How do I get rid of depreciated code in this class file for java antlr? - antlr

Question

import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.ParseTree;
import java.io.FileInputStream;
import java.io.InputStream;
public class Calc {
public static void main(String[] args) throws Exception {
String inputFile = null;
if ( args.length>0 ) inputFile = args[0];
InputStream is = System.in;
if ( inputFile!=null ) is = new FileInputStream(inputFile);
ANTLRInputStream input = new ANTLRInputStream(is);
CalculatorLexer lexer = new CalculatorLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
CalculatorParser parser = new CalculatorParser(tokens);
ParseTree tree = parser.program(); // parse
CalcVisitor calcc = new CalcVisitor();
calcc.visit(tree);
}
}
As far as I know, I am pretty sure the ANTLRFileStream is what is depricated, but I have tried replacing it with CharStreams, but the code I try and run keeps resulting in an error. How can I fix this?

Answer 1

Try something like this:
public static void main(String[] args) throws Exception {
CharStream charStream = args.length > 0
? CharStreams.fromFileName(args[0])
: CharStreams.fromStream(System.in);
CalculatorLexer lexer = new CalculatorLexer(charStream);
CommonTokenStream tokens = new CommonTokenStream(lexer);
CalculatorParser parser = new CalculatorParser(tokens);
ParseTree tree = parser.program(); // parse
CalcVisitor calcc = new CalcVisitor();
calcc.visit(tree);
}