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，至少包括其构造方法，以及获取面积和周长的方法等。



（3）通过输人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。-Calculation of area and perimeter of triangles, the following: (1) design point type (point type). (2) triangle-type design, including its structure, at least, as well as access to the area and perimeter of the methods. (3) through the three input methods to determine the coordinates of a triangle, and the output of the triangle area, perimeter and so on.