A few notes on using jflex and byaccj

Token values declared in the yacc file become static constants in
Parser.y.  For example, %token HELLO_tok may produce:
     public final static short HELLO_tok=257;
so in your lex file you would write:
     hello            { return Parser.HELLO_tok; }

You will create an intance of your scanner class (class Yylex) from
your parser.  Since you will need a FileReader to pass to the
constructor for your scanner (which is now created from the parser),
you will write a new constructor for the parser which will accept a
FileReader parameter and then create the scanner.

The parser will call a method (from its own class) called yylex()
which you must provide.  You can write a method which just calls the
yylex() method from class Yylex.

An appropriate third section of your yacc file which will accomplish
this is:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

     %%
     
     private Yylex scanner;
     
     public Parser(FileReader fr)
     {
        this();
        scanner = new Yylex(fr);
     }
     
     
     int yylex()
     {
        try
        {
           return scanner.yylex();
        }
        catch (IOException e)
        {
           System.out.println("Exception caught: " + e);
           return 0;
        }
     }
     
     void yyerror(String s)
     {
        System.out.println("parse error on line " + scanner.line_num);
        System.exit(1);
     }

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Be sure to import java.io.*; inside %{ ... %} in the first section of
your yacc file.

In your lex file you should put %byaccj at the beginning of the second
section and DO NOT change the name of the generated class with
%class (byaccj expects the default class name Yylex).

In your main you will create a FileReader object and pass it to the
(new, written by you) Parser constructor.  To start parsing call the
yyparse() method from this class.