A List Implementation That Links Data - Data Structures and Abstractions with Java - page 354

reference must change to refer to the new last entry. The following statements perform these
steps, as Figure 14-9 illustrates:
lastNode.setNextNode(newNode);
lastNode = newNode;

FIGURE 14-9

Adding a node to the end of a nonempty chain that has a tail
reference

After executing
lastNode.setNextNode(newNode);

(a)

lastNode

newNode

After executing
lastNode = newNode;

(b)

lastNode newNode

The following revision of the first add method reflects the previous comments:
public void add(T newEntry)
{

Node newNode = new Node(newEntry);
if (isEmpty())
firstNode = newNode;
else
lastNode.setNextNode(newNode);
lastNode = newNode;
numberOfEntries++;
} // end add

Note that the method no longer calls getNodeAt to establish lastNode , as it did in Segment 14.9.

14.23

Adding to the list at a given position. Adding to a list by position affects the tail reference only
when we are adding to an empty list or adding to the end of a nonempty list. Other cases do not
affect the tail reference, so we treat them as we did in Segment 14.11 when we did not have a
tail reference.
Thus, the implementation of the method that adds by position is

public boolean add( int newPosition, T newEntry)
{

boolean isSuccessful = true ;
if ((newPosition >= 1) && (newPosition <= numberOfEntries + 1))
{

Node newNode = new Node(newEntry);
if (isEmpty())
{