title: How to read subcollections from a document snapshot
body: <p>I have two documents in one collection,
  each document has an object in it, so me i want to read them differently.    </p>
  
  <pre><code>data.get().addOnSuccessListener(new OnSuccessListener&lt;DocumentSnapshot&gt;(){   
      @Override
      public void onSuccess(DocumentSnapshot documentSnapshot) {
          if (!documentSnapshot.exists()){
  
          }
      }
  });
  </code></pre>