LinkedList insert After node

Question

I've been trying to insert a node into a linked list after the current node using Java. I've been able to get the insertion before the current node but I cannot get this to work:

Here is the code for insertNodeBefore. I just want to know if there is a way to adapt this to be able to insert after the current node?

// Insert new node nVal to the list before current node curVal 
public void insertNodeBefore(E nVal, E curVal) {
    Node<E> newNode = new Node<E>(nVal);

    Node<E> curr = head;
    Node<E> prev = null;

    if (head.getNodeValue() == curVal) {
        newNode.setNext(head);
        head = newNode;
        return;
    }

    // scan until locate node or come to end of list
    while (curr != null) {
        // have a match 
        if (curr.getNodeValue() == curVal) {
            // insert node
            newNode.setNext(curr);
            prev.setNext(newNode);
            break;
        } else {
            // advanced curr and prev
            prev = curr;
            curr = curr.getNext();
        }
    }
}

Answer 1

Basically find the node and then:

• set the next of new node equals to the current
• set the next of the current to the new node

Something like this should work:

public void insertNodeBeAfter(E nVal, E curVal) {
    Node<E> newNode = new Node<E>(nVal);

    Node<E> curr = head;

    // scan until locate node or come to end of list
    while (curr != null) {
        // have a match 
        // Replaced == with .equals
        if (curr.getNodeValue().equals(curVal)) {
            // insert node
            newNode.setNext(curr.getNext());
            curr.setNext(newNode);
            break;
        } else {
            curr = curr.getNext();
        }
    }
}

Note is not necessary to have a different treatement for the head because it doesn't change.

Note: could be interesting to handle NOT silently if the list is empty or if the curVal is not found, for example throwing a RuntimeException.

Answer 2

I tried to separate traversal code and the insertion code, it is all taken from the supplied code in your question.

private void insert(Node<E> prev, Node<E> after, Node<E> newNode) {
    newNode.setNext(after);
    if (prev != null) {
        prev.setNext(newNode);
    } else {
        head = newNode;
    }
}
public Node<E> findPrevOf(E curVal) {
    Node<E> curr = head;
    Node<E> prev = null;
    // scan until locate node or come to end of list
    while (curr != null) {
        // have a match 
        if (curr.getNodeValue() == curVal) {
            return prev;
        } else {
            // advanced curr and prev
            prev = curr;
            curr = curr.getNext();
        }
    }
    throw new Exception("throw an exception to indicate that value does not exist");
}
public void insertNodeAfter(E nVal, E curVal) {
    Node<E> prev = findPrevOf(curVal);
    Node<E> curr = null;
    if (prev == null) {
        curr = head;
    } else {
        curr = prev.getNext();
    }
    Node<E> newNode = new Node<E>(nVal);
    insert(curr, (curr == null ? curr: curr.getNext()), newNode);
}
// Insert new node nVal to the list before current node curVal 
public void insertNodeBefore(E nVal, E curVal) {
    Node<E> prev = findPrevOf(curVal);
    Node<E> newNode = new Node<E>(nVal);
    insert(prev, (prev == null ? head : prev.getNext()), newNode);
}