All code is correct but there are two methods below in red where you need to do the logic for the game. Basically, checking the board to see if anyone has won and if there are more spaces to be selected.

import javax.swing.*; import java.awt.geom.*; import java.awt.*; import java.awt.event.*; import java.awt.Color; public class TicTacToe extends JPanel implements ActionListener { JLabel greeting = new JLabel("Tic Tac Toe"); JLabel promptLabel = new JLabel("Choose one button"); JLabel result = new JLabel(); Font headlineFont = new Font("Helvetica", Font.BOLD, 20); Font mediumFont = new Font("Helvetica", Font.BOLD, 14); final int SIZE = 9; final static int ROW_SIZE = 3; final static int COL_SIZE = 3; int x, y; JButton[][] gameGrid = new JButton[ROW_SIZE][COL_SIZE]; final static String BLANK = " "; final static String XString = "X"; final static String OString = "O"; int row = 0, col = 0; int num; boolean spotFound; boolean isDone = false; boolean playersTurn = true; boolean isWinPossible = false; String msg = ""; String gridString; char winChar; public static boolean checkForWinner(JButton [][] gameGrid) { boolean isDone = false; // Your code goes here //The code to check for winners needs to be implemented //checkForWinner returns a boolean value representing a winner or not return isDone; } public static boolean spacesRemain(JButton[][] grid) { // Your code goes here // spacesRemain returns a boolean value indicating that there are stillDigitsLeft // spaces to be selected. return stillDigitsLeft; } public static void chooseSpot(JButton[][] gameGrid) { int x, y; boolean placementMade = false; for(x = 0; x < ROW_SIZE && !placementMade; ++x) { if(gameGrid[x][0].getText().equals(OString) && gameGrid[x][1].getText().equals(OString) && gameGrid[x][2].getText().equals(BLANK)) { gameGrid[x][2].setText(OString); placementMade = true; } else if(gameGrid[x][0].getText().equals(OString) && gameGrid[x][2].getText().equals(OString) && gameGrid[x][1].getText().equals(BLANK)) { gameGrid[x][1].setText(OString); placementMade = true; } else if(gameGrid[x][1].getText().equals(OString) && gameGrid[x][2].getText().equals(OString) && gameGrid[x][0].getText().equals(BLANK)) { gameGrid[x][0].setText(OString); placementMade = true; } } for(y = 0; y < COL_SIZE && !placementMade; ++y) { if(gameGrid[0][y].getText().equals(OString) && gameGrid[1][y].getText().equals(OString) && gameGrid[2][y].getText().equals(BLANK)) { gameGrid[2][y].setText(OString); placementMade = true; } else if(gameGrid[0][y].getText().equals(OString) && gameGrid[2][y].getText().equals(OString) && gameGrid[1][y].getText().equals(BLANK)) { gameGrid[1][y].setText(OString); placementMade = true; } else if(gameGrid[1][y].getText().equals(OString) && gameGrid[2][y].getText().equals(OString) && gameGrid[0][y].getText().equals(BLANK)) { gameGrid[0][y].setText(OString); placementMade = true; } } if(!placementMade) if(gameGrid[0][0].getText().equals(OString) && gameGrid[1][1].getText().equals(OString) && gameGrid[2][2].getText().equals(BLANK)) { gameGrid[2][2].setText(OString); placementMade = true; } else if(gameGrid[0][0].getText().equals(OString) && gameGrid[2][2].getText().equals(OString) && gameGrid[1][1].getText().equals(BLANK)) { gameGrid[1][1].setText(OString); placementMade = true; } else if(gameGrid[2][2].getText().equals(OString) && gameGrid[1][1].getText().equals(OString) && gameGrid[0][0].getText().equals(BLANK)) { gameGrid[0][0].setText(OString); placementMade = true; } else if(gameGrid[0][2].getText().equals(OString) && gameGrid[1][1].getText().equals(OString) && gameGrid[2][0].getText().equals(BLANK)) { gameGrid[2][0].setText(OString); placementMade = true; } else if(gameGrid[0][2].getText().equals(OString) && gameGrid[2][0].getText().equals(OString) && gameGrid[1][1].getText().equals(BLANK)) { gameGrid[1][1].setText(OString); placementMade = true; } else if(gameGrid[1][1].getText().equals(OString) && gameGrid[2][0].getText().equals(OString) && gameGrid[0][2].getText().equals(BLANK)) { gameGrid[0][2].setText(OString); placementMade = true; } if(!placementMade) { while(!placementMade) { placementMade = true; int num = (int)((Math.random() * 100) % 9); x = num / 3; y = num % 3; if(!gameGrid[x][y].getText().equals(BLANK)) placementMade = false; } gameGrid[x][y].setText(OString); } } public TicTacToe() { greeting.setFont(headlineFont); add(greeting); promptLabel.setFont(mediumFont); add(promptLabel); for(x = 0; x < ROW_SIZE; ++x) for(y = 0; y < COL_SIZE; ++y) { gameGrid[x][y] = new JButton(); gameGrid[x][y].setText(BLANK); add(gameGrid[x][y]); gameGrid[x][y].addActionListener(this); } add(result); } @Override public void actionPerformed(ActionEvent e) { isDone = false; Object squareChosen = e.getSource(); for(x = 0; x < ROW_SIZE; ++x) for(y = 0; y < COL_SIZE; ++y) if(squareChosen == gameGrid[x][y]) { row = x; col = y; x = ROW_SIZE; y = COL_SIZE; } if(gameGrid[row][col].getText().equals(XString) || gameGrid[row][col].getText().equals(OString)) { msg = "That position is already taken "; } else { gameGrid[row][col].setText(XString); msg = ""; isDone = checkForWinner(gameGrid); msg = ""; if(isDone) { msg = "You win! "; winChar = 'x'; } else if(!spacesRemain(gameGrid)) { isDone = true; msg = " Tie game"; winChar = 't'; } if(isDone) result.setText("Game over! " + msg); else { chooseSpot(gameGrid); isDone = checkForWinner(gameGrid); if(isDone) { result.setText("Sorry - you lose"); winChar = 'o'; } } } if(isDone) repaint(); } @Override public void paintComponent(Graphics gr) { super.paintComponent(gr); float startx = 30f; float starty = 210f; float width = 50f; float height = 50f; Graphics2D g = (Graphics2D)gr; BasicStroke aStroke = new BasicStroke(6.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND); g.setStroke(aStroke); g.setColor(Color.BLUE); if(winChar == 'x') { g.draw(new Line2D.Float(startx, starty, startx + width, starty + height)); g.draw(new Line2D.Float(startx, starty + height, startx + width, starty)); } else if(winChar == 'o') { g.draw(new Ellipse2D.Float(startx, starty, width, height)); } else if(winChar == 't') { g.draw(new Line2D.Float(startx, starty, startx + width, starty + height)); g.draw(new Line2D.Float(startx, starty + height, startx + width, starty)); g.setColor(Color.RED); g.draw(new Ellipse2D.Float(startx, starty, width, height)); } } public static void main(String[] args) { JFrame frame = new JFrame(); frame.add(new TicTacToe()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(300, 300); frame.setVisible(true); } }