Mastering Java: The Ultimate Quiz for 'Thinking in Java'

The purpose of the Iterator interface is to allow movement through a collection, which means it allows us to access and traverse elements in a sequential manner. Option A is incorrect because the Iterator interface only allows movement in one direction, which is forward. Option B is incorrect because the add() method is not a part of the Iterator interface. If we want to add elements to a collection, we can use methods specific to that collection such as add() for ArrayList and put() for HashMap. Option D is incorrect because the Iterator interface is not responsible for sorting elements in a collection. Instead, we can use the Collections class for sorting collections.