public class LLQueue<E> implements QueueInterface<E>
{
    LinkedList<E> queueLL;
    
    @Override
    public int size()
    {
	return queueLL.size();
    }

    @Override
    public boolean isEmpty()
    {
	return size()==0;
    }

    @Override
    public E first()
    {
	if (isEmpty()) return null;
	return queueLL.first();
    }

    @Override
    public void enqueue(E e)
    {
	queueLL.addLast(e);
    }
    
    @Override
    public E dequeue()
    {
	if (isEmpty()) return null;
	return queueLL.removeFirst();
    }
    
    public LLQueue()
    {
	queueLL = new LinkedList<E>();
    }
    
    @Override
    public String toString()
    {
	return queueLL.toString();
    }

    public static void main(String[] args)
    {
	LLQueue<Integer> qqq = new LLQueue<>();
	qqq.enqueue(5);
	System.out.println(qqq);
	qqq.enqueue(3);
	System.out.println(qqq);
	qqq.dequeue();
	System.out.println(qqq);
	qqq.enqueue(7);
	System.out.println(qqq);
	qqq.dequeue();
	System.out.println(qqq);
	System.out.println("First:"+qqq.first());
	qqq.dequeue();
	System.out.println(qqq);
	qqq.dequeue();
	System.out.println(qqq.isEmpty());
	qqq.enqueue(9);
	System.out.println(qqq);
	qqq.enqueue(7);
	System.out.println(qqq);
	System.out.println("Size: " + qqq.size());
	qqq.enqueue(3);
	System.out.println(qqq);
	qqq.enqueue(5);
	System.out.println(qqq);
	qqq.dequeue();
	System.out.println(qqq);
    }
}