Design and code a Swing GUI for a two-player tic-tac-toe game on a 3 by 3 game board. The JFrame should use a BorderLayout with a JLabel in the NORTH region to display messages (e.g. who won the game), and a JPanel in the CENTER region to display the game board. For the game board in the JPanel, use a GridLayout manager with a 3 by 3 layout of JButtons in each cell to display the game board. The button labels should initially be blank. When a player clicks on an empty button an appropriate "X" or "O" should be placed in the label field of the button. If there is a winner (three in a row) then the program should display the winner in the JLabel located at the top of the window. If all nine cells have been filled without a winner the program should indicate that there was a tie.

The declaration of the TicTacToe class specifies that it implements the ActionListener method. You should provide an implementation of the method:

public void actionPerformed(ActionEvent evt) {
// ...
}
that handles checking for a tie or winner on clicking a button.
Make sure that your implementation correctly handles the case where the user clicks a button for a cell that already contains an X or O.
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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
* Simple tic-tac-toe application.
*/
public class TicTacToe extends JFrame implements ActionListener {
// --------------------------------
// ----- ENTER YOUR CODE HERE -----
// --------------------------------

// --------------------------------
// --------- END USER CODE --------
// --------------------------------
public static void main(String[] args) {
TicTacToe ttt = new TicTacToe();
ttt.setSize(400, 400);
ttt.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ttt.setVisible(true);
}
}