code: public static VaadinConfirmDialog show(final UI ui, final Listener listener) {
          return show(ui, null, null, null, null, listener);
      }
docs: Show a modal VaadinConfirmDialog in a window.
  
  @param ui the UI in which the dialog is to be show
  @param listener the listener to be notified
  @return the VaadinConfirmDialog instance created