Singly Linked List in Java

// Linked in Java Program
import java.lang.*;

class LinkedList
{
  Node head;
  // not using parameterized constructor would by default
  // force head instance to become null
  // Node head = null;  // can also do this, but not required

  // Node Class
  class Node
  {
    int data;
    Node next;

      Node (int x)		// parameterized constructor
    {
      data = x;
      next = null;
    }
  }

  public Node insertNode (int data)
  {
    // Using constructor to create memory and value assignment
    Node new_node = new Node (data);
    // current head becomes this new_node's next
    new_node.next = head;

    // changing head to this newly created node
    head = new_node;

    return head;
  }

  public void delete ()
  {
    if (head == null)
      {
	System.out.println ("List is empty, not possible to delete");
	return;
      }

    System.out.println ("Deleted: " + head.data);
    // move head to next node
    head = head.next;
  }



  public void display ()
  {
    Node node = head;
    //as linked list will end when Node reaches Null
    while (node != null)
      {
	System.out.print (node.data + " , ");
	node = node.next;
      }
    System.out.println ();
  }

}

class Main
{

  public static void main (String args[])
  {
    LinkedList listObj = new LinkedList ();

      listObj.insertNode (25);
      listObj.insertNode (20);
      listObj.insertNode (15);
      listObj.insertNode (10);
      listObj.insertNode (5);

      listObj.display ();

      listObj.delete ();
      listObj.delete ();
      listObj.delete ();

      listObj.display ();

  }
}

import java.lang.*;

// Node Class
class Node {
    int data;
    Node next;

    Node(int x) // parameterized constructor
    {
        data = x;
        next = null;
    }
}

class Main
{
    static Node insertStart(Node head, int data)
    {
        // Creating newNode memory & assigning data value
        Node newNode = new Node(data);

        // assigning this newNode's next as current head node
        newNode.next = head;
        // re-assigning head to this newNode
        head = newNode;

        return head;
    }

    public static Node delete(Node head)
    {
        if (head == null){
            System.out.println("List is empty, not possible to delete");
            return head;
        }

        System.out.println("Deleted: " + head.data);
        // move head to next node
        head = head.next;

        return head;
    }

    static void display(Node node) {

        //as linked list will end when Node is Null
        while (node != null) {
            System.out.print(node.data + " ");
            node = node.next;
        }
        System.out.println("");
    }

    public static void main(String args[])
    {
        Node head = null;
        head = insertStart(head,6);
        head = insertStart(head,5);
        head = insertStart(head,4);
        head = insertStart(head,3);
        head = insertStart(head,2);
        head = insertStart(head,1);

        display(head);

        head = delete(head);
        head = delete(head);
        head = delete(head);

        display(head);


    }
}