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Once more, I bring you the Java implementation of this Data Structure. Note: this Queue takes objects, not primitive types. This actually makes things much easier, even though I wouldn't admit it when I first started working with Queues (or other structures for that matter). Note that this Queue is based on a Doubly Linked List, which I have also noded. Enjoy!


//************************************************************
// This class defines a Queue.
// It is based on a Linked List.
//************************************************************

public class MyQueue extends ListClass
{

//************************************************************
// Declares an integer to hold the number of elements on the
// Queue.
//************************************************************

	private int numOnQueue = 0;	

//************************************************************
// This is the default constructor for the MyQueue class.
// It assigns all omnipresent nodes to null.
//************************************************************

	public MyQueue()
	{
	start = current = end = null;
	}

//************************************************************
// This method, dequeue() removes the first elements from the
// queue, and returns it to the calling object. It also
// decrements numOnQueue.
//************************************************************

	public Object dequeue()
	{
		Object o = null;
		current = start;

		if(this.isEmpty() == false)
		{
			if(start.getNext() == null)
			{
				o = start.getObject();
				current = start = end = null;
				numOnQueue--;
				return(o);
			}
			else
			{
				o = start.getObject();
				start = current = start.getNext();
				numOnQueue--;
				return(o);
			}
		}
		return("If you see this, there is an error.");
	}

//************************************************************
// This method, enqueue() takes an object and adds it to the
// end of the queue. It also increments numOnQueue.
//************************************************************

	public void enqueue(Object o)
	{
		addAfter(o);
		numOnQueue++;
	}

//************************************************************
// This method, getNumOnQueue() returns the current int value
// of numOnQueue.
//************************************************************

	public int getNumOnQueue()
	{
	return numOnQueue;
	}

//************************************************************
// This method, isEmpty() determines if the queue is empty,
// using the value of numOnQueue as an indicator.
//************************************************************

	public boolean isEmpty()
	{
		if(numOnQueue == 0)
			return true;
		else
			return false;
	}
}