提问人：Amanda James 提问时间：11/3/2023 最后编辑：StackFlowedAmanda James 更新时间：11/3/2023 访问量：44
LinkedList 空指针错误。当我尝试打印 LinkedList [duplicate] 中的元素时，我不断收到空指针异常
LinkedList null pointer error. I keep on getting a null pointer exception when trying to print the elements in the LinkedList [duplicate]
问：
尝试打印列表中的元素时，我不断收到空指针异常。异常命中了 print（） 中我开始 while 循环的行。有没有办法解决这个问题？谢谢
class LinkedLists {
private Node node;
public LinkedLists() {
}
public void add(int d) {
Node newNode = new Node(d);
Node curr = node;
if(curr == null)
curr = newNode;
while(curr.next != null) {
curr = curr.next;
}
curr.next = newNode;
return;
}
public void print() {
Node curr = node;
while(curr.next != null) {
System.out.println(curr.data);
curr = curr.next;
}
System.out.println(curr.data);
}
public static void main(String[] args) {
LinkedLists list = new LinkedLists();
list.add(3);
list.add(12);
list.add(99);
list.add(6);
list.print();
}
}
public class Node {
Node next;
int data;
public Node(int d) {
data = d;
next = null;
}
}
答：
-1赞
Awwal15
11/3/2023
#1
尝试这样做
public class Node
{
Node? next;
int data;
public Node(int d)
{
this.data = d;
this.next = null;
}
}
不要担心这个关键词
1赞
StackFlowed
11/3/2023
#2
问题是你总是在开始时设置。
Node curr = node;
您需要在检查后执行此操作。
class LinkedLists {
private Node headNode;
public LinkedLists() {
}
public void add(int d) {
Node newNode = new Node(d);
//remove it from here
if(headNode == null) {
headNode = newNode;
return;
}
//Added it here
curr = headNode;
while(curr.next != null) {
curr = curr.next;
}
curr.next = newNode;
return;
}
public void print() {
Node curr = headNode;
while(curr.next != null) {
System.out.println(curr.data);
curr = curr.next;
}
System.out.println(curr.data);
}
public static void main(String[] args) {
LinkedLists list = new LinkedLists();
list.add(3);
list.add(12);
list.add(99);
list.add(6);
list.print();
}
}
public class Node {
Node next;
int data;
public Node(int d) {
data = d;
next = null;
}
}
评论
node如果列表为空，则为 null。您需要处理这种情况。