import java.io.*;import javax.swing.*;import java.awt.*;public class Sudoku { public JFrame sudokuGui = new JFrame(); public JButton[][] squares; public void createGui() { squares[0][0] = new JButton("Test"); sudokuGui.setTitle("Sudokuuuuuu"); sudokuGui.setSize(400,400); sudokuGui.setVisible(true); sudokuGui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); sudokuGui.setLayout(new GridLayout(3,3)); sudokuGui.add(squares[0][0]); } public Sudoku() { createGui(); } public static void main(String[] args) { Sudoku test = new Sudoku(); }}