private void screenshot() throws Exception
  {
     SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd hh mm ss a");

      Calendar now = Calendar.getInstance();
      Robot robot = new Robot();
      BufferedImage screenShot = robot.createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
      ImageIO.write(screenShot, "JPG", new File("Ruta de las imagenes\\"+formatter.format(now.getTime())+".jpg"));
      System.out.println(formatter.format(now.getTime()));
  }