This is the Java version of NickHolcombe's ListAdapterWithHeader which was originally wrote in Kotlin, after spending countless hours online looking for a way to add a header to my PagedListAdapter I finally found a solution https://gist.github.com/NickHolcombe/0e1c27892d6b73271f10e12268f40187 except it was in Kotlin, I managed to rewrite it in …

ListAdapterWithHeader.java

import androidx.recyclerview.widget.AsyncDifferConfig;
import androidx.recyclerview.widget.AsyncListDiffer;
import androidx.recyclerview.widget.DiffUtil;
import androidx.recyclerview.widget.ListUpdateCallback;
import androidx.recyclerview.widget.RecyclerView;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.List;
import kotlin.jvm.internal.Intrinsics;

/**
 * {@link RecyclerView.Adapter RecyclerView.Adapter} base class based on
 * {@link ListAdapter} for presenting List data with header rows in a
 * {@link RecyclerView}, including computing diffs between Lists on a background thread.
 * 
 * @param <T> Type of the Lists this Adapter will receive.
 * @param <VH> A class that extends ViewHolder that will be used by the adapter.
 * @param diffCallback DiffUtil.ItemCallback<T> class used by DiffUtils for comparing <T> items
 * @param headerOffset Int number of header rows before list
 */


public abstract class ListAdapterWithHeader<T, VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {


    private int headerOffset = 1;
    private AsyncListDiffer<T> asyncListDiffer;


    public ListAdapterWithHeader(DiffUtil.ItemCallback<T> diffCallback) {
        super();
        this.asyncListDiffer = new AsyncListDiffer<>(new OffsetListUpdateCallback(this, headerOffset),
                new AsyncDifferConfig.Builder<>(diffCallback).build());
    }


    public void submitList(List<T> items) {
        asyncListDiffer.submitList(items);
    }


    private  List<T> getCurrentList() {
        return asyncListDiffer.getCurrentList();
    }


    public final T getItem(int position) {
        return this.asyncListDiffer.getCurrentList().get(position - this.headerOffset);
    }

    @Override
    public int getItemCount() {
        return this.asyncListDiffer.getCurrentList().size() + this.headerOffset;
    }


    private final class OffsetListUpdateCallback implements ListUpdateCallback {
        private final RecyclerView.Adapter adapter;
        private final int offset;

        OffsetListUpdateCallback(@NotNull RecyclerView.Adapter adapter, int offset) {
            Intrinsics.checkParameterIsNotNull(adapter, "adapter");
            this.adapter = adapter;
            this.offset = offset;
        }

        final int offsetPosition(int originalPosition) {
            return originalPosition + this.offset;
        }

        public void onInserted(int position, int count) {
            this.adapter.notifyItemRangeInserted(this.offsetPosition(position), count);
        }

        public void onRemoved(int position, int count) {
            this.adapter.notifyItemRangeRemoved(this.offsetPosition(position), count);
        }

        public void onMoved(int fromPosition, int toPosition) {
            this.adapter.notifyItemMoved(this.offsetPosition(fromPosition), this.offsetPosition(toPosition));
        }

        public void onChanged(int position, int count, @Nullable Object payload) {
            this.adapter.notifyItemRangeChanged(this.offsetPosition(position), count, payload);
        }
    }
}

Great, thanks