Java program to delete a node from the beginning of the singly linked list

Java program to delete a node from the beginning of the singly linked list

public class DeleteStart

{ 

 

    //Represent a node of the singly linked list 

    class Node

    { 

        int data; 

        Node next; 

 

        public Node(int data) { 

            this.data = data; 

            this.next = null; 

        } 

    } 

 

    //Represent the head and tail of the singly linked list 

    public Node head = null; 

    public Node tail = null; 

 

    //addNode() will add a new node to the list 

    public void addNode(int data)

    { 

        //Create a new node 

        Node newNode = new Node(data); 

 

        //Checks if the list is empty 

        if(head == null)

        { 

            //If list is empty, both head and tail will point to new node 

            head = newNode; 

            tail = newNode; 

        } 

        else

        { 

            //newNode will be added after tail such that tail's next will point to newNode 

            tail.next = newNode; 

            //newNode will become new tail of the list 

            tail = newNode; 

        } 

    } 

 

    //deleteFromStart() will delete a node from the beginning of the list 

    public void deleteFromStart()

    { 

 

        //Checks if the list is empty 

        if(head == null)

        { 

            System.out.println("List is empty"); 

            return; 

        } 

        else

        { 

            //Checks whether the list contains only one node 

            //If not, the head will point to next node in the list and tail will point to the new head. 

            if(head != tail)

            { 

                head = head.next; 

            } 

            //If the list contains only one node 

            //then, it will remove it and both head and tail will point to null 

            else

            { 

                head = tail = null; 

            } 

        } 

    } 

 

    //display() will display all the nodes present in the list 

    public void display()

    { 

        //Node current will point to head 

        Node current = head; 

        if(head == null)

        { 

            System.out.println("List is empty"); 

            return; 

        } 

        while(current != null)

        { 

            //Prints each node by incrementing pointer 

            System.out.print(current.data + " "); 

            current = current.next; 

        } 

        System.out.println(); 

    } 

 

    public static void main(String[] args)

    { 

 

        DeleteStart sList = new DeleteStart(); 

 

        //Adds data to the list 

        sList.addNode(1); 

        sList.addNode(2); 

        sList.addNode(3); 

        sList.addNode(4); 

 

        //Printing original list 

        System.out.println("Original List: "); 

        sList.display(); 

 

        while(sList.head != null)

        { 

            sList.deleteFromStart(); 

            //Printing updated list 

            System.out.println("Updated List: "); 

            sList.display(); 

        } 

    } 

} 

OUTPUT:-