CareerCup

class Stack<T>{
	private Queue<T> q1 = new LinkedList();
	private Queue<T> q2 = new LinkedList();

	public void push(T elem){
		q1.offer(elem);
	}

	public T pop(){
		while(q1.size() > 1) 	{
			q2.offer(q1.poll());
		}	

		T result = q1.poll();

		while(!q2.isEmpty()) {
			q1.offer(q2.poll);
		}

		return result;
	}
}

Queue is an interface,so you cannot create object. You need to do it as
Queue<Integer> q=new LinkedList<Integer>():..or someother data structure.

your queue can be of Integer.Max in Java because when you look at the java code of Queue you will find that capacity is an int.

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

public class QueueStack<T> {
	Queue<T> queue1 = new ConcurrentLinkedQueue<T>();
	Queue<T> queue2 = new ConcurrentLinkedQueue<T>();
	
	public void push(T elem){
		queue1.offer(elem);
	}
	
	public T pop(){
		if(!queue1.isEmpty()){
			while(queue1.size()>1){
				queue2.offer(queue1.poll());
			}
			return queue1.poll();
		}else if(!queue2.isEmpty()){
			while(queue2.size()>1){
				queue1.offer(queue2.poll());
			}
			return queue2.poll();
		}else{
			return null;
		}
	}
	
	public T peek(){
		if(!queue1.isEmpty()){
			while(queue1.size()>1){
				queue2.offer(queue1.poll());
			}
			return queue1.peek();
		}else if(!queue2.isEmpty()){
			while(queue2.size()>1){
				queue1.offer(queue2.poll());
			}
			T desiredelem = queue2.poll();
			queue1.offer(desiredelem);
			return desiredelem;
		}else{
			return null;
		}
	}
	
	public static void main(String[] args){
		QueueStack<Integer> testStack = new QueueStack<Integer>();
		testStack.push(1);
		testStack.push(2);
		testStack.push(3);
		System.out.println(testStack.pop());
		System.out.println(testStack.pop());
		System.out.println(testStack.pop());
	}

}

I think 32768.. ( Max size until stack overflow occurs(65536) /2 )

Infinite number of elements but you can choose to implement the Queue yourself and place a restriction on the max number of elements you wanna be able to add.
So you had a Google and Microsoft interview on the same day!
Either a weird coincidence or some simple homework.