The following code compiled fine under Processing 00135, but it fails with a NullPointerException in 1.0.1.

It fails in the following code around the second "n.applyForce(f);"

Any ideas what could be the problem?

-- Ian


void doLayout() {
 
 //calculate forces on each node
 //calculate spring forces on each node
 for (int i=0; i<g.getNodes().size(); i++) {
   ForcedNode n = (ForcedNode)g.getNodes().get(i);
   ArrayList edges = (ArrayList)g.getEdgesFrom(n);
   n.setForce(new Vector3D(0,0,0));
   for (int j=0; edges != null && j<edges.size(); j++) {
     SpringEdge e = (SpringEdge)edges.get(j);
     Vector3D f = e.getForceFrom();
     n.applyForce(f);
   }
   
   edges = (ArrayList)g.getEdgesTo(n);
   for (int j=0; edges != null && j<edges.size(); j++) {
     SpringEdge e = (SpringEdge)edges.get(j);
     Vector3D f = e.getForceTo();
     n.applyForce(f);
   }
   
 }
 
 
 
 //calculate the anti-gravitational forces on each node
 //this is the N^2 shittiness that needs to be optimized
 //TODO: at least make it N^2/2 since forces are symmetrical
 for (int i=0; i<g.getNodes().size(); i++) {
   ForcedNode a = (ForcedNode)g.getNodes().get(i);
   for (int j=0; j<g.getNodes().size(); j++) {
     ForcedNode b = (ForcedNode)g.getNodes().get(j);
     if (b != a) {
       float dx = b.getX() - a.getX();
       float dy = b.getY() - a.getY();
       float r = sqrt(dx*dx + dy*dy)/0.25;
       //F = G*m1*m2/r^2
       
       if (r != 0) { //don't divide by zero.
         float f = 100*(a.getMass()*b.getMass()/(r*r));
         Vector3D vf = new Vector3D(-dx*f, -dy*f, 0);
         a.applyForce(vf);
       }              
     }
   }
 }
 
 // Calculate the repulsive forces on each node
 // from the edge of the screen
 for (int i=0; i<g.getNodes().size(); i++) {
   
   ForcedNode a = (ForcedNode)g.getNodes().get(i);
   
   ForcedNode[] screenEdge = new ForcedNode[4];
   screenEdge[0] = new ForcedNode(new Vector3D(a.getX(), -500, 0));
   screenEdge[1] = new ForcedNode(new Vector3D(a.getX(), width + 500, 0));
   screenEdge[2] = new ForcedNode(new Vector3D(-500, a.getY(), 0));
   screenEdge[3] = new ForcedNode(new Vector3D(height + 500, a.getY(), 0));
   
   for (int j = 0; j < screenEdge.length; j++)
   {
       screenEdge[j].setMass(a.getMass() * (600/(a.getMass())));
       float dx = screenEdge[j].getX() - a.getX();
       float dy = screenEdge[j].getY() - a.getY();
       float r = sqrt(dx*dx + dy*dy)/0.25;
       //F = G*m1*m2/r^2  
       
       if (r != 0) { //don't divide by zero.
         float f = 100*(a.getMass()*screenEdge[j].getMass()/(r*r));
         Vector3D vf = new Vector3D(-dx*f, -dy*f, 0);
         a.applyForce(vf);
       }
   }
   
 }
 
 //move nodes according to forces
 for (int i=0; i<g.getNodes().size(); i++) {
   ForcedNode n = (ForcedNode)g.getNodes().get(i);
   if (n != g.getDragNode()) {
     n.setPosition(n.getPosition().add(n.getForce()));
     if (n.getPosition().getX() > width)
       n.getPosition().setX(width - 10);
     if (n.getPosition().getX() < 0)
       n.getPosition().setX(10);
     if (n.getPosition().getY() > height)
       n.getPosition().setY(height - 10);
     if (n.getPosition().getY() < 0)
       n.getPosition().setY(10);
   }
 }
}