/** ListNode is a class for storing a single node of a linked list that stores int values. 
 *  It stores an integer value and a link to the next node of the linked list. */
public class ListNode {
   int data;
   ListNode next;
   
   /** Creates a terminal ListNode with 0 as its data. */
   public ListNode() {
      this(0, null);
   }
   
   /** Creates a terminal ListNode with data as its data. */
   public ListNode(int data) {
      this(data, null);
   }
   
   /** Creates a ListNode with data as its data and next as the node it points to. */
   public ListNode(int data, ListNode next) {
      this.data = data;
      this.next = next;
   }
   
   /* Ignore this for now */
   public String toString() {
      String result = "[";
      ListNode current = this;
      while (current.next != null) {
         result += current.data + ", ";
         current = current.next;
      }
      while (current != null) {
         result += current.data;
         current = current.next;
      }
      return result + "]";
   }
}