//	Create dimension and QuadTree
Rectangle dimension = new Rectangle(0, 0, 100, 100);
//	First arg always is 0 (root node or level 0)
QuadTree quadTree = new QuadTree(0, dimension);

//	Sprite class has a Rectangle associated to detect collision
Sprite player = new Sprite(...);
Rectangle r1 = player.getBoundingRectangle();
//	Create more rectangles
Rectangle r2 = new Rectangle(50, 10, 40, 20);
Rectangle r3 = new Rectangle(50.5f, 10.47f, 40.5f, 20.7f);

//	Add rectangles
quadTree.insert(r1);
quadTree.insert(r2);
quadTree.insert(r3);

Array<Rectangles> allRectangles, list;

// main loop
// other code

quadTree.clear()
//	Insert all rectangles
for (Rectangle r : allRectangles)
	quadTree.insert(r);

//	Get all rectangles in list that verify the area
list.clear()
Rectangle areaSelected = new Rectangle(20, 20, 10, 30);
quadTree.retrieve(list, areaSelected);

//	Check for collisions
for (Rectangle r : list)
{
	//	Algorithm to check collisions
}

//	A example: If some rectangle collides with the player then increment counter
for (Rectangle r : list)
{
	if (rPlayer.overlaps(r))
		numCollision++;
}

//	other code
//	end main loop

public Array<Rectangle> retrieveFast(Array<Rectangle> list, Rectangle area)
{
	int index = getIndex(area);

	if (index != -1 & nodes[0] != null)
		nodes[index].retrieveFast(list, area);

	if (level == MAX_LEVEL || level == MAX_LEVEL-1) // (*)
		list.addAll(objects);

	return list;
}