try-with-resources and null resource (original) (raw)
Jesper Öqvist jesper.oqvist at cs.lth.se
Fri Jan 28 01:55:58 PST 2011
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Hi Reinier,
On 2011-01-28 06:50, Reinier Zwitserloot wrote:
I have a question, and, presupposing either answer, a followup question:
1. In the above snippet, is t final? Yes 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 Class.getResourceAsStream returns null, it means the resource could not be found. In most cases you want to handle this scenario explicitly instead of skipping the resource entirely.
If the try with resources-statement would silently ignore that the resource was null, then possible errors might go unnoticed by the programmer.
I believe that suppressing NPEs just serves to obscure actual problems in the handling of your resources.
This whole discussion highlights why programming with null is a bad idea, but if we must use null then there should be exceptions whenever we try to use null. Java is already a bit confused on this point - in some cases null means "nothing" while in other cases it means "invalid/error".
Jesper
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