Point3D继承Point2D，实例化两个2D、两个3D点，并随机打印2D或3D点 Point3D继承Point2D，实例化两个2D、两个3D点，并随机打印2D或3D点Point3D继承Point2D，实例化两个2D、两个3D点，并随机打印2D或3D点-//Write a program that implements the concept of an abstract class.)