code: public static boolean looksLikeXHTML (@Nullable final String sText)
    {
      // If the text contains an open angle bracket followed by a character that
      // we think of it as HTML
      // (?s) enables the "dotall" mode - see Pattern.DOTALL
      return StringHelper.hasText (sText) && RegExHelper.stringMatchesPattern ("(?s).*<[a-zA-Z].+", sText);
    }
docs: Check whether the passed text looks like it contains XHTML code. This is a
  heuristic check only and does not perform actual parsing!
  
  @param sText
  The text to check.
  @return <code>true</code> if the text looks like HTML