// Textbook fragment 03.11
  /** Returns a simple character string showing the current board */
  public String toString() {
    String s = "";
    for (int i=0; i<3; i++) {
      for (int j=0; j<3; j++) {
        switch (board[i][j]) {
        case X:         s += "X"; break;
        case O:         s += "O"; break;
        case            EMPTY: s += " "; break;
        }
        if (j < 2) s += "|";                    // column boundary
      }
      if (i < 2) s += "\n-----\n";              // row boundary
    }
    return s;
  }
  /** Test run of a simple game */
  public static void main(String[] args) {
    TicTacToe game = new TicTacToe();
    /* X moves: */              /* O moves: */
    game.putMark(1,1);          game.putMark(0,2);
    game.putMark(2,2);          game.putMark(0,0);
    game.putMark(0,1);          game.putMark(2,1);
    game.putMark(1,2);          game.putMark(1,0);
    game.putMark(2,0);
    System.out.println(game.toString());
    int winningPlayer = game.winner();
    if (winningPlayer != 0)
      System.out.println(winningPlayer + " wins");
    else
      System.out.println("Tie");
  }
}