private boolean colTie() {
    boolean[] tied = { false, false, false };
    for (int col = 0; col < TicTacToeFrame.COLS; col++) {
        TicTacToeButton button1 = buttons[col][0];
        TicTacToeButton button2 = buttons[col][1];
        TicTacToeButton button3 = buttons[col][2];
        if (button1.state() == State.X && (button2.state() == State.O || button3.state() == State.O)) {
            tied[col] = true;
        }
        if (button2.state() == State.X && (button1.state() == State.O || button3.state() == State.O)) {
            tied[col] = true;
        }
        if (button3.state() == State.X && (button1.state() == State.O || button2.state() == State.O)) {
            tied[col] = true;
        }
    }
    return (tied[0] && tied[1] && tied[2]);
}