MUC create room error in v3

It is my program to create a new room where “start” is an existing room and I would like to create a new room

public static void creatChatRoom(String roomname){

try{

XMPPConnection con = getCommonConnection(acct, password);

// Create a MultiUserChat using an XMPPConnection for a room

MultiUserChat muc = new MultiUserChat(con, “start@conference.”+hostname);

System.out.println(“Start creating MUC room”);

// Create the room

muc.create(roomname);

// Send an empty room configuration form which indicates that we want

// an instant room

muc.sendConfigurationForm(new Form(Form.TYPE_SUBMIT));

}catch(XMPPException e){

System.out.println(“Error occur when creating MUC room\n”+ e);

}

}

And I call this by creatChatRoom(“event1”);

And an exception is caught:

"Error occur when creating MUC room

Creation failed - Missing acknowledge of room creation.: "

Why I got this exception ? and how can I solve this ?

Thanks for attention

I has modified the code as below:

public static void creatChatRoom(String roomname){

try{

XMPPConnection con = getCommonConnection(acct, password);

// Create a MultiUserChat using an XMPPConnection for a room

MultiUserChat muc = new MultiUserChat(con, roomname*"@conference."*hostname);

System.out.println(“Start creating MUC room”);

// Create the room
muc.create(acct);

System.out.println(“Start joining MUC room”);
muc.join(acct);

// Send an empty room configuration form which indicates that we want
// an instant room
muc.sendConfigurationForm(new Form(Form.TYPE_SUBMIT));
}catch(XMPPException e){

System.out.println(“Error occur when creating MUC room\n”+ e);

}

}

And I call this by creatChatRoom(“event1”);

It sucessfully ran, but I cannot find the new chatroom at all in server admin.

Why is that ? and how can I solve this ?

Thanks for attention