code: private static StringBuffer doAppendClosingTag(StringBuffer buffer, String tag)
  	{
  		buffer.append(SEQUENCE__TAG__BEGIN_CLOSING_TAG).append(tag).append(SEQUENCE__TAG__END_OF_TAG);
  		return buffer;
  	}
docs: Add a closing tag to a StringBuffer.
  
  If the buffer is null, a new one is created.
  
  @param buffer
  StringBuffer to fill
  @param tag
  the tag to close
  @return the buffer