1. Link Nodes¶

In this module, we introduce the idea of a link node. A link node has some sort of value field, and a pointer to another link node. Later, you will learn about linked lists, which are made from link nodes. For now, we will just use them as a simple way to connect some objects together.

Here is a class definition for a basic link object. Note that, while the next field references another link object, the data field is of type Object. This denotes that we don't really care what sort of thing one stores in a link node's data field.

class Link {
  public Link next; //Point to next node in list
  public Object data; //Value for this node

  //Constructors
  public Link(Object dataIn, Link nextIn) {
    this.data = dataIn;
    this.next = nextIn;
  }

  public Link(Link nextIn) {
    this.data = null;
    this.next = nextIn;
  }

  Object getData() { // Return the data field
    return data;
  }

  void setData(Object newData) { // Set the data field
    data = newData;
  }

  Link getNext() { // Return the next field
    return next;
  }

  void setNext(Link newNext) { // Set the next field
    next = newNext;
  }
}

Now we'll see some examples for how to use link nodes to put chains together.

1 / 5 Settings

<<<>>>

We'll start with the following four Link objects, already connected together, and the first one pointed to by reference variable head. By the way, notice that we use a slash through a Next field to represent null, in the last Link here.

• Link p = head;
• Link q = head.next;
• Link r = q.next;
• Integer myVal = q.data;

1. 30

20

30

10

5

head

p

q

r

myVal

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How do we set up the chain to begin with?

1 / 7 Settings

<<<>>>

Now lets see how to construct that original chain of Link nodes

• Link head = new Link(null);
• head.data = new Integer(20);
• head.next = new Link(new Integer(30), null);
• head.next.next = new Link(new Integer(10), null);
• Link temp = head.next.next;
• temp.next = new Link(new Integer(5), null);

null

30

10

5

head

temp

Saving...
Server Error
Resubmit

Here is an exercise to practice manipulating link nodes.