Implementation of Queues using Linked List in Java

import java.util.*;
public class Main
{
  private Node front, rear;
  private int s;		// number of items

  //class to define linked node
  private class Node
  {
    int data;
    Node next;
  }


  public Main ()
  {
    front = null;
    rear = null;
    s = 0;
  }

  public boolean isEmpty ()
  {
    return (s == 0);
  }

  public void disp ()
  {
    if (s == 0)
      {
	System.out.println ("queue is empty");
	return;
      }
    Node temp = front;
    while (temp != null)
      {
	System.out.print (" " + temp.data);
	temp = temp.next;
      }

  }
  //to Remove item
  public void dequeue ()
  {
    int data = front.data;
    front = front.next;
    if (isEmpty ())
      {
	rear = null;
      }
    s--;

  }

  //to Add data .
  public void enqueue (int data)
  {
    Node old = rear;
    rear = new Node ();
    rear.data = data;
    rear.next = null;
    if (isEmpty ())
      {
	front = rear;
      }
    else
      {
	old.next = rear;
      }
    s++;
    System.out.println (data + " added to the queue");
  }

  public static void main (String args[])
  {

    Main queue = new Main ();
    queue.enqueue (1);
    queue.enqueue (2);
    queue.enqueue (3);
    queue.enqueue (4);
    System.out.println ("Original queue :");
    queue.disp ();
    System.out.println ();

    queue.dequeue ();
    queue.dequeue ();
    System.out.println ("Queue after dequeue");
    queue.disp ();
  }
}