Java Reference
In-Depth Information
Node Inner Classes
You can make a linked list, or any similar data structures, self-contained by making the
node class an inner class. In particular, you can make the class
LinkedList1
more self-
contained by making
Node1
an inner class, as follows:
public class
LinkedList1
{
private class
Node1
{
<The rest of the definition of Node1 can be
the same as in Display 15.2.>
}
private
Node1 head;
<The constructor and methods in Display 15.3 are inserted here.>
}
Note that we have made the class
Node1
a private inner class. If an inner class is
not intended to be used elsewhere, it should be made private. Making
Node1
a private
inner class hides all objects of the inner class and avoids a privacy leak.
If you are going to make the class
Node1
a private inner class in the definition of
LinkedList1
, then you can safely simplify the definition of
Node1
by eliminating the
accessor and mutator methods (the
set
and
get
methods) and just allowing direct
access to the instance variables (
item
,
count
, and
link
) from methods of the outer
class. In Display 15.7, we have written a class similar to
LinkedList1
in this way. The
rewritten version, named
LinkedList2
, is like the class
LinkedList1
in Display 15.3
in that it has the same methods that perform basically the same actions. To keep the
discussion simple,
LinkedList2
has only one data field instead of two. We could easily
have retained the two data fields, but we wanted a notationally simple example without
any distracting details. (See Self-Test Exercise 8 for a version that has the same kind of
data in each node as in the nodes of
LinkedList1
.)
Display 15.7
A Linked List Class with a Node Inner Class
(part 1 of 3)
1
public class
LinkedList2
2 {
3
private class
Node
4 {
5
private
String item;
6
private
Node link;
7
public
Node( )
8 {
9 item =
null
;
10 link =
null
;
11 }
