Linked lists - Data Structures and Problem Solving Using Java - page 627

1 /**
2 * Construct the list
3 */
4 public LinkedList( )
5 {
6 header = new ListNode<AnyType>( null );
7 }
8
9 /**
10 * Test if the list is logically empty.
11 * @return true if empty, false otherwise.
12 */
13 public boolean isEmpty( )
14 {
15 return header.next == null;
16 }
17
18 /**
19 * Make the list logically empty.
20 */
21 public void makeEmpty( )
22 {
23 header.next = null;
24 }
25
26 /**
27 * Return an iterator representing the header node.
28 */
29 public LinkedListIterator<AnyType> zeroth( )
30 {
31 return new LinkedListIterator<AnyType>( header );
32 }
33
34 /**
35 * Return an iterator representing the first node in the list.
36 * This operation is valid for empty lists.
37 */
38 public LinkedListIterator<AnyType> first( )
39 {
40 return new LinkedListIterator<AnyType>( header.next );
41 }

figure 17.9
Some LinkedList
class one-liners

Let us revisit the issue of whether all three classes are necessary. For
instance, couldn't we just have the LinkedList class maintain a notion of a
current position? Although this option is feasible and works for many
applications, using a separate iterator class expresses the abstraction that the