Java Class Fields Definition

Question

I've came across with the next code lines, which are part of the implementation of a Node class :

public class Node {

    private String data;
    private Node next;

I wonder how is it possible to use private Node next; as a field of Node ? How come this 'self-instance' is legal and how does it work ? I'll be grateful if anyone could explain this.

It's not a self reference. It's a reference to an object of the same type. — Sotirios Delimanolis, Oct 08 '13 at 22:20
Just as the name suggests `next` should refer to a `Node` object. And there would definitely be a public method that takes Node object and assigns that to `next` — Prateek, Oct 08 '13 at 22:22
An application of this is used in a Linked list data structure: http://en.wikipedia.org/wiki/Linked_list — scrappedcola, Oct 08 '13 at 22:23

ssantos · Answer 1 · 2013-10-08T22:32:01.567

2

Node next will just keep a reference to a different instance of Node class, which means Node class has-a Node.

I'm guessing that class belongs to a simple 'linked list' implementation, where each node keeps a reference to the next node in the list.

edited Oct 08 '13 at 22:32

answered Oct 08 '13 at 22:23

ssantos

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Doesn't need to be a different instance. – Dave Newton Oct 08 '13 at 22:23
Well, not necessarily, but most probably. – ssantos Oct 08 '13 at 22:25

score 1 · Answer 2 · answered Oct 08 '13 at 22:31

You probably meant something on these terms

  public class Node {

        private int info;
        private Node next;

        Node(int info, Node next) {
            this.info = info;
            this.next = next;
        }

When you actually use this in a linked list kind of structures the next points to another (or same) kind of object of type Node

score 1 · Accepted Answer · answered Oct 08 '13 at 22:33

1

Is not a self-instance, but, it will refer a instance of an object on memory, of the same type, a Node.

Att: The reffered object can be itself.

answered Oct 08 '13 at 22:33

Cold

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That's what i've asked - how come the reffered object could be itself ? – Oct 09 '13 at 07:19
Well, you can look at `next` variable as a recipient that recieves an address of memory of `Node` type. When u create a `Node`, it can store on `next` variable (an recipient) the memory address of an variable of `Node` type. It´s clear? – Cold Oct 09 '13 at 11:02
Or, u can see a `Node` as a house. Every house has an address, and inside of every house u can have a paper with address of other houses. In my house, i can put on this paper the reference of my own house. – Cold Oct 09 '13 at 11:03

Java Class Fields Definition

3 Answers3