Java Programming: Lesson 63 - List Iterators

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In the previous lesson (https://youtu.be/4jHQuaMOnOU), we learned about enumerations, which are similar to iterators but do not offer a remove( ) method. Inversely, in this video we will study an object which is even stronger than a regular iterator. It can traverse a list in both directions. We will discuss this in more depth in the next video. https://youtu.be/IqkZmd8EvVg

An enumeration is like an iterator, but with longer method names and no remove method. You can call an enumeration on a Vector or Stack, but not on other data structures. You're better off importing Iterator and creating an Iterator object on a particular data structure. But for enumerations:
1. import java.util.Enumeration;
2. create an Enumeration object on your data structure
3. while( enumeration.hasMoreElements( ) )
4. System.out.println( enumeration.nextElement( ) )

A list iterator is like an iterator, but with more methods available. You can call a list iterator on an ArrayList, LinkedList, Vector, or Stack, but not on other data structures.
1. import java.util.ListIterator;
2. create a ListIterator object on your data structure
3. while( listIterator.hasNext( ) )
4. System.out.println( listIterator.next( ) )
5. while( listIterator.hasPrevious( ) )
6. System.out.println( listIterator.previous( ) ) //can traverse a list iterator in BOTH directions, unlike a traditional iterator as studied previously. Better than an iterator, way better than an enumeration...

The point is that
enumerations: can check for a next element, can return it if there is one
iterators: can ALSO remove elements from the underlying data structure
list iterators: can ALSO add elements to the underlying data structure, and can ALSO traverse a vector or stack in the opposite direction (e.g. myStack.hasPrevious( ) or myVector.previous() )

0:29 Review of Stacks and Iterators
7:55 Review of Enumerations
11:07 NEW: List Iterators

If justice still hasn't been done to the topic of list iterators, I provide another example in lesson 70: https://youtu.be/Vr9ZVFrb4zk (and in other videos around there)

In the next video, we will see something called hash tables, which is basically the same as reviewing hash maps. https://youtu.be/IqkZmd8EvVg (but write Hashtable instead of HashMap in your import, your declaration, and your initialization. That's it.)

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