public class LoadJustHardPostFromFireBase implements ItemsForPost{
private ArrayList<String> exerciseHard;
private ArrayList<String> otherData;
private int type;

public ArrayList getTrainingEx(DatabaseReference myRef, final FirebaseUser user, int id)
{ получаю данные в список из firebase  return exerciseHard;}

public ArrayList getOtherData(DatabaseReference myRef, final FirebaseUser user, long id)
{получаю вторые данные в список из firebase return otherData;}

public class LoadJustCardioPostFromFireBase implements ItemsForPost{
private ArrayList<String> exerciseCard;
private ArrayList<String> otherData;
private int type;

public ArrayList getCardioEx(DatabaseReference myRef, final FirebaseUser user, int id)
{ получаю данные в список из firebase  return exerciseCard;}

public ArrayList getOtherData(DatabaseReference myRef, final FirebaseUser user, long id)
{получаю вторые данные в список из firebase return otherData;}

public class LoadFullGroupPostFromFireBase implements ItemsForPost{
private ArrayList<String> otherData;
private ArrayList<String> exerciseHard;
private ArrayList<String> exerciseCard;
private int type;

public ArrayList getTrainingEx(DatabaseReference myRef, final FirebaseUser user, int id)
{ получаю данные в список из firebase  return exerciseHard;}

public ArrayList getCardioEx(DatabaseReference myRef, final FirebaseUser user, int id)
{ получаю данные в список из firebase  return exerciseCard;}

public ArrayList getOtherData(DatabaseReference myRef, final FirebaseUser user, long id)
{получаю вторые данные в список из firebase return otherData;}

public interface ItemsForPost {
    int getItemType ();
}

public class RecyclerAdapterForPost extends RecyclerView.Adapter<RecyclerAdapterForPost.myVH3> {
ArrayList<ItemsForPost> items;
private final int TYPE_ITEM_HARD = 1;
private final int TYPE_ITEM_CARDIO = 2;
private final int TYPE_ITEM_GROUP = 0;
private FirebaseAuth mAuth = FirebaseAuth.getInstance();
private FirebaseUser user = mAuth.getCurrentUser();
private DatabaseReference myRef = FirebaseDatabase.getInstance().getReference();

public RecyclerAdapterForPost(ArrayList<ItemsForPost> items){
    this.items = items;
}


@Override
public myVH3 onCreateViewHolder(ViewGroup parent, int viewType) {
    View v;

    switch (viewType) {
        case TYPE_ITEM_HARD:
            v = LayoutInflater.from(parent.getContext()).inflate(R.layout.conteiner_post_hard, parent, false);
            break;
        case TYPE_ITEM_CARDIO:
            v = LayoutInflater.from(parent.getContext()).inflate(R.layout.conteiner_post_cardio, parent, false);
            break;
        default:
            v = LayoutInflater.from(parent.getContext()).inflate(R.layout.conteiner_post_group, parent, false);
    }
    return new myVH3(v);
}

@Override
public void onBindViewHolder(myVH3 holder, int position) {
    int type = getItemViewType(position);

    switch (type) {
        case TYPE_ITEM_HARD:{

            LoadJustHardPostFromFireBase loadHard = (LoadJustHardPostFromFireBase) items.get(position);

            ArrayList<String> dataOne = loadHard.getTrainingEx(myRef, user, position);
            ArrayList<String> dataThree = loadHard.getOtherData(myRef,user,position);
        }
            break;
        case TYPE_ITEM_CARDIO:{
            LoadJustCardioPostFromFireBase loadCardio = (LoadJustCardioPostFromFireBase) items.get(position);

            ArrayList<String> dataTwo  = loadCardio.getCardioEx(myRef,user,position);
            ArrayList<String> dataThree = loadCardio.getOtherData(myRef,user,position);
        }
            break;
        case TYPE_ITEM_GROUP:{
            LoadFullGroupPostFromFireBase  loadGroup = (LoadFullGroupPostFromFireBase) items.get(position);

            ArrayList<String> dataOne = loadGroup.getTrainingEx(myRef, user, position);
            ArrayList<String> dataTwo = loadGroup.getCardioEx(myRef,user,position);
            ArrayList<String> dataThree = loadGroup.getOtherData(myRef,user,position);
        }
            break;
    }
}

@Override
public int getItemCount() {
    return items.size();
}

@Override
public int getItemViewType(int position) {
    // определяем какой тип в текущей позиции
    int type = items.get(position).getItemType();
    if (type == 1) return TYPE_ITEM_HARD;
    else if (type == 2) return TYPE_ITEM_CARDIO;
    else return TYPE_ITEM_GROUP;

}

public class myVH3 extends RecyclerView.ViewHolder{

     TextView name_person_post;
     TextView data_person_post;
     TextView tonnageNow;
     TextView kpwNow;
     TextView intencityNow;
     TextView timeForTrain;
     TextView exCount;
     TextView myWeightFromProfile;



public myVH3(View itemView) {
    super(itemView);
    name_person_post= itemView.findViewById(R.id.name_person_post);
    data_person_post= itemView.findViewById(R.id.data_person_post);
    tonnageNow= itemView.findViewById(R.id.tonnageNow);
    kpwNow= itemView.findViewById(R.id.kpwNow);
    intencityNow= itemView.findViewById(R.id.intencityNow);
    timeForTrain= itemView.findViewById(R.id.timeForTrain);
    exCount= itemView.findViewById(R.id.exCCount);
    myWeightFromProfile= itemView.findViewById(R.id.myWeightFromProfile);
}
}
}

LoadFullGroupPostFromFireBase  loadGroup = (LoadFullGroupPostFromFireBase) items.get(position);

            ArrayList<String> dataOne = loadGroup.getTrainingEx(myRef, user, position);

ArrayList<String> dataOne = new ArrayList(); внутри onBindViewHolder

....
private ArrayList<ItemsForPost>   items = new ArrayList<>();
public View onCreateView(...){
items.add(new LoadJustCardioPostFromFireBase(2));
}
....