors are set via configuration options