how to stop opening of duplicate window using Smack API in swing?

Question

I have 2 swing classes which extends JFrame. Both have show() method in there constructor. From ClassOne i called ClassTwo like new ClassTwo() on button click event. But if i press the button again new window for ClassTwo is opened. So how can i stop opening of ClassTwo window if one ClassTwo window is opened ?

Edit

now this problem is solved but now when i first open ClassTwo window it shows one window. Then after closing it when i again open ClassTwo window it opens two window and this count keep on increamenting. Why this is happening?

EDIT 2

I found that its not swing problem but its problem from MultiUsreChat class of Samck API. So anyone who have worked on it help me.

the code in ClassOne is:

if(!winList.contains(room_jid)){
    new ClassTwo(room_jid,....);
    winList.add(room_jid);
}

and in ClassTwo is:

public ClassTwo(....){
......
    this.muc = new MultiUserChat(connection, room_jid);
    if(!muc.isJoined())
        muc.join(this.user_id);      //---- This line opens previously closed window.
.....

    if(!isVisible())
       show();

}

Edit 3

constructor of classone

public ClassOne(){
  JButton btn = new JButton("Open");
  btn.addActionListener(new ActionListener(){
     public void actionPerformed(ActionEvent e){
       if(!winList.contains(room_jid)){
           new ClassTwo(room_jid,....);
            winList.add(room_jid);
       }
     }
  });
}

Answer 1

Don't make the frame visible in the ClassTwo constructor. Instead, keep a reference to classTwo in classOne, and when the button is clicked, make it visible, like so:

//on button click
if(classTwo == null){
    classTwo = new ClassTwo();
}
classTwo.setVisible(true);

Also change classTwo's default close operation to hide on close, instead of exit:

setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);

So it doesn't matter how many times the button is clicked, because all it does is make the existing instance visible. It doesn't create new instances.

Answer 2

In ClassOne you could simply remember whether you opened a new ClassTwo using a boolean.

//in event handler for the button
if (!classTwoShown)
{
  classTwoShown = true;
  new ClassTwo();
}

You should also hook into the dispose event of class two to reset the classTwoShown flag.