title: Unable to get access token with GoogleCredentials
body: <p>I'm trying to get access token using my service account JSON file. However I'm unable to get access token.</p>
  
  <pre><code>GoogleCredential googleCredential = GoogleCredential.fromStream(new FileInputStream(serviceAccountJsonFile));
  System.out.print(googleCredential.getAccessToken());
  </code></pre>
  
  <p>I get <code>null</code> every time.
  I am able to use the same credentials with Python APIs.</p>
  
  <p>Can someone point me if I'm missing something here. </p>