import java.util.Vector;

/**
 * An implementation of mutable lists that uses vectors.
 *
 * @author Samuel A. Rebelsky
 * @author Yvonne Palm
 * @author Jonathan Wellons
 */
public class VectorBasedList
  implements MutableList
{
  // +-------+---------------------------------------------------
  // | Notes |
  // +-------+

  // +-----------+-----------------------------------------------
  // | Constants |
  // +-----------+

  // +--------+--------------------------------------------------
  // | Fields |
  // +--------+

  /**
   * The actual contents of the list, stored in a Vector.
   */
  Vector contents;


  // +--------------+--------------------------------------------
  // | Constructors |
  // +--------------+

  /**
   * Build an empty list.
   */
  public VectorBasedList()
  {
    this.contents = new Vector();
  } // VectorBasedList()

  // +------------------+----------------------------------------
  // | Exported Methods |
  // +------------------+

  /**
   * Determine if the list is empty
   */
  public boolean isEmpty()
  {
    return this.contents.isEmpty();
  } // isEmpty()

  /**
   * Update the list by adding an element to the front.
   */
  public void addToFront(Object newThingy) {
    this.contents.add(0, newThingy);
  } // addToFront(Object)

  public void oldAddToFront(Object newThingy) {
    // Make a new Vector
    Vector newVector = new Vector();
    // Put the new element at the front.
    newVector.add(newThingy);
    // Copy everything else over.
    int numValues = this.contents.size();
    for (int i = 0; i < numValues; i++)
      newVector.add(this.contents.get(i));
    // Update this.contents to the new Vector.
    this.contents = newVector;
  } // oldAddToFront(Object)

  /**
   * Update the list by removing the first element.  Return
   * that element.
   */
  public Object removeFirst()
  {
    return this.contents.remove(0);
  } // removeFirst()

  private Object oldRemoveFirst()
  {
    // Use a for loop to move everything down one.
    // Grab the first element
    Object returnMe = this.contents.get(0);
    int numValues = this.contents.size();
    for (int i = 0; i < numValues-1; i++) {
      this.contents.set(i, this.contents.get(i+1));
    } // for
    // Delete that last element
    this.contents.setSize(numValues-1);
    // Return the first element
    return returnMe;
  } // removeFirst()

  /**
   * Get the length.
   */
  public int length() 
  {
    return this.contents.size();
  } // length()

  /**
   * Get the first element (non-destructively).
   */
  public Object getFirst()
  {
    return this.contents.get(0);
  } // getFirst()

  /**
   * Convert to a string for ease of printing.
   */
  public String toString()
  {
    if (this.contents.isEmpty())
      return "()";
    String result = "(" + this.contents.get(0);
    int numValues = this.contents.size();
    for (int i = 1; i < numValues; i++)
      result = result + " " + this.contents.get(i);
    result = result + ")";
    return result;
  } // toString()

  /**
   * Make an independent copy of this list.
   */
  public MutableList copyMe()
  {
    return null;   // STUB
  } // copyMe()
} // class VectorBasedList