Behavioral Patterns : Iterator

Properties:

-          Enables traversal of collections.

Implementation:

-          Aggregate declares method to return iterator of the collection.

-          ConcreteAggregate represents the collection which creates an iterator for traversal of contained objects.

-          Iterator declares methods to iterate over a collection

-          ConcreteIterator a collection specific implementation of Iterator interface.

Java Standard Library Implementations:

-          java.util.Iterator represents Iterator interface

-          java.lang.Iterable represents Aggregate interface

-          Java collections framework implements java.util.Iterator interface.

Example Usage:

    List<File> paths=...;

   

    // obtain iterator

    Iterator<File> pathsIterator = paths.iterator();

   

    while (pathsIterator.hasNext()) {

        File path = pathsIterator.next();

       

        System.out.println(path.getName());

    }