ArrayList<Object> array;

	public ArrayListStack() {
		array = new ArrayList<Object>();
	}

	public void push(Object o) {
		array.add(o);
	}

	public Object pop() {
		if(array.size() == 0) {
			throw new NoSuchElementException("The stack is empty");
		} else {
			Object toReturn = array.get(array.size()-1);
			array.remove(array.size()-1);
			return toReturn;
		}
	}

	public Object peek() {
		if(array.size() == 0) {
			throw new NoSuchElementException("The stack is empty");
		} else {
			return array.get(array.size()-1);
		}
	}

	public boolean isEmpty() {
		return array.size() == 0;
	}

	public int size() {
		return array.size();
	}