Java SE (Java Platform, Standard Edition)

I've a problem on a desktop MDI application, when the user click on and image, the application open a JFrame for the larger image, but every time the user click on it it open a new window.

How can i prevent this? Can i check if the window is already opened?

here is my code:

public void mouseClicked(MouseEvent e) {
                DettaglioImmagine formdettimm = new DettaglioImmagine(MainForm.WorkingDir + "/immagini/DimCatene/" + catena.getChild("immaginedimensionigrande").getText());
                formdettimm.setVisible(true);
            }