How to wait in the code till the required data is downloaded from the firestore?

Question

I am able to read the data from my firestore database, but I am not able to wait in the code till the entire data is loaded. So what is happening is that my code executes forward even before the data required is actually loaded. I want to know how can I wait while reading data from firestore, and once the data is fetched, then only make the other code execute. PFB my code snippet.

public void getFoodMenu(String clientID){
    clientFullMenu.clear();
        DocumentReference docRef = mDatabase.collection("MenuDetails").document(clientID);
        docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                if(documentSnapshot.exists()){
                    String sMenuCurrency  = documentSnapshot.getString("menu_currency");
                    colRefMenuType = docRef.collection("MenuType");
                    colRefMenuType.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                        @Override
                        public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                         List<DocumentSnapshot> menuTypeDocuments =  queryDocumentSnapshots.getDocuments();
                         for(int i=0; i<menuTypeDocuments.size();i++){
                             DocumentSnapshot menuTypeDoc = menuTypeDocuments.get(i);
                             String sMenuType = menuTypeDoc.getId();
                             String sSubMenuPriority  = menuTypeDoc.getString("priority");
                             Log.i("XXXX","document::"+menuTypeDoc.getId()+", priority::"+sSubMenuPriority);
                             colRefMenuItems = colRefMenuType.document(sMenuType).collection("MenuItems");
                             colRefMenuItems.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                                 @Override
                                 public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                                    List<DocumentSnapshot> menuItemDocuments = queryDocumentSnapshots.getDocuments();
                                    for(int  j=0;j<menuItemDocuments.size();j++){
                                        DocumentSnapshot menuItemDoc = menuItemDocuments.get(j);
                                        String sFoodItemID = menuItemDoc.getId();
                                        String sFoodItemPriority = menuItemDoc.getString("food_item_priority");
                                        String sFoodItem  = menuItemDoc.getString("food_item");
                                        String sFoodItemDesc = menuItemDoc.getString("food_item_description");
                                        String sImageUrl  = menuItemDoc.getString("food_item_image_location");
                                        String sFoodItemPrice = menuItemDoc.getString("food_item_price");
                                        Log.i("XXXX","FoodItem::"+menuItemDoc.getId()+", priority::"+sFoodItemPriority);
                                        boolean  bMenuType = false;


                                        FoodMenu menu = new FoodMenu();
                                        menu.sFoodItemID = sFoodItemID;
                                        menu.sFoodItem = sFoodItem;
                                        menu.sFoodItemDesc  = sFoodItemDesc;
                                        menu.sFoodMenuCurrency = sMenuCurrency;
                                        menu.iFoodItemPrice = Integer.parseInt(sFoodItemPrice);
                                        menu.sImageUrl = sImageUrl;
                                        menu.sMenuItemPriority = sFoodItemPriority;

                                        //code to add the item under its corresponding food menu type (viz BREAKFAST, LUNCH, DINNER) in case it already exists
                                        for (int i = 0; i < clientFullMenu.size(); i++) {
                                            Log.i("MainActivity","clientFullMenu.get(i).sMenuType:" + clientFullMenu.get(i).sMenuType+" ,sMenuType:"+sMenuType);
                                            if (clientFullMenu.get(i).sMenuType.equalsIgnoreCase(sMenuType)) {
                                                clientFullMenu.get(i).subFoodMenu.add(menu);
                                                bMenuType = true;
                                            }
                                        }
                                        //code to add a new arraylist of food menu type (viz BREAKFAST, LUNCH, DINNER) in case it doesn't exist already
                                        if (!bMenuType) {
                                            ClientFullMenu clientSubMenu = new ClientFullMenu();
                                            clientSubMenu.sMenuType = sMenuType;
                                            clientSubMenu.sMenuPriority = sSubMenuPriority;
                                            ArrayList<FoodMenu> subFoodMenu = new ArrayList<FoodMenu>();
                                            subFoodMenu.add(menu);
                                            clientSubMenu.subFoodMenu = subFoodMenu;
                                            clientFullMenu.add(clientSubMenu);
                                            Log.i("XXXX","Final clientFullMenu.size()1:" + clientFullMenu.size()); //it prints the correct size
                                        }

                                    }
                                 }
                             });

                         }
                        }
                    });
                }
            }
        });
    Log.i("XXXX","Final clientFullMenu.size()2:" + clientFullMenu.size()); //It prints size as 0
}