title: Can a reference of an interface = null?
body: <p>I read this code in a book just now.</p>
  
  <pre><code>public class AdapterWrapper implements ListAdapter {
    ListAdapter delegate=null;
  
    // other code
  
  }
  </code></pre>
  
  <p>The <code>ListAdapter</code> is a public interface and a reference of that interface has been made and assigned null. Is this valid? I'm really confused by this. </p>