try-with-resources and null resource (original) (raw)
Serge Boulay serge.boulay at gmail.com
Wed Jan 26 08:43:18 PST 2011
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true, but that same example works in c# as Jesper has pointed out. Not that we are trying to copy the exact semantics of c# but I do wonder what their rational was. Perhaps we can learn from some of the decisions they made (good & bad).
using (IDisposable x = null) { Console.WriteLine("we got here"); }
This example writes "we got here".
On Wed, Jan 26, 2011 at 11:04 AM, Paul Benedict <pbenedict at apache.org>wrote:
Jesper,
I don't see how ignoring null helps the programmer. What does such a syntax mean? As I see it, try-with-resources is about obtaining a resource, doing work, and closing it. And since you can't obtain a resource out of a null reference, I think that is an error. That's why I prefer NPE. Paul 2011/1/26 Jesper Öqvist <jesper.oqvist at cs.lth.se> > Rémi Forax wrote: > >> On 01/21/2011 07:24 PM, Paul Benedict wrote: >> >> >>> The NPE is more useful than the language silently doing nothing with a >>> null pointer. While your idea is convenient, I believe it assumes too much. >>> If anything, perhaps the language shouldn't allow an explicit null >>> assignment in a try-with-resources block. >>> >>> >> >> Hi Paul, >> the null assignement is just an example. Perhaps, you prefer this one: >> >> 4. try(AutoCloseable c = getAnAutoCloseableThatMayBeNull()) { >> 5. // nothing >> 6. } >> >> Rémi >> >> > > I am concerned about the consistency between what the programmer expects > and what the compiler produces. > > It seems to me that the following code should be legal, and execute without > throwing an NPE: > > try (Resource r = null) { > r = new SomeResource(); > } > > However with a null check in the try part of the try-with-resource > statement, or an NPE, execution might not pass through the statement as the > programmer expects it to. > > Jesper >
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