code: public void showDialog() {
  		if (!isControlCreated()) {
  			createDialog();
  		}
  		if (!isShowing()) {
  			onAboutToShow();
  			if (getLocation() != null) {
  				dialog.setLocation(getLocation());
                  dialog.setPreferredSize(getPreferredSize());
  			}
  			else {
  				WindowUtils.centerOnParent(dialog, getLocationRelativeTo());
  			}
  
  			dialog.setVisible(true);
  		}
  	}
docs: <p>
  Show the dialog. The dialog will be created if it doesn't exist yet.
  Before setting the dialog visible, a hook method onAboutToShow is called
  and the location will be set.
  </p>
  <p>
  When showing the dialog several times, it will always be opened on the
  location that has been set, or relative to the parent. (former location
  will not persist)
  </p>