title: Detect if a child exists
body: <p>I'm trying to check if a child exists in a location like this:</p>
  
  <pre><code>public static boolean checkIfNotebookExists(String notebookName) {
      if (notebooksRef.child(notebookName) == null)
          return false;
      else
          return true;
  }
  </code></pre>
  
  <p>Whenever I call this function, I always get <code>true</code> even though the parameter that I include doesn't exist yet on the database.</p>