Box b1, b2;  // Two boxes with balls in them

void setup() {
   size(500, 500);
   b1 = new Box(50, 50, 150, 150, 30);  // 30 balls
   b2 = new Box(250, 50, 150, 150, 50);  // 50 balls
   } // setup()

void draw() {
   background(255);
   b1.display();
   b1.update();
   b2.display();
   b2.update();
   } // draw()