Define Linked-List Write java program to perform a)Declare Node b)Add item in the Node c)Display the entire List d)Add Item at Start e)Add Item at End

Sure, here is an example Java program that demonstrates the basic operations of a singly linked-list:

public class LinkedListExample {

    class Node {
        int data;
        Node next;

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

    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;
        }
    }

    public void addAtStart(int data) {
        Node newNode = new Node(data);

        if (head == null) {
            head = newNode;
        } else {
            newNode.next = head;
            head = newNode;
        }
    }

    public void addAtEnd(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;
        }
    }

    public void display() {
        Node current = head;

        if (head == null) {
            System.out.println("List is empty.");
        } else {
            while (current != null) {
                System.out.print(current.data + " -> ");
                current = current.next;
            }
            System.out.println("null");
        }
    }

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

        // add items to the list
        list.add(5);
        list.add(10);
        list.add(15);

        // display the list
        System.out.println("Original List:");
        list.display();

        // add item at start
        list.addAtStart(1);
        System.out.println("List after adding item at start:");
        list.display();

        // add item at end
        list.addAtEnd(20);
        System.out.println("List after adding item at end:");
        list.display();
    }
}

Here is a brief explanation of the program:

- The `Node` class represents a single node in the linked-list. It has two attributes: `data` to store the value of the node and `next` to store a reference to the next node in the list.
- The `LinkedListExample` class represents the linked-list itself. It has a `head` attribute which stores a reference to the first node in the list.
- The `add` method adds a new node to the end of the list. It first creates a new node with the given data. If the list is empty (i.e. `head` is `null`), it sets the new node as the head. Otherwise, it traverses the list until it reaches the last node and sets the `next` attribute of the last node to the new node.
- The `addAtStart` method adds a new node to the beginning of the list. It first creates a new node with the given data. If the list is empty (i.e. `head` is `null`), it sets the new node as the head. Otherwise, it sets the `next` attribute of the new node to the current head and sets the new node as the head.
- The `addAtEnd` method adds a new node to the end of the list, similar to the `add` method.
- The `display` method traverses the list and prints the value of each node. If the list is empty, it prints a message indicating that the list is empty.
- The main method creates a new `LinkedListExample` object, adds some items to the list, and calls the `display` method to print the original list. Then, it adds an item at the start of the list and calls `display` again to print the updated list. Finally, it adds an item at the end of the list and calls `display` again to print the final list.