AndroidFileSystem.txt

public static void save(ArrayList<Element> elements, File file, Context context){
        try {
            ObjectOutputStream obos = new ObjectOutputStream(context.openFileOutput(file.getName(),Context.MODE_PRIVATE));
            obos.writeObject(elements);
            obos.close();
        }catch (IOException io){
            Log.e("Exception", "File write failed: " + io.toString());
        }
    }

    public static ArrayList<Element> remember(File file, Context context){
        ArrayList<Element> elements = new ArrayList<>();
        try{
            InputStream inputStream = context.openFileInput(file.getName());
            if (inputStream != null){
                ObjectInputStream obis = new ObjectInputStream(inputStream);
                elements = (ArrayList<Element>) obis.readObject();
                obis.close();
            }else {
                MainActivity.toaster(context,"inputStream == null");
            }

        }catch (IOException io){
            Log.e("Exception", "Can not read file: " + io.toString());
        }catch (ClassNotFoundException cnfe){
            Log.e("Exception", "Class not found: " + cnfe.toString());
        }
        return elements;
    }