Java Question:

I need to add an iterator to LinkedDropOtuStackQueue class.

The example is for the LinkedList.java is as follows:

package jsjf;

import jsjf.exceptions.*; import java.util.*;

/** * LinkedList represents a linked implementation of a list. * * @author Java Foundations * @version 4.0 */ public class LinkedList implements ListADT, Iterable { protected int count; protected LinearNode head, tail; protected int modCount;

/** * Creates an empty list. */ public LinkedList() { count = 0; head = tail = null; modCount = 0; } public void addElement(T element) { LinearNode node = new LinearNode(element); if (isEmpty()) head = node; else tail.setNext(node); tail = node; count++; } /** * Removes the first element in this list and returns a reference * to it. Throws an EmptyCollectionException if the list is empty. * * @return a reference to the first element of this list * @throws EmptyCollectionException if the list is empty */ public T removeFirst() throws EmptyCollectionException { if (isEmpty()) throw new EmptyCollectionException("LinkedList"); T result = head.getElement(); head = head.getNext(); count--; if (isEmpty()) tail = null; return result; }

/** * Removes the last element in this list and returns a reference * to it. Throws an EmptyCollectionException if the list is empty. * * @return the last element in this list * @throws EmptyCollectionException if the list is empty */ public T removeLast() throws EmptyCollectionException { if (isEmpty()) throw new EmptyCollectionException("LinkedList"); LinearNode current = head; LinearNode current1=null; while (current != tail){ current1=current; current = current.getNext(); // make current points to next element } T a=tail.getElement(); tail=current1; if(tail==null) head=null; else tail.setNext(null); if(tail==null) head=null; else tail.setNext(null); count--; return a; }

/** * Removes the first instance of the specified element from this * list and returns a reference to it. Throws an EmptyCollectionException * if the list is empty. Throws a ElementNotFoundException if the * specified element is not found in the list. * * @param targetElement the element to be removed from the list * @return a reference to the removed element * @throws EmptyCollectionException if the list is empty * @throws ElementNotFoundException if the target element is not found */ public T remove(T targetElement) throws EmptyCollectionException, ElementNotFoundException { if (isEmpty()) throw new EmptyCollectionException("LinkedList");

boolean found = false; LinearNode previous = null; LinearNode current = head;

while (current != null && !found) if (targetElement.equals(current.getElement())) found = true; else { previous = current; current = current.getNext(); }

if (!found) throw new ElementNotFoundException("LinkedList");

if (size() == 1) // only one element in the list head = tail = null; else if (current.equals(head)) // target is at the head head = current.getNext(); else if (current.equals(tail)) // target is at the tail { tail = previous; tail.setNext(null); } else // target is in the middle previous.setNext(current.getNext());

count--; modCount++;

return current.getElement(); }

/** * Returns the first element in this list without removing it. * * @return the first element in this list * @throws EmptyCollectionException if the list is empty */ public T first() throws EmptyCollectionException { if(isEmpty()) { throw new EmptyCollectionException("LinkedList"); } return head.getElement(); }

/** * Returns the last element in this list without removing it. * * @return the last element in this list * @throws EmptyCollectionException if the list is empty */ public T last() throws EmptyCollectionException { if(isEmpty()) { throw new EmptyCollectionException("LinkedList"); } return tail.getElement(); }

/** * Returns true if the specified element is found in this list and * false otherwise. Throws an EmptyCollectionException if the list * is empty. * * @param targetElement the element that is sought in the list * @return true if the element is found in this list * @throws EmptyCollectionException if the list is empty */ public boolean contains(T targetElement) throws EmptyCollectionException { if(isEmpty()) { throw new EmptyCollectionException("LinkedList"); } return (count==0); }

/** * Returns true if this list is empty and false otherwise. * * @return true if the list is empty, false otherwise */ public boolean isEmpty() { return (count==0); }

/** * Returns the number of elements in this list. * * @return the number of elements in the list */ public int size() { return count; }

