Created a simple collision detection by iterating each boats per update. Working but sequential checks can be costly.

#story[1117]

src/main/java/seng302/model/Yacht.java

@@ -14,6 +14,7 @@ import javafx.beans.property.ReadOnlyLongWrapper;
 import javafx.scene.paint.Color;
 import seng302.gameServer.GameState;
 import seng302.model.mark.CompoundMark;
+import seng302.utilities.GeoUtility;
 
 /**
  * Yacht class for the racing boat.
@@ -110,7 +111,15 @@ public class Yacht {
         }
 
         Double metersCovered = velocity * secondsElapsed;
-        location = getGeoCoordinate(location, heading, metersCovered);
+        GeoPoint calculatedPoint = getGeoCoordinate(location, heading, metersCovered);
+
+        // Collision detection. Update boat only if no collision.
+        Yacht collidedYacht = checkCollision(calculatedPoint);
+        if (collidedYacht != null) {
+//            System.out.println("Collision of boat " + this.getSourceId() + " and " + collidedYacht.getSourceId());
+        } else {
+            location = calculatedPoint;
+        }
     }
 
     public void adjustHeading(Double amount) {
@@ -215,12 +224,16 @@ public class Yacht {
 
     public Integer getSourceId() {
         //@TODO Remove and merge with Creating Game Loop
-        if (sourceId == null) return 0;
+        if (sourceId == null) {
+            return 0;
+        }
         return sourceId;
     }
 
     public String getHullID() {
-        if (hullID == null) return "";
+        if (hullID == null) {
+            return "";
+        }
         return hullID;
     }
 
@@ -233,7 +246,9 @@ public class Yacht {
     }
 
     public String getCountry() {
-        if (country == null) return "";
+        if (country == null) {
+            return "";
+        }
         return country;
     }
 
@@ -410,4 +425,25 @@ public class Yacht {
     public void setLocation(GeoPoint geoPoint) {
         location = geoPoint;
     }
+
+    /**
+     * Collision detection which iterates through all the yachts and check if any yacht collided
+     * with this yacht. Return collided yacht or null if no collision.
+     *
+     * @param calculatedPoint point will the yacht will move next
+     * @return yacht which collided with this yacht
+     */
+    private Yacht checkCollision(GeoPoint calculatedPoint) {
+        Double COLLISIONFACTOR = 25.0;  // Collision detection in meters
+
+        for (Yacht yacht : GameState.getYachts().values()) {
+            if (yacht != this) {
+                Double distance = GeoUtility.getDistance(yacht.getLocation(), calculatedPoint);
+                if (distance < COLLISIONFACTOR) {
+                    return yacht;
+                }
+            }
+        }
+        return null;
+    }
 }