try-with-resources and null resource

[Florian Weimer]

* Reinier Zwitserloot:

> 2 if yes: Well, then, calling a method that returns null, such as for
> example Class.getResourceAsStream, is going to be an unbelievable pain. As
> the NPE is then unavoidable, you'd need to assign it to a variable, check
> that variable, and if that variable is not null, start a try block, which
> REQUIRES that you create a NEW variable. urghhhhh!!!!!!! What do I name
> this? out1 and out2? I've got a very big problem with this. even if t is not
> final, I'd have to create a dummy input stream just to have something to
> close.

If t is not referenced (so its declared type does not matter) and can
be null, use a utility method which returns a dummy AutoCloseable
instance if the passed argument is null.

If you reference t on some path, you need to generate a dynamic proxy
for the null case which throws some suitable exception on all method
calls except close().  It's ugly, but it's doable.  I don't think it's
necessary to have direct support for such an edge case.

By the way, has anybody else seen this phenomenon in their code base?

  InputStream in = null;
  try {
    in = new FileInputStream(path);
    useFile(in);
  } finally {
    if (in != null) {
      in.close();
    }
  }

I'm wondering where this is coming from.

-- 
Florian Weimer                <fweimer at bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
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