linkedlist: insert node at head of linkedlist Java

Asked Jun 25 '15 at 23:37

Active Jun 25 '15 at 23:48

Viewed 44 times

I am just learning linkedlists and trying to insert a node at the head. Here is my code:

Node Insert(Node head,int x) {

    Node tmp = new Node();

    if (head == null) {
        head = tmp;
        tmp.data = x;

    }
    tmp.data = x;
    tmp = head;
    tmp.next = head;

    return tmp;
}

I am not sure what is going wrong. My logic:

Create a new node 'tmp'
assign that value of 'x' and the reference to tmp would be null
MAke tmp's next i.e. reference to the head of the linkedlist
if head is null then tmp's data becomes head's data and tmp's reference become null

edited Jun 25 '15 at 23:48

asked Jun 25 '15 at 23:37

fscore

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You haven't _Create a new node 'tmp'_. – Sotirios Delimanolis Jun 25 '15 at 23:41
`tmp` is always `null` when you try to use it – Jeff Storey Jun 25 '15 at 23:41
Start making the distinction between objects, variables, and references. – Sotirios Delimanolis Jun 25 '15 at 23:41
@SotiriosDelimanolis if I create Node tmp = new Node() then what is wrong in the rest of my code? – fscore Jun 25 '15 at 23:48
Step through your code with a debugger. Please don't change your question like that. – Sotirios Delimanolis Jun 25 '15 at 23:49
One of the problems was the null pointer that you mentioned but marking it as a duplicate is not valid at all as it doesn't help me. – fscore Jun 26 '15 at 00:53

linkedlist: insert node at head of linkedlist Java

0 Answers0