/**********************************************************
* A Generic Linked List class with a private static inner Node class.
*********************************************************/
// We want to "throw" Java exceptions in our code,
// so we must import them first:
import java.util.NoSuchElementException;


// make class name of generic type
public class GenericLinkedList<T> implements SimpleList<T>
{
   /*******************************************************
     The private inner class "Node" 
    *******************************************************/
   // make Node class name of generic type
   private class Node<T>
   {
      // Node instance variable is generic
      private T item;
      private Node<T> next;

      // parameters in constructor generic
      public Node(T item, Node<T> next)
      {
         this.item = item;
         this.next = next;
      }

      public String toString(){ return "" + this.item; }
   } // End of private inner class "Node"


   /********************************************************/
   // SimpleLinkedList instance variable "first" is declared of
   // type "Node", i.e. the inner class defined above
   // first is generic node

   private Node<T> first;

   // Constructs an empty list
   public GenericLinkedList()
   {
      first = null;
   }

   // Returns true if the list is empty
   public boolean isEmpty()
   {
      return first==null;
   }

   // Returns a string representation
   public String toString()
   {
      String output = "";

      if(first == null) 
         return "[NULL]";

      Node<T> tmp = first;
      while(tmp != null) 
      {
         output += tmp + " -> ";
         tmp = tmp.next;
      }
      output += "[NULL]";
      return output;
   }

   // I will use addFirst() to make a linked list to demo the other methods
   public void addFirst(T item)
   {
      Node<T> newNode = new Node<T>(item, first);
      first = newNode;
   }

   // Returns the first element (item) in the list
   // returns generic type
   public T getFirst()
   {
      if(isEmpty())
      {
         throw new NoSuchElementException();
      }
      return first.item;
   }

   // Returns the last element (item) in the list
   // returns generic type; Nodes are generic
   public T getLast()
   {
      if(isEmpty())
      {
         throw new NoSuchElementException();
      }

      Node<T> current = first;
      while(current.next!=null)
      {
         current = current.next;
      }
      return current.item;
   }


   // Returns the item at the specified position in the list.
   // Note: Assume that pos is the index of the node, and that
   // node indexes start at zero!
   public T get(int pos)
   {
      // Coding strategy: Start by solving the general case, then add checks
      // for edge cases (e.g. What if "pos" is out-of-bound?)

      if(isEmpty())
      { // empty list
         throw new NoSuchElementException();
      }

      int i = 0;
      Node<T> current = first;
      while( i < pos )
      {
         i++;
         current = current.next;

         if(current==null)
         { // pos past end of list
            throw new NoSuchElementException();
         }
      }
      return current.item;
   }

   public T removeFirst() { return null; }
   public void addLast(T item) { }
   public T removeLast() { return null; }
   public void remove(T key) { }
} // End of class