public static CharStream fromFileName(String fileName) throws IOException {
		return fromPath(Paths.get(fileName), StandardCharsets.UTF_8);
	}
Creates a {@link CharStream} given a string containing a
path to a UTF-8 file on disk.

Reads the entire contents of the file into the result before returning.
runtime/Java/src/org/antlr/v4/runtime/CharStreams.java