Cannot Find Symbol when compiling a java code

Compiling this using cmd : javac Test.java. However compilation fails, saying it cant find symbol parser.prog(). Any ideas?

import org.antlr.runtime.*;
    
    public class TestT {
        public static void main(String[] args) throws Exception {
    
            // Create an TLexer that feeds from that stream
            //TLexer lexer = new TLexer(new ANTLRInputStream(System.in));
            TLexer lexer = new TLexer(new ANTLRFileStream("input.txt"));
    
            // Create a stream of tokens fed by the lexer
            CommonTokenStream tokens = new CommonTokenStream(lexer);
    
            // Create a parser that feeds off the token stream
            TParser parser = new TParser(tokens);
    
            // Begin parsing at rule prog
            parser.prog();
        }
    }

In your T.g4 grammar (or T.g), you must also have a parser rule named prog:

grammar T;

prog
 : ...
 ;

...

Looking at your generated parser, I see you have a parser rule like this:

filter
 : expression EOF
 ;

Use that instead:

// Begin parsing at rule prog
parser.filter();