Design a Recoverable Iterator

Implement an iterator over a sequence that supports both normal traversal and state recovery. Design a class `RecoverableIterator` initialized with an array or list of elements. It must support the following operations: - `hasNext()`: return whether there is another element to read. - `next()`: return the next element and advance the iterator. - `saveState()`: return an opaque snapshot token representing the iterator's current position. - `restoreState(token)`: restore the iterator to the position captured by a previous snapshot. Requirements: 1. After restoring a saved state, subsequent calls to `next()` and `hasNext()` must behave exactly as if no operations had happened after that snapshot was taken. 2. Multiple saved states may exist at the same time, and restoring one state must not invalidate the others. 3. The design should be efficient in both time and space. 4. Discuss edge cases, such as restoring the initial state, restoring the end state, and calling `next()` when no elements remain. As a follow-up, explain how your design would change if the iterator were reading from a stream instead of an in-memory collection.