title: AdMob Ad and ErrorCode cannot be resolved to a type
body: <p>I have added this code to see the error if App fails to receive ads.</p>
  
  <pre><code>    // Create an ad request. Check logcat output for the hashed device ID to
      // get test ads on a physical device.
      AdRequest adRequest = new AdRequest.Builder()
          .addTestDevice(AdRequest.DEVICE_ID_EMULATOR)
          .addTestDevice("INSERT_YOUR_HASHED_DEVICE_ID_HERE")
          .build();
  
      // Start loading the ad in the background.
      adView.loadAd(adRequest);
   // Set AdListener
      adView.setAdListener(new AdListener() {
          @Override
          public void onFailedToReceiveAd(Ad ad, ErrorCode error) {
              System.err.println("Ad failed: " + ad.toString() + error.toString());    
          }
  
          @Override
          public void onReceiveAd(Ad ad) {
              System.out.println("Ad received: " + ad.toString());
          }
      });
    }
  </code></pre>
  
  <p>Unfortunately doesn't work because cannot find <code>Ad</code> and <code>ErrorCode</code> probably because in latest library have changed something. </p>
  
  <p>How could I fix this?</p>