public class FirstLastList {
private Link first; // ref to first link
private Link last; // ref to last link
public FirstLastList() {
first = null;
last = null;
}
public boolean isEmpty() {
return first == null;
}
public void insertFirst(long dd) {
Link newLink = new Link(dd); // make new link
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.dData;
if (first.next == null) // if only one item
last = null;
first = first.next;
return temp;
}
public void displayList() {
System.out.print("List: ");
Link current = first;
while (current != null)
{
current.displayLink();
current = current.next;
}
System.out.println("");
}
public static void main(String[] args) { // make a new list
FirstLastList theList = new FirstLastList();
theList.insertFirst(22);
theList.insertFirst(44);
theList.insertLast(33);
theList.insertLast(55);
theList.displayList();
theList.deleteFirst();
theList.deleteFirst();
theList.displayList();
}
class Link {
public long dData;
public Link next;
public Link(long d) {
dData = d;
}
public void displayLink() {
System.out.print(dData + " ");
}
}
}
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