【说明】一条直线是由两个点组成的,代码如下。 public class Point { private int x, y; //coordinate public Point (int x, int y) { (1) =x; (2) ;} public int GetX() { return x; } public int GetY() { return y; } } class Line //line segment { private (3) ; //extremc points Line (Point a, Point b)//constructor { p1 = (4) ;p2= (5) ; } public double Length() { return Math.sqrt (Math.pow (p2.GetX()-pl.GetX(),2)+Math.pow (p2.GetY()-p1.GetY(),2)) ; } }