When you add the array to the list, it's not copied. The list is just a list of references, and you add the reference to the array, not a copy of the array. You add the same array three times to the list, so all the items in the list will be the same actual array. When you change the contents of the array, it will change the contents of all items in the list, as they are all the same object.
--- single minded; short sighted; long gone;