int p2 = n;
push (Object data) {
	if (p1 + p2 == n)
		throw new StackOverFlow exeption
	else {
		p2--;
		arr[p2] == data;
	}
}

Object pop () {
	if (!isEmpty()) {
		Object data = arr[p2];
		p2++;
		return data;
	}
}

boolean isEmpty() {
	if (p2 >= n)
		return true;
	return false;
}