class Tt {

    public static void main(String args[]) {
        Timer tim = new Timer();
       tim.schedule(new MyTimer(), 1000,2000);
    }
}
class MyTimer extends TimerTask{
    public void run(){
        System.out.println("2秒一次");
        try {
            new Robot().keyPress(KeyEvent.VK_ALT);
            new Robot().keyPress(KeyEvent.VK_TAB);
        } catch (AWTException ex) {
            Logger.getLogger(MyTimer.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}