code: public void setOutputFormat(Properties format)
      {
          /*
           * If "format" does not contain the property
           * S_USE_URL_ESCAPING, then don't set this value at all,
           * just leave as-is rather than explicitly setting it.
           */
          String value; 
          value = format.getProperty(OutputPropertiesFactory.S_USE_URL_ESCAPING);
          if (value != null) {
              m_specialEscapeURLs =
                  OutputPropertyUtils.getBooleanProperty(
                      OutputPropertiesFactory.S_USE_URL_ESCAPING,
                      format);
          }
  
          /*
           * If "format" does not contain the property
           * S_OMIT_META_TAG, then don't set this value at all,
           * just leave as-is rather than explicitly setting it.
           */
          value = format.getProperty(OutputPropertiesFactory.S_OMIT_META_TAG);
          if (value != null) {
             m_omitMetaTag =
                  OutputPropertyUtils.getBooleanProperty(
                      OutputPropertiesFactory.S_OMIT_META_TAG,
                      format);
          }
  
          super.setOutputFormat(format);
      }
docs: Specifies an output format for this serializer. It the
  serializer has already been associated with an output format,
  it will switch to the new format. This method should not be
  called while the serializer is in the process of serializing
  a document.
  
  This method can be called multiple times before starting
  the serialization of a particular result-tree. In principle
  all serialization parameters can be changed, with the exception
  of method="html" (it must be method="html" otherwise we
  shouldn't even have a ToHTMLStream object here!)
  
  @param format The output format or serialzation parameters
  to use.