> In my defence, I have never, in all my years of working, had to ever read standard input, let alone write it out again.

Yeah, but there is nothing different from this and having to copy data from an input stream to an output stream. If you can't remember how to do that, it kind of raises the question of what you were doing in Java.

Not knowing if you need to buffer is actually fine in my book. That's an optimization thing. Not knowing how to make the code correct though...