New dialog has no size

I created a dialog:

public class SearchDialog extends JDialog {
    public SearchDialog() {
        setTitle("Find jars");
    }
}

Then, I created a new dialog in an action:

class DialogAction extends AnAction {
     def actionPerformed(e: AnActionEvent): Unit = {
          def dialog = new SearchDialog
          dialog.setSize(500, 420)
          dialog.setVisible(true)
     }
}

But the "dialog.setSize(...)" doesn't work, the new created dialog is on the left top of the screen, and has no size.

See the attached image.

Attachment(s):
QQ截图20110707124104.png