How to make sure that points drawn on JFrame at random location does not overlap already drawn shapes?

Question

I am creating 100 particles at random location all over my JPanel using random function to calculate x and y. But I have two rectangles also drawn on the panel and I do not want my points to overlap on that area.

Is there any way, by which I can create the particles all over the JPanel except those areas covered by rectangle?

            int x,y=0;
            super.paintComponent(g);

            for(int i=0;i<list.size();i++)
            {
                x=randomInteger(11,670); // bounds of x between which the particles should be generated (reduced by 1 each)
                y=randomInteger(11,440);   // bounds of y between which the particles should be generated (reduced by 1 each)
                int radius = 4;
                g.fillOval(x, y, radius, radius);
            }

            x=randomInteger(11,670); 
            y=randomInteger(11,440);

            drawRobot(g,x,y,50);
            createObstacles(g,150,225,100,40);
            createObstacles(g,500,300,40,100);

            int xpoints[] = {50, 40, 60, 120};
            int ypoints[] = {50, 75, 100, 130};
            int npoints = 4;
            createPolygonObstacle(g,xpoints,ypoints,npoints);          

        }

        private void createPolygonObstacle(Graphics g, int xpoints[], int ypoints[], int npoints)
        {
             g.fillPolygon(xpoints, ypoints, npoints);
        }

        private void createObstacles(Graphics g, int x, int y, int width, int height)
        {
            g.setColor(Color.BLACK);
            g.fillRect(x, y, width, height);
        }

        private void drawRobot(Graphics g, int x, int y, int radius)
        {
            g.setColor(Color.GREEN);
            g.fillOval(x, y, radius, radius);           
        }

        private static int randomInteger(int min, int max)
        {
            Random rand = new Random();
            int randomNum = rand.nextInt((max - min) + 1) + min;
            return randomNum;
        }

Answer 1

You could take advantage of the Shape API...

Rectangle rect = new Rectangle (x, y, width, height);

Then you could use it's contains method to determine if it contains a given point...

if (rect.contains(x, y)) {
    // You bad little particle...
}

You should also know that the Graphics2D can also draw and paint Shape , so you could also do...

((Graphics2D)g).fill(rect);

Which should make your life some what easier. As of Java 1.4 (I think), the paint engine is guaranteed to use Graphics2D , so your paintComponent method will always receive an instance of a Graphics2D object.

Take a look at 2D Graphics for more details

Answer 2

Random r = new Random();
public void generateParticle(){
    int x = r.nextInt();
    int y = r.nextInt();
    if(x > LeftEdgeOfRectangle || x < RightEdgeOfRectangle){
         generateParticle();
         return();
    }
    if(y > TopEdgeOfRectangle || y < BottomEdgeOfRectangle){
         generateParticle();
         return();
    }
    [drawParticleHere]
}