Why do you need someone to implement this for you? What kind of list should it iterate over? Do you have some particular project in mind where you need this?
The existence of this class is primarily useful along with the List interface. Notice that it has methods that return ListIterator. If you call any of these methods, you don't have to worry about who the concrete class is that implements this interface. You only need to know that this class certainly implements all the methods required by the ListIterator documentation.
So in the end, if you are using the standard Collections API, you don't need to worry about writing your own class to implement this interface. One exists already. However, if you are writing your own class to implement the List interface, then you probably need to create a companion class that implements ListIterator as well. I don't think someone will just do this for you.
In the Java Collections API, there are some methods that are declared to return an Iterator, and other that return a ListIterator. Without exception (at least, without exception that comes to mind) these methods return an instance of a private inner class of the Collection they're invoked on. Because an inner class has special access to the data of its outer class, they are ideally suited for implementing fast and efficient Iterators and ListIterators.