Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java
===================================================================
diff -u -r18704961d531a547a8a96928980c43a3bf169fd2 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java	(.../Activity.java)	(revision 18704961d531a547a8a96928980c43a3bf169fd2)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/Activity.java	(.../Activity.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -9,6 +9,8 @@
 import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;
+import org.lamsfoundation.lams.lesson.LessonClass;
+import org.lamsfoundation.lams.usermanagement.User;
 import org.lamsfoundation.lams.util.Nullable;
 
 /**
@@ -457,4 +459,19 @@
 	    return toolActivities;
 	    
 	}
+	
+	public Group getGroupFor(User learner)
+	{
+	    if(this.getGrouping()==null)
+	        throw new IllegalArgumentException("Exception occured in " +
+	        		"getGroupFor, no grouping has been defined");
+	    for(Iterator i=this.getGrouping().getGroups().iterator();i.hasNext();)
+	    {
+	        Group group = (Group)i.next();
+	        if(this.getGrouping().isLearnerGroup(group)&&group.hasLearner(learner))
+	            return group;
+	    }
+	    
+	    return new NullGroup();
+	}
 }
\ No newline at end of file
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/ChosenGrouping.java
===================================================================
diff -u -rd7f8bd90added31c1bbadc8ebd51e301d13965b6 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/ChosenGrouping.java	(.../ChosenGrouping.java)	(revision d7f8bd90added31c1bbadc8ebd51e301d13965b6)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/ChosenGrouping.java	(.../ChosenGrouping.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -30,7 +30,7 @@
      * So it always return <code>true</code>.
      * @see org.lamsfoundation.lams.learningdesign.Grouping#isLearnerGroup(org.lamsfoundation.lams.learningdesign.Group)
      */
-    protected boolean isLearnerGroup(Group group)
+    public boolean isLearnerGroup(Group group)
     {
         return true;
     }
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/Group.java
===================================================================
diff -u -r1d40a310039a2975dc474f61e9a732f90f86c707 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/Group.java	(.../Group.java)	(revision 1d40a310039a2975dc474f61e9a732f90f86c707)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/Group.java	(.../Group.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -2,18 +2,21 @@
 
 import java.io.Serializable;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Set;
 import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;
+import org.lamsfoundation.lams.usermanagement.User;
+import org.lamsfoundation.lams.util.Nullable;
 
 
 /** 
  *        @hibernate.class
  *         table="lams_group"
  *     
 */
-public class Group implements Serializable {
+public class Group implements Serializable,Nullable {
 
     public final static int STAFF_GROUP_ORDER_ID = 1;
     
@@ -192,4 +195,28 @@
             .toHashCode();
     }
 
+    /**
+     * Return whether the target user is in this group or not.
+     * @param learner the target user
+     * @return boolean value to indicate whether the user is in.
+     */
+    public boolean hasLearner(User learner)
+    {
+        for(Iterator i=this.getUsers().iterator();i.hasNext();)
+        {
+            User user = (User)i.next();
+            if(user.getUserId().intValue()==learner.getUserId().intValue())
+                return true;
+        }
+        return false;
+    }
+
+    /**
+     * @see org.lamsfoundation.lams.util.Nullable#isNull()
+     */
+    public boolean isNull()
+    {
+        return false;
+    }
+
 }
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/Grouping.java
===================================================================
diff -u -rd7f8bd90added31c1bbadc8ebd51e301d13965b6 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/Grouping.java	(.../Grouping.java)	(revision d7f8bd90added31c1bbadc8ebd51e301d13965b6)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/Grouping.java	(.../Grouping.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -196,6 +196,6 @@
     /**
      * @return
      */
-    protected abstract boolean isLearnerGroup(Group group);
+    public abstract boolean isLearnerGroup(Group group);
 
 }
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/NullGroup.java
===================================================================
diff -u
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/NullGroup.java	(revision 0)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/NullGroup.java	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -0,0 +1,45 @@
+/*
+	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;
+
+/**
+ * 
+ * @author Jacky Fang 2005-2-21
+ * 
+ */
+public class NullGroup extends Group
+{
+    /**
+     * 
+     */
+    public NullGroup()
+    {
+        super();
+    }
+
+    /**
+     * @see org.lamsfoundation.lams.util.Nullable#isNull()
+     */
+    public boolean isNull()
+    {
+        return true;
+    }
+}
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouping.java
===================================================================
diff -u -rd7f8bd90added31c1bbadc8ebd51e301d13965b6 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouping.java	(.../RandomGrouping.java)	(revision d7f8bd90added31c1bbadc8ebd51e301d13965b6)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouping.java	(.../RandomGrouping.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -66,7 +66,7 @@
      * So it always return <code>true</code>.
      * @see org.lamsfoundation.lams.learningdesign.Grouping#isLearnerGroup(org.lamsfoundation.lams.learningdesign.Group)
      */
-    protected boolean isLearnerGroup(Group group)
+    public boolean isLearnerGroup(Group group)
     {
         return true;
     }
Index: lams_common/src/java/org/lamsfoundation/lams/lesson/LessonClass.java
===================================================================
diff -u -rd7f8bd90added31c1bbadc8ebd51e301d13965b6 -rd6e24451f694815d6138e6189fa8ba2294ee6944
--- lams_common/src/java/org/lamsfoundation/lams/lesson/LessonClass.java	(.../LessonClass.java)	(revision d7f8bd90added31c1bbadc8ebd51e301d13965b6)
+++ lams_common/src/java/org/lamsfoundation/lams/lesson/LessonClass.java	(.../LessonClass.java)	(revision d6e24451f694815d6138e6189fa8ba2294ee6944)
@@ -52,7 +52,7 @@
     /**
      * @see org.lamsfoundation.lams.learningdesign.Grouping#isLearnerGroup(org.lamsfoundation.lams.learningdesign.Group)
      */
-    protected boolean isLearnerGroup(Group group)
+    public boolean isLearnerGroup(Group group)
     {
         if(group.getGroupId()==null||staffGroup.getGroupId()==null)
             throw new IllegalArgumentException("Can't check up whether group" +