Queue implemented by a Linked List in core-java example

Queue implemented by a Linked List:

/**
 * @author Abhinaw.Tripathi
 *
 */

class Link
{

 public long dData;
 public Link next;

 public Link(long dd)
 {
dData=dd;
 }

 public void displayLink()
 {
 System.out.println(dData+ " ");
 }

}

class FirstLastList
{
  private Link first;
  private Link last;

  public FirstLastList()
  {
first=null;
last=null;
  }

  public boolean isEmpty()
  {
return (first==null);
  }

  public void insertLast(long dd)
  {
 Link newLink=new Link(dd);
 if(isEmpty())
 first=newLink;
 else
 last.next=newLink;
 last=newLink;
  }

  public long deleteFirst()
  {
 long temp=first.dData;
 if(first.next == null)
 last=null;
 first=first.next;
 return temp;
  }

  public void displayList()
  {
Link current=first;
while(current!=null)
{
current.displayLink();
current=current.next;
}

System.out.println(" ");
   }

}

class LinkQueue
{
private FirstLastList theList;

public LinkQueue()
{
theList=new FirstLastList();
}

public boolean isEmpty()
{
return (theList.isEmpty());
}

public void insert(long j)
{
theList.insertLast(j);

}

public long remove()
{
return theList.deleteFirst();
}

public void displayQueue()
{
System.out.println("Queue (front ---> rear:)");
theList.displayList();
}
}

public class LinkQueueApp {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
     LinkQueue theQueue=new LinkQueue();
     theQueue.insert(20);
     theQueue.insert(40);
   
     theQueue.displayQueue();
   
     theQueue.insert(60);
     theQueue.insert(80);
   
     theQueue.displayQueue();
   
     theQueue.remove();
     theQueue.remove();
   
     theQueue.displayQueue();
}


}

The desire output will be

Stack  (top---->bottom:)
40 
20 

Stack  (top---->bottom:)
80 
60 
40 
20 

Stack  (top---->bottom:)
40 
20