双端链表

public class Link {
public long lData;
public Link next;//reference to next Link
public Link(long lData){
this.lData=lData;
}
public void displayLink1(){
System.out.print("{"+lData+"}");
}
}

public class FirstLastList {
private Link first;
private Link last;

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

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

public void insertFirst(long dd){//insert at front of list
Link newLink = new Link(dd);
if(isEmpty()){
last=newLink;
}
newLink.next=first;
first=newLink;
}

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.lData;
if(first.next==null){
last = null;
}
first=first.next;
return temp;
}

public void displayList(){
Link current =first;
while(current!=null){
current.displayLink1();
current=current.next;
}
}
}

public class FirstLastListApp {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
FirstLastList theList = new FirstLastList();
theList.insertFirst(22);
theList.insertFirst(44);
theList.insertFirst(66);

theList.insertLast(11);
theList.insertLast(33);
theList.insertLast(55);

theList.displayList();

theList.deleteFirst();
theList.deleteFirst();

theList.displayList();
}
}