title: the add method of LinkedList (with supertype) isn't every thing alright?
body: <pre><code>package pkg_2;
  
  import java.util.*;
  
  class shape{}
  
  class Rect extends shape{}
  
  class circle extends shape{}
  
  class ShadeRect extends Rect{}
  
  public class OnTheRun {
  
      public static void main(String[] args) throws Throwable {
          ShadeRect sr = new ShadeRect();
          List&lt;? extends shape&gt; list = new LinkedList&lt;ShadeRect&gt;();       
          list.add(0,sr);
      }
  
  }
  </code></pre>