Stack Implemented by a Linked List in core-java example

Stack implementation 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 LinkList
{
private Link first;

public LinkList()
{
first=null;
}

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

public void insertFirst(long dd)
{
Link newLink=new Link(dd);
newLink.next=first;
first=newLink;
}

public Link deleteFirst()
{
Link temp=first;
first=first.next;
return temp;
}

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

}

class LinkStack
{
 private LinkList theList;

 public LinkStack()
 {
theList=new LinkList();
 }

 public void push(long j)
 {
theList.insertFirst(j);
 }

 public Link pop()
 {
return (theList.deleteFirst());
 }

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

 public void displayStack()
 {
System.out.println("Stack  (top---->bottom:)");
theList.displayList();
 }

}



public class LinkStackApp
{
public static void main(String[] args)
{
LinkStack theStack=new LinkStack();
theStack.push(20);
theStack.push(40);

theStack.displayStack();

theStack.push(60);
theStack.push(80);
        theStack.displayStack();
     
        theStack.pop();
        theStack.pop();
     
        theStack.displayStack();
}


}

The desire output will be 

Stack  (top---->bottom:)

40 

20 

Stack  (top---->bottom:)

80 

60 

40 

20 

Stack  (top---->bottom:)

40 

20