使用Java AWT Robot类的问题

Question

I am using the robot class and trying to stroke the keys ctrl+alt+del
Below is the code

public class RobotClassDemo{

    public static void main(String[] args) {

         try {
             Robot robot = new Robot();

             robot.keyPress(KeyEvent.VK_CONTROL);
             System.out.println("ctrl pressed");
             robot.keyPress(KeyEvent.VK_ALT);
             System.out.println("alt pressed");
             robot.keyPress(KeyEvent.VK_DELETE);
             System.out.println("delete pressed");

         } catch (AWTException e) {
             e.printStackTrace();
         } 
     }
 } 

But it is not giving me any option like I am asuming here that it will move to screen which will contain lock , shut down , change password etc.(as in window 7 happens when we press ctrl+alt+del).I am running this program on windows 7.I sthere any limitations or access previliges? Or what is the problem?
Edit: Even My this code is working great

public void alt_tab() {
    Robot robot = new Robot();
    robot.keyPress(KeyEvent.VK_ALT);
    robot.keyPress(KeyEvent.VK_CONTROL);
    robot.keyPress(KeyEvent.VK_TAB);
    robot.delay(100);
    robot.keyRelease(KeyEvent.VK_TAB);
    robot.keyRelease(KeyEvent.VK_CONTROL);
    robot.keyRelease(KeyEvent.VK_ALT);
}

But dont know what is the problem with the first one

Answer 1

I wouldn't be completely surprised if this were forbidden by the OS or environment; however, have you tried adding robot.keyRelease events? At the moment it's as though you're holding the keys down forever. This may be insufficient to fire the appropriate key up/down/press events that the OS uses to recognise this key combination.