// A LinkedIntList object represents an ordered list of linked nodes.  
// Like ArrayIntList, LinkedIntList is an implementation of the List ADT.
public class LinkedIntList {
  private ListNode front;

  public LinkedIntList() {
    front = null;
  }

  // post: adds num to the end of the list
  public void add(int value) {
    // get to the end (almost)
    // add to the end
    if (front == null) {
      front = new ListNode(num);
    } else {
      ListNode current = front;
      while (current.next != null) {
        current = current.next;
      }
      // current = ... will NEVER change the list
      // two ways to change:
      //    current.next
      //    front
      current.next = new ListNode(num);
    }
  }

  
  // pre : 0 <= index < size(), throws IndexOutOfBoundsException otherwise
  // post: returns the element at index
  public int get(int index) {
    if (index < 0) {
      throw new IndexOutOfBoundsException();
    }
    for (int i = 0; i < index; i++) {
      if (current == null) {
        throw new IndexOutOfBoundsException();
      }
      current = current.next;
    }
    return current.data;
  }

  public int size() {
    int size = 0;
    ListNode current = front;
    while (current != null) {
      size++;
      current = current.next;
    }
    return size;
  }
  
  // post: returns a string representation of the list
  public String toString() {
    String listString = "[";
    if (front != null) {
      ListNode current = front;
      listString += current.data;
      current = current.next;
      while (current != null) {
        listString += ", " + current.data;
        current = current.next;
      }
    } 
    listString += "]";
    return listString;
  }
}