You can try this:-
Robot object=new Robot();
object.keyPress(KeyEvent.VK_ESCAPE);
object.keyRelease(KeyEvent.VK_ESCAPE);
In above code 'Escape' key use for close popup.
you can use this also for click on 'Cancel' button:-
object.keyPress(KeyEvent.VK_TAB);
object.keyRelease(KeyEvent.VK_TAB);
object.keyPress(KeyEvent.VK_TAB);
object.keyRelease(KeyEvent.VK_TAB);
object.keyPress(KeyEvent.VK_TAB);
object.keyRelease(KeyEvent.VK_TAB);
// Press Enter
object.keyPress(KeyEvent.VK_ENTER);
// Release Enter
object.keyRelease(KeyEvent.VK_ENTER);
Try this for click on 'Ok' button:-
// Press Down
object.keyPress(KeyEvent.VK_DOWN);
// Press Down
object.keyRelease(KeyEvent.VK_DOWN);
// Press Enter
object.keyPress(KeyEvent.VK_ENTER);
// Release Enter
object.keyRelease(KeyEvent.VK_ENTER);