将笛卡尔坐标系上的点定义为一个服务类point，point类求坐标系上两点间的距离。设计测试point服务类的应用程序主类，显示输出已创建对象间的距离。(The point on the Descartes coordinate system is defined as a service class point, and the point class is used to find the distance between two points in the coordinate system. Design the main class of the application class for testing the point service class, showing the distance between the objects that have been created.)