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Nils Christian Svihus

Here is a TicTacToe applet/application hybrid.
It runs as an applet in a browser and as an application when launched from the command prompt.

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

/**
 * A tictactoe button
 */
class TTTBtn extends JButton {
  private int btnNo=-1;
  private boolean hit=false;
  private int value=-1;
  public TTTBtn (int btnNo) {
    super();
    this.btnNo=btnNo;
  }
  public void setHit (boolean p1p2) {
    super.setText(p1p2 ? "X" : "O");
    value= p1p2 ? 1 : 4;
  }
  public int getValue() {
    return value;
  }
  public boolean isHit () {
    return value > 0;
  }
  public void reset() {
    setText("");
    value=-1;
  }
  public int getButtonNo () {
    return btnNo;
  }
}
/**
 * A tictactoe applet
 */
public class TicTacToe
    extends JApplet
    implements ActionListener {

  JLabel messagesLabel = new JLabel("X goes first");
  JPanel displayPanel = new JPanel(new GridLayout(3, 3));
  private TTTBtn[] bb = new TTTBtn[9];
  private int [][] winLine={
      {0,1,2}, // horizontal
      {3,4,5},
      {6,7,8},
      {0,3,6}, // vertical
      {1,4,7},
      {2,5,8},
      {0,4,8}, // diagonal
      {6,4,2}
  };
  private JButton resetBtn=new JButton("Reset");
  private boolean player1 = true;

  public void init() {
    messagesLabel.setOpaque(true);
    messagesLabel.setHorizontalAlignment(SwingConstants.CENTER);
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(messagesLabel, BorderLayout.NORTH);
    getContentPane().add(resetBtn, BorderLayout.SOUTH);
    getContentPane().add(displayPanel, BorderLayout.CENTER);

    resetBtn.addActionListener(this);

    for (int i = 0; i < 9; i++) {
      bb[i] = new TTTBtn(i);
      bb[i].addActionListener(this);
      displayPanel.add(bb[i]);
    }

  }
  public int getWinner() {
    for (int i=0; i<winLine.length; i++) {
      int ret = lineWin(winLine[i]);
      if (ret > 0) return ret;
    }
    return -1;
  }
  private int lineWin(int [] pos) {
    int sum=
        bb[pos[0]].getValue()+
        bb[pos[1]].getValue()+
        bb[pos[2]].getValue();
    if (sum==3) return 1;
    if (sum==12) return 2;
    return -1;
  }
  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == resetBtn) {
      resetGame();
    }
    else if (e.getSource()instanceof TTTBtn) {
      TTTBtn btn = (TTTBtn) e.getSource();
      if (!btn.isHit()) {
        if (haveWinner(btn)) {
          enableButtons(false);
        }
      }
    }
  }

  private void enableButtons(boolean enabled) {
    for (int i=0; i<bb.length; i++) {
      bb[i].setEnabled(enabled);
    }
  }

  private boolean haveWinner(TTTBtn btn) {
    bb[btn.getButtonNo()].setHit(player1);
    int winner = getWinner();
    if (winner > 0) {
      messagesLabel.setBackground(Color.green);
      messagesLabel.setText("Player " + winner + " wins");
      return true;
    }
    else {
      player1 = !player1;
      return false;
    }
  }

  private void resetGame() {
    for (int i=0; i<bb.length; i++) {
      bb[i].reset();
    }
    player1=true;
    messagesLabel.setBackground(Color.lightGray);
    messagesLabel.setText("X goes first");
    enableButtons(true);
  }
  /**
   * Test driver main
   */
  public static void main(String[] args) {
    JFrame f=new JFrame("Tic Tac Toe");
    f.getContentPane().setLayout(new GridLayout());
    TicTacToe ttt=new TicTacToe();
    f.getContentPane().add(ttt);
    f.addWindowListener(new WindowAdapter() {
      public void windowClosed(WindowEvent e) {
        System.exit(0);
      }
    });
    ttt.init();
    f.setBounds(100,100,300,270);
    f.setVisible(true);
  }
}