/* ListNode.java */

package list;

/** ListNodes are used in building List structure. 
 */

class ListNode {
  Object    item;
  ListNode  next;

  /** Construct a new ListNode with item it and a null next.
   */
  ListNode(Object it) {
    item = it;
    next = null;
  }

  /** Construct a new ListNode with item it and a next n.
   */
  ListNode(Object it, ListNode n) {
    item = it;
    next = n;
  }

  /** Find the node at the given position.
   * Assumes this list is acyclic.
   * @return a reference to the node at the given position.  
   *  If position < 1 or position > the      
   *       size number of nodes in the list, returns null.         */
  public ListNode ptrTo (int position) {
    if (position < 1) {
      return null;
    }
    else if (position == 1) {
      return this;
    }
    else if (next == null) {
      return null;
    }
    else {
      return next.ptrTo(position-1);
    }
  }
}