Set<String> winIds = driver.getWindowHandles();
System.out.println("Total windows -> "+ winIds.size());
if(winIds.size() == 2){
Iterator<String> iter = winIds.iterator();
String mainWinID = iter.next();
String popupWinID = iter.next();
driver.switchTo().window(popupWinID);
driver.close();
driver.switchTo().window(mainWinID);
}