code: public String getAuthorizationHeader() {
      StringBuilder buf = new StringBuilder("OAuth");
      appendParameter(buf, "realm", realm);
      appendParameter(buf, "oauth_callback", callback);
      appendParameter(buf, "oauth_consumer_key", consumerKey);
      appendParameter(buf, "oauth_nonce", nonce);
      appendParameter(buf, "oauth_signature", signature);
      appendParameter(buf, "oauth_signature_method", signatureMethod);
      appendParameter(buf, "oauth_timestamp", timestamp);
      appendParameter(buf, "oauth_token", token);
      appendParameter(buf, "oauth_verifier", verifier);
      appendParameter(buf, "oauth_version", version);
      // hack: we have to remove the extra ',' at the end
      return buf.substring(0, buf.length() - 1);
    }
docs: Returns the {@code Authorization} header value to use with the OAuth parameter values found in
  the fields.