public void addRule(String nonterminal, List<String> rhs)
    {
        addRule(null, nonterminal, "", false, rhs);
    }
public void addRule ( String nonterminal , List < String > rhs ) { addRule ( null , nonterminal , "" , false , rhs ) ; }
Adds new rule if the same rule doesn't exist already.
@param nonterminal Left hand side of the rule.
@param rhs