title: how I can represent the '?' symbol in a JavaCC grammar?
body: <p>I would like to know how I can represent the '?' symbol in a JavaCC grammar ?
  The '?' symbol means that there can be at most one grammar symbol when you use '?' or zero.
  For example:</p>
  
  <p>S -> a? B
     B -> b;</p>
  
  <p>So, you can have at most one 'a'. Is not possible more than one a, so you cannot have 'aaaaa';</p>
  
  <p>Thanks;</p>