/** * Returns a string representation of this list. * * @return a string representation of the list */ public String toString() { String result = ""; // initialize it to empty string LinearNode t = head; // start from top while (t != null) // iterate until it reaches the end of the list (end of list is when current == null) { result = result + (t.getElement()).toString() + "\t"; // append it's value to result string t = t.getNext(); // make current points to next element } return result; // return result string

}

/** * Returns an iterator for the elements in this list. * * @return an iterator over the elements of the list */ public Iterator iterator() { return new LinkedListIterator(); }

/** * LinkedIterator represents an iterator for a linked list of linear nodes. */ private class LinkedListIterator implements Iterator { private int iteratorModCount; // the number of elements in the collection private LinearNode current; // the current position

/** * Sets up this iterator using the specified items. * * @param collection the collection the iterator will move over * @param size the integer size of the collection */ public LinkedListIterator() { current = head; iteratorModCount = modCount; }

/** * Returns true if this iterator has at least one more element * to deliver in the iteration. * * @return true if this iterator has at least one more element to deliver * in the iteration * @throws ConcurrentModificationException if the collection has changed * while the iterator is in use */ public boolean hasNext() throws ConcurrentModificationException { if (iteratorModCount != modCount) throw new ConcurrentModificationException();

return (current != null); }

/** * Returns the next element in the iteration. If there are no * more elements in this iteration, a NoSuchElementException is * thrown. * * @return the next element in the iteration * @throws NoSuchElementException if the iterator is empty */ public T next() throws ConcurrentModificationException { if (!hasNext()) throw new NoSuchElementException();

T result = current.getElement(); current = current.getNext(); return result; }

/** * The remove operation is not supported. * * @throws UnsupportedOperationException if the remove operation is called */ public void remove() throws UnsupportedOperationException { throw new UnsupportedOperationException(); } } }

Can you please Add an iterator to the LinkedDropOutStack.java as there is an iterator in the LinkedList.java class:

package jsjf;

import jsjf.exceptions.*;

import java.util.EmptyStackException;

/** * Represents a linked implementation of a stack. * * @author Java Foundations * @version 4.0 */ public class LinkedDropOutStack implements StackADT { private int count; private LinearNode top; private int limit = 5;

/** * Creates an empty stack. */ public LinkedDropOutStack() { count = 0; top = null; }

/** * Adds the specified element to the top of this stack. * @param element element to be pushed on stack */ public void push(T element) {

if (count < limit) { LinearNode temp = new LinearNode(element); temp.setNext(top); top = temp; } else if (count == limit){ LinearNode temp = new LinearNode(element); if (isEmpty()) throw new EmptyCollectionException("stack");

T result = top.getElement(); top = top.getNext(); temp.setNext(top); top = temp; } count++; }

/** * Removes the element at the top of this stack and returns a * reference to it. * @return element from top of stack * @throws EmptyCollectionException if the stack is empty */ public T pop() throws EmptyCollectionException { if (isEmpty()) throw new EmptyCollectionException("stack");

T result = top.getElement(); top = top.getNext(); count--;

return result; }

/** * Returns a reference to the element at the top of this stack. * The element is not removed from the stack. * @return element on top of stack * @throws EmptyCollectionException if the stack is empty */ public T peek() throws EmptyCollectionException { if (isEmpty()) throw new EmptyCollectionException("Stack");

else return top.getElement(); // temp }

/** * Returns true if this stack is empty and false otherwise. * @return true if stack is empty */ public boolean isEmpty() { if (count == 0) { return true; // temp } else return false; }

/** * Returns the number of elements in this stack. * @return number of elements in the stack */ public int size() { // To be completed as a Programming Project return count - 1; // temp }

/** * Returns a string representation of this stack. * @return string representation of the stack */ public String toString() { String result = ""; LinearNode values = top; while (values != null){ result += values.getElement().toString() + " "; values = values.getNext(); } return result; // temp } }

Thanks