code: public static void fillCircle(Graphics g, int centerX, int centerY, int diam){
  		g.fillOval((int) (centerX-diam/2), (int) (centerY-diam/2), diam, diam);
  	}
docs: Draws a circle with the specified diameter using the given point coordinates as center
  and fills it with the current color of the graphics context.
  @param g Graphics context
  @param centerX X coordinate of circle center
  @param centerY Y coordinate of circle center
  @param diam Circle diameter