Implementing Linked List

Top addFirst() addLast() removeFirst() display() main() Output

        
LINKED LIST IMPLEMENTATION
    
class SinglyLinkedList1 {
    // Node class
    

        private static class Node {
        String data;
        Node next;

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

    
Singly Linked List variables
    
private Node head; 
 // points to the first node
    
private Node tail; 
 // points to the last node
    
private int size;  
 // tracks number of nodes

    
Constructor
    
public SinglyLinkedList1() {
        head = null;
        tail = null;
        size = 0;
    }

      
To insert an element at the head (beginning) of the list:
      
//    Create a new node containing the new element.
//    Set its next reference to the current head node.
//    Reassign the head to point to this new node.
//    Increase the list size by one.

    // Add an element at the beginning of the list
   


    public void addFirst(String data) {
        Node newest = new Node(data);
        newest.next = head; // link new node to old head
        head = newest;      // update head to new node
        if (tail == null)   // if list was empty
            tail = newest;
        size++;
    }
      
  Link
 
   

       
To insert element at Last Steps (Algorithm addLast(e))
//    Create a new node containing the element e.
//    Set its next reference to null (it will become the last node).
//    Set the current tail’s next to this new node (link old tail → new node).
//    Update tail to point to this new node.
//    Increment size by one.

    public void addLast(String data) {
        Node newest = new Node(data);
        if (head == null) { // if list is empty
            head = newest;
            tail = newest;
        } else {
            tail.next = newest;
            tail = newest;
        }
        size++;
    }
    
  Link



     
Tod Delete Element at first -Removing from the Head (Front)
//    Move the head pointer to the next node (head = head.next)
//    Decrease the list’s size count (size--)
//    Remove the first element

    public String removeFirst() {
        if (head == null) {
            System.out.println("List is empty.");
            return null;
        }

        String removedElement = head.data;
        head = head.next;
        size--;

        if (head == null)
            tail = null;

        return removedElement;
    }


    
Display the list
    

    public void display() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " -> ");
            current = current.next;
        }
        System.out.println("null");
    }

    
 Main method to test
    

    public static void main(String[] args) {
        SinglyLinkedList1 list = new SinglyLinkedList1();

        list.addFirst("CHENNAI");
        list.display();
        list.addFirst("TRICHY");
        list.display();
        list.addFirst("MADURAI");
        list.display();
        list.addLast("TIRUNELVELI");
        list.display();
        list.addFirst("TUTICORIN");
        list.removeFirst();
        list.display();
        
        System.out.println("Removed: " + list.removeFirst());
        list.display();
     }
}

 OUTPUT

CHENNAI -> null
TRICHY -> CHENNAI -> null
MADURAI -> TRICHY -> CHENNAI -> null
MADURAI -> TRICHY -> CHENNAI -> TIRUNELVELI -> null
MADURAI -> TRICHY -> CHENNAI -> TIRUNELVELI -> null
Removed: MADURAI
TRICHY -> CHENNAI -> TIRUNELVELI -> null