title: Cannot resolve symbol retrofit
body: <p>I followed this example <a href="https://futurestud.io/tutorials/oauth-2-on-android-with-retrofit" rel="nofollow noreferrer">https://futurestud.io/tutorials/oauth-2-on-android-with-retrofit</a></p>
  
  <pre><code>    public static &lt;S&gt; S createService(
              Class&lt;S&gt; serviceClass, final String authToken) {
          if (!TextUtils.isEmpty(authToken)) {
              AuthenticationInterceptor interceptor =
                      new AuthenticationInterceptor(authToken);
  
              if (!httpClient.interceptors().contains(interceptor)) {
                  httpClient.addInterceptor(interceptor);
  
                  builder.client(httpClient.build());
                  retrofit = builder.build();
              }
          }
  
          return retrofit.create(serviceClass);
      }
  </code></pre>
  
  <p>but at <code>retrofit = builder.build()</code> I got cannot resolve symbol. Please help. </p>