设计一个描述二维平面上点的类Position，该类需要描述点的横坐标和纵坐标，并提供访问器方法（set方法和get方法）和计算两点间距离的方法。写一个程序测试这个类-Design of a two-dimensional plane descr iption class Position point, the class needs to describe the point of abscissa and ordinate and provide accessor methods (set a