import javax.swing.*;
import java.util.ArrayList;

public class Window extends JFrame {
    private ArrayList<ArrayList<JButton>> fields = new ArrayList<>();
    private JButton start = new JButton("start");

    void gameSetup() {
        start.setVisible(false);
        for(int i = 0; i < 9; i++) {
            fields.add(new ArrayList<>());
            for(int j = 0; j < 9; j++) {
                fields.get(i).add(new JButton("A"));
                fields.get(i).get(j).setBounds(j*50, i*50, 49, 49);
                fields.get(i).get(j).setVisible(true);

                add(fields.get(i).get(j));
                System.out.println(i + " " + j);
            }
        }
    }

    Window() {
        super("GUI");
        setSize(500, 500);

        setLayout(null);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setVisible(true);

        start.setBounds(100, 100, 200, 30);

        add(start);

        start.addActionListener(e -> {
            gameSetup();
        });
    }
}