code: public boolean isItemTheSame(@Nullable final T oldItem, @Nullable final T newItem) {
  
          if (oldItem == null && newItem == null) {
              return true;
          }
          if (oldItem == null || newItem == null) {
              return false;
          }
  
          final Object oldId = getItemId(oldItem);
          final Object newId = getItemId(newItem);
  
          return (oldId == newId) || (oldId != null && oldId.equals(newId));
      }
docs: Called by the DiffUtil to decide whether two object represent the same Item.
  <p>
  For example, if your items have unique ids, this method should check their id equality.
  
  @param oldItem The position of the item in the old list
  @param newItem The position of the item in the new list
  @return True if the two items represent the same object or false if they are different.
  @see #getItemId(Object)