import java.util.*;

public class LinkedList<E>
{
	private ListNode head;

	public LinkedList()
	{
		head = null;
	}

	public int length()
	{
		int count = 0;
		ListNode position = head;
		while(position != null)
		{
			count++;
			position = position.link;
		}
		return count;
	}

	/**
	 The added node will be the first node in the list.
	*/
	public void addANodeToStart(E addData)
	{
		head = new ListNode(addData, head);
	}

	public void deleteHeadNode()
	{
		if(head != null)
			head = head.link;
		else
		{
			System.out.println("Deleting from an empty list.");
			System.exit(0);
		}
	}

	public boolean onList(E target)
	{
		return(Find(target) != null);
	}

	/**
	 Finds the first node containing the target data,
	 and returns a reference to that node.  If target is not
	 in the list, null is returned.
	*/
	private ListNode Find(E target)
	{
		ListNode position;
		position = head;
		E dataAtPosition;
		while(position != null)
		{
			dataAtPosition = position.data;
			if(dataAtPosition.equals(target))
				return position;
			position = position.link;
		}
		//target not found
		return null;
	}

	public void showList()
	{
		ListNode position;
		position = head;
		ListNode dataAtPosition;
		while(position != null)
		{
			System.out.println(position.data);
			position = position.link;
		}
	}

	public Vector<E> vectorCopy()
	{
		Vector<E> v = new Vector<E>(length());

		ListNode position;
		position = head;

		while(position != null)
		{
			v.addElement(position.data);
			position = position.link;
		}
		return v;
	}

	private class ListNode
	{
		private E data;
		private ListNode link;

		public ListNode()
		{
			link = null;
			data = null;
		}

		public ListNode(E newData, ListNode linkValue)
		{
			data = newData;
			link = linkValue;
		}
	}
}