title: Error while calling interface parameter method with implemented class
body: <p>I have a method that receives 2 parameters: List of interface.
  I get an error when I try to call this method with List of class that implements that interface.</p>
  
  <p>The input must be of type class, I don't want to change it to List of interface.</p>
  
  <pre><code>List&lt;Io&gt; oldList;
  List&lt;Io&gt; newList;
  handleIo(oldList, newList); //Here I get the error
  
  public void handleIo(List&lt;IIo&gt; oldIos, List&lt;IIo&gt; newIos) {...}
  
  public class Io implements IIo {...}
  
  public interface IIo {...}
  </code></pre>
  
  <p>I thought this is the idea of interfaces, I can't figure out what is wrong. The error asking to change the type of the parameters I send to the method.</p>