编写程序建模二维平面坐标系中的直线，并提供函数实现判断两条直线是否相交。此题目要求提供多种构造函数。（练习设计类与构造函数）-Programming modeling of two-dimensional coordinate system lines, and provides functions to achieve determine whether two lines intersect. This topic requires a variety of constructors. (Exercises designed classes and constructors)