java.lang.IndexOutOfBoundsException: Index: 2, Size: 2
              at java.util.ArrayList.get(ArrayList.java:411)
              at com.tijdelijk.firebasetest.Start$1.populateViewHolder(Start.java:69)
              at com.tijdelijk.firebasetest.Start$1.populateViewHolder(Start.java:64)

public class CategoryFragment extends Fragment {

View myFragment;

RecyclerView listCategory;
RecyclerView.LayoutManager layoutManager;
FirebaseRecyclerAdapter<Category, CategoryViewHolder> adapter;

FirebaseDatabase database;

DatabaseReference categories;
DatabaseReference subCategory;

public static CategoryFragment newInstance() {
    CategoryFragment fragment = new CategoryFragment();
    return fragment;
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    database = FirebaseDatabase.getInstance();
    categories = database.getReference("Category");
    subCategory = database.getReference("SubCategory");

}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    myFragment = inflater.inflate(R.layout.fragment_category, container, false);

    listCategory = (RecyclerView) myFragment.findViewById(R.id.listCategory);
    listCategory.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(container.getContext());
    listCategory.setLayoutManager(layoutManager);

    loadCategories();


    return myFragment;
}

private void loadCategories() {
    adapter = new FirebaseRecyclerAdapter<Category, CategoryViewHolder>(
            Category.class,
            R.layout.category_layout,
            CategoryViewHolder.class,
            categories
    ) {


        @Override
        protected void populateViewHolder(CategoryViewHolder viewHolder, final Category model, int position) {
            viewHolder.category_name.setText(model.getName());
            Picasso.with(getActivity())
                    .load(model.getImage())
                    .into(viewHolder.category_image);

            viewHolder.setItemClickListener(new ItemClickListener() {
                @Override
                public void onClick(View view, int position, boolean isLongClick) {
                    Intent startGame = new Intent(getActivity(), Start.class);
                    Common.categoryId = adapter.getRef(position).getKey();
                    loadSubCategory(Common.categoryId);

                    startActivity(startGame);
                }
            });
        }
    };
    adapter.notifyDataSetChanged();
    listCategory.setAdapter(adapter);
}

private void loadSubCategory(String categoryId) {

    //Clear list if there are old subCategory
    if (Common.subCategoryList.size() > 0) {
        Common.subCategoryList.clear();
    }

    subCategory.orderByChild("CategoryId").equalTo(categoryId)
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                        SubCategory ques = postSnapshot.getValue(SubCategory.class);
                        Common.subCategoryList.add(ques);
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
}

public class Start extends AppCompatActivity {


FirebaseDatabase database;
DatabaseReference subCategory;

FirebaseRecyclerAdapter<SubCategory, SubCategoryViewHolder> adapter;
RecyclerView listSubCategory;
RecyclerView.LayoutManager layoutManager;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start);

    database = FirebaseDatabase.getInstance();
    subCategory = database.getReference("SubCategory");

    listSubCategory = findViewById(R.id.listSubCategory);
    listSubCategory.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(getBaseContext());
    listSubCategory.setLayoutManager(layoutManager);

    loadSubCategories();
    adapter.notifyDataSetChanged();
    listSubCategory.setAdapter(adapter);
}




private void loadSubCategories() {
    adapter = new FirebaseRecyclerAdapter<SubCategory, SubCategoryViewHolder>(
            SubCategory.class,
            R.layout.subcategory_layout,
            SubCategoryViewHolder.class,
            subCategory
    ) {


        @Override
        protected void populateViewHolder(SubCategoryViewHolder viewHolder, SubCategory model, int position) {
            viewHolder.subcategory_nlname.setText(Common.subCategoryList.get(position).getLatijnseNaam());
            viewHolder.subcategory_ltname.setText(Common.subCategoryList.get(position).getNederlandseNaam());


            viewHolder.setItemClickListener(new ItemClickListener() {
                @Override
                public void onClick(View view, int position, boolean isLongClick) {
                    Intent startGame = new Intent(Start.this, Start.class);
                    Common.categoryId = adapter.getRef(position).getKey();

                    startActivity(startGame);
                }
            });
        }


    };
}

public class SubCategoryViewHolder extends RecyclerView.ViewHolder
implements View.OnClickListener{

public TextView subcategory_nlname;
public TextView subcategory_ltname;


private ItemClickListener itemClickListener;

public SubCategoryViewHolder(View itemView) {
    super(itemView);
    subcategory_ltname = itemView.findViewById(R.id.latijnse_naam);
    subcategory_nlname =  itemView.findViewById(R.id.nederlandse_naam);

public void setItemClickListener(ItemClickListener itemClickListener) {
    this.itemClickListener = itemClickListener;
}

@Override
public void onClick(View view) {
    itemClickListener.onClick(view,getAdapterPosition(),false);
}