Hi,

I am trying to create an inner class, its something that Ive never done
before, but I did a Google search and found some information on it, Ive
coded something that I think should work, but I dont know if Ive gone the
right way around it.

Please find the code below. It compiles fine, but I get a
NullPointerException when I do the check for if(point1.getY() <
point2.getY()). For some reason both of the points are null, I know for sure
that the ArrayList poly that I get the Points from are not null, so all I
can think is that it is something to do with the way I have coded the inner
class.

Thanks for your help,

Paul Morrison

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public class AETFillAlgorithm extends AbstractScanlineFillAlgorithm {
   ArrayList edgeTable = new ArrayList();

 AETFillAlgorithm(String n, App a, DrawingArea d) {
   super(n, a, d);
 }

 public class Edge{
     Point point1;
     Point point2;

     Edge(Point point1, Point point2) {
         point1 = this.point1;
         point2 = this.point2;
     }

     public Point getPoint1() {
         return point1;
     }

     public Point getPoint2() {
         return point2;
     }

     public ArrayList addEdgeToStore(Edge edge) {
         //get ymin
         ArrayList temp = new ArrayList();
         Point point1 = edge.getPoint1();
         Point point2 = edge.getPoint2();
         if(point1.getY() < point2.getY())   *** This is where the
NullPointerException is thrown.
             temp.add(point1.getY());
         else
             temp.add(point2.getY());

         //get ymax
         if(point1.getY() > point2.getY())
             temp.add(point1.getY());
         else
             temp.add(point2.getY());

         //get xvalue associated with ymin
         if(point1.getY() < point2.getY())
             temp.add(point1.getX());
         else
             temp.add(point2.getX());

         //get 1/m value
         double m = (point1.getY() - point2.getY()) / point1.getX() -
point2.getX();
         temp.add(1/m);

         return temp;
     }
 }

 void fillPoly(Color lineColor, Color fillColor, List<Point> poly) {
     for(int i = 0; i < poly.size() - 1; i++) {
         Point one = (Point) poly.get(i);
         Point two = (Point) poly.get(i+1);
         Edge edge = new Edge(one, two);
         edgeTable.add(edge.addEdgeToStore(edge));
     }
     Edge edge = new Edge(poly.get(0), poly.get(poly.size()-1));
     edgeTable.add(edge.addEdgeToStore(edge));
 }
}