Forum: Nullpointer exvept, java problem?

import java.util.ArrayList;
import java.util.Iterator;
import se.lth.cs.ptdc.window.SimpleWindow;
import se.lth.cs.ptdc.shapes.Shape;
 
public class Circle extends Shape{
 
	public ArrayList<Point> collisionList;
	private int radian;
 
	public Circle(int x, int y, int radian){
		super(x,y);
		this.radian = radian;
		makeCollisionList();
	}
	/**
        * Ritar upp Cirkeln i fönstret w
        **/
	public void draw(SimpleWindow w){
		Iterator<Point> colIt = collisionList.iterator();
		while (colIt.hasNext()){
			w.lineTo(colIt.next().getX(), colIt.next().getY());
		}
 
 
	}
	/**
        *gör en kollisionslista
         **/
	private void makeCollisionList(){
		int dir = 0;
		int startX = x;
		int startY = y;
		calculateXY(radian, dir, startX, startY);
		while (dir <= 361){
			collisionList.add(new Point(x,y));
			calculateXY(radian, dir, startX, startY);
			dir++;
		}
 
	}
 
        /**
       * Räknar ut nästa punkts positioner i cirkeln
        **/
	private void calculateXY(int n, int dir, int startX, int startY) {
		double radians = Math.toRadians(dir);
		x = startX +(int) Math.round(n * Math.cos(radians));
		y = startY + (int) Math.round(n * Math.sin(radians));
 
	}
}

while(iterator.hasNext()){
    iterator.next().draw();
}

public ArrayList<Point> collisionList; // collisionList initieras till null

collisionList.add(...  // Yikes, NullPointerException

private ArrayList<Point> collisionList = new ArrayList();

public Circle() {
    collisionList = new ArrayList();