Question

Using Doubly Linked List, create a java code that does the following Without using LinkedList from the JAVA LIBRARY. and please include methods for each function.

Create a menu that contains the following operations :

1. Add new node to DLL. ( as a METHOD )

2. Delete a node from DLL. ( as a METHOD )

3. Show how many nodes in DLL. ( as a METHOD )

4. Print all data in the DLL. ( as a METHOD )

5. Exit.

Important notes :

1. Write the operations from the pseudocode.

2. The user should insert all data even in the first node.

3. The menu should be repeated each time until the user 5 (Exit).

Answer 1

Code - JAVA

DoublyLinkedList.java
public class DoublyLinkedList {  
  
  
    class Node{  
        int data;  
        Node previous;  
        Node next;  
  
        public Node(int data) {  
            this.data = data;  
        }  
    }  
  
    //Represent the head and tail of the doubly linked list  
    Node head, tail = null;  
  
    //addNode() will add a node to the list  
    public void addNode(int data) {  
        //Create a new node  
        Node newNode = new Node(data);  
  
        //If list is empty  
        if(head == null) {  
            //Both head and tail will point to newNode  
            head = tail = newNode;  
            //head's previous will point to null  
            head.previous = null;  
            //tail's next will point to null, as it is the last node of the list  
            tail.next = null;  
        }  
        else {  
            //newNode will be added after tail such that tail's next will point to newNode  
            tail.next = newNode;  
            //newNode's previous will point to tail  
            newNode.previous = tail;  
            //newNode will become new tail  
            tail = newNode;  
            //As it is last node, tail's next will point to null  
            tail.next = null;  
        }  
    }  
  
    public void display() {  
        Node current = head;  
        if(head == null) {  
            System.out.println("List is empty");  
            return;  
        }  
        System.out.println("Nodes of doubly linked list: ");  
        while(current != null) {  
            //Prints each node by incrementing the pointer.  
  
            System.out.print(current.data + " ");  
            current = current.next;  
        }  
    }  
  public void count_nodes()  {
       Node current = head;
        int count=0;
        while(current!=NULL)  {
        count++;
        }
         return count;
}
 public static void main(String[] args) {  
  
        DoublyLinkedList dList = new DoublyLinkedList();  
        //Add nodes to the list  
        dList.addNode(1);  
        dList.addNode(2);  
        dList.addNode(3);  
        dList.addNode(4);  
        dList.addNode(5);  
  
        dList.display();
        
        dList.count_nodes();  
    }  
}  

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