Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ActivityOrderComparator.java
===================================================================
diff -u -rf6b57f7fc79528760e004b09322b56f0b0ef3ddd -rb6b326d086fe25330c98956012a4e5773fcfa1dc
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ActivityOrderComparator.java	(.../ActivityOrderComparator.java)	(revision f6b57f7fc79528760e004b09322b56f0b0ef3ddd)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ActivityOrderComparator.java	(.../ActivityOrderComparator.java)	(revision b6b326d086fe25330c98956012a4e5773fcfa1dc)
@@ -1,26 +1,56 @@
-/*
- * Created on 16/02/2005
- *
- * TODO To change the template for this generated file go to
- * Window - Preferences - Java - Code Style - Code Templates
- */
+/***************************************************************************
+ * Copyright (C) 2005 LAMS Foundation (http://lamsfoundation.org)
+ * =============================================================
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+ * USA
+ * 
+ * http://www.gnu.org/licenses/gpl.txt
+ * ***********************************************************************/
+
 package org.lamsfoundation.lams.learningdesign;
 
 import java.io.Serializable;
 import java.util.Comparator;
 
 /**
- * @author dgarth
- *
- * TODO To change the template for this generated type comment go to
- * Window - Preferences - Java - Code Style - Code Templates
+ * The activity order comparator used for sorted set. Order id is used as
+ * the primary comparing criteria as it is unique within a complex activity.
+ * If they are the same, activity id are used for comparison to ensure the
+ * sorted set won't treat two activities with the same order id as the 
+ * same activity.
+ * 
+ * @author dgarth, Jacky Fang
  */
 public class ActivityOrderComparator implements Comparator, Serializable {
 
+    /**
+     * Compare the order.
+     * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
+     */
     public int compare(Object o1, Object o2) {
         Activity activity1 = (Activity)o1;
         Activity activity2 = (Activity)o2;
-        return activity1.getActivityId().compareTo(activity2.getActivityId());
+        
+        int orderDiff = activity1.getOrderId().compareTo(activity2.getOrderId());
+        //return order id compare result if they are not the same
+        if(orderDiff!=0)
+            return orderDiff;
+        //if order id are the same, compare activity id.
+        else
+            return activity1.getActivityId().compareTo(activity2.getActivityId());
     }
     
 }
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java
===================================================================
diff -u -r1298a23011114e3088ec0e9686e0ceac246d9a6f -rb6b326d086fe25330c98956012a4e5773fcfa1dc
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java	(.../ComplexActivity.java)	(revision 1298a23011114e3088ec0e9686e0ceac246d9a6f)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ComplexActivity.java	(.../ComplexActivity.java)	(revision b6b326d086fe25330c98956012a4e5773fcfa1dc)
@@ -4,6 +4,8 @@
 import java.util.Date;
 import java.util.Iterator;
 import java.util.Set;
+import java.util.TreeSet;
+
 import org.apache.commons.lang.builder.ToStringBuilder;
 
 /**
@@ -78,11 +80,13 @@
 	 *  
 	 */
 	public Set getActivities() {
+	    if(this.activities==null)
+	        setActivities(new TreeSet(new ActivityOrderComparator()));
 		return this.activities;
 	}
 
 	public void setActivities(Set activities) {
-		this.activities = activities;
+	    this.activities=activities;
 	}
 	public void addActivity(Activity activity){
 		this.activities.add(activity);