Problems finding the interception point of two lines

Question

Hi there,
I've written a class "Linie", which extends the Line2D.Float class, and added a method to determine the interception point of two lines.
One of the two lines can be anything except horizontal and vertical, the other one (which is the one that is passed to the method) can only be horizontal or vertical (I hoped this would make it easier).
public Point schneidet(Linie l){
          Point schnitt = new Point();
          float m = (y1-y2)/(x1-x2);
          int n = Math.round(y1-(x1*m));
          if (l.y1==l.y2){               // Is line l horizontal?
               int poX = Math.round((l.y1-n)/m);
               schnitt.setLocation(poX,(int)l.y1);
          else if (l.x1==l.x2){               // Is line l vertical?
               int poY = Math.round((m*l.x1)+n);
               schnitt.setLocation((int)l.x1,poY);
          return schnitt;
     }The equation of a line is
y = m*x + n.
Because the line l can only be horizontal or vertical, one coordinate of the interception point is always clear from the beginning, the other one is supposed to be calculated and stored in poX or poY.
But this is where the method doesn't do what it's supposed to. There must be some mistake inside the calculation with the slope (m) and n. Any ideas?

Answer 1

Why so complicated? Are the lines real lines (straight connections between 2 points) or curves? If they are lines, you just need to inspect the coordinates of all 4 points (2 * 2 end points) and show if the points are "within" the other points ...
Intersection point of two lines
Line Intersection and its Applications
SIMPLE ALGORITHMS I - INTERSECTION OF LINES