Converted ChaosGameObserver to an interface.

src/main/java/edu/ntnu/stud/chaosgame/controller/ChaosGameObserver.java

 package edu.ntnu.stud.chaosgame.controller;
 
 import edu.ntnu.stud.chaosgame.model.game.ChaosCanvas;
+import edu.ntnu.stud.chaosgame.model.game.ChaosGame;
 import edu.ntnu.stud.chaosgame.model.game.ChaosGameDescription;
 
 /**
- * Observer class for monitoring changes to the active
- * ChaosGameDescription {@link ChaosGameDescription} or the canvas {@link ChaosCanvas}
+ * Observer interface for monitoring changes to the active
+ *
  */
-public class ChaosGameObserver {
-// TODO: Create class
+public interface ChaosGameObserver {
+// TODO: Create interface
+
+  /**
+   * Perform update
+   */
+  void update(ChaosGame game);
 }

src/main/java/edu/ntnu/stud/chaosgame/model/game/ChaosGame.java

 package edu.ntnu.stud.chaosgame.model.game;
 
+import edu.ntnu.stud.chaosgame.controller.ChaosGameObserver;
 import edu.ntnu.stud.chaosgame.model.data.Vector2D;
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Random;
 
 /**
@@ -19,9 +22,9 @@ public class ChaosGame {
   private ChaosGameDescription description;
 
   /**
-   * The description for this ChaosGame
+   * Observers monitoring this ChaosGame.
    */
-  // private ChaosGameDescription description;
+ private ArrayList<ChaosGameObserver> observers;
 
   /**
    * The current point in the chaos game.
@@ -38,6 +41,11 @@ public class ChaosGame {
    */
   private int numOfTransforms;
 
+  /**
+   * Basic parameterised constructor.
+   * @param description the ChaosGameDescription.
+   * @param canvas the ChaosCanvas.
+   */
   public ChaosGame(ChaosGameDescription description, ChaosCanvas canvas) {
     this.canvas = canvas;
     this.description = description;
@@ -46,6 +54,21 @@ public class ChaosGame {
     this.currentPoint = new Vector2D(0, 0);
   }
 
+  /**
+   * Parameterised constructor with observers
+   * @param description the ChaosGameDescription.
+   * @param canvas the ChaosCanvas.
+   * @param observers the ChaosGameObservers to be added.
+   */
+  public ChaosGame(ChaosGameDescription description, ChaosCanvas canvas, ChaosGameObserver... observers) {
+    this.canvas = canvas;
+    this.description = description;
+    this.random = new Random();
+    this.numOfTransforms = description.getTransforms().size();
+    this.currentPoint = new Vector2D(0, 0);
+    this.observers.addAll(Arrays.asList(observers));
+  }
+
   /**
    * Get the canvas of this chaos game.
    * @return the canvas.