The "type" attribute gives the type of the objects contained in the collection. In other words, it should be the type of what you want to get by the bean specified by "id".
In your original example, I see Integer being added to the List and Integers only would be returned. "id" would give you those elements you added to the list, 1 in each iteration. The second link helps in understanding this.
Try to shoot the trouble now and get back if you need more help