javascript:void(0)真正含义

public class ScreenSnapshot {

public static void main(String[] args) {
try {
int width = (int)Toolkit.getDefaultToolkit().getScreenSize().getWidth();
int height = (int)Toolkit.getDefaultToolkit().getScreenSize().getHeight();
Robot robot = new Robot();
BufferedImage image = robot.createScreenCapture(new Rectangle(width,height));
ImageIO.write (image, "png" , new File("c:/cross/test/1.png"));

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