Java Reference
In-Depth Information
Display 15.17
A Linked List with an Iterator
(part 2 of 3)
17
public
List2Iterator( )
18
{
19
position = head;
//Instance variable head of outer class.
20
previous =
null
;
21
}
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
);
