//---------------------------------------------------------------------------
// ArrayBndQueue.java          by Dale/Joyce/Weems                  Chapter 5
//
// Implements BoundedQueueInterface with an array to hold the queue elements.
//
// ajg version: formatting, private, capacity->size, if-then-else
//              Just the DWC (davis weird constructor)
//---------------------------------------------------------------------------

package ch05.queues;

public class ArrayBndQueue<T> implements BoundedQueueInterface<T> {
    private T[] queue;              // queue elements
    private int numElements = 0;    // number of elements n the queue
    private int front = 0;          // index of front of queue
    private int rear;               // index of rear of queue
    
    public ArrayBndQueue(T[] queue)  {
	this.queue = queue;
	rear = queue.length - 1;
    }
    
    public boolean isEmpty() { return (numElements == 0); }
    public boolean isFull()  { return (numElements == queue.length); }

    public void enqueue(T element) {
	// Throws QueueOverflowException if this queue is full;
	// otherwise, adds element to the rear of this queue.
	if (isFull())
	    throw new QueueOverflowException("Helpful message.");
	rear = (rear + 1) % queue.length;
	queue[rear] = element;
	numElements++;
    }

    public T dequeue() {
	// Throws QueueUnderflowException if this queue is empty;
	// otherwise, removes front element from this queue and returns it.
	if (isEmpty())
	    throw new QueueUnderflowException("Dequeue attempted on empty queue.");
	T ans = queue[front];
	queue[front] = null;
	front = (front + 1) % queue.length;
	numElements--;
	return ans;
    }
}
// Local Variables:
// compile-command: "cd ../../; javac ch05/queues/ArrayBndQueue.java"
// End: