In a Doubly Linked List, what does the first node’s previous pointer point to?

Java MCQ: In a Doubly Linked List, what does the first node’s previous pointer point to?

Answer:

Explanation:

In a Doubly Linked List, the first node’s previous pointer points to null. This indicates that the first node does not have any preceding nodes and serves as the entry point for traversing the list from the beginning. The null pointer is crucial for identifying the start of the list and helps prevent errors when traversing backwards from any given node.

A Doubly Linked List allows traversal in both directions because each node contains two pointers: one pointing to the next node and one pointing to the previous node. The first node’s null previous pointer ensures that backward traversal terminates correctly:

class Node {
    int data;
    Node next;
    Node prev;

    Node(int data) {
        this.data = data;
        this.next = null;
        this.prev = null;
    }
}

class DoublyLinkedList {
    Node head;

    public void add(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
            newNode.prev = current;
        }
    }
}

In this example, the first node’s prev pointer remains null, indicating that it is the starting point of the list. Understanding the significance of the null previous pointer in a doubly linked list is essential for correctly implementing operations like traversal, insertion, and deletion, ensuring the list maintains its bidirectional capabilities.

Reference links:

https://www.javaguides.net/p/java-doubly-linked-list-tutorial.html