How to create Group in aSmack xmpp in android ?

I am getting class cast exception while creating muc in android.

E/AndroidRuntime(31002): Caused by: java.lang.ClassCastException:   
org.jivesoftware.smack.packet.DefaultPacketExtension
E/AndroidRuntime(31002):    at  
org.jivesoftware.smackx.muc.MultiUserChat.getMUCUserExtension(MultiUserChat.java:2000)
E/AndroidRuntime(31002):    at    
org.jivesoftware.smackx.muc.MultiUserChat.create(MultiUserChat.java:364)

You can create user Group by ,

public boolean createGroup(XMPPConnection connection,String groupName) {
if (connection == null)
return false;
try {
connection.getRoster().createGroup(groupName);
Log.v("Group created : ", groupName);
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
}
}

If you wated to create Group Chat in xmpp try the following method. (** UNCHECKED )

public class createMucAT extends AsyncTask<Void, Void, MultiUserChat> {

    private RosterGroup group;
    private Connection conn;
    private String groupId;
    private String groupName;


    public createMucAT(Connection conn, RosterGroup group, String groupId,
            String groupName) {
        this.group = group;
        this.conn = conn;
        this.groupId = groupId;
        this.groupName = groupName;


    }

    @Override
    protected MultiUserChat doInBackground(Void... params) {
        String groupTag = group.getName();
        MultiUserChat chat = null;
        try {
            chat = createGroupChat(conn, groupId, groupTag, conn.getUser());
        } catch (XMPPException e) {
            e.printStackTrace();
        }
        return chat;
    }

    @Override
    protected void onPostExecute(MultiUserChat result) {
        super.onPostExecute(result);
        //handle the result here
    }

    private MultiUserChat createGroupChat(Connection conn, String groupId, String groupName, String nickname) throws XMPPException {
        MultiUserChat muc = new MultiUserChat(conn, groupId + "@" + ConnectionService.CONFERENCE_IP_ADDRESS);
        muc.create(nickname);
        Form form = muc.getConfigurationForm();
        Form submitForm = form.createAnswerForm();
        for (Iterator<FormField> fields = form.getFields(); fields.hasNext();) {
            FormField field = (FormField) fields.next();
            if (!FormField.TYPE_HIDDEN.equals(field.getType()) && field.getVariable() != null) {
                submitForm.setDefaultAnswer(field.getVariable());
                }
        }
        List<String> owners = new ArrayList<String>();
        owners.add(ConnectionService.getConnection().getUser().toString());
        submitForm.setAnswer("muc#roomconfig_roomowners", owners);
        submitForm.setAnswer("muc#roomconfig_persistentroom", true);
        submitForm.setAnswer("muc#roomconfig_roomdesc", groupName);
        muc.sendConfigurationForm(submitForm);
        return muc;
    }
}