Generic Queue Using Resized Array And Iterator - Coursera Algorithms

To make the stack generic and to hide the internal representation of a queue from client, we can use Generics and Iterator.

Following is the program:

	package queues;
	import java.util.Iterator;
	public class GenericQueueResizeArrayItr<Item> implements Iterable<Item>{
	public class ArrayIterator implements Iterator<Item>{
	private int i = fwdIndex;
	@Override
	public boolean hasNext() {
	return (i<bckIndex);
	}
	@Override
	public Item next() {
	return queue[i++];
	}
	}
	@Override
	public Iterator<Item> iterator() {
	return new ArrayIterator();
	}
	int fwdIndex=0, bckIndex=0;
	Item[] queue;
	public GenericQueueResizeArrayItr(int cap) {
	queue = (Item[]) new Object[cap];
	}
	public void enqueue(Item s) {
	int l = queue.length;
	if(bckIndex==l) {
	resize(2*l);
	}
	queue[bckIndex++] = s;
	if(isEmpty()) {
	fwdIndex = bckIndex;
	}
	}
	public Item dequeue() {
	if(isEmpty()) {
	System.out.println("empty Q");
	return null;
	}
	int l = queue.length;
	if(bckIndex==l/2) {
	resize(l/4);
	}
	Item s = queue[fwdIndex];
	queue[fwdIndex++] = null;
	return s;
	}
	public int size() {
	return (bckIndex-fwdIndex);
	}
	public boolean isEmpty() {
	return (size()==0);
	}
	public void print() {
	System.out.println("==========================");
	for(int i=fwdIndex;i<bckIndex;i++) {
	System.out.println(queue[i]);
	}
	}
	public void resize(int cap) {
	Item[] copy = (Item[])new Object[cap];
	for(int i=fwdIndex;i<bckIndex;i++) {
	copy[i]=queue[i];
	}
	queue = copy;
	}
	public int length() {
	return queue.length;
	}
	public static void main(String[] args) {
	GenericQueueResizeArrayItr<String> queue = new GenericQueueResizeArrayItr<String>(5);
	queue.enqueue("to");
	queue.enqueue("be");
	queue.enqueue("or");
	queue.enqueue("not");
	queue.enqueue("to");
	queue.print();
	System.out.println("stack util is "+queue.size()+" out of "+queue.length());
	queue.enqueue("be");
	System.out.println("stack util is "+queue.size()+" out of "+queue.length());
	//queue.print();
	System.out.println("-------------Iterator-----------");
	for(String s: queue) {
	System.out.println(s);
	}
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	System.out.println("DQd "+queue.dequeue());
	queue.print();
	//===========Integer===============
	GenericQueueResizeArrayItr<Integer> queueInt = new GenericQueueResizeArrayItr<>(5);
	queueInt.enqueue(1);
	queueInt.enqueue(2);
	queueInt.enqueue(3);
	queueInt.enqueue(4);
	queueInt.enqueue(5);
	queueInt.enqueue(6);
	//queueInt.print();
	System.out.println("-------------Iterator-----------");
	for(Integer i: queueInt) {
	System.out.println(i);
	}
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	System.out.println("DQd "+queueInt.dequeue());
	queueInt.print();
	}
	}

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