title: Iterable as a return type - Iterable itself or a subclass?
body: <p>I'm having trouble understanding getAvailableRooms method. I have methods that I need to fill out, but I don't really understand Iterabl getAvailableRooms method.</p>
  <pre><code>public interface BookingManager {
  
  public boolean isRoomAvailable(Integer room, LocalDate date);
  
  public void addBooking(String guest, Integer room, LocalDate date);
  
  public Iterabl&lt;Integer&gt; getAvailableRooms(LocalDate date);
  }
  </code></pre>
  <p>How can Iterable be a return type and how is it used? Is it suppose to return a Iterable object or any of subclasses such as List?</p>