Java Program to Create and Count Nodes in a Singly Linked List

In this article, we are going to see how we can create and count nodes in a singly linked list by using Java programming language.

Java Program to Create and Count Nodes in a Singly Linked List

Each element in linkedlist is called as a node. Here we need to first create nodes and then count the number of nodes. To create nodes we need to add elements into the linkedlist and to count the number of nodes traverse the linkedlist starting from head to tail and keep a track on its total count.

Let’s see the program to understand it clealry.

Approach:

• Create a linked list by creating an object of that class.
• Call the user defined count( ) method to print the number of nodes in the list.
• Add some elements to the list.
• Print the linked list by calling user defined method show() in which we will traverse each element one by one and print it.
• Call the count( ) method again and see the number of nodes after the elements have been added.

Program:

import java.util.*;
// Main class
public class Main
{
    // Class Node that defines the two linked list variables
    class Node
    {
        int data;
        Node nextNode;
        // constructor to create a node
        public Node(int data) 
        {    
            this.data = data;    
            this.nextNode = null;    
        }    
    }

    // Setting the head and end of the node as NULL  
    public Node head = null;    
    public Node tail = null;  
    // Count the number of nodes in the linked list
    public void count()
    {
        int c = 0;
        Node curr = head;
        //continue it till curr refers to null
        while(curr!=null)
        {
            c++;
            curr = curr.nextNode;
        }
        System.out.println("The number of nodes in the linked list currently are: "+c);
    }
    
    // method to add a node to the linked list
    public void add(int data)
    {
        Node newNode = new Node(data);
        // Checks if there was any previous node
        //if the list is empty then head and tail both will point to newNode
        if(head==null)
        {
            head = newNode;
            tail = newNode;
        }
        else
        {
            tail.nextNode = newNode;
            tail = newNode;
        }
    }
    
    // Method to display all the nodes of the linked list
    public void show()
    {
        Node curr = head;
        // If the head is pointing to no node then the linked list is empty
        if(head==null)
            System.out.println("Linked List is empty");
        else
        {
            System.out.println("The nodes are:");
            while(curr!=null)
            {
                System.out.print(curr.data+",");
                curr = curr.nextNode;
            }
            System.out.println();
        }
    }
    
    //Driver method
    public static void main(String[] args) 
    {
        // create an object of the main class
        Main ll = new Main();
        // Counts the number of nodes in the linked list
        ll.count();
        // add elements to the linked list
        ll.add(10);
        ll.add(20);
        ll.add(30);
        ll.add(40);
        ll.add(50);
        // display the nodes
        ll.show();
        // Again counts the number of nodes
        ll.count();
    }
}

Output:

The number of nodes in the linked list currently are: 0
The nodes are:
10,20,30,40,50,
The number of nodes in the linked list currently are: 5

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