title: Is DiffUtil.Callback with nested arraylist possible
body: <p>I have a question about the DiffUtil.Callback class in Android which is used to compute the differences between two lists efficiently. It is often used in combination with the RecyclerView.
  In all examples I have found, they use lists like </p>
  
  <pre><code>ArrayList&lt;CustomObject&gt; newList;
  ArrayList&lt;CustomObject&gt; oldList;
  
  // the other methods that need to be overridden
  // e.g. getOldListSize(), getNewListSize() etc.
  </code></pre>
  
  <p>My question is: Is it possible to write the DiffUtil.Callback with a list of lists like the following ... </p>
  
  <pre><code>ArrayList&lt;ArrayList&lt;CustomObject&gt;&gt; oldList;
  ArrayList&lt;ArrayList&lt;CustomObject&gt;&gt; newList;
  </code></pre>
  
  <p>Is is possible ? If not, why not. If yes, how would the class extending DiffUtil.Callback would look like ? </p>