$9\mathrm{.}31$ LAB: Iterable $2-3-4$ tree

In this lab, the Tree$234$ class is extended to support iteration with an enhanced for loop. Such support is provided via the implementation of an iterator that can iterate through the tree's keys in ascending order.

An iterator is an object that maintains a reference to a specific element in a collection and can move to the next element. Ex: A Tree$234$ iterator references the tree's minimum key upon construction. The iterator can then move to the second to minimum key, then the third to minimum, and so on$.$ Eventually the iterator moves to the last key and can move no further.

Overview of Iterable and Iterator in Java

Enhanced for loops work on any class that implements the Iterable interface. Tree$234$ stores a collection of integer keys, so the Tree$234$ class implements Iterable