final static int ARRAY_MAX = 4;

    public static void swapXY(Movable object) throws NullPointerException
    {
        if (object == null)
            throw new NullPointerException ("Object is not created");
        System.out.println("Coordinates: X = " + object.getX() + ", Y = " + object.getY());
        object.moveTo(object.getY(), object.getX());
        System.out.println("Coordinates was changed: X = " + object.getX() + ", Y = " + object.getY());
    }

    public static void main(String[] args) {
        Point p = new Point(5, 5);
        p.draw(); // 5 5
        p.moveTo(10, 10);
        p.draw(); // 10 10
        p.move(-5, 5);
        p.draw(); // 5 15

        Background b = new Background(10, "mytexture.tt");
        b.draw(); // 10 mytexture.tt
        b.setColor(20);
        b.setTextureName("furt.tt");
        b.draw(); // 20 furt.tt

        Circle c = new Circle(5, 5, 3);
        c.draw(); // 5 5 3
        c.setRadius(10);
        c.moveTo(1, 1);
        c.draw(); // 1 1 10

        Rectangle r = new Rectangle(5, 5, 10, 20);
        r.draw(); // 5 5 10 20
        r.moveTo(1, 1);
        r.setWidth(50);
        r.setHeight(25);
        r.draw(); // 1 1 50 25

        Rectangle e = new Ellipse(2, 2, 10, 15);
        e.draw(); // 2 2 10 15
        e.move(1, 1);
        e.setWidth(40);
        e.setHeight(250);
        e.draw(); // 3 3 40 250

        Point p1 = new Point(15, 16);
        Point p2 = new Point(23, 42);
        //Point p3 = new Point(42, 108);

        Movable movableArray[];
        movableArray = new Movable[ARRAY_MAX];
        movableArray[0] = p;
        movableArray[1] = p1;
        movableArray[2] = p2;
        //movableArray[3] = p3; //

        for (int i = 0; i < ARRAY_MAX; i++) {
            try {
                swapXY(movableArray[i]);
            }
            catch (NullPointerException ex) {
                System.out.println ("Error while swapping coordinates.");
                ex.printStackTrace();
            };
        }
    }