Re:timer duvida

public static void main(String[] args) {
        final JFrame j = new JFrame();
        j.setTitle("aaaaaa");
        j.setSize(300, 300);
        j.setVisible(true);
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {
            private boolean firstExecution = true;
            public void run() {
                if(firstExecution){
                    j.setVisible(true);
                    firstExecution = false;
                }else{
                    j.dispose();
                    System.exit(0);
                }
            }
        }, 1000, 5000);
    }