package horstmann.ch09_queue3;
import java.util.ArrayList;
/**
    A first-in, first-out bounded collection of objects.
 */
public class BoundedQueue<E>
{
  /**
       Constructs an empty queue.
       @param capacity the maximum capacity of the queue
   */
  public BoundedQueue(int capacity)
  {
    elements = new ArrayList<E>(capacity);
    head = 0;
    tail = 0;
    size = 0;
  }

  /**
       Removes the object at the head.
       @return the object that has been removed from the queue
   */
  public synchronized E remove()
      throws InterruptedException
  {
    while (size == 0) wait();
    E r = elements.get(head);
    head++;
    size--;
    if (head == elements.size())
      head = 0;
    notifyAll();
    return r;
  }

  /**
       Appends an object at the tail.
       @param newValue the object to be appended
   */
  public synchronized void add(E newValue)
      throws InterruptedException
  {
    while (size == elements.size()) wait();
    elements.set(tail,newValue);
    tail++;
    size++;
    if (tail == elements.size())
      tail = 0;
    notifyAll();
  }

  private ArrayList<E> elements;
  private int head;
  private int tail;
  private int size;
}