I trying to add a Parson in Doubly linked list. I write the code and I haven't seen any error. But in a run there is error. Any on can help me??
public class LinkedList{
Node head, tail;
int size;
public LinkedList()
{ head = null; tail = null; size = 0; }
public void addFirst(Node z){
Node w = head.getNext();
z.setNext(w);
z.setPrevioue(head);
w.setPrevioue(z);
head.setNext(z);
size = size+1;
}
public void Display()
{
System.out.println("Douply Linked List: " + size);
Node car = head;
while(car != null){
System.out.println(car.getNumber() + " <-> ");
car = car.getNext();
} }
the main:
public class DouplyLinkedList {
public static void main(String[] args) {
LinkedList dll = new LinkedList();
dll.addFirst(new Node(20, null, null));
dll.addFirst(new Node(90,null,null));
dll.Display();
youre not checking if head is null, if it is, you will get null point exception. try this code :
public void addFirst(Node z){
if (head == null) {
head = z;
tail = z;
size = 1;
} else {
head.setPrevious(z);
z.setNext(head);
head = z;
size = size+1;
}
}
Initially head is null . You can try the following for addFirst method.
public void addFirst(Node z){
if(head == null) {
head = z;
tail = z;
} else {
z.setNext(head);
head.setPrevioue(z);
}
size++;
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.