code: public BoxRequestsFile.DownloadAvatar getDownloadAvatarRequest(File target, String userId) throws IOException{
          if (!target.exists()){
              throw new FileNotFoundException();
          }
          BoxRequestsFile.DownloadAvatar request = new BoxRequestsFile.DownloadAvatar(userId, target, getAvatarDownloadUrl(userId), mSession)
                  .setAvatarType(BoxRequestsFile.DownloadAvatar.LARGE);
          return request;
      }
docs: Gets a request that downloads an avatar of the target user id.
  
  @param target    target file to download to, target can be either a directory or a file
  @param userId    id of user to download avatar of
  @return  request to download a thumbnail to a target file
  @throws IOException throws FileNotFoundException if target file does not exist.