code: public static String getOtpAuthURL(String issuer,
                                         String accountName,
                                         GoogleAuthenticatorKey credentials)
      {
  
          return String.format(
                  TOTP_URI_FORMAT,
                  internalURLEncode(getOtpAuthTotpURL(issuer, accountName, credentials)));
      }
docs: Returns the URL of a Google Chart API call to generate a QR barcode to
  be loaded into the Google Authenticator application.  The user scans this
  bar code with the application on their smart phones or enters the
  secret manually.
  <p/>
  The current implementation supports the following features:
  <ul>
  <li>Label, made up of an optional issuer and an account name.</li>
  <li>Secret parameter.</li>
  <li>Issuer parameter.</li>
  </ul>
  
  @param issuer      The issuer name. This parameter cannot contain the colon
  (:) character. This parameter can be null.
  @param accountName The account name. This parameter shall not be null.
  @param credentials The generated credentials.  This parameter shall not be null.
  @return the Google Chart API call URL to generate a QR code containing
  the provided information.
  @see <a href="https://code.google.com/p/google-authenticator/wiki/KeyUriFormat">Google Authenticator - KeyUriFormat</a>