Implement SnapshotSet

Design a generic class SnapshotSet that behaves like a mutable set but can also produce immutable snapshots of its state at any moment. The class must support the following operations: add(T element) – inserts the element into the set. remove(T element) – deletes the element from the set. contains(T element) – returns true if the element is currently in the set, false otherwise. iterator() – returns an iterator over the elements that were present in the set at the exact time…