Is it possible to detect null references with JSoup?

I am trying to get some data of a webpage with JSoup in Java. I am using a mix of JSoup and a JSON parser to do that.
Suppose that in the webpage there is a lot of elements with the same class name inside another element with its respectively class name also, for example:
<div class="foo">
    <span class="bar">Whatever</span>
</div>

and I retrieve the data inside bar class of all elements like this:
Elements elements = Jsoup
.parse(html)
.body().select(".foo .bar");

The problems comes because there are some divs that does not have the span tag inside so when I retrieve the full collection of elements that the webpage has, the elements that does not exists are not appended (it has sense, but I need to detect these elements).
I want to store all data somewhere later, but  maintaining the sequency of the list, I mean, to put an - in the elements in which the span does not exist because if not, if you have the following sequence:
1. foo
2. null
3. bar

only the first and third position data will be stored, and the third position will be the second one.
Is it possible to detect null references with JSoup?
Thanks in advance!

Jsoup selects return only existing elements. 
To detect missing elements you can query the top selector first, and the iterate over results to check if top element contains the needed child:
Elements fooElements = Jsoup
.parse(html)
.body().select(".foo");

Elements elements = new Elements()
for(Element el : fooElements) {
    elements.add(el.select(".bar").first());
}

In the example above elements will contain both spans with foo class and nulls.