private void putChecker(int player, int column) {
        if ((column < -1) || (column > NUM_POINTS)) {
            System.err.println("Error, out of range.");
        } else {
            int p_type = pType(player);
            if (column==-1 || column==NUM_POINTS) {
                in_home[player]++;
            } else if (p_type * board[column] >= 0) {
                board[column] += p_type;
            } else if (board[column] == -p_type) {
                board[column] = p_type;
                on_bar[((player+1) % 2)]++;
            } else {
                System.err.println("Error, too many opponent pieces at this locations.");
            }
        }
        
    }