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From Chris Gray <chris.g...@kiffer.be>
Subject Re: NullPointerException
Date Mon, 20 Mar 2006 13:55:13 GMT
On Monday 20 March 2006 14:21, Mikhail Loenko wrote:
> 2006/3/19, Chris Gray <chris.gray@kiffer.be>:
> > I prefer to let these things happen automatically whenever possible.
> > Introducing an explicit check adds extra bytecodes and probably extra CPU
> > cycles in the non-null case. On some VMs null.someMethod() might be
> > slower in the null case, but if the RI also throws NPE then these cases
> > should be truly exceptional in the sense that they indicate a programming
> > error or a missing resource.
> I do not agree that performance in case of 'exceptional' behavior
> is not important.
> Would you use for example a browser that hangs your machine up for an hour
> if you type wrong URL? Or if it crashes when some site misses some gif
> file?

<aside>I can remember browsers that did that (or at least waited for DNS to 
time out).</aside>

I never claimed that performance in case of 'exceptional' behavior is not 
important. However it is less important than performance in the normal case; 
for example it would not make sense for Apache to optimise the processing of 
mistyped URLs at the expense of correctly-typed ones. Ideally the most 
frequently executed code paths should also be the shortest.

There are cases where a 'catch' clause can be executed very often, such as the 
ClassNotFoundException which is thrown when a class loader delegates to its 
parent and the parent does not find the class. In such cases one might 
consider optimising this path; but NPEs generally do not fall into this 
category, they most often indicate a programmer error (not user error) or the 
absence of some required resource (installation error). That is what I meant 
by "truly exceptional".



Chris Gray        /k/ Embedded Java Solutions      BE0503765045
Embedded & Mobile Java, OSGi    http://www.k-embedded-java.com/
chris.gray@kiffer.be                             +32 3 216 0369

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