//StringLinkedListSelfcontained.java

public class StringLinkedListSelfcontained
{
    private ListNode head;

    public StringLinkedListSelfcontained( )
    {
        head = null;
    }

    /**
     Returns the number of nodes in the list.
    */
    public int length( )
    {
        int count = 0;
        ListNode position = head;
        while (position != null)
        {
            count++;
            position = position.link;
        }
        return count;
    }

    /**
     Adds a node at the start of the list. The added node has
     addData as its data. The added node will be the first
     node in the list.
    */
    public void addANodeToStart(String 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(String 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(String target)
    {
        ListNode position;
        position = head;
        String dataAtPosition;
        while (position != null)
        {
            dataAtPosition = position.data;
            if (dataAtPosition.equals(target))
                return position;
            position = position.link;
        }
        //target was not found
        return null;
    }

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

    public String[] arrayCopy( )
    {
        String[] a = new String[length( )];

        ListNode position;
        position = head;
        int i = 0;
        while (position != null)
        {
            a[i] = position.data;
            i++;
            position = position.link;
        }

        return a;
    }


    private class ListNode
    {
        private String data;
        private ListNode link;
        public ListNode( )
        {
            link = null;
            data = null;
        }
        public ListNode(String newData, ListNode linkValue)
        {
            data = newData;
            link = linkValue;
        }
    }

} //end of StringLinkedListSelfcontained