ANTLRInputStream and ANTLRFileStream are deprecated, what are the alternatives?

You can use the CharStreams class instead of the deprecated classes as below.

CharStream codePointCharStream = CharStreams.fromFileName("myfile.testlang");
TESTLANGLexer lexer = new TESTLANGLexer(codePointCharStream);
TESTLANGParser parser = new TESTLANGParser(new CommonTokenStream(lexer));
parser.addParseListener(new TESTLANGEventListener());

// Start parsing
parser.testlangFile();