public static CharStream fromFileName(String fileName, Charset charset) throws IOException {
		return fromPath(Paths.get(fileName), charset);
	}
Creates a {@link CharStream} given a string containing a
path to a file on disk and the charset of the bytes
contained in the file.

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