Question

我试图在Doubly链表中添加一个Parson。我写代码，我没有看到任何错误。但在运行中有错误。任何可以帮助我??

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();
    } }

主要：

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();

Answer 1

你没有检查head是否为null，如果是，你将得到零点异常。试试这段代码：

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;
    }
}

Answer 2

最初头 null 。您可以尝试以下 addFirst 方法。

public void addFirst(Node z){

    if(head == null) {
       head = z;
       tail = z;
    } else {
       z.setNext(head);
       head.setPrevioue(z);
    }
    size++;
}

在链接列表java

2 个答案: