public void checkCollisions() {

        Rectangle r3 = craft.getBounds();

        for (int j = 0; j<aliens.size(); j++) {
            Alien a = (Alien) aliens.get(j);
            Rectangle r2 = a.getBounds();

            if (r3.intersects(r2)) {
                craft.setVisible(false);
                a.setVisible(false);
                ingame = false;
            }
        }

        ArrayList ms = craft.getMissiles();

        for (int i = 0; i < ms.size(); i++) {
            Missile m = (Missile) ms.get(i);

            Rectangle r1 = m.getBounds();

            for (int j = 0; j<aliens.size(); j++) {
                Alien a = (Alien) aliens.get(j);
                Rectangle r2 = a.getBounds();

                if (r1.intersects(r2)) {
                    m.setVisible(false);
                    a.setVisible(false);
                }
            }
        }
    }