Consider the following code which implements the add method in the DList class f

Question

Consider the following code which implements the add method in the DList class from the course videos:

public void add(int pIndex, Integer pData) throws IndexOutOfBoundsException {

    if (pIndex < 0 || pIndex > getSize())

        throw new IndexOutOfBoundsException();

    if (pIndex == getSize()) { //adding node to the end of the list

        Node newNode = new Node(pData, getTail(), null);

        if (isEmpty())

            setHead(newNode); //////////LINE 1

        else

            getTail().setNext(newNode); //////////LINE 2

        setTail(newNode);

    }

    else {

        Node node = getNodeAt(pIndex);

        Node newNode = new Node(pData, node.getPrev(), node);

        if (pIndex != 0)

            node.getPrev().setNext(newNode);

        node.setPrev(newNode);

        if (pIndex == 0)

            setHead(newNode);

    }

    setSize(getSize() + 1);

}

Explain what will happen if the lines indicated are swapped.

Explanation / Answer

Hi,

As per normal flow of your code the "Line 1" is inserting a node at the beginning of the linked list if the list is empty. And Line 2 will get executed if the list is non empty. Line 2 will make the last node of the linked list to point to the newly inserted node.

Now, if we swap the Line 1 with Line 2, then as the list is empty,the new node is inserted as the first node. If line 2 is swapped by line 1 then everytime a new node is inserted in a non-empty list, the new node is inserted at the beginning of the list.

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