package samplelist;

public class LinkedList {
  Node sentinelNode;
  Node cursor = null;

  // initialize the sentinel node
  {
    sentinelNode = new Node("");
    sentinelNode.next = sentinelNode;
    sentinelNode.prev = sentinelNode;
  }

  // helper function that inserts a new node after the
  // specified node
  void insertAfter(Node n, String value) {
     Node nextNode = n.next;
     Node newNode = new Node(value);

     // re-link items in the forward direction
     n.next = newNode;
     newNode.next = nextNode;

     // re-link items in the reverse direction
     newNode.prev = n;
     nextNode.prev = newNode;
   }

  public void append(String value) {
      insertAfter(sentinelNode.prev, value);
  }

   public void prepend(String value) {
      insertAfter(sentinelNode, value);
   } 

   public String get() {
     return cursor.value;
   }

   public boolean endOfList() {
     return cursor == sentinelNode;
   }

   public void first() {
     cursor = sentinelNode.next;
   }

   public void last() {
     cursor = sentinelNode.prev;
   }
   
   public void next() {
     cursor = cursor.next;
   }

   public void prev() {
     cursor = cursor.prev;
   }
}