title: Android firebase true way for subscribe to multiple topics
body: <p>How to subscribe to multiple topics?</p>
  
  <p>for loop example in my android app:</p>
  
  <pre><code>foreach (String[] all_following_topics_from_user: String topic_name) {
       FirebaseMessaging.getInstance().subscribeToTopic(topic_name);
  }
  
  // example:
  FirebaseMessaging.getInstance().subscribeToTopic("topic_name_1");
  FirebaseMessaging.getInstance().subscribeToTopic("topic_name_2");
  FirebaseMessaging.getInstance().subscribeToTopic("topic_name_3");
  .
  .
  .
  FirebaseMessaging.getInstance().subscribeToTopic("topic_name_589");
  FirebaseMessaging.getInstance().subscribeToTopic("topic_name_590");
  </code></pre>
  
  <p>Is true way subscribe to all by loop? or exists another way?</p>