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Iterators

Iterators. Dan Fleck. Iterators. 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. Iterator Example. ArrayList aList = new ArrayList();

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Iterators

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  1. Iterators Dan Fleck

  2. Iterators • Iterator • Object that can access a collection of objects one object at a time • Traverses the collection of objects • JCF defines generic interfacejava.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…)?

  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()

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