HashTable using separate chaining

Question

I'm trying to make a HashTable class using separate chaining. A problem exists that when I use the "insert" method like this:

public void insert(int k, int v) {
    if (k < 0 || k >= 10) {
        throw new IllegalArgumentException();
    }
    ListNode front = hTable.get(k);
    if (front.data == 0 && front.next == null) {
        front.data = v;
    } else { 
        front = new ListNode(v, front);
    }
}

my list ends up having only one node. Maybe because something happens when I insert the value at the front:

else { 
        front = new ListNode(v, front);
    }

But when I change this method and attempt to insert at the end of the list:

else {
        while (front.next != null) {
            front = front.next;
        }
        front.next = new ListNode(v);
    }

The list now works and could contain several values. Why I cannot insert at the front of the list?

Answer 1

front = new ListNode(v, front); changes the value of the local variable front, but not the value of hTable.get(k) . hTable.get(k) still returns the old value after changing front. To make this work, you also need to update hTable to store this new front as beginning of the chain.