Firebase to custom Java object
<pre><code>{
  "users": {
    "mchen": {
      "friends": { "brinchen": true },
      "name": "Mary Chen",
      "widgets": { "one": true, "three": true }
    },
    "brinchen": { ... },
    "hmadi": { ... }
  }
}
</code></pre>

<p>How to write custom object class for the above example? The guides in Firebase only show simple example.</p>