I'm currently working on creating a doubly linked list, but I'm struggling to do so because the constructor requires the previous element and the next element. However, checking the list just results in two null elements, the head and the tail. The constructor for a node is
public Node(Node prev, Node next, String link) {
this.prev = prev;
this.next = next;
this.link = link;
}
The constructor for the empty list that I have is
public DoublyLinkedList() {
head = tail = null;
}
My code for adding an element is
public void addElement(String link) {
Node n = new Node(tail.prev, tail, link);
if (head == null) {
head = n;
head.next = n;
}
tail.prev = n;
tail = n;
}
I know that the reason I'm resulting in null is because tail == null when I pass it into the constructor. However, I don't know how to update the value of tail before creating a new Node. I tried constructing the empty list with
public DoublyLinkedList() {
head = tail = null;
head.prev = null;
head.next = tail;
tail.next = null;
tail.prev = head;
}
But that isn't showing the elements as being added either.
Am going to assume that addElement
adds an element to the end of the list if that is the case try this instead
Node n = new Node(tail, null, link); // The new tail
if (head == null) {
head = n;
tail = n;
}else{
tail.next = n;
tail = n;
}
For that you can create a class like this: Just for start.
public class DLinkedList{
private node pHead;
private node pTail;
public DLinkedList()
{
this.pHead=null;
this.pTail=null;
}
public insert(String newLink)
{
node newNode = new node():
newNode.link = newLink;
if(pHead==null)
{
pHead=newNode;
pTail=pHead;
}
else
{
newNode.prev=pTail;
pTail.next=newNode;
pTail= pTail.next;
}
}
}
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