A) The following is an implementation of an link based queue. Implement Iterator

Question

A) The following is an implementation of an link based queue. Implement Iterator for this class. Do not implement modChange.

public class LinkedQueue implements QueueADT {

    private int count;

    private LinearNode head, tail;

    public LinkedQueue() {

        count = 0;

        head = tail = null;

    }

    public void enqueue(T element) {

        LinearNode node = new LinearNode(element);

        if (isEmpty())

            head = node;

        else

            tail.setNext(node);

        tail = node;

        count++;

    }

    public T dequeue() throws EmptyCollectionException {

        if (isEmpty())

            throw new EmptyCollectionException("queue");

        T result = head.getElement();

        head = head.getNext();

        count--;

        if (isEmpty())

            tail = null;

        return result;

    }

    //omitted: first, isEmpty, size, and toString.

B) In the last question, you did not implement modChange. Is this an issue? Either give an example where your improved queue class will fail, or explain why everything will be fine.

Explanation / Answer

Iterator for the Class

public Iterator<T> iterator(){
   LinkedQueueIterator temp = new LinkedQueueIterator();
   return temp;
}

class LinkedQueueIterator implements Iterator<AnyType>{
   LinearNode temp;
   public LinkedQueueIterator(){
       temp = head;
   }
   public boolean hasNext(){
       if (temp == null)
           return false;
       return true;
   }
   public T next(){
       if (hasNext() == false)
           throw new EmptyCollectionException("queue");
       T res = temp.getElement();
       temp = temp.getNext();
       return T;
   }  
}

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