try-with-resources and null resource (original) (raw)
Rémi Forax forax at univ-mlv.fr
Wed Jan 26 05:58:14 PST 2011
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On 01/25/2011 07:09 PM, Tim Peierls wrote:
On Tue, Jan 25, 2011 at 12:40 PM, Rémi Forax <forax at univ-mlv.fr_ _<mailto:forax at univ-mlv.fr>> wrote:
All cited construct including try() may dereference a value hence throw a NPE. switch(null) can jump to default or at the end of the switch block, if there is no default. for(Object o:null) { } can do not execute its body. synchronized(null) can synchronized to a special token. try(Object o = null) { } can do not execute its body But for switch, for and synchronized it was chosen to throw a NPE.
This is a misleading analogy. The thing that a resource declaration most resembles is not try, switch, for, or synchronized, but an ordinary variable declaration with initializer. This code doesn't throw NPE when initializing r with null: R r = get(); try { maybeUse(r); } finally { r.close(); } Nor should this code: try ( R r = get(); ) { maybeUse(r); } --tim
Again, your talking about implementation of the construct and not semantics of the construct. Perhaps, it's because try-with-resources reuses the same keyword as try/finally which doesn't help.
try-with-resources is a new construct of the language, the question is what should this construct do if the resource is null.
To make things crystal-clear, what should you be the semantics of: using(R r = get()) { maybeUse(r); } if get() returns null.
Rémi
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