Linked Data Structures - Absolute Java - page 837

Display 15.17 A Linked List with an Iterator (part 2 of 3)

22 public void restart( )
23 {
24 position = head; //Instance variable head of outer class.
25 previous = null ;
26 }

27 public String next( )
28 {
29 if (!hasNext( ))

30 throw new NoSuchElementException( );

31 String toReturn = position.item;
32 previous = position;
33 position = position.link;
34 return toReturn;

35 }

36 public boolean hasNext( )
37 {
38 return (position != null );

39 }
40 /**
41 Returns the next value to be returned by next( ).
42 Throws an IllegalStateExpression if hasNext( ) is false.
43 */
44 public String peek( )
45 {
46

if (!hasNext( ))

47 throw new IllegalStateException( );

48 return position.item;

49 }

50 /**
51 Adds a node before the node at location position.
52 previous is placed at the new node. If hasNext( ) is
53 false, then the node is added to the end of the list.
54 If the list is empty, inserts node as the only node.
55 */
56 public void addHere(String newData)
57 {
58 if (position == null && previous != null )
59 // at end of the list, add to end
60 previous.link = new Node(newData, null );
61 else if (position == null || previous == null )
62 // list is empty or position is head node
63 LinkedList2.this.addtoStart(newData);

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