Close one jInternalFrame before opening another

I'm doing a browser project (where I myself create the "pages" in netbeans design - All offline ) just to learn on vacation. But I have a doubt, I believe it is simple but as I am starting I am still trying to understand the logic.

I have a jTextFieldPesquisa and in it the person will type the site that they want to open and I have a button in the front that when clicked, it will open the screen of the site. (In the future I will still do without the jButton, but at the beginning I thought it best to separate so I can understand the operation of the two).

Here is an example of my jButtonEnterActionPerformed:

    if((jTextFieldPesquisa.getText().equals("www.facebook.com.br")) || (jTextFieldPesquisa.getText().equals("facebook.com.br")) || (jTextFieldPesquisa.getText().equals("31.13.85.36"))) {

        Facebook obj1=new Facebook();
        jDesktopPaneBG.add(obj1);
        try{
            obj1.setMaximum(true);
            obj1.setVisible(true);
            obj1.setPosicao();

        } catch (PropertyVetoException e) {
            JOptionPane.showMessageDialog(rootPane, e);
        }

    }

In this if above, when the user clicks on jTextFieldPesquisa and enter , the page I created from facebook will appear inside jDesktopPane . It is worth mentioning that I am using jTabbedPane to open jInternalFrame and in that jInternalFrame the page itself is opened.

The problem: When I open a page (www.facebook.com.br), and then I type (www.google.com.br) that was another page that I drew in jInternalFrame. The google page is on top of the facebook page. I would like to hide the facebook page before opening the google.

At first my logic would be to insert a boolean public variable starting with false and every time it enters into the if, it would be true. So, I would know that this page would be open because it has the value true, I would have to close it first to open another one. So far so good (in my logic).

Dai I needed to know the value of the screen object that was open. As for each screen, I instantiated an obj1, obj2, obj3 I just created a public variable also started with 0. Each time I entered that if, this variable would save the "object value" and then I would know which instance of the object was open and could close it before opening the other.

It would look like this:

public boolean page = false; public int numObject = 0;

    if((jTextFieldPesquisa.getText().equals("www.facebook.com.br")) || (jTextFieldPesquisa.getText().equals("facebook.com.br")) || (jTextFieldPesquisa.getText().equals("31.13.85.36"))) {

        Facebook obj1=new Facebook();
        jDesktopPaneBG.add(obj1);
        try{
            obj1.setMaximum(true);
            obj1.setVisible(true);
            obj1.setPosicao();

            pagina = true;  //pagina esta aberta
            numObjeto = 1; //igual obj1
        } catch (PropertyVetoException e) {
            JOptionPane.showMessageDialog(rootPane, e);
        }

    }

If anyone wants to see the project, it's in github marciellioliveira