Is it safe not to close a Java Scanner, provided I close the underlying readable?

It depends what you want to be safe against.

• If you are just trying to ensure that the underlying stream is closed, then either approach is fine.

• If you also want the Scanner to be marked as closed (so that all subsequent operations on the object will fail immediately), then you should call Scanner.close().

This is a general principle; i.e. it also applies to various kinds of streams that do in-memory buffering, one way or another.