for(int i=0;i<circles.length;i++){
            size[i] = (Math.random()*40)+20;
            posX[i] = (Math.random()*600);
            posY[i] = (Math.random()*400);
            velX[i] = (Math.random()*2)+1;
            velY[i] = (Math.random()*2)+1;
            circles[i] = new Ellipse2D.Double(posX[i],posY[i],size[i],size[i]);
        }