antlr4 example CodePointCharStream

    private static final String someLangSourceCode =
            "class SomeClass {\n"+
                    "    fun1 {\n"+
                    "        instruction11\n"+
                    "        instruction12\n"+
                    "    }\n"+
                    "    fun2 {\n"+
                    "        instruction21\n"+
                    "        instruction22\n"+
                    "    }\n"+
                    "}";

    public static void main( String[] args ) throws IOException {
        System.out.println( "Hello world!" );

        try {
            CodePointCharStream codePointCharStream = CharStreams.fromString(someLangSourceCode, "string");
            SomeLanguageLexer lexer = new SomeLanguageLexer(codePointCharStream);
            TokenStream tokens = new CommonTokenStream(lexer);
            SomeLanguageParser parser = new SomeLanguageParser(tokens);
            parser.classDeclaration().children.forEach(System.out::println);
        } catch (RecognitionException e) {
            throw new IllegalStateException("Recognition exception is never thrown, only declared.");
        }
    }

Must provide a sourceName as the second parameter in CharStreams.fromString()

g4 file must be put under src/your/package/full/name/grammar-filename.g4