Google Plus list activities - java api

List retval = new ArrayList();
    
    Plus.Activities.List listActivities =
        plusSvc.activities().list(userid, "public");

    listActivities.setMaxResults(100L);

    // get the 1st page of activity objects
    ActivityFeed activityFeed = listActivities.execute();

    // unwrap the request and extract the pieces we want
    List pageOfActivities = activityFeed.getItems();

    // loop through until we arrive at an empty page
    while (pageOfActivities != null) {
      for (Activity activity : pageOfActivities) {
        retval.add(activity);
        System.out.println("ID " + activity.getId() + " Content: " +
                           activity.getPlusObject().getContent());
      }

      // we will know we are on the last page when the next page token
      // is null (in which case, break).
      if (activityFeed.getNextPageToken() == null) {
        break;
      }

      // prepare to request the next page of activities
      listActivities.setPageToken(activityFeed.getNextPageToken());

      // execute and process the next page request
      activityFeed = listActivities.execute();
      pageOfActivities = activityFeed.getItems();
    }