Question

I’m reading this book and there is this chapter on liked list and it starts with the implementation of a single linked list, it goes like this:

Creating a Linked List:

class Node {
    Node next = null;
    int data;

    public Node(int d) {
        data = d;
    }

    void appendToTail(int d) {
        Node end = new Node(d);
        Node n = this;
        while (n.next != null) {
            n = n.next;
        }
        n.next = end;
    }
}

My questions:

First: I can’t understand how this works. Is this really that complex to understad it or I’m missing something?

Second: Can this “Node” class be considered a linked list? I know it’s missing some functionality but is this a linked list on it’s own?

Third: I’ve googled LinkedList implementations in java and glanced at the original class in java api and it’s a totally different approach. To what approach should I stick?

Answer 1

The problem with this code is that the Node class is a node and a linked list at the same time, which is confusing. Other than that it should be pretty straightforward.

class Node {
    Node next = null;
    int data;

The next holds the next node in a list. If it is the last node, it holds null. The data is a data associated with this node, which in this case is of type int(BTW it should be final).

public Node(int d) {
    data = d;
}

This is a simple constructor which just copies the argument to its field. It represent the head of the list and a list itself.

void appendToTail(int d) {        
    Node n = this;
    while (n.next != null) {
        n = n.next;
    }

This is where find the meet. I’ve rearranged the code a bit to make it easier to understand. The appendToTail method adds a node at the and of the list. In the code above it traverses the list (starting with this which is a head of the list) to find the last node (the one with next field set to null).

    Node end = new Node(d);
    n.next = end;
}

Here a new node is created and added as the next node to the current last thus making it the last node of the list.