title: Null Integer object assigned to primitive int throws NullPointerException
body: <pre><code>Integer i = null;
  int j = i;
  System.out.println(j);
  </code></pre>
  
  <p>Why does it throw <code>NullPointerException</code> and doesn't print the value of <code>j</code> as <code>0</code>?</p>