Why are there no specific implementations provided for the Iterator interface?

The Iterator interface defines a contract for traversing collections. Specific implementations depend on the internal structure of the collections (e.g., ArrayList, LinkedList, HashSet). Providing a universal implementation would be inefficient or impossible, as it must account for the characteristics of each collection type.

For example:

• ArrayList.iterator() traverses elements by index.
• LinkedList.iterator() traverses elements following pointers between nodes.
• HashSet.iterator() traverses elements using an internal array of buckets and linked lists/red-black trees.

Only the collection itself knows how to most efficiently provide an iterator for its data structure.