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class ConcertActivity : AppCompatActivity() {
    private val adapter = ConcertAdapter()

    // Use the 'by viewModels()' Kotlin property delegate
    // from the activity-ktx artifact
    private val viewModel: ConcertViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState);
        viewModel.concerts.observe(this, Observer { adapter.submitList(it) })
    }
}

public class ConcertActivity extends AppCompatActivity {
    private ConcertAdapter adapter = new ConcertAdapter();
    private ConcertViewModel viewModel;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        viewModel = new ViewModelProvider(this).get(ConcertViewModel.class);
        viewModel.concertList.observe(this, adapter::submitList);
    }
}

class ConcertAdapter() :
        PagedListAdapter<Concert, ConcertViewHolder>(DIFF_CALLBACK) {
    override fun onBindViewHolder(holder: ConcertViewHolder, position: Int) {
        val concert: Concert? = getItem(position)

        // Note that "concert" is a placeholder if it's null.
        holder.bindTo(concert)
    }

    companion object {
        private val DIFF_CALLBACK = ... // See Implement the diffing callback section.
    }
}

public class ConcertAdapter
        extends PagedListAdapter<Concert, ConcertViewHolder> {
    protected ConcertAdapter() {
        super(DIFF_CALLBACK);
    }

    @Override
    public void onBindViewHolder(@NonNull ConcertViewHolder holder,
            int position) {
        Concert concert = getItem(position);

        // Note that "concert" can be null if it's a placeholder.
        holder.bindTo(concert);
    }

    private static DiffUtil.ItemCallback<Concert> DIFF_CALLBACK
            = ... // See Implement the diffing callback section.
}

private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Concert>() {
    // The ID property identifies when items are the same.
    override fun areItemsTheSame(oldItem: Concert, newItem: Concert) =
            oldItem.id == newItem.id

    // If you use the "==" operator, make sure that the object implements
    // .equals(). Alternatively, write custom data comparison logic here.
    override fun areContentsTheSame(
            oldItem: Concert, newItem: Concert) = oldItem == newItem
}

private static DiffUtil.ItemCallback<Concert> DIFF_CALLBACK =
        new DiffUtil.ItemCallback<Concert>() {

    @Override
    public boolean areItemsTheSame(Concert oldItem, Concert newItem) {
        // The ID property identifies when items are the same.
        return oldItem.getId() == newItem.getId();
    }

    @Override
    public boolean areContentsTheSame(Concert oldItem, Concert newItem) {
        // Don't use the "==" operator here. Either implement and use .equals(),
        // or write custom data comparison logic here.
        return oldItem.equals(newItem);
    }
};