title: Android giving IOException with 'unable to create directory: /tokens' when using google calendar api
body: <p>Trying to implement the Calendar Quickstart API into Android but when I declare tokens as demonstrated.
  <code>private final String TOKENS_DIRECTORY_PATH = "tokens";</code></p>
  
  <p>That String is then used in the builder</p>
  
  <pre><code>GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                  HTTP_TRANSPORT, JSON_FACTORY, clientSecrets, SCOPES)
                  .setDataStoreFactory(new FileDataStoreFactory(new java.io.File(TOKENS_DIRECTORY_PATH)))
                  .setAccessType("offline")
                  .build();
  </code></pre>
  
  <p>But Android returns this error when setting the <code>DataStoreFactory</code></p>
  
  <p><code>java.io.IOException: unable to create directory: /tokens</code></p>
  
  <p>Is there a different method to creating a directory that will work? or must I change the file path of <code>TOKENS_DIRECTORY_PATH</code>?</p>