Java Reference
In-Depth Information
Defining an Iterator Class
In Display 15.17, we have rewritten the class
LinkedList2
from Display 15.7 so that it
has an inner class for iterators and a method
iterator( )
that returns an iterator for
its calling object. We have made the inner class
List2Iterator
public so that we can
have variables of type
List2Iterator
outside the class
LinkedList2
, but we do not
otherwise plan to use the inner class
List2Iterator
outside of the outer class
LinkedList2
.
Use of iterators for the class
LinkedList2
is illustrated by the program in Display
15.18. Note that, given a linked list named
list
, an iterator for
list
is produced by
the method
iterator
as follows:
LinkedList2.List2Iterator i = list.iterator( );
The iterator
i
produced in this way can only be used with the linked list named
list
.
Be sure to notice that outside of the class, the type name for the inner class iterator
must include the name of the outer class as well as the inner
iterator class. The class
name for one of these iterators is
LinkedList2.List2Iterator
Display 15.17
A Linked List with an Iterator
(part 1 of 3)
1
import
java.util.NoSuchElementException;
This is the same as the class in Displays 15.7 and
15.11 except that the
List2Iterator
inner class
and the
iterator( )
method have been added.
2
public
class
LinkedList2
3{
4
private
class
Node
5
{
6
private
String item;
7
private
Node link;
<
The rest of the definition of the
Node
inner class is given in Display 15.7.
>
8
}
//End of Node inner class
9
/**
10
If the list is altered any iterators should invoke restart or
11
the iterator's behavior may not be as desired.
12
*/
An inner class for iterators for
LinkedList2
.
13
public
class
List2Iterator
14
{
15
private
Node position;
16
private
Node previous;
//previous value of position
(continued)
