/**
 * CSE 373, Spring 2011, Jessica Miller
 * The LinkedListQueue is an implementation of the StrQueue interface.  This 
 * implementation uses a linked list to implement the queue.
 */
import java.util.NoSuchElementException;

public class LinkedListQueue implements StrQueue {
	private LinkedListQueueNode back;
	private LinkedListQueueNode front;

	public LinkedListQueue() {
		back = null;
		front = null;
	}

	public boolean isEmpty() {
		return front == null;
	}

	public void enqueue(String str) {
		LinkedListQueueNode newNode = new LinkedListQueueNode(str);
		
		if (isEmpty()) {
			front = back = newNode;
		} else {
			back.next = newNode;
			back = newNode;
		}
	}

	public String dequeue() {
		if (isEmpty()) {
			throw new NoSuchElementException();
		} 
		
		String result = front.value;
		front = front.next;
		
		return result;
	}
}