直线 $$\begin{gathered} \left\{x=2+t \\ y=-1-t\right\}\left(t\mathrm{为参数}\right) \end{gathered}$$与曲线 $$\begin{gathered} \left\{x=3\cos \alpha \\ y=3\sin \alpha \right\}\left(\alpha \mathrm{为参数}\right) \end{gathered}$$的交点个数为.