I'm looking for a data structure that will push its oldest/last element out if a new element is inserted. For example, let D represent the structure. D contains 3 elements of the type Number D's default values will be initialized to 1, 2 and 3.
$$D = [1, 2, 3]$$
If a Number that contains the value 5 is inserted into D, 3 will be pushed out, while 1 and 2 are shifted right.
$$D = [5, 1, 2]$$
The first thing that comes to mind would be an array, but the definition does not include the pushing behavior.