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Question

I am reading "Cracking the Coding interview" and I noticed the code below for a Linked List implementation in Java.

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;
    }
}

The line Node n = this; confuses me very much. We are supposed to start at the head of the list and go till the end of the list. "This" in java usually refers to the current instance. So, how are these two related? I'm sure I am missing something here. Please help!

Answer 1

Whenever, for Node reference someNode , someNode.appendToTail(x) is called, it will create a new Node with data value x , and append it to the tail of whatever list contains someNode . If someNode is not already part of a list, it will, afterwards, be the head of a two node list with the new node as tail. If someNode is part of a longer list, the new node will be the tail of that list.

To do that, appendToTail has to find the tail note, the one with a null next pointer. It starts the search with itself, using this . If it is the tail of its list, the loop will be skipped because next is null , and the n.next = end; assignment will have the effect of next = end; . If there are more nodes in the list, the while loop will skip over them until it finds the current tail.