Use this code..  
MultiUserChat muc = new MultiUserChat(connection, "roomname@<server>");
muc.create("nickname1");
Form form = muc.getConfigurationForm();
Form submitForm = form.createAnswerForm();
for (Iterator fields = form.getFields();fields.hasNext();){
  FormField field = (FormField) fields.next();
    if(!FormField.TYPE_HIDDEN.equals(field.getType()) && field.getVariable()!= null){
        submitForm.setDefaultAnswer(field.getVariable());
    }
}               
submitForm.setAnswer("muc#roomconfig_publicroom", true);
muc.sendConfigurationForm(submitForm);
muc.join("nickname1");
}catch (Exception e) {
   e.printStackTrace();
}
also Configure the Provider manager manually before you LOGGING IN with this method
public void configure(ProviderManager pm) {
    //  Private Data Storage
    pm.addIQProvider("query","jabber:iq:private", new PrivateDataManager.PrivateDataIQProvider());
    //  Time
    try {
        pm.addIQProvider("query","jabber:iq:time", Class.forName("org.jivesoftware.smackx.packet.Time"));
    } catch (ClassNotFoundException e) {
        Log.w("TestClient", "Can't load class for org.jivesoftware.smackx.packet.Time");
    }
    //  Roster Exchange
    pm.addExtensionProvider("x","jabber:x:roster", new RosterExchangeProvider());
    //  Message Events
    pm.addExtensionProvider("x","jabber:x:event", new MessageEventProvider());
    //  Chat State
    pm.addExtensionProvider("active","http://jabber.org/protocol/chatstates", new ChatStateExtension.Provider());
    pm.addExtensionProvider("composing","http://jabber.org/protocol/chatstates", new ChatStateExtension.Provider()); 
    pm.addExtensionProvider("paused","http://jabber.org/protocol/chatstates", new ChatStateExtension.Provider());
    pm.addExtensionProvider("inactive","http://jabber.org/protocol/chatstates", new ChatStateExtension.Provider());
    pm.addExtensionProvider("gone","http://jabber.org/protocol/chatstates", new ChatStateExtension.Provider());
    //  XHTML
    pm.addExtensionProvider("html","http://jabber.org/protocol/xhtml-im", new XHTMLExtensionProvider());
    //  Group Chat Invitations
    pm.addExtensionProvider("x","jabber:x:conference", new GroupChatInvitation.Provider());
    //  Service Discovery # Items    
    pm.addIQProvider("query","http://jabber.org/protocol/disco#items", new DiscoverItemsProvider());
    //  Service Discovery # Info
    pm.addIQProvider("query","http://jabber.org/protocol/disco#info", new DiscoverInfoProvider());
    //  Data Forms
    pm.addExtensionProvider("x","jabber:x:data", new DataFormProvider());
    //  MUC User
    pm.addExtensionProvider("x","http://jabber.org/protocol/muc#user", new MUCUserProvider());
    //  MUC Admin    
    pm.addIQProvider("query","http://jabber.org/protocol/muc#admin", new MUCAdminProvider());
    //  MUC Owner    
    pm.addIQProvider("query","http://jabber.org/protocol/muc#owner", new MUCOwnerProvider());
    //  Delayed Delivery
    pm.addExtensionProvider("x","jabber:x:delay", new DelayInformationProvider());
    //  Version
    try {
        pm.addIQProvider("query","jabber:iq:version", Class.forName("org.jivesoftware.smackx.packet.Version"));
    } catch (ClassNotFoundException e) {
        //  Not sure what's happening here.
    }
    //  VCard
    pm.addIQProvider("vCard","vcard-temp", new VCardProvider());
    //  Offline Message Requests
    pm.addIQProvider("offline","http://jabber.org/protocol/offline", new OfflineMessageRequest.Provider());
    //  Offline Message Indicator
    pm.addExtensionProvider("offline","http://jabber.org/protocol/offline", new OfflineMessageInfo.Provider());
    //  Last Activity
    pm.addIQProvider("query","jabber:iq:last", new LastActivity.Provider());
    //  User Search
    pm.addIQProvider("query","jabber:iq:search", new UserSearch.Provider());
    //  SharedGroupsInfo
    pm.addIQProvider("sharedgroup","http://www.jivesoftware.org/protocol/sharedgroup", new SharedGroupsInfo.Provider());
    //  JEP-33: Extended Stanza Addressing
    pm.addExtensionProvider("addresses","http://jabber.org/protocol/address", new MultipleAddressesProvider());
    //   FileTransfer
    pm.addIQProvider("si","http://jabber.org/protocol/si", new StreamInitiationProvider());
    pm.addIQProvider("query","http://jabber.org/protocol/bytestreams", new BytestreamsProvider());
    //  Privacy
    pm.addIQProvider("query","jabber:iq:privacy", new PrivacyProvider());
    pm.addIQProvider("command", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider());
    pm.addExtensionProvider("malformed-action", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider.MalformedActionError());
    pm.addExtensionProvider("bad-locale", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider.BadLocaleError());
    pm.addExtensionProvider("bad-payload", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider.BadPayloadError());
    pm.addExtensionProvider("bad-sessionid", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider.BadSessionIDError());
    pm.addExtensionProvider("session-expired", "http://jabber.org/protocol/commands", new AdHocCommandDataProvider.SessionExpiredError());
}
just call this method using-  configure(ProviderManager.getInstance());