Re: unbelievable NullPointerException

From:
Tom Anderson <twic@urchin.earth.li>
Newsgroups:
comp.lang.java.programmer
Date:
Fri, 10 Jul 2009 13:28:51 +0100
Message-ID:
<alpine.DEB.1.10.0907101323280.30152@urchin.earth.li>
On Fri, 10 Jul 2009, Pif wrote:

Thanks a lot for you help... so I've found the explanation.

Integer centerId = conf.getCenterId();
new CenterService().getCenter(centerId);

This throws an exception that does not appear in the debug mod because
this is internally managed by the JDK. Exactly, the exception is thrown
by the Autoboxing : NullPointerException is throws when trying to
convert null to int !!!!


This is exactly what i was going to suggest - glad you've found it. The
NPE from unboxing is a potent source of 'impossible' exceptions.

I would point out that *none* of the code you posted before this would
actually have allowed us to diagnose this problem. First, you posted:

Service service = new Service().getObject(int id);

Which isn't even syntactically correct - that 'int' is out of place. Then
it was:

public class CenterService {

etc, which was the first we'd heard of the CenterService class. And then:

Center center = service.getCenter(5);

In which you used a literal 5, not a variable of type Integer, thus
eliminating the key quirk through which your problem was occurring.

How on earth do you expect to get help with bugs in your code if you don't
show us the code? It's no use telling us what you *think* your code says -
if you were right, you wouldn't have a bug, would you?

tom

--
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