Не сохраняется прогресс. Как добавить функцию автосохранения/или функцию сохранения?

Не могу сохранить прогресс

package sudoku.persistance;

import sudoku.problemdomain.IStorage;
import sudoku.problemdomain.SudokuGame;

import java.io.*;

public class LocalStorageImpl implements IStorage {
    private static File GAME_DATA = new File (
            System.getProperty ("user.home"),
            "gamedata.txt"
    );

    @Override
    public void updateGameData(SudokuGame game) throws IOException {
        try {
            FileOutputStream fileOutputStream = new FileOutputStream(GAME_DATA);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
            objectOutputStream.writeObject(game);
            objectOutputStream.close();
        } catch (IOException e) {
            throw new IOException("Unable to access Game Data");
        }
    }

    @Override
    public SudokuGame getGameData() throws IOException {
        FileInputStream fileInputStream = new FileInputStream(GAME_DATA);
        ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);

        try {
            SudokuGame gameState = (SudokuGame) objectInputStream.readObject();
            objectInputStream.close();
            return gameState;
        } catch (ClassNotFoundException e) {
            throw new IOException("File Not Found");
        }
    }
}

Методы зовутся в двух классах: SudokuBuildLogic:

package sudoku.buildlogic;

import sudoku.computationlogic.GameLogic;
import sudoku.persistance.LocalStorageImpl;
import sudoku.problemdomain.IStorage;
import sudoku.problemdomain.SudokuGame;
import sudoku.userinterface.IUserInterfaceContract;
import sudoku.userinterface.logic.ControlLogic;

import java.io.IOException;

public class SudokuBuildLogic {
    public static void build (IUserInterfaceContract.View userInterface) throws IOException, ClassNotFoundException {
        SudokuGame initialState;
        IStorage storage = new LocalStorageImpl();

        try {
            initialState = storage.getGameData();
        } catch (IOException e) {
            initialState = GameLogic.getNewGame();
            storage.updateGameData(initialState);
        }

        IUserInterfaceContract.EventListener uiLogic
                = new ControlLogic(storage, userInterface);

        userInterface.setListener(uiLogic);
        userInterface.updateBoard(initialState);
    }
}

И в ControlLogic:

package sudoku.userinterface.logic;

import sudoku.computationlogic.GameLogic;
import sudoku.constants.GameState;
import sudoku.constants.Messages;
import sudoku.problemdomain.IStorage;
import sudoku.problemdomain.SudokuGame;
import sudoku.userinterface.IUserInterfaceContract;

import java.io.IOException;

public class ControlLogic implements IUserInterfaceContract.EventListener {

    private IStorage storage;

    private IUserInterfaceContract.View view;

    public ControlLogic(IStorage storage, IUserInterfaceContract.View view) {
        this.storage = storage;
        this.view = view;
    }

    @Override
    public void onSudokuInput(int x, int y, int input) {
        try {
            SudokuGame gameData = storage.getGameData();
            int [][] newGridState = gameData.getCopyOfGridState();
            newGridState[x][y] = input;

            gameData = new SudokuGame(
                    GameLogic.checkForCompletion(newGridState),
                    newGridState
            );

            storage.updateGameData(gameData);

            view.updateSquare(x, y, input);

            if (gameData.getGameState() == GameState.COMPLETE) {
                view.showDialog (Messages.GAME_COMPLETE);
            }

        } catch (IOException e){
            e.printStackTrace();
            view.showError(Messages.ERROR);
        }
    }

    @Override
    public void onDialogClick() {
        try {
            storage.updateGameData(
                    GameLogic.getNewGame()
            );

            view.updateBoard(storage.getGameData());
        } catch (IOException e) {
            view.showError(Messages.ERROR);
        }
    }
}

Метод getGameData() зовётся здесь:

package sudoku.problemdomain;

import java.io.IOException;

public interface IStorage {
    void updateGameData (SudokuGame game) throws IOException;
    SudokuGame getGameData () throws IOException;
}

Далее не разбираюсь

Вот весь код: https://github.com/shodmon/JavaDesktopSudokuDemo