Java Tic Tac Toe Tutorial With Source Code

/*
Java Tic-Tac-Toe
By: Garrett Mickley
*/

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TicTacToe implements ActionListener 
{
        //Variables
        private int[][] winCombinations = new int[][] //Possible win combinations
        {
            {0, 1, 2}, {3, 4, 5}, {6, 7, 8}, //Horizontal
            {0, 3, 6}, {1, 4, 7}, {2, 5, 8}, //Vertical
            {0, 4, 8}, {2, 4, 6}             //Diagonal
        };
        private JFrame frame = new JFrame("Garrett's Tic Tac Toe Game");
        private JButton buttons[] = new JButton[9];
        private int count = 0;
        private int xscore = 0;
        private int oscore = 0;
        private String letter = "";
        private boolean win = false;
        private Icon xicon;
        private Icon oicon;

        //Game stuff starts here
        public H4_TicTacToe()
        {
        
            //Create window
            frame.setSize(500,500);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLayout(new GridLayout(3,3));
            frame.setLocation(300,200);
            xicon = new ImageIcon(getClass().getResource("xicon.png"));
            oicon = new ImageIcon(getClass().getResource("oicon.png"));
        
            //Window buttons
            for(int i=0; i<=8; i++)
            {
                buttons[i] = new JButton();
                frame.add(buttons[i]);
                buttons[i].addActionListener(this);
            }
        
            //Window visiblity
            frame.setVisible(true);
        }
        
        //User input stuff starts here
        public void actionPerformed(ActionEvent a) 
        {
                count++;
                
                //Who's turn
                if(count % 2 == 0)
                {
                    letter = "O";
                    oscore++;
                }
                else 
                {
                    letter = "X";
                    xscore++;
                }

                //Change button to letter
                if(letter == "X")
                {
                    JButton pressedButton = (JButton)a.getSource();
                    pressedButton.setText(letter);
                    pressedButton.setIcon(xicon);
                    pressedButton.setEnabled(false);
                }
                else if(letter == "O")
                {
                    JButton pressedButton = (JButton)a.getSource();
                    pressedButton.setText(letter);
                    pressedButton.setIcon(oicon);
                    pressedButton.setEnabled(false);
                }
                
                //Who won
                for(int i=0; i<=7; i++)
                {
                    if( buttons[winCombinations[i][0]].getText().equals(buttons[winCombinations[i][1]].getText()) && 
                        buttons[winCombinations[i][1]].getText().equals(buttons[winCombinations[i][2]].getText()) && 
                        buttons[winCombinations[i][0]].getText() != "")
                    {
                        win = true;
                    }
                }
                
                //Dialog for end of game
                if(win == true)
                {
                    JOptionPane.showMessageDialog(null, letter + " wins the game! Player X made " + xscore + " moves and player O made " + oscore + " moves!");
                    System.exit(0);
                }
                else if(count == 9 && win == false)
                {
                    JOptionPane.showMessageDialog(null, "It's a tie! There is no winner. Player X made " + xscore + " moves and player O made " + oscore + " moves!");
                    System.exit(0);
                }               
        }
        
        public static void main(String[] args)
        {
            JOptionPane.showMessageDialog(null,"Welcome to Garrett's Tic Tac Toe Game! Player X is first.");
            H4_TicTacToe starter = new H4_TicTacToe();
        }
}