Question

For some reason I am getting errors in this code. It is saying that the variables are not visible. I will be providing one of the methods as well as the Node class. This is for a Linked list in Java.

Here is the method giving me errors saying "the field Node<E>.item is not visible" as well as "Node<E>.next is not visible.

public void addFirst(E e) {                // adds element e to the front of the list
          Node<E> node = new Node<>(e);
       node.item = e;
       node.next = head;
       head = node;
      
       if(tail == null)
           tail = head;
          }

Here is the Node class

public class Node<E extends Comparable<E>> {

   private E item;            // reference to the element stored at this node
    private Node<E> next;         // reference to the subsequent node in the list
    /**
     * Creates a node with the given element and next node.
     *
     * @param e the element to be stored
     * @param n reference to a node that should follow the new node
     */
    public Node(E e, Node<E> n) {
       item = e;
      next = n;
    }
  
    public Node(E e) {
       item = e;
      next = null;
    }
    // Accessor methods
    public E getItem() { return item; }
    public Node<E> getNext() { return next; }
    // Modifier methods
    public void setNext(Node<E> n) { next = n; }
} //----------- end of nested Node class -----------

Answer 1

public void addFirst(E e) {                // adds element e to the front of the list
    Node<E> node = new Node<>(e);
    // here .item is not required, since we are already setting that using the constructor above
    node.setNext(head); // use setNext instead of .next
    head = node;

    if (tail == null)
        tail = head;
}

you must use setters and getters instead of directly accessing data members..