计算三角形的面积和周长，要求如下：

（1）设计出point类（点类）

（2）设计出triangle类(三角形类)，至少包括其构造方法，获取面积和周长的方法。

（3）通过输入三点坐标的方法来确定一个三角形，并输出三角形的面积周长等内容。

-Calculate the area and perimeter of triangles, requirements are as follows: (1) design point class (point) (2) design triangle class (triangle), including at least the constructor for area and perimeter. (3) Three-point coordinates to determine a triangle, and to output the contents of the area of ​ ​ the triangle perimeter.