Receive a Position!

  • Explain how Position is different from the Node (inner) class.

Here is the implementation of delete from an earlier exercise:

public void delete(Node<T> target) {
  Node<T> prevNode = target.prev;
  Node<T> nextNode = target.next;

  prevNode.next = nextNode;
  nextNode.prev = prevNode;
}

Exercise Update delete so that it receives a "Position" instead of a "Node".

// Pre: target's actual type is Node
public void delete(Position<T> target) {
  // TODO Implement Me!
}
Solution
// Pre: target's "actual" type is Node
public void delete(Position<T> target) {
  Node<T> targetNode = (Note<T>) target;

  Node<T> prevNode = targetNode.prev;
  Node<T> nextNode = targetNode.next;

  prevNode.next = nextNode;
  nextNode.prev = prevNode;
}

Notice we must explicitly downcast target to access the next and prev reference variables.