public boolean placeBall(int player, int row, int column){
        if(row>=0 && column>=0 && player>0 && row<size && column<size){
            if(fields[row][column]==0){
                fields[row][column]=player;
                notifyBoardListeners(player, new Point(row, column));
                return true;
            } else {
                return false;
            }
        } else {
            return false;
        }
    }