Generated Source of Initial Page
If we view HTML source of the initial page, it includes a series of forms:
<html><head></head><body>
<form action=http://sirah...:8081/dbc/servlet/VendingMachine>
<input type=submit name=selection value="Chips">
</form>
<form action=http://sirah...:8081/dbc/servlet/VendingMachine>
<input type=submit name=selection value="Popcorn">
</form>
<form action=http://sirah...:8081/dbc/servlet/VendingMachine>
<input type=submit name=selection value="Peanuts">
</form>
...
</body></html>
selections was null, and initially there are no hidden fields.