插入已排序的链表

Question

我在这行得到nullpointerexception ：

while(data > current.data)

我有一个按升序排序的有序列表，即insertInPos()将节点插入适当的位置。 但是为什么我会得到nullpointer ？

public void insertInPos(int data){
        if(head == null){
            head = new Node(data, null);
        }
        else if(head.data > data){
            Node newNode = new Node(data, null);
            newNode.next = head;
            head = newNode;
        }
        else{
            Node newNode = new Node(data, null);
            Node current = head;
            Node previous = null;
            while(data > current.data){
                previous = current;
                current = current.next;
            }
            previous.next = newNode;
            newNode.next = current;
        }
    }

主班

public class Tester {

    public static void main(String[] args){
        LinkedList myList = new LinkedList();
        myList.insertInPos(1);
        myList.insertInPos(2);//Getting nullpointer from here
        myList.insertInPos(3);
        myList.insertInPos(4);
        myList.insertInPos(7);
        myList.insertInPos(7);
        myList.insertInPos(8);
        System.out.println();

        myList.displayList();
    }
}

Answer 1

您收到错误消息是因为在列表末尾， current变为null 。

将您的条件更改为关注

while(current != null && data > current.data){
    previous = current;
    current = current.next;
}