1. Iterators
Dan Fleck

2. Iterators Iterator JCF defines generic interface java.util.Iterator
Object that can access a collection of objects one object at a time
Traverses the collection of objects
JCF defines generic interface java.util.Iterator
And a subinterface ListIterator

3. Iterator Example ArrayList aList = new ArrayList();
populateListWithStrings(aList);
Iterator itr = aList.iterator();
while (itr.hasNext()) {
String nextStr = (String)itr.next();
System.out.printf(“List item is: %s”, nextStr); }

4. Iterator Example with Generics
ArrayList<String> aList = new ArrayList<String>();
populateListWithStrings(aList);
Iterator<String> itr = aList.iterator();
while (itr.hasNext()) {
String nextStr = itr.next();
System.out.printf(“List item is: %s”, nextStr); }

5. Iterator methods See Javadoc for Iterator
Do all Iterators implement the remove operation? What happens if they don’t?
What is another way to iterate through a Collection (ArrayList, Vector, Set, HashSet, LinkedList, etc…)?
Answer: New for loop!

6. ListIterator Extends iterator to allow reverse iteration of a List
“hasPrevious()”, “previous” methods
Has an add() method
Has a set() method to replace elements
Lets you get the index of the element
Int nextIndex(), int previousIndex()