Игра "Пятнашки"

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
public class App extends JFrame {
private JPanel panel = new JPanel(new GridLayout(4, 4, 2, 2));
private int[][] numbers = new int[4][4];
public App() {
super("Help");
setBounds(200, 200, 300, 300);
setResizable(false);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
Container container = getContentPane();
panel.setDoubleBuffered(true);
container.add(panel);
rundombutton();
repaintField();
createMenu();
}
public void rundombutton()
{
Random generator = new Random();
int[] invariants = new int[16];
do {
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
numbers[i][j] = 0;
invariants[i * 4 + j] = 0;
}
}
for (int i = 1; i < 16; i++) {
int k, l;
do {
k = generator.nextInt(4);
l = generator.nextInt(4);
}
while (numbers[k][l] != 0);
numbers[k][l] = i;
invariants[k * 4 + l] = i;
}
}
while (!canBeSolved(invariants));
}
private boolean canBeSolved(int[] invariants) {
int sum = 0;
for (int i = 0; i < 16; i++) {
if (invariants[i] == 0) {
sum += i / 4;
continue;
}
for (int j = i + 1; j < 16; j++) {
if (invariants[j] < invariants[i])
sum ++;
}
}
System.out.println(sum % 2 == 0);
return sum % 2 == 0;
}
public void repaintField() {
panel.removeAll();
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
JButton button = new JButton(Integer.toString(numbers[i][j]));
button.setFocusable(false);
panel.add(button);
if (numbers[i][j] == 0) {
button.setVisible(false);
} else
button.addActionListener(new ClickListener());
}
}
panel.validate();
panel.repaint();
}
public boolean checkWin() {
boolean status = true;
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
if (i == 3 && j > 2)
break;
if (numbers[i][j] != i * 4 + j + 1) {
status = false;
}
}
}
return status;
}
private void createMenu() {
JMenuBar menu = new JMenuBar();
JMenu fileMenu = new JMenu("Файл");
for (String fileItem : new String [] { "Новая игра", "Выход" }) {
JMenuItem item = new JMenuItem(fileItem);
item.setActionCommand(fileItem.toLowerCase());
item.addActionListener(new NewMenuListener());
fileMenu.add(item);
}
fileMenu.insertSeparator(1);
menu.add(fileMenu);
setJMenuBar(menu);
}
private class NewMenuListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if ("выход".equals(command)) {
System.exit(0);
}
if ("новая игра".equals(command)) {
rundombutton();
repaintField();
}
}
}
private class ClickListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JButton button = (JButton) e.getSource();
button.setVisible(false);
String name = button.getText();
change(Integer.parseInt(name));
}
}
public void change(int num) {
int i = 0, j = 0;
for (int k = 0; k < 4; k++) {
for (int l = 0; l < 4; l++) {
if (numbers[k][l] == num) {
i = k;
j = l;
}
}
}
if (i > 0) {
if (numbers[i - 1][j] == 0) {
numbers[i - 1][j] = num;
numbers[i][j] = 0;
}
}
if (i < 3) {
if (numbers[i + 1][j] == 0) {
numbers[i + 1][j] = num;
numbers[i][j] = 0;
}
}
if (j > 0) {
if (numbers[i][j - 1] == 0) {
numbers[i][j - 1] = num;
numbers[i][j] = 0;
}
}
if (j < 3) {
if (numbers[i][j + 1] == 0) {
numbers[i][j + 1] = num;
numbers[i][j] = 0;
}
}
repaintField();
if (checkWin()) {
JOptionPane.showMessageDialog(null, "ВЫ ВЫИГРАЛИ!", "ПОЗДРАВЛЯЮ!", JOptionPane.INFORMATION_MESSAGE);
rundombutton();
repaintField();
}
}
 public static void main(String[] args) {
JFrame app = new App();
app.setVisible(true);
}
